Publications by authors named "Shih-Ming Hsu"

30 Publications

  • Page 1 of 1

Modern Rotational Radiation Techniques with Volumetric Modulated Arc Therapy or Helical Tomotherapy for Optimal Sparing of the Lung and Heart in Left-Breast Cancer Radiotherapy Plus Regional Nodal Irradiation: A Comparative Dosimetric Analysis.

Cancers (Basel) 2021 Oct 9;13(20). Epub 2021 Oct 9.

Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Taipei 30010, Taiwan.

Background: For advanced breast cancer with lymph node involvement, adjuvant radiotherapy (RT) with regional nodal irradiation (RNI) has been indicated to reduce cancer recurrence and mortality. However, an extensive RT volume is associated with normal organ exposure, which increases the toxicity and affects patient outcomes. Modern arc RT techniques can improve normal organ sparing compared with conventional techniques. The aim of this study was to explore the optimal technique for left-breast RT with RNI.

Methods: We retrospectively reviewed patients receiving RT with RNI for left-breast cancer. We used modern arc RT techniques with either volumetric-modulated arc therapy (VMAT) or helical tomotherapy (HT) with a novel block technique, and compared differences in dosimetry parameters between the two groups. Subgroup analysis of RNI with or without internal mammary node (IMN) volume was also performed.

Results: A total of 108 eligible patients were enrolled between 2017 and 2020, of whom 70 received VMAT and 38 received HT. The median RT dose was 55 Gy. No significant differences were found regarding the surgery, RT dose, number of fractions, target volume, and RNI volume between the VMAT and HT groups. VMAT reduced the heart mean dose more than HT (3.82 vs. 5.13 Gy, < 0.001), as well as the cardiac parameters of V5-V20, whole-lung mean dose, lung parameters of V5-V20, and contralateral-breast and esophagus mean dose. In the subgroup analysis of RNI with IMNs, the advantage of VMAT persisted in protecting the heart, lung, contralateral breast, and esophagus. HT was beneficial for lowering the thyroid mean dose. For RNI without IMN, VMAT improved the low-dose exposure of the heart and lung, but HT was similar to VMAT in terms of heart, whole-lung, and contralateral-breast mean dose.

Conclusions: For patients with left-breast cancer receiving adjuvant RT with RNI, VMAT reduced the exposure dose to the heart, lung, contralateral breast, and esophagus compared with HT. VMAT was superior to HT in terms of normal organ sparing in the patients who underwent RNI with IMN irradiation. Considering the reduction in normal organ exposure and potential toxicity, VMAT is the optimal technique for patients receiving RNI when deep inspiration breath-hold is not available.
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http://dx.doi.org/10.3390/cancers13205043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8534109PMC
October 2021

Simple parameters of synthetic MRI for assessment of bone density in patients with spinal degenerative disease.

J Neurosurg Spine 2021 Oct 15:1-8. Epub 2021 Oct 15.

1Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan.

Objective: Good bone quality is the key to avoiding osteoporotic fragility fractures and poor outcomes after lumbar instrumentation and fusion surgery. Although dual-energy x-ray absorptiometry (DEXA) screening is the current standard for evaluating osteoporosis, many patients lack DEXA measurements before undergoing lumbar spine surgery. The present study aimed to investigate the utility of using simple quantitative parameters generated with novel synthetic MRI to evaluate bone quality, as well as the correlations of these parameters with DEXA measurements.

Methods: This prospective study enrolled patients with symptomatic lumbar degenerative disease who underwent DEXA and conventional and synthetic MRI. The quantitative parameters generated with synthetic MRI were T1 map, T2 map, T1 intensity, proton density (PD), and vertebral bone quality (VBQ) score, and these parameters were correlated with T-score of the lumbar spine.

Results: There were 62 patients and 238 lumbar segments eligible for analysis. PD and VBQ score moderately correlated with T-score of the lumbar spine (r = -0.565 and -0.651, respectively; both p < 0.001). T1 intensity correlated fairly well with T-score (r = -0.411, p < 0.001). T1 and T2 correlated poorly with T-score. Receiver operating characteristic curve analysis demonstrated area under the curve values of 0.808 and 0.794 for detecting osteopenia/osteoporosis (T-score ≤ -1.0) and osteoporosis (T-score ≤ -2.5) with PD (both p < 0.001).

Conclusions: PD and T1 intensity values generated with synthetic MRI demonstrated significant correlation with T-score. PD has excellent ability for predicting osteoporosis and osteopenia.
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http://dx.doi.org/10.3171/2021.6.SPINE21666DOI Listing
October 2021

Correlation of bone density to screw loosening in dynamic stabilization: an analysis of 176 patients.

Sci Rep 2021 09 1;11(1):17519. Epub 2021 Sep 1.

Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, No. 155, Sec. 2, Li-Nong St., Beitou District, Taipei, 112, Taiwan, ROC.

Although osteoporosis has negative impacts on lumbar fusion, its effects on screw loosening in dynamic stabilization remain elusive. We aimed to correlate bone mineral density (BMD) with screw loosening in Dynesys dynamic stabilization (DDS). Consecutive patients who underwent 2- or 3-level DDS for spondylosis, recurrent disc herniations, or low-grade spondylolisthesis at L3-5 were retrospectively reviewed. BMD was assessed by the Hounsfield Unit (HU) in vertebral bodies (VB) and pedicles with and without cortical bone (CB) on pre-operative computed tomography (CT). Screw loosening was assessed by radiographs and confirmed by CT. HU values were compared between the loosened and intact screws. 176 patients and 918 screws were analyzed with 78 loosened screws found in 36 patients (mean follow-up: 43.4 months). The HU values of VB were similar in loosened and intact screws (p = 0.14). The HU values of pedicles were insignificantly less in loosened than intact screws (including CB: 286.70 ± 118.97 vs. 297.31 ± 110.99, p = 0.45; excluding CB: 238.48 ± 114.90 vs. 240.51 ± 108.91, p = 0.88). All patients had clinical improvements. In conclusion, the HU values, as a surrogate for BMD, were unrelated to screw loosening in DDS. Therefore, patients with compromised BMD might be potential candidates for dynamic stabilization rather than fusion.
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http://dx.doi.org/10.1038/s41598-021-95232-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8410763PMC
September 2021

Salvage Boron Neutron Capture Therapy for Malignant Brain Tumor Patients in Compliance with Emergency and Compassionate Use: Evaluation of 34 Cases in Taiwan.

Biology (Basel) 2021 Apr 15;10(4). Epub 2021 Apr 15.

Department of Neurosurgery, Taipei Medical University Hospital, Taipei City 110301, Taiwan.

