Publications by authors named "Yemliha Dolek"

12 Publications

  • Page 1 of 1

Role of 68-Ga-PSMA-PET/CT in pelvic radiotherapy field definitions for lymph node coverage in prostate cancer patients.

Radiother Oncol 2020 10 28;151:222-227. Epub 2020 Aug 28.

Department of Radiation Oncology, Hacettepe University, Faculty of Medicine, Ankara, Turkey.

Purpose: To evaluate the distribution of metastatic lymph nodes (LN) detected on Ga-PSMA-positron emission tomography/computed tomography (PET/CT) in treatment-naïve prostate cancer (PC) patients and to analyze the LN coverage rates of the pelvic fields defined in the GETUG trial and RTOG guidelines and a pelvic field extending superiorly from the L4/L5 interspace.

Materials And Methods: Ga-PSMA-PET/CT images obtained at diagnosis of 138 PC patients were retrospectively analyzed. The number and locations of Ga-PSMA-positive LNs were co-registered with one single-planning CT. The numbers, locations, and sizes of LNs located outside the three pelvic volumes were investigated for the entire cohort and for patients with LN metastasis in the pelvic area only.

Results: A total of 441 PSMA-PET-positive LN metastases were identified. The most frequent metastatic LNs were internal iliac LNs (25.2%). Para-aortic and presacral LNs outside the three pelvic fields were present in 20 (14.5%) and 22 patients (15.9%), respectively. The LN coverage rates according to the GETUG trial, the RTOG guidelines, and the pelvic field extending superiorly from L4/L5 were 44.2%, 52.2%, and 71, respectively, in the entire cohort and 51.7%, 61 and 83.1%, respectively, in patients with only pelvic LN metastasis. The number of metastatic LNs was a predictive factor for LNs located outside the three pelvic fields.

Conclusions: Extending the cranial margin of the pelvic field from L5/S1 to L4/L5 increases the accuracy of pelvic field irradiation in approximately 20% of patients, highlighting the importance of proximal common iliac irradiation, particularly in patients with multiple LN metastasis.
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http://dx.doi.org/10.1016/j.radonc.2020.08.021DOI Listing
October 2020

Incidental testicular doses during volumetric-modulated arc radiotherapy in prostate cancer patients.

Radiol Med 2020 Aug 3;125(8):777-783. Epub 2020 Mar 3.

Adana Dr. Turgut Noyan Research and Treatment Center, Department of Radiation Oncology, Baskent University Faculty of Medicine, 01120, Adana, Turkey.

Purpose: To compare the incidental testicular doses during volumetric-modulated arc therapy (VMAT) in patients receiving prostate-only and pelvic lymphatic irradiation.

Materials And Methods: Testicular doses in 40 intermediate- and high-risk prostate cancer patients were determined on treatment planning system (TPS) using the VMAT technique at 6 MV. Scattered testicular doses were also measured by MOSFET detectors placed on testis surface. The testicular doses of patients treated with prostate-only and pelvic field irradiation were compared.

Results: The median testicular doses measured per 200 cGy fraction by TPS and MOSFET detectors were 1.7 cGy (0.7-4.1 cGy) and 4.8 cGy (3.6-8.8 cGy), respectively. The TPS doses and MOSFET readings showed a significant strong correlation (Pearson r = 0.848, p < 0.001). The testicular doses measured by TPS (1.34 ± 0.36 cGy vs. 2.60 ± 0.95 cGy; p < 0.001) and MOSFET (4.52 ± 0.64 cGy vs. 6.56 ± 1.23 cGy; p < 0.001) were significantly lower in patients with prostate-only irradiation than in those with pelvic field irradiation. The mean cumulative scattered dose for prostate-only field delivering 78 Gy was 1.8 Gy and that for pelvic field irradiation was 2.6 Gy, consistent with the reported findings.