Although boron neutron capture therapy (BNCT) is a promising treatment option for malignant brain tumors, the optimal BNCT parameters for patients with immediately life-threatening, end-stage brain tumors remain unclear. We performed BNCT on 34 patients with life-threatening, end-stage brain tumors and analyzed the relationship between survival outcomes and BNCT parameters. Before BNCT, MRI and F-BPA-PET analyses were conducted to identify the tumor location/distribution and the tumor-to-normal tissue uptake ratio (T/N ratio) of F-BPA. No severe adverse events were observed (grade ≥ 3). The objective response rate and disease control rate were 50.0% and 85.3%, respectively. The mean overall survival (OS), cancer-specific survival (CSS), and relapse-free survival (RFS) times were 7.25, 7.80, and 4.18 months, respectively. Remarkably, the mean OS, CSS, and RFS of patients who achieved a complete response were 17.66, 22.5, and 7.50 months, respectively. Kaplan-Meier analysis identified the optimal BNCT parameters and tumor characteristics of these patients, including a T/N ratio ≥ 4, tumor volume < 20 mL, mean tumor dose ≥ 25 Gy-E, MIB-1 ≤ 40, and a lower recursive partitioning analysis (RPA) class. In conclusion, for malignant brain tumor patients who have exhausted all available treatment options and who are in an immediately life-threatening condition, BNCT may be considered as a therapeutic approach to prolong survival.
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http://dx.doi.org/10.3390/biology10040334DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8071294PMC
April 2021

Treatment with a New Barbituric Acid Derivative Exerts Antiproliferative and Antimigratory Effects against Sorafenib Resistance in Hepatocellular Carcinoma.

Molecules 2020 Jun 20;25(12). Epub 2020 Jun 20.

Division of Gastroenterology, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei 116, Taiwan.

Hepatocellular carcinoma (HCC) is a common cause of cancer death worldwide. Sorafenib, a multikinase inhibitor, is the first-line drug approved by the Food and Drug Administration (FDA) for the treatment of patients with advanced HCC. However, most patients who continuously receive sorafenib may acquire resistance to this drug. Therefore, it is important to develop a new compound to treat liver cancer and sorafenib-resistant liver cancer. Barbituric acid derivatives have been used as antiasthmatic drugs in the clinic. We previously reported that a novel barbituric acid derivative inhibited carbon tetrachloride-induced liver fibrosis in mice, but its effects on liver cancer remain unknown. Thus, the purpose of this study was to investigate the antitumor effect of barbituric acid derivatives on HCC cells and sorafenib-resistant HCC cells (HCC-SRs). Our findings reveal that one of the barbituric acid derivatives, BA-5, significantly inhibited HCC and HCC-SR cell viability in a dose- and time-dependent manner. Therefore, compound BA-5 was selected for further experiments. Western blot data revealed that BA-5 treatment decreased the phosphorylation of AKT/p70s6k without affecting the MAPK pathway and increased cleaved PARP and cleaved caspase-7 in both HCC and HCC-SR cells. Since epithelial-mesenchymal transition plays a significant role in regulating cancer invasion and migration, we used the wound healing assay to evaluate the antimigratory effect of compound BA-5. The results showed that BA-5 treatment inhibited HCC and HCC-SR cell migration and reduced Vimentin protein expression. These results were confirmed by microarray analysis showing that BA-5 treatment influenced cancer cell motility and growth-related pathways. In the xenograft mouse model experiment, BA-5 administration significantly inhibited HCC cancer cell growth in mice. Furthermore, the combination of BA-5 with a low dose of regorafenib synergistically inhibited HCC-SR cell proliferation. In conclusion, our study showed that the barbituric acid derivative BA-5 is a new candidate for HCC and sorafenib-resistant HCC therapy.
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http://dx.doi.org/10.3390/molecules25122856DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7355767PMC
June 2020

Radiological and clinical outcomes of 3-level cervical disc arthroplasty.

J Neurosurg Spine 2019 Nov;32(2):174-181

3Department of Biomedical Imaging and Radiological Sciences, and.

Objective: One- and two-level cervical disc arthroplasty (CDA) has been compared to anterior cervical discectomy and fusion (ACDF) in several large-scale, prospective, randomized trials that have demonstrated similar clinical outcomes. However, whether these results would be similar when treating 3-level disc herniation and/or spondylosis has remained unanswered. This study aimed to investigate the differences between 3-level CDA and ACDF.

Methods: A series of 50 patients who underwent 3-level CDA at C3-7 was retrospectively reviewed and compared with another series of 50 patients (age- and sex-matched controls) who underwent ACDF at C3-7. Clinical outcomes were measured using the visual analog scale (VAS) for neck and arm pain, the modified Japanese Orthopaedic Association (mJOA) scale, and the Neck Disability Index (NDI). Radiological outcomes included range of motion (ROM) at the index levels. Every patient was evaluated by CT for the presence of fusion in the ACDF group. Also, complication profiles were investigated.

Results: The demographics and levels of distribution in both groups were very similar. During the follow-up period of 24 months, clinical outcomes improved (overall and respectively in each group) for both the CDA and ACDF patients when compared with the patients' preoperative condition. There were essentially few differences between the two groups in terms of neck and arm pain VAS scores, mJOA scores, and NDI scores preoperatively and at 3, 6, 12, and 24 months postoperatively. After the 3-level surgery, the CDA group had an increased mean ROM of approximately 3.4°, at 25.2° ± 8.84°, compared to their preoperative ROM (21.8° ± 7.20°) (p = 0.001), whereas the ACDF group had little mobility (22.8° ± 5.90° before and 1.0° ± 1.28° after surgery; p < 0.001). The mean operative time, estimated blood loss, and complication profiles were similar for both groups.

Conclusions: In this selectively matched retrospective study, clinical outcomes after 3-level CDA and ACDF were similar during the 2-year follow-up period. CDA not only successfully preserved but slightly increased the mobility at the 3 index levels. However, the safety and efficacy of 3-level CDA requires more long-term data for validatation.
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http://dx.doi.org/10.3171/2019.8.SPINE19545DOI Listing
November 2019

Image-guided study of inter-fraction and intra-fraction set-up variability and margins in reverse semi-decubitus breast radiotherapy.

Radiat Oncol 2018 Dec 27;13(1):254. Epub 2018 Dec 27.

Department of Radiation Oncology, MacKay Memorial Hospital, 92, Section 2, Chung-Shan North Road, Taipei, 104, Taiwan.

Background: This study aimed to evaluate the inter-fraction set-up error and intra-fraction motion during reverse semi-decubitus (RSD) breast radiotherapy, and to determine a planning target volume (PTV) margin.

Material And Methods: Pre- and post-treatment cone-beam computed tomography (CBCT) scans were prospectively acquired at fractions 1, 4, 7, 8, 11, and 14 for 30 patients who underwent RSD breast radiotherapy. Online correction for initial set-up error greater than 5 mm or 2° was performed and post-correction CBCT was acquired. An off-line analysis was performed to quantify initial and residual inter-fraction set-up errors and intra-fraction motion in three-dimensions. Patient inter-fraction errors were analysed for time trends during the course of radiotherapy. PTV margins were calculated from the systematic and random errors.

Results: The initial inter-fraction population systematic errors were 1.8-3.3 mm (translation) and 0.5° (rotation); random errors were 1.8-2.1 mm (translation) and 0.3-0.5° (rotation). After online correction, the residual inter-fraction population systematic errors were 1.2-1.8 mm (translation) and 0.3-0.4° (rotation); random errors were 1.4-1.6 mm (translation) and 0.3-0.4° (rotation). Intra-fraction population systematic and random errors were ≤ 1.3 mm (translation) and ≤ 0.2° (rotation). The magnitude of inter-fraction set-up errors in the anterior-posterior direction, roll, and yaw were significantly correlated with higher body weight and body mass index (BMI). The inter-fraction set-up error did not change significantly as a function of time during the course of radiotherapy. The magnitude of intra-fraction motion was not correlated with patient characteristics and treatment time. The total PTV margins accounting for pre-correction and intra-fraction errors were 6.5-10.2 mm; those accounting for post-correction and intra-fraction errors were 4.7-6.3 mm.

Conclusions: CBCT is an effective modality to evaluate and improve the inter-fraction set-up reproducibility in RSD breast radiotherapy, particularly for patients with higher BMI. Intra-fraction motion was minimal during RSD breast radiotherapy.
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http://dx.doi.org/10.1186/s13014-018-1200-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6307193PMC
December 2018

Construction of the REACHES climate database based on historical documents of China.

Sci Data 2018 12 18;5:180288. Epub 2018 Dec 18.

School of Big Data Management, Soochow University, 70 Linhsi Road, Shihlin, Taipei City 111, Taiwan.

This paper describes the methodology of an ongoing project of constructing an East Asian climate database REACHES based on Chinese historical documents. The record source is Compendium of Meteorological Records of China in the Last 3000 Years which collects meteorology and climate related records from mainly official and local chronicles along with a small number of other documents. We report the digitization of the records covering the period 1644-1795. An example of the original records is translated to illustrate the typical contents which contain time, location and type of events. Chinese historical times and location names are converted into Gregorian calendar and latitudes and longitudes. A hierarchical database system is developed that consists of the hierarchies of domains, main categories, subcategories, and further details. Historical events are then digitized and categorized into such a system. Code systems are developed at all levels such that the original descriptive entries are converted into digitized records suitable for treatment by computers. Statistics and characteristics of the digitized records in the database are described.
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http://dx.doi.org/10.1038/sdata.2018.288DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6298253PMC
December 2018

The Dosimetric Impact of Shifts in Patient Positioning during Boron Neutron Capture Therapy for Brain Tumors.

Biomed Res Int 2018 1;2018:5826174. Epub 2018 Oct 1.

Department of Oncology, Taipei Veterans General Hospital, Taipei, Taiwan.

Unlike conventional photon radiotherapy, sophisticated patient positioning tools are not available for boron neutron capture therapy (BNCT). Thus, BNCT remains vulnerable to setup errors and intra-fractional patient motion. The aim of this study was to estimate the impact of deviations in positioning on the dose administered by BNCT for brain tumors at the Tsing Hua open-pool reactor (THOR). For these studies, a simulated head model was generated based on computed tomography (CT) images of a patient with a brain tumor. A cylindrical brain tumor 3 cm in diameter and 5 cm in length was modeled at distances of 6.5 cm and 2.5 cm from the posterior scalp of this head model (T and T, respectively). Radiation doses associated with positioning errors were evaluated for each distance, including left and right shifts, superior and inferior shifts, shifts from the central axis of the beam aperture, and outward shifts from the surface of the beam aperture. Rotational and tilting effects were also evaluated. The dose prescription was 20 Gray-equivalent (Gy-Eq) to 80 % of the tumor. The treatment planning system, NCTPlan, was used to perform dose calculations. The average decreases in mean tumor dose for T for the 1 cm, 2 cm, and 3 cm lateral shifts composed by left, right, superior, and inferior sides, were approximately 1 %, 6 %, and 11 %, respectively, compared to the dose administered to the initial tumor position. The decreases in mean tumor dose for T were approximately 5 %, 11 %, and 15 % for the 1 cm, 2 cm, and 3 cm outward shifts, respectively. For a superficial tumor at T, no significant decrease in average mean tumor dose was observed following lateral shifts of 1 cm. Rotational and tilting up to 15° did not result in significant difference to the tumor dose. Dose differences to the normal tissues as a result of the shifts in positioning were also minimal. Taken together, these data demonstrate that the mean dose administered to tumors at greater depths is potentially more vulnerable to deviations in positioning, and greater shift distances resulted in reduced mean tumor doses at the THOR. Moreover, these data provide an estimation of dose differences that are caused by setup error or intra-fractional motion during BNCT, and these may facilitate more accurate predictions of actual patient dose in future treatments.
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http://dx.doi.org/10.1155/2018/5826174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6188766PMC
February 2019

The Effect of Body Mass Index and Weight Change on Late Gastrointestinal Toxicity in Locally Advanced Cervical Cancer Treated With Intensity-modulated Radiotherapy.

Int J Gynecol Cancer 2018 09;28(7):1377-1386

Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan.

Objective: To evaluate the effects of body mass index (BMI) and weight change during radiotherapy on the development of toxicity in patients with locally advanced cervical cancer (LACC) treated with intensity-modulated radiotherapy (IMRT).

Methods: A total of 245 patients were analyzed after undergoing definitive IMRT treatment between 2004 and 2015 for stage IB2 to stage IVA LACC. The patients were divided into 3 groups: underweight (BMI <18.5 kg/m), normal weight (BMI 18.5-24.9 kg/m), and overweight (BMI ≥25.0 kg/m). The relationships between toxicity, clinical factors, and the bowel dose-volume histogram were analyzed. V45 indicated the bowel volume that received a radiation dose of 45 Gy.

Results: The median follow-up period was 63 months. The V45 was similar among the 3 groups. The 5-year rates of grade 3 or higher late gastrointestinal toxicities were 18.6%, 4.0%, and 4.2% for the underweight, normal weight, and overweight groups, respectively (P = 0.002). In the multivariable analysis, underweight (hazard ratio, 13.99; 95% confidence interval, 3.22-60.82; P < 0.001) and weight loss (> -5%) (hazard ratio, 5.91; 95% confidence interval, 1.75-19.98; P = 0.004) were significant predictors of grade 3 or higher-grade late gastrointestinal toxicities.