Conclusions: The patients with prostate-only irradiation received lower testicular doses than those with additional pelvic field irradiation possibly due to the increased scattered doses in large field irradiation using the VMAT technique. The clinical response to increased incidental testicular doses due to pelvic field irradiation remains unknown, and it warrants further investigation.
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http://dx.doi.org/10.1007/s11547-020-01158-2DOI Listing
August 2020

Dosimetric comparison of vaginal vault brachytherapy vs applicator-guided stereotactic body radiotherapy with volumetric modulated arc therapy and helical tomotherapy for endometrium cancer patients.

Med Dosim 2019 Winter;44(4):332-338. Epub 2018 Dec 11.

Department of Radiation Oncology, Baskent University Faculty of Medicine, 01120 Adana, Turkey. Electronic address:

We performed this dosimetric study to compare a nonstandard volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) techniques with high-dose rate (HDR) brachytherapy (BRT) plan of vaginal vault in patients with postoperative endometrial cancer (EC). Twelve postoperative patients with early stage EC were included in this study. Three plans were performed for each patient; dosimetric and radiobiological comparisons were made using dose-volume histograms and equivalent dose for determining the planning target volume (PTV) coverages in brachytherapy and external beam radiotherapy, and organs-at-risk (OARs) doses between three different delivery techniques. All the plans achieved adequate dose coverage for PTV; however, the VMAT plan yielded better dose conformity, and the HT plan showed better homogeneity for target volume. With respect to the OARs, the bladder D was significantly lower in the BRT plan than in the VMAT and HT plans, with the highest bladder D value being observed in the HT plan. However, no difference was observed in the rectum D of the three plans. Other major advantages of the BRT plan over the VMAT and HT plans were the relatively lower body integral doses and femoral head doses as well as the fact that the integral doses were significantly lower in the BRT plan than in the VMAT and HT plans. This is the first dosimetric comparison of vaginal vault treatment for EC with BRT, VMAT, and HT plans. Our analyses showed the feasibility of stereotactic body radiotherapy technique as an alternative to HDR-BRT for postoperative management of EC patients.
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http://dx.doi.org/10.1016/j.meddos.2018.11.005DOI Listing
April 2020

Dosimetric comparison of 3-dimensional conformal radiotherapy, volumetric modulated arc therapy, and helical tomotherapy for postoperative gastric cancer patients.

Jpn J Radiol 2018 Jan 3;36(1):30-39. Epub 2017 Nov 3.

Department of Radiation Oncology, Adana Dr Turgut Noyan Research and Treatment Centre, Baskent University Faculty of Medicine, 01120, Adana, Turkey.

Purpose: To compare dosimetric data for the planning target volume (PTV) and organs at risk (OARs) between 3-dimensional conformal radiotherapy (3DCRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy [1].

Materials And Methods: The dosimetric data for 15 gastric cancer patients treated with 3DCRT, VMAT, or HT techniques were used. Cumulative dosimetric parameters, homogeneity index (HI), and conformal index (CI) were compared for the PTV and OARs.

Results: The average maximum doses of PTV were significantly higher in VMAT plans than in 3DCRT (p = 0.04) and HT (p = 0.02) plans, whereas minimum dose values were significantly lower in 3DCRT plans compared with VMAT (p < 0.001) and HT (p = 0.02) plans. Liver mean dose (D ) and D values for both kidneys were significantly lower in HT plans than in 3DCRT and VMAT plans. The doses in high dose regions (V30-V45) using 3DCRT plans were significantly higher compared to both VMAT and HT plans. The bowel V5-V30 and V45 was significantly less in HT plans compared to VMAT plans. There were no significant differences in dose sparing of the spinal cord.

Conclusions: The HT plans reduced the maximum dose applied to the target and improved the conformality and homogeneity of radiation, while providing sufficient PTV coverage.
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http://dx.doi.org/10.1007/s11604-017-0696-xDOI Listing
January 2018

Effects of vaginal cylinder position on dose distribution in patients with endometrial carcinoma in treatment of vaginal cuff brachytherapy.

J Contemp Brachytherapy 2017 Jun 5;9(3):230-235. Epub 2017 Jun 5.

Department of Radiation Oncology, Baskent University Faculty of Medicine, Adana, Turkey.