Conclusion: A BMI of less than 18.5 kg/m and weight loss (> -5%) were associated with a higher risk of grade ≥3 or higher late gastrointestinal toxicity in patients with LACC treated with definitive IMRT. Future research on the development of a standardized and structured approach to improve the therapeutic ratio for the supportive care of patients with LACC is needed.
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http://dx.doi.org/10.1097/IGC.0000000000001312DOI Listing
September 2018

Skeletal Muscle Loss Is an Imaging Biomarker of Outcome after Definitive Chemoradiotherapy for Locally Advanced Cervical Cancer.

Clin Cancer Res 2018 10 29;24(20):5028-5036. Epub 2018 Jun 29.

Department of Radiation Oncology, MacKay Memorial Hospital, Taipei, Taiwan.

This study investigates the association between body composition change during concurrent chemoradiotherapy (CCRT) and outcome in patients with locally advanced cervical cancer (LACC). Pre- and posttreatment CT images of 245 patients with LACC who were treated between 2004 and 2015 were analyzed. Skeletal muscle index (SMI) and density (SMD), subcutaneous adipose tissue index (SATI), and visceral adipose tissue index (VATI) were measured from two sets of CT images at the level of the L3 vertebra. Sarcopenia and a low SMD were defined using published cut-off points. Predictors of overall survival (OS) and cancer-specific survival (CSS) were analyzed using Cox regression models. The median follow-up was 62.7 (range, 7.3-152.3) months. Among the 245 patients, 127 (51.8%) had pretreatment sarcopenia, and 154 (62.9%) had a low SMD. SMI did not decrease significantly during CCRT, 0.6%/150 days [95% confidence interval (CI), -1.8-0.6; = 0.35]. However, SMI loss during CCRT of >10.0%/150 days was independently associated with poorer OS (HR, 6.02; 95% CI, 3.04-11.93; < 0.001) and CSS (HR, 3.49; 95% CI, 1.44-8.42; = 0.006) when adjusted for FIGO stage, pathology, and treatment. Pretreatment sarcopenia and change of SMD, SATI, and VATI during CCRT were not associated with survival. Skeletal muscle measurements could be imaging biomarkers to predict outcomes for patients with LACC in clinical practice. Further studies are needed to determine whether multimodal interventions can preserve skeletal muscle mass and thereby improve survival. .
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http://dx.doi.org/10.1158/1078-0432.CCR-18-0788DOI Listing
October 2018

Calcium Phosphate Cement with Antimicrobial Properties and Radiopacity as an Endodontic Material.

Materials (Basel) 2017 Oct 31;10(11). Epub 2017 Oct 31.

Department of Dental Hygiene, China Medical University, Taichung 404, Taiwan.

Calcium phosphate cements (CPCs) have several advantages for use as endodontic materials, and such advantages include ease of use, biocompatibility, potential hydroxyapatite-forming ability, and bond creation between the dentin and appropriate filling materials. However, unlike tricalcium silicate (CS)-based materials, CPCs do not have antibacterial properties. The present study doped a nonwashable CPC with 0.25-1.0 wt % hinokitiol and added 0, 5, and 10 wt % CS. The CPCs with 0.25-0.5 wt % hinokitiol showed appreciable antimicrobial properties without alterations in their working or setting times, mechanical properties, or cytocompatibility. Addition of CS slightly retarded the apatite formation of CPC and the working and setting time was obviously reduced. Moreover, addition of CS dramatically increased the compressive strength of CPC. Doping CS with 5 wt % ZnO provided additional antibacterial effects to the present CPC system. CS and hinokitiol exerted a synergic antibacterial effect, and the CPC with 0.25 wt % hinokitiol and 10 wt % CS (doped with 5 wt % ZnO) had higher antibacterial properties than that of pure CS. The addition of 10 wt % bismuth subgallate doubled the CPC radiopacity. The results demonstrate that hinokitiol and CS can improve the antibacterial properties of CPCs, and they can thus be considered for endodontic applications.
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http://dx.doi.org/10.3390/ma10111256DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5706203PMC
October 2017

Dosimetric comparison of different treatment modalities for stereotactic radiotherapy.

Radiat Oncol 2017 Sep 16;12(1):155. Epub 2017 Sep 16.

Medical Physics and Radiation Measurements Laboratory, National Yang-Ming University, Taipei, Taiwan, ROC.

Background: The modalities for performing stereotactic radiotherapy (SRT) on the brain include the cone-based linear accelerator (linac), the flattening filter-free (FFF) volumetric modulated arc therapy (VMAT) linac, and tomotherapy. In this study, the cone-based linac, FFF-VMAT linac, and tomotherapy modalities were evaluated by measuring the differences in doses delivered during brain SRT and experimentally assessing the accuracy of the output radiation doses through clinical measurements.

Methods: We employed a homemade acrylic dosimetry phantom representing the head, within which a thermoluminescent dosimeter (TLD) and radiochromic EBT3 film were installed. Using the conformity/gradient index (CGI) and Paddick methods, the quality of the doses delivered by the various SRT modalities was evaluated. The quality indicators included the uniformity, conformity, and gradient indices. TLDs and EBT3 films were used to experimentally assess the accuracy of the SRT dose output.

Results: The dose homogeneity indices of all the treatment modalities were lower than 1.25. The cone-based linac had the best conformity for all tumors, regardless of the tumor location and size, followed by the FFF-VMAT linac; tomography was the worst-performing treatment modality in this regard. The cone-based linac had the best gradient, regardless of the tumor location and size, whereas the FFF-VMAT linac had a better gradient than tomotherapy for a large tumor diameter (28 mm). The TLD and EBT3 measurements of the dose at the center of tumors indicated that the average difference between the measurements and the calculated dose was generally less than 4%. When the 3% 3-mm gamma passing rate metric was used, the average passing rates of all three treatment modalities exceeded 98%.

Conclusions: Regarding the dose, the cone-based linac had the best conformity and steepest dose gradient for tumors of different sizes and distances from the brainstem. The results of this study suggest that SRT should be performed using the cone-based linac on tumors that require treatment plans with a steep dose gradient, even as the tumor is slightly irregular, we should also consider using a high dose gradient of the cone base to treat and protect the normal tissue. If normal tissues require special protection exist at positions that are superior or inferior to the tumor, we can consider using tomotherapy or Cone base with couch at 0° for treatment.
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http://dx.doi.org/10.1186/s13014-017-0890-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5602945PMC
September 2017

Impact of radiation attenuation by a carbon fiber couch on patient dose verification.

Sci Rep 2017 02 27;7:43336. Epub 2017 Feb 27.

Medical Physics and Radiation Measurements Laboratory, Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, ROC.

The aim of this study was to understand the difference between the measured and calculated irradiation attenuations obtained using two algorithms and to identify the influence of couch attenuation on patient dose verification. We performed eight tests of couch attenuation with two photon energies, two longitudinal couch positions, and two rail positions. The couch attenuation was determined using a radiation treatment planning system. The measured and calculated attenuations were compared. We also performed 12 verifications of head-and-neck and rectum cases by using a Delta phantom. The dose deviation (DD), distance to agreement (DTA), and gamma index of pencil-beam convolution (PBC) verifications were nearly the same. The agreement was least consistent for the anisotropic analytical algorithm (AAA) without the couch for the head-and-neck case, in which the DD, DTA, and gamma index were 74.4%, 99.3%, and 89%, respectively; for the rectum case, the corresponding values were 56.2%, 95.1%, and 92.4%. We suggest that dose verification should be performed using the following three metrics simultaneously: DD, DTA, and the gamma index.
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http://dx.doi.org/10.1038/srep43336DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5327409PMC
February 2017

Development of delineation for the left anterior descending coronary artery region in left breast cancer radiotherapy: An optimized organ at risk.

Radiother Oncol 2017 03 10;122(3):423-430. Epub 2017 Jan 10.

Department of Radiation Oncology, MacKay Memorial Hospital, Taipei, Taiwan; Department of Medicine, MacKay Medical College, Taiwan. Electronic address:

Background And Purpose: The left anterior descending coronary artery (LAD) and diagonal branches (DBs) are blurred on computed tomography (CT). We aimed to define the LAD region (LADR) with adequate inclusion of the LAD and DBs and contouring consistency.

Methods And Materials: The LADR was defined using coronary CT angiograms. The inclusion ratio was used to assess the LAD and DBs inclusion by the LADR. Four radiation oncologists delineated the LAD and LADR, using contrast-enhanced CT of 15 patients undergoing left breast radiotherapy. The Sørensen-Dice similarity index (DSI), Jaccard similarity index (JSI), and Hausdorff distance (HD) were calculated to assess similarity. The mean dose (D) and maximum dose (D) to the LAD and LADR were calculated to compare consistency. Correlations were evaluated using Pearson's correlation coefficient.

Results: The inclusion ratio of the LAD by the LADR was 96%. The mean DSI, JSI, and HD values were respectively 27.9%, 16.7%, and 0.42mm for the LAD, and 83.1%, 73.0%, and 0.18mm for the LADR. The D between the LAD and LADR were strongly correlated (r=0.93).

Conclusion: Delineation of the LADR significantly improved contouring similarity and consistency for dose reporting. This could optimize dose estimation for breast radiotherapy.
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http://dx.doi.org/10.1016/j.radonc.2016.12.029DOI Listing
March 2017

Feasibility Study on Applying Radiophotoluminescent Glass Dosimeters for CyberKnife SRS Dose Verification.

PLoS One 2017 3;12(1):e0169252. Epub 2017 Jan 3.

Medical Physics Graduate Program at Duke Kunshan University, Kunshan, Jiangsu, China.

CyberKnife is one of multiple modalities for stereotactic radiosurgery (SRS). Due to the nature of CyberKnife and the characteristics of SRS, dose evaluation of the CyberKnife procedure is critical. A radiophotoluminescent glass dosimeter was used to verify the dose accuracy for the CyberKnife procedure and validate a viable dose verification system for CyberKnife treatment. A radiophotoluminescent glass dosimeter, thermoluminescent dosimeter, and Kodak EDR2 film were used to measure the lateral dose profile and percent depth dose of CyberKnife. A Monte Carlo simulation for dose verification was performed using BEAMnrc to verify the measured results. This study also used a radiophotoluminescent glass dosimeter coupled with an anthropomorphic phantom to evaluate the accuracy of the dose given by CyberKnife. Measurements from the radiophotoluminescent glass dosimeter were compared with the results of a thermoluminescent dosimeter and EDR2 film, and the differences found were less than 5%. The radiophotoluminescent glass dosimeter has some advantages in terms of dose measurements over CyberKnife, such as repeatability, stability, and small effective size. These advantages make radiophotoluminescent glass dosimeters a potential candidate dosimeter for the CyberKnife procedure. This study concludes that radiophotoluminescent glass dosimeters are a promising and reliable dosimeter for CyberKnife dose verification with clinically acceptable accuracy within 5%.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0169252PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5207685PMC
August 2017

A volume-equivalent spherical necrosis-tumor-normal liver model for estimating absorbed dose in yttrium-90 microsphere therapy.

Med Phys 2016 Nov;43(11):6082

Medical Physics and Radiation Measurements Laboratory, Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan 112, Republic of China; Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan 112, Republic of China; and Biophotonics and Molecular Imaging Research Center, National Yang-Ming University, Taipei, Taiwan 112, Republic of China.

Purpose: Primary hepatocellular carcinoma and metastatic liver tumors are highly malignant tumors in Asia. The incidence of fatal liver cancer is also increasing in the United States. The aim of this study was to establish a spherical tumor model and determine its accuracy in predicting the absorbed dose in yttrium-90 (Y-90) microsphere therapy for liver cancer.

Methods: Liver morphology can be approximated by a spherical model comprising three concentric regions representing necrotic, tumor, and normal liver tissues. The volumes of these three regions represent those in the actual liver. A spherical tumor model was proposed to calculate the absorbed fractions in the spherical tumor, necrotic, and normal tissue regions. The THORplan treatment planning system and Monte Carlo N-particle extended codes were used for this spherical tumor model. Using the volume-equivalent method, a spherical tumor model was created to calculate the total absorbed fraction [under different tumor-to-healthy-liver ratios (TLRs)]. The patient-specific model (THORplan) results were used to verify the spherical tumor model results.

Results: The results for both the Y-90 spectrum and the Y-90 mean energy indicated that the absorbed fraction was a function of the tumor radius and mass. The absorbed fraction increased with tumor radius. The total absorbed fractions calculated using the spherical tumor model for necrotic, liver tumor, and normal liver tissues were in good agreement with the THORplan results, with differences of less than 3% for TLRs of 2-5. The results for the effect of TLR indicate that for the same tumor configuration, the total absorbed fraction decreased with increasing TLR; for the same shell tumor thickness and TLR, the total absorbed fraction was approximately constant; and for tumors with the same radius, the total fraction absorbed by the tumor increased with the shell thickness.