Purpose: To investigate the impact of different cylinder positions on dosimetry of critical structures in patients with endometrial carcinoma undergoing three-dimensional image-based vaginal cuff brachytherapy (VCB).

Material And Methods: We delivered VCB at a dose of 4 Gy to a depth of 5 mm in the vaginal cuff of 15 patients using three different cylinder positions (neutral [N], parallel [P], and angled [A]) according to the longitudinal axis of the patient. We analyzed the dose-volume distribution and volumetric variability of the rectum and bladder. We converted the total doses to equivalent doses in 2 Gy (EQD) using a linear-quadratic model (a/b = 3 Gy).

Results: The mean rectum volume for the N, P, and A positions was 68.2 ± 22.7 cc, 79.3 ± 33.7 cc, and 74.2 ± 29.6 cc, respectively. The mean rectum volume for the P position was significantly larger than that for the N position ( = 0.03). Relative to the N position, the A position resulted in a lower total EQD in the highest irradiated 2 cc (D; = 0.001), 1 cc (D; = 0.004), and 0.1 cc (D; = 0.047) of the rectum. Similarly, the P position resulted in a lower EQD in the D ( = 0.018) and D ( = 0.024) of the rectum relative to the N position. In the bladder, the P position resulted in a higher EQD in the D relative to the N position ( = 0.02). There was no dosimetric difference between the P and A positions in either the rectum or the bladder.

Conclusions: Vaginal cuff brachytherapy in the P and A positions is significantly superior to that in the N position in terms of rectum dosimetry. The bladder dose in the N position is considerably lower than that in the other positions.
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http://dx.doi.org/10.5114/jcb.2017.68171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5509981PMC
June 2017

The impact of androgen deprivation therapy on setup errors during external beam radiation therapy for prostate cancer.

Strahlenther Onkol 2017 Jun 13;193(6):472-482. Epub 2017 Apr 13.

Faculty of Medicine, Adana Dr. Turgut Noyan Research and Treatment Centre, Department of Radiation Oncology, Baskent University, 01120, Adana, Turkey.

Purpose: To determine whether setup errors during external beam radiation therapy (RT) for prostate cancer are influenced by the combination of androgen deprivation treatment (ADT) and RT.

Materials And Methods: Data from 175 patients treated for prostate cancer were retrospectively analyzed. Treatment was as follows: concurrent ADT plus RT, 33 patients (19%); neoadjuvant and concurrent ADT plus RT, 91 patients (52%); RT only, 51 patients (29%). Required couch shifts without rotations were recorded for each megavoltage (MV) cone beam computed tomography (CBCT) scan, and corresponding alignment shifts were recorded as left-right (x), superior-inferior (y), and anterior-posterior (z). The nonparametric Mann-Whitney test was used to compare shifts by group. Pearson's correlation coefficient was used to measure the correlation of couch shifts between groups. Mean prostate shifts and standard deviations (SD) were calculated and pooled to obtain mean or group systematic error (M), SD of systematic error (Σ), and SD of random error (σ).

Results: No significant differences were observed in prostate shifts in any direction between the groups. Shifts on CBCT were all less than setup margins. A significant positive correlation was observed between prostate volume and the z‑direction prostate shift (r = 0.19, p = 0.04), regardless of ADT group, but not between volume and x‑ or y‑direction shifts (r = 0.04, p = 0.7; r = 0.03, p = 0.7). Random and systematic errors for all patient cohorts and ADT groups were similar.

Conclusion: Hormone therapy given concurrently with RT was not found to significantly impact setup errors. Prostate volume was significantly correlated with shifts in the anterior-posterior direction only.
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http://dx.doi.org/10.1007/s00066-017-1131-zDOI Listing
June 2017

The role of delineation education programs for improving interobserver variability in target volume delineation in gastric cancer.

Br J Radiol 2017 May 24;90(1073):20160826. Epub 2017 Mar 24.