Conclusions: The results from spherical tumor models with different tumor-to-healthy-liver ratios were highly consistent with the reference results (THORplan). These findings indicate that a spherical tumor model can provide good estimates of Y-90 doses in microsphere therapy and can be considered a first approximation for dose estimation in Y-90 microsphere therapy.
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http://dx.doi.org/10.1118/1.4965044DOI Listing
November 2016

Glycine N-methyltransferase deficiency in female mice impairs insulin signaling and promotes gluconeogenesis by modulating the PI3K/Akt pathway in the liver.

J Biomed Sci 2016 Oct 4;23(1):69. Epub 2016 Oct 4.

Department of Microbiology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.

Background: Glycine N-methyltransferase (GNMT) is abundantly expressed in the normal liver but is down-regulated in liver cancer tissues. GNMT knockout (Gnmt-/-) mice can spontaneously develop chronic hepatitis, fatty liver, and liver cancer. We previously demonstrated that hepatic GNMT is decreased in high-fat-diet-induced type 2 diabetes mellitus, but its contribution to metabolic syndrome is unclear. Here we show that GNMT modulates key aspects of metabolic syndrome in mice.

Methods: Eleven-week-old Gnmt-/- and wild-type (WT) mice with a C57BL/6 genetic background were used in this study. The metabolic defects of GNMT deficiency were measured by glucose and insulin tolerance tests, lipid homeostasis, gluconeogenesis, and insulin signaling.

Results: Gnmt-/- mice, especially females, exhibited glucose intolerance and insulin resistance. However, their body fat and lean mass, food and water intakes, and energy expenditure did not differ from those of WT mice. In addition, glucose-stimulated insulin secretion and insulin-stimulated glucagon secretion were normal in the serum and pancreatic islets of Gnmt-/- mice. Importantly, we found that GNMT deficiency increased lipogenesis and triglycerides in the liver. The elevated triglycerides disrupted the ability of insulin to induce Akt and S6 ribosomal protein phosphorylation, and then triggered insulin resistance and gluconeogenesis in female Gnmt-/- mice.

Conclusions: Our data indicate that hepatic GNMT regulates lipid and glucose homeostasis, and provide insight into the development of insulin resistance through modulating the PI3K/Akt pathway.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5050923PMC
http://dx.doi.org/10.1186/s12929-016-0278-8DOI Listing
October 2016

Niemann-Pick Type C2 Protein Mediates Hepatic Stellate Cells Activation by Regulating Free Cholesterol Accumulation.

Int J Mol Sci 2016 Jul 13;17(7). Epub 2016 Jul 13.

School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, 110 Taipei, Taiwan.

In chronic liver diseases, regardless of their etiology, the development of fibrosis is the first step toward the progression to cirrhosis, portal hypertension, and hepatocellular carcinoma. Hepatic stellate cells (HSCs) are the main profibrogenic cells that promote the pathogenesis of liver fibrosis, and so it is important to identify the molecules that regulate HSCs activation and liver fibrosis. Niemann-Pick type C2 (NPC2) protein plays an important role in the regulation of intracellular cholesterol homeostasis by directly binding with free cholesterol. However, the roles of NPC2 in HSCs activation and liver fibrosis have not been explored in detail. Since a high-cholesterol diet exacerbates liver fibrosis progression in both rodents and humans, we propose that the expression of NPC2 affects free cholesterol metabolism and regulates HSCs activation. In this study, we found that NPC2 is decreased in both thioacetamide- and carbon tetrachloride-induced liver fibrosis tissues. In addition, NPC2 is expressed in quiescent HSCs, but its activation status is down-regulated. Knockdown of NPC2 in HSC-T6 cells resulted in marked increases in transforming growth factor-β1 (TGF-β1)-induced collagen type 1 α1 (Col1a1), α-smooth muscle actin (α-SMA) expression, and Smad2 phosphorylation. In contrast, NPC2 overexpression decreased TGF-β1-induced HSCs activation. We further demonstrated that NPC2 deficiency significantly increased the accumulation of free cholesterol in HSCs, increasing Col1a1 and α-SMA expression and activating Smad2, and leading to sensitization of HSCs to TGF-β1 activation. In contrast, overexpression of NPC2 decreased U18666A-induced free cholesterol accumulation and inhibited the subsequent HSCs activation. In conclusion, our study has demonstrated that NPC2 plays an important role in HSCs activation by regulating the accumulation of free cholesterol. NPC2 overexpression may thus represent a new treatment strategy for liver fibrosis.
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http://dx.doi.org/10.3390/ijms17071122DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4964497PMC
July 2016

HDR Brachytherapy Dose Distribution is Influenced by the Metal Material of the Applicator.

Sci Rep 2015 Dec 11;5:17863. Epub 2015 Dec 11.

Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, ROC.

Applicators containing metal have been widely used in recent years when applying brachytherapy to patients with cervical cancer. However, the high dose rate (HDR) treatment-planning system (TPS) that is currently used in brachytherapy still assumes that the treatment environment constitutes a homogeneous water medium and does not include a dose correction for the metal material of the applicator. The primary purpose of this study was to evaluate the HDR (192)Ir dose distribution in cervical cancer patients when performing brachytherapy using a metal-containing applicator. Thermoluminescent dosimeter (TLD) measurements and Monte Carlo N-Particle eXtended (MCNPX) code were used to explore the doses to the rectum and bladder when using a Henschke applicator containing metal during brachytherapy. When the applicator was assumed to be present, the absolute dose difference between the TLD measurement and MCNPX simulation values was within approximately 5%. A comparison of the MCNPX simulation and TPS calculation values revealed that the TPS overestimated the International Commission of Radiation Units and Measurement (ICRU) rectum and bladder reference doses by 57.78% and 49.59%, respectively. We therefore suggest that the TPS should be modified to account for the shielding effects of the applicator to ensure the accuracy of the delivered doses.
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http://dx.doi.org/10.1038/srep17863DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4675994PMC
December 2015

Niemann-Pick type C2 protein regulates liver cancer progression via modulating ERK1/2 pathway: Clinicopathological correlations and therapeutical implications.

Int J Cancer 2015 Sep 24;137(6):1341-51. Epub 2015 Mar 24.

Center for Infections Disease and Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan.

Primary hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide and the third leading cause of cancer-related death. It is important to identify new targets for early diagnosis and treatment of HCC. Niemann-Pick type C2 (NPC2) plays an important role in the regulation of intracellular cholesterol homeostasis via direct binding with free cholesterol. However, little is known about the significance of NPC2 in HCC tumorigenesis. In this study, we showed that NPC2 is abundantly expressed in normal liver, but is downregulated in human HCC tissues. The patients with NPC2 downregulation expressed much higher α-fetoprotein, multiple tumor type, vascular invasion, later pathological stage and shorter survival rate. Knockdown NPC2 in liver cancer cell lines promote cell proliferation, migration and xenograft tumorigenesis. In contrast, NPC2 overexpression inhibits HuH7 promoted tumor growth. Furthermore, administration of hepatotropic adeno-associated virus 8 (AAV8) delivered NPC2 decreased the inflammatory infiltration, the expression of two early HCC markers-glypican 3 and survivin and suppressed the spontaneous HCC development in mice. To identify the NPC2-dependent mechanism, we emphasized on the status of MAPK/ERK signaling. MEK1/2 inhibitor treatment demonstrated that the expression of NPC2 affected the activation of ERK1/2 but not MEK1/2. In addition, cholesterol trafficking inhibitor treatment did not alter the cell proliferation and the activation of MEK/ERK. In conclusion, our study demonstrates that NPC2 may play an important role in negatively regulate cell proliferation and ERK1/2 activation that were independent of cholesterol accumulation. AAV-NPC2 may thus represent a new treatment strategy for liver cancer.
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http://dx.doi.org/10.1002/ijc.29507DOI Listing
September 2015

Influence of metal of the applicator on the dose distribution during brachytherapy.

PLoS One 2014 18;9(8):e104831. Epub 2014 Aug 18.

Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, ROC; Biophotonics and Molecular Imaging Research Center, National Yang-Ming University, Taipei, Taiwan, ROC.

This study explores how the metal materials of the applicator influence the dose distribution when performing brachytherapy for cervical cancer. A pinpoint ionization chamber, Monte Carlo code MCNPX, and treatment planning system are used to evaluate the dose distribution for a single Ir-192 source positioned in the tandem and ovoid. For dose distribution in water with the presence of the tandem, differences among measurement, MCNPX calculation and treatment planning system results are <5%. For dose distribution in water with the presence of the ovoid, the MCNPX result agrees with the measurement. But the doses calculated from treatment planning system are overestimated by up to a factor of 4. This is due to the shielding effect of the metal materials in the applicator not being considered in the treatment planning system. This result suggests that the treatment planning system should take into account corrections for the metal materials of the applicator in order to improve the accuracy of the radiation dose delivered.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0104831PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4136780PMC
May 2015

A study on the dose distributions in various materials from an Ir-192 HDR brachytherapy source.

PLoS One 2012 5;7(9):e44528. Epub 2012 Sep 5.

Department of Biomedical Imaging and Radiological Science, China Medical University Hospital, Taichung, Taiwan, ROC.

Dose distributions of (192)Ir HDR brachytherapy in phantoms simulating water, bone, lung tissue, water-lung and bone-lung interfaces using the Monte Carlo codes EGS4, FLUKA and MCNP4C are reported. Experiments were designed to gather point dose measurements to verify the Monte Carlo results using Gafchromic film, radiophotoluminescent glass dosimeter, solid water, bone, and lung phantom. The results for radial dose functions and anisotropy functions in solid water phantom were consistent with previously reported data (Williamson and Li). The radial dose functions in bone were affected more by depth than those in water. Dose differences between homogeneous solid water phantoms and solid water-lung interfaces ranged from 0.6% to 14.4%. The range between homogeneous bone phantoms and bone-lung interfaces was 4.1% to 15.7%. These results support the understanding in dose distribution differences in water, bone, lung, and their interfaces. Our conclusion is that clinical parameters did not provide dose calculation accuracy for different materials, thus suggesting that dose calculation of HDR treatment planning systems should take into account material density to improve overall treatment quality.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0044528PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3434140PMC
February 2013

The clinical application of 4D 18F-FDG PET/CT on gross tumor volume delineation for radiotherapy planning in esophageal squamous cell cancer.

J Radiat Res 2012 Jul 5;53(4):594-600. Epub 2012 Jun 5.

Department of Radiation Oncology, China Medical University Hospital, Taichung, Taiwan.

A combination of four-dimensional computed tomography with (18)F-fluorodeoxyglucose positron emission tomography (4D CT-FDG PET) was used to delineate gross tumor volume (GTV) in esophageal cancer (EC). Eighteen patients with EC were prospectively enrolled. Using 4D images taken during the respiratory cycle, the average CT image phase was fused with the average FDG PET phase in order to analyze the optimal standardized uptake values (SUV) or threshold. PET-based GTV (GTV(PET)) was determined with eight different threshold methods using the auto-contouring function on the PET workstation. The difference in volume ratio (VR) and conformality index (CI) between GTV(PET) and CT-based GTV (GTV(CT)) was investigated. The image sets via automatic co-registrations of 4D CT-FDG PET were available for 12 patients with 13 GTV(CT) values. The decision coefficient (R(2)) of tumor length difference at the threshold levels of SUV 2.5, SUV 20% and SUV 25% were 0.79, 0.65 and 0.54, respectively. The mean volume of GTV(CT) was 29.41 ± 19.14 ml. The mean VR ranged from 0.30 to 1.48. The optimal VR of 0.98, close to 1, was at SUV 20% or SUV 2.5. The mean CI ranged from 0.28 to 0.58. The best CI was at SUV 20% (0.58) or SUV 2.5 (0.57). The auto-contouring function of the SUV threshold has the potential to assist in contouring the GTV. The SUV threshold setting of SUV 20% or SUV 2.5 achieves the optimal correlation of tumor length, VR, and CI using 4D-PET/CT images.
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http://dx.doi.org/10.1093/jrr/rrs009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3393356PMC
July 2012

Air kerma standard and measurement comparison on source strength determination for high-dose rate 192Ir brachytherapy in Taiwan.

Radiat Prot Dosimetry 2011 Jul 16;146(1-3):100-2. Epub 2011 Apr 16.

Health Physics Division, Institute of Nuclear Energy Research, 1000, Wen-Hua Road, Longtan Township, Taoyuan County 32546, Taiwan.

This paper describes the establishment by the Institute of Nuclear Energy Research (INER, Taiwan) of the reference air kerma rate (RAKR) calibration standard for measurement of high-dose rate (HDR) (192)Ir brachytherapy source strength. A bilateral comparison has been made in the RAKR standards for HDR (192)Ir brachytherapy sources at the INER and Physikalisch-Technische Bundesanstalt (PTB, Germany) and the measurement difference was within the overall standard uncertainty and showed good agreement between the two calibration standard systems established at the INER and the PTB. Besides, INER also worked with 20 domestic hospitals to organise an on-site measurement comparison programme to explore the status of HDR (192)Ir brachytherapy source strength determination in Taiwan. The comparison results presented the ratios of RAKR with vendor values, as determined by INER and hospitals from the programme. The ratios fall in all cases within the ± 3 % guaranteed by the vendors for a coverage factor of k = 2 or at 95 % confidence level.
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http://dx.doi.org/10.1093/rpd/ncr121DOI Listing
July 2011

Dose measurements for gamma knife with radiophotoluminescent glass dosemeter and radiochromic film.