3 Department of Radiation Oncology, Faculty of Medicine, Ege University, Izmir, Turkey.

Objective: To assess whether delineation courses for radiation oncologists improve interobserver variability in target volume delineation for post-operative gastric cancer radiotherapy planning.

Methods: 29 radiation oncologists delineated target volumes in a gastric cancer patient. An experienced radiation oncologist lectured about delineation based on contouring atlas and delineation recommendations. After the course, the radiation oncologists, blinded to the previous delineation, provided delineation for the same patient.

Results: The difference between delineated volumes and reference volumes for pre- and post-course clinical target volume (CTV) were 19.8% (-42.4 to 70.6%) and 12.3% (-12.0 to 27.3%) (p = 0.26), respectively. The planning target volume (PTV) differences pre- and post-course according to the reference volume were 20.5% (-40.7 to 93.7%) and 13.1% (-10.6 to 29.5%) (p = 0.30), respectively. The concordance volumes between the pre- and post-course CTVs and PTVs were 467.1 ± 89.2 vs 597.7 ± 54.6 cm (p < 0.001) and 738.6 ± 135.1 vs 893.2 ± 144.6 cm (p < 0.001), respectively. Minimum and maximum observer variations were seen at the cranial part and splenic hilus and at the caudal part of the CTV. The kappa indices compared with the reference contouring at pre- and post-course delineations were 0.68 and 0.82, respectively.

Conclusion: The delineation course improved interobserver variability for gastric cancer. However, impact of target volume changes on toxicity and local control should be evaluated for further studies. Advances in knowledge: This study demonstrated that a delineation course based on current recommendations helped physicians delineate smaller and more homogeneous target volumes. Better target volume delineation allows proper target volume irradiation and preventing unnecessary normal tissue irradiation.
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http://dx.doi.org/10.1259/bjr.20160826DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5605107PMC
May 2017

Is it essential to use fiducial markers during cone-beam CT-based radiotherapy for prostate cancer patients?

Jpn J Radiol 2017 Jan 11;35(1):3-9. Epub 2016 Oct 11.

Department of Radiation Oncology, Baskent University Faculty of Medicine, 01120, Adana, Turkey.

Purpose: To compare soft-tissue cone-beam computed tomography (CBCT-P) and fiducial marker (CBCT-FM)-based image guided radiotherapy in prostate cancer patients.

Materials And Methods: Sixteen prostate cancer patients were treated with volumetric modulated arc therapy. Manual alignment using CBCT-P and CBCT-FM was performed for each patient. Couch shifts were calculated and compared between methods in the left-right (x), superior-inferior (y), and anterior-posterior (z) directions.

Results: CBCT-P and CBCT-FM alignments were compared using 252 scans from the 16 patients. Mean displacement from zero was 2.4 ± 1.3, 1.7 ± 1.2, and 1.8 ± 1.1 mm for CBCT-P and 2.3 ± 1.3, 1.7 ± 1.1 and 1.8 ± 1.1 mm for CBCT-FM in the x, y and z directions, respectively. There was no difference in median displacement between CBCT-P and CBCT-FM; however, there was a significant positive correlation between CBCT-P- and CBCT-FM-based displacements in the x (r = 0.881; p < 0.001), y (r = 0.789; p < 0.001) and z (r = 0.856; p < 0.001) directions by linear regression analysis. Systematic deviations within each group were <1 mm; however, random and systematic errors were similar in the x and y directions but larger in the z direction.

Conclusion: Our study demonstrated that CBCT-FM was not superior to CBCT-P for image-guided radiotherapy in prostate cancer patients.
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http://dx.doi.org/10.1007/s11604-016-0590-yDOI Listing
January 2017

Dosimetric analysis of testicular doses in prostate intensity-modulated and volumetric-modulated arc radiation therapy at different energy levels.

Med Dosim 2016 Winter;41(4):310-314. Epub 2016 Sep 10.

Department of Radiation Oncology, Baskent University Faculty of Medicine, Adana, Turkey.