Radiat Prot Dosimetry 2011 Jul 14;146(1-3):256-9. Epub 2011 Apr 14.

Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan.

Stereotactic radiosurgery (SRS) is designed for patients with small lesion areas that are not suitable for actual surgery. SRS delivers high dose to the lesion with high gradient on the irradiation margin area. In this study, radiophotoluminescent glass dosemeter (RPLGD) and radiochromic film were used to measure the output factor of a gamma knife. Also, a Monte Carlo code (OMEGA/BEAM) was applied to simulate the output factor. For 14 and 8 mm sizes of helmet collimators, the variations of output factors determined with RPLGD, radiochromic film, the Monte Carlo code and Elekta were all within 0.5 %. When helmet collimator size was 4 mm, the output factors detected from RPLGD, radiochromic film and Monte Carlo simulation were all within 3.2 % when compared with Elekta. Taken together, RPLGD, radiochromic film and Monte Carlo simulation will be used as precise tools to measure the output factor of a gamma knife.
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http://dx.doi.org/10.1093/rpd/ncr164DOI Listing
July 2011

Potential dose reduction of optimal ECG-controlled tube current modulation for 256-slice CT coronary angiography.

Acad Radiol 2011 Jun 21;18(6):731-7. Epub 2011 Mar 21.

Department of Radiological Technology, Tzu Chi College of Technology, Hualien, Taiwan.

Rationale And Objectives: The purpose of this study was to design an optimized heart rate (HR)-dependent electrocardiogram (ECG) pulsing protocol for computed tomography coronary angiography (CTCA) on a 256-slice CT scanner and to assess its potential dose reduction retrospectively, based on the retrospective ECG gating data without dose modulation.

Materials And Methods: A total of 137 patients were enrolled to perform CTCA with a 256-slice scanner. Two independent radiologists graded image quality of coronary artery segments (1 = excellent, no motion artifacts; 4 = poor, severe motion artifacts) to define optimal reconstruction window in end-systolic phase, mid-diastolic phase, and the combination of both cardiac phases. According to statistical analysis for HR against image quality, four HR-depended ECG-pulsing protocols were proposed. We also demonstrated the potential dose reduction of the proposed technique.

Results: For patients with HR <59 beats/min (group 1), 60-72 beats/min (group 2), 73-84 beats/min (group 3), and >85 beats/min (group 4), the optimal reconstruction windows were at 74.1-81.3%, 73.4-82.2%, 38.3-82.3%, and 37.2-61.6% of R-R interval, respectively. The ECG-pulsing protocols with minimal radiation dose (ie, no tube current outside the pulsing window) can reduce the effective dose of CTCA by 79.5%, 75.7%, 38.3%, and 57.4% for HR groups 1 to 4, respectively. The corresponding results for reducing tube current by 80% outside the pulsing window were 63.7%, 56.6%, 32.0%, and 46.0%.

Conclusion: Through the optimization of ECG-pulsed tube-current modulation, radiation exposure can be greatly reduced, especially in patients with HR <72 beats/min or >85 beats/min.
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http://dx.doi.org/10.1016/j.acra.2011.01.028DOI Listing
June 2011

Clinical application of radiophotoluminescent glass dosimeter for dose verification of prostate HDR procedure.

Med Phys 2008 Dec;35(12):5558-64

Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan, Republic of China.

High dose rate brachytherapy (HDR-BT) is one of the many modalities for prostate cancer treatment. Due to the nature of HDR-BT, in vivo dosimetry is feasible and can be used to verify consistent dose delivery. In order to validate a dose verification system for HDR-BT prostate cancer treatment, a radiophotoluminescent glass dosimeter (RPLGD) was used and the measurements were compared with those from a thermoluminescent dosimeter. The RPLGD shows many advantages in HDR-BT dose measurement, such as repeatability, stability, and small effective size. These advantages make the RPLGD a superior option for use as a dosimeter in HDR-BT. The results described here show that the difference between the measured dose and the treatment planned dose is less than 5%. A Monte Carlo simulation for the dose was performed using Monte Carlo N -particle to investigate position error. This study concludes that the RPLGD is a promising and reliable dosimeter for HDR-BT in vivo dosimetry with clinically acceptable accuracy.
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http://dx.doi.org/10.1118/1.3005478DOI Listing
December 2008

Spatially dispersive displacement sensor utilizing a semiconductor gain chip.

Appl Opt 2007 Feb;46(5):680-4

Laser Application Technology Center, Industrial Technology Research Institute, Tainan County, Taiwan.

We demonstrate the development of a simply equipped displacement sensor utilizing spatially dispersive confocal technology. It feeds the amplified spontaneous emission (ASE) of a laser diode to a wavelength-selective feedback structure that corresponds to the position of a measured surface. The displacement sensor has a detecting range of 4 microm and precision of less than 2 nm, as proven by the analysis of the spectral shifts of the multipassed amplified output ASE. As compared with traditional sensors, the displacement sensor presented in our study requires fewer components and has as high precision as complex systems and a higher measurement rate due to the simpler strategy of displacement determination.
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http://dx.doi.org/10.1364/ao.46.000680DOI Listing
February 2007

Comparison on characteristics of radiophotoluminescent glass dosemeters and thermoluminescent dosemeters.

Radiat Prot Dosimetry 2006 18;119(1-4):327-31. Epub 2006 May 18.

Department of Medical Radiation Technology, National Yang-Ming University, 155, Li-Nong Street Sec. 2, Pei-tou, Taipei 112, Taiwan, Republic of China.

The radiophotoluminescent glass dosemeter (RPLGD) system is applicable for measurement of radiation dose of X rays and gamma rays by using radiophotoluminescent glass (silver-activated phosphate glass). When the radiophotoluminescent glass is exposed to ionizing radiation, stable luminescent centres are created. During pulsed ultraviolet laser excitation (337.1 nm) in the reader, the centres emit a radiation induced orange fluorescent light (600-700 nm). This phenomenon is called radiophotoluminescence. This study compared the RPLGD system with lithium fluoride (LiF) thermoluminescence dosimetry system and the results of the study revealed that the RPLGD had not only good basic characteristics for reproducibility of readout value, dose linearity, energy dependence and fading, but also infinite repeatable measurements and could be one of the most important radiation dose measurement instruments.
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http://dx.doi.org/10.1093/rpd/nci510DOI Listing
December 2006
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