The aim of this study is to evaluate the incidental testicular doses during prostate radiation therapy with intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) at different energies. Dosimetric data of 15 patients with intermediate-risk prostate cancer who were treated with radiotherapy were analyzed. The prescribed dose was 78Gy in 39 fractions. Dosimetric analysis compared testicular doses generated by 7-field intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy with a single arc at 6, 10, and 15MV energy levels. Testicular doses calculated from the treatment planning system and doses measured from the detectors were analyzed. Mean testicular doses from the intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy per fraction calculated in the treatment planning system were 16.3 ± 10.3cGy vs 21.5 ± 11.2cGy (p = 0.03) at 6MV, 13.4 ± 10.4cGy vs 17.8 ± 10.7cGy (p = 0.04) at 10MV, and 10.6 ± 8.5cGy vs 14.5 ± 8.6cGy (p = 0.03) at 15MV, respectively. Mean scattered testicular doses in the phantom measurements were 99.5 ± 17.2cGy, 118.7 ± 16.4cGy, and 193.9 ± 14.5cGy at 6, 10, and 15MV, respectively, in the intensity-modulated radiotherapy plans. In the volumetric-modulated arc radiotherapy plans, corresponding testicular doses per course were 90.4 ± 16.3cGy, 103.6 ± 16.4cGy, and 139.3 ± 14.6cGy at 6, 10, and 15MV, respectively. In conclusions, this study was the first to measure the incidental testicular doses by intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy plans at different energy levels during prostate-only irradiation. Higher photon energy and volumetric-modulated arc radiotherapy plans resulted in higher incidental testicular doses compared with lower photon energy and intensity-modulated radiotherapy plans.
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http://dx.doi.org/10.1016/j.meddos.2016.07.004DOI Listing
August 2017

Uterine perforation during 3-dimensional image-guided brachytherapy in patients with cervical cancer: Baskent University experience.

Int J Gynecol Cancer 2014 Feb;24(2):346-51

Departments of *Radiation Oncology, Baskent University Faculty of Medicine, Adana; and †Radiology, Baskent University Faculty of Medicine, Ankara, Turkey.

Objectives: This study aimed to determine the incidence and characteristics of uterine perforation at our department using 3-dimensional computed tomography (CT)-based brachytherapy (BRT). The characteristics of the patients presenting with perforation and impact of the perforation on the treatment course were also analyzed.

Materials And Methods: The clinical and radiologic data of 200 patients with biopsy-proven cervical cancer treated using CT-based BRT were retrospectively evaluated. All patients had undergone tandem-based intracavitary BRT, and 67 patients had undergone magnetic resonance imaging (MRI) before BRT.

Results: Of the 200 patients, 17 (8.5%) had uterine perforation. Of the 626 applications with CT images, 30 (4.8%) resulted in uterine perforation. The median age of patients with perforation was higher (68 years; range, 44-89 years) than that of the patients without perforation (59 years; range, 21-87 years), and the mean (SD) tumor size at diagnosis was larger in patients with perforation (7.0 [1.5] cm) than in patients without perforation (5.0 [1.5] cm). The most frequent perforation site was the posterior uterine wall (8 patients), followed by the fundus (5 patients) and anterior wall (4 patients). Of the 7 patients with a retroverted uterus, 4 had uterine perforation during BRT. In 67 patients with MRI delivered before BRT, only 3 (4%) had uterine perforation, and 2 of the 3 patients with uterine perforation had a retroverted uterus. However, of the 133 patients with no MRI evaluation before BRT, 14 (11%) had uterine perforation. No life-threatening complications or signs of intraperitoneal tumor cell seeding were observed.

Conclusions: Older age, larger tumors, a retroverted uterus, and a stenotic cervical os were all predisposing factors for uterine perforation during BRT. Preoperative MRI is a feasible and safe method to decrease the risks of uterine perforation and could be used preoperatively in centers where intraoperative ultrasonography is not used in routine practice.
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http://dx.doi.org/10.1097/IGC.0000000000000048DOI Listing
February 2014

Dosimetric comparison of the field-in-field technique and tangential wedged beams for breast irradiation.

Jpn J Radiol 2012 Apr 21;30(3):218-26. Epub 2011 Dec 21.

Department of Radiation Oncology, Adana Research and Treatment Centre, Baskent University Faculty of Medicine, 01120 Adana, Turkey.

Purpose: To analyze tangential wedged beam and field-in-field (FIF) technique doses using dose-volume histograms and conformality indices for target volume and healthy tissues within the irradiated volume.

Materials And Methods: Thirty patients treated with breast-conserving surgery and postoperative whole breast radiotherapy were enrolled. Three plans were generated: a standard tangential plan with either one outer field wedge or bilateral wedges, and an FIF plan. Three indices were used: the dose homogeneity index (DHI), PTV dose improvement index (PDI(index)) and geometric conformity index (g). Also ipsilateral lung, heart and contralateral breast doses were compared for each plan.

Results: Dose homogeneity index was significantly lower for the FIF (0.117 ± 0.021) than for the single wedge (0.131 ± 0.025, p = 0.02) and double wedged plan (0.128 ± 0.025, p = 0.04), respectively. The g was significantly less in the FIF (0.70 ± 0.14) compared to the wedge plans (0.80 ± 0.17, p = 0.02 and 0.83 ± 0.16, p = 0.003). Contralateral breast doses were significantly lower in the FIF plan. The FIF plan significantly lowered MU compared to both the single wedge and bilateral wedge plans.

Conclusion: The dose distribution within the target was more homogenous, and the doses for healthy tissue were less in the FIF plan compared to the tangential wedge plans.
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http://dx.doi.org/10.1007/s11604-011-0034-7DOI Listing
April 2012

Comparison of CT and integrated PET-CT based radiation therapy planning in patients with malignant pleural mesothelioma.

Radiat Oncol 2009 Sep 16;4:35. Epub 2009 Sep 16.

Department of Radiation Oncology, Baskent University Medical Faculty, Adana Medical and Research Center, Kisla Campus, Adana, Turkey.

Background: When combined with adequate tumoricidal doses, accurate target volume delineation remains to be the one of the most important predictive factors for radiotherapy (RT) success in locally advanced or medically inoperable malignant pleural mesothelioma (MPM) patients. Recently, 18-fluorodeoxyglucose positron emission tomography (PET) has demonstrated significant improvements in diagnosis and accurate staging of MPM. However, role of additional PET data has not been studied in RT planning (RTP) of patients with inoperable MPM or in those who refuse surgery. Therefore, we planned to compare CT with co-registered PET-CT as the basis for delineating target volumes in these patients group.

Methods: Retrospectively, the CT and co-registered PET-CT data of 13 patients with histologically proven MPM were utilized to delineate target volumes separately. For each patient, target volumes (gross tumor volume [GTV], clinical target volume [CTV], and planning target volume [PTV]) were defined using the CT and PET-CT fusion data sets. The PTV was measured in two ways: PTV1 was CTV plus a 1-cm margin, and PTV2 was GTV plus a 1-cm margin. We analyzed differences in target volumes.

Results: In 12 of 13 patients, compared to CT-based delineation, PET-CT-based delineation resulted in a statistically significant decrease in the mean GTV, CTV, PTV1, and PTV2. In these 12 patients, mean GTV decreased by 47.1% +/- 28.4%, mean CTV decreased by 38.7% +/- 24.7%, mean PTV1 decreased by 31.1% +/- 23.1%, and mean PTV2 decreased by 40.0% +/- 24.0%. In 4 of 13 patients, hilar lymph nodes were identified by PET-CT that was not identified by CT alone, changing the nodal status of tumor staging in those patients.

Conclusion: This study demonstrated the usefulness of PET-CT-based target volume delineation in patients with MPM. Co-registration of PET and CT information reduces the likelihood of geographic misses, and additionally, significant reductions observed in target volumes may potentially allow escalation of RT dose beyond conventional limits potential clinical benefits in tumor control rates, which needs to be tested in future studies.
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http://dx.doi.org/10.1186/1748-717X-4-35DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2754492PMC
September 2009