Publications by authors named "Avinav Bharati"

6 Publications

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Dosimetric evaluation of different planning techniques based on flattening filter-free beams for central and peripheral lung stereotactic body radiotherapy.

Biomed Phys Eng Express 2021 Oct 12. Epub 2021 Oct 12.

Department of Radiotherapy, Government Medical College Patiala, Sangrur Road, Patiala, Punjab, 147001, INDIA.

This study aimed to dosimetrically compare and evaluate the flattening filter-free (FFF) photon beam-based three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) for lungstereotactic body radiotherapy (SBRT). RANDO phantom computed tomography (CT) images were used for treatment planning. Gross tumor volumes (GTVs) were delineated in the central and peripheral lung locations. Planning target volumes (PTVs) was determined by adding a 5 mm margin to the GTV. 3DCRT, IMRT, and VMAT plans were generated using a 6-MV FFF photon beam. Dose calculations for all plans were performed using the anisotropic analyticalalgorithm (AAA) and Acuros XB algorithms. The accuracy of the algorithms was validated using the dose measured in a CIRS thorax phantom. The conformity index (CI), high dose volume (HDV), low dose location (D), and homogeneity index (HI) improved with FFF-VMAT compared to FFF-IMRT and FFF-3DCRT, while low dose volume (R) and gradient index (GI) showed improvement with FFF-3DCRT. Compared with FFF-3DCRT, a drastic decrease in the mean treatment time (TT) value was observed with FFF-VMAT for different lung sites between 57.09 % and 60.39 %, while with FFF-IMRT it increased between 10.78 % and 17.49 %. The dose calculation with Acuros XB was found to be superior to that of AAA. Based on the comparison of dosimetric indices in this study, FFF-VMAT provides a superior treatment plan to FFF-IMRT and FFF-3DCRT in the treatment of peripheral and central lung PTVs. This study suggests that Acuros XB is a more accurate algorithm than AAA in the lung region.
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http://dx.doi.org/10.1088/2057-1976/ac2f0dDOI Listing
October 2021

Radiotherapy plan evaluation indices: A dosimetrical suitability check.

J Cancer Res Ther 2021 Apr-Jun;17(2):455-462

Department of Radiation Oncology, RMLIMS, Lucknow, Uttar Pradesh, India.

Purpose: To classify the available plan evaluation indices and compare the dosimetric suitability of these indices.

Materials And Methods: Available published plan evaluation indices were categorized. Conformity index (CI) into two groups, one group contains those CI formulas which do not consider critical structure and other group contains those CI formulas which consider planning target volume (PTV) coverage, normal tissue and critical structure sparing simultaneously. Various homogeneity index (HI) formulas extracted from literature. Structure data sets of 25 patients were taken under consideration comprising of various sites. For each patient, two plans were created using Volumetric Arc Therapy technique. First type of plan (Plan-A) were generated considering all tissue objectives for targets and Organ at Risks (OARs) whereas second type of plan (Plan-B) were generated considering only targets tissue objectives and excluding OARs tissue objectives during plan optimization and dose calculation. Planning evaluation parameters were compared between Plan-A and Plan-B.

Results: CI calculated by various formulas in two different scenarios presented <2% variation. Any commonly used CI formula failed to differentiate the two different planning situations. On comparison between HI of two different scenario, it is observed that there are four formulas of HI which showed negligible variation but two formulae: S-index and HI (D) showed marginal variation. It is also observed that when OARs are removed from optimization dose homogeneity improved which is specifically pointed by sigma index formula.

Conclusion: CI, which has assimilated the presence of OAR in their formulation, shows more reliability in plan evaluation. Sigma index was found to be more efficient formula while evaluating homogeneity of a treatment plan.
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http://dx.doi.org/10.4103/jcrt.JCRT_417_19DOI Listing
June 2021

Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors.

Biomed Phys Eng Express 2021 May 11;7(4). Epub 2021 May 11.

Department of Physics, Dr Bhimrao Ambedkar University, Agra, Uttar Pradesh, 282004, India.

The present study aimed to dosimetrically evaluate the small-fields of a 6 MV flattening filter-free (FFF) photon beam using different detectors.The 6 MV FFF photon beam was used for measurement of output factor, depth dose, and beam profile of small-fields of sizes 0.6 cm × 0.6 cm to 6.0 cm × 6.0 cm. The five detectors used were SNC125c, PinPoint, EDGE, EBT3, and TLD-100. All measurements were performed as per the International Atomic Energy Agency TRS 483 protocol. Output factors measured using different detectors as direct reading ratios showed significant variation for the smallest fields, whereas after correcting them according to TRS 483, all sets of output factors were nearly compatible with each other when measurement uncertainty was also considered. The beam profile measured using SNC125c showed the largest penumbra for all field sizes, whereas the smallest was recorded with EDGE. Compared with that of EBT3, the surface dose was found to be much higher for all the other detectors. PinPoint, EBT3, TLD-100, and EDGE were found to be the detector of choice for small-field output factor measurements; however, PinPoint needs special attention when used for the smallest field size (0.6 cm × 0.6 cm). EDGE and EBT3 are optimal for measuring beam profiles. EBT3, PinPoint, and EDGE can be selected for depth dose measurements, and EBT3 is suitable for surface dose estimation.
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http://dx.doi.org/10.1088/2057-1976/abfd80DOI Listing
May 2021

Patterns of failure and clinical outcomes of post-operative buccal mucosa cancers treated with adjuvant ipsilateral radiotherapy.

Radiat Oncol J 2020 Sep 9;38(3):189-197. Epub 2020 Sep 9.

Department of Radiation Oncology, Dr Ram Manohar Lohia Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.

Purpose: Adjuvant radiotherapy (RT) in buccal mucosa cancers is guided by histopathological factors. The decision to treat ipsilateral or bilateral draining lymph node is on physician discretion and guidelines do not have a defined indication regarding this. We aimed to analyze the failure patterns and survival in buccal mucosa cancers treated with adjuvant ipsilateral RT.

Materials And Methods: One hundred sixteen cases of post-operative buccal mucosa cancers-pT3 or more, node positive, close margins (1-5 mm), lymphovascular invasion positive, perineural invasion positive, depth of invasion >4 mm-treated with RT to primary and ipsilateral nodes from May 2013 to May 2019 were retrospectively analyzed. Patients were treated to a dose of 60-66 Gy (44 Gy in the first phase and a coned down boost of 16-22 Gy in the second phase) with three-dimensional conformal radiotherapy on a linear accelerator. Primary end point was to assess control rates and secondary end point was to evaluate the overall survival (OS) and disease-free survival (DFS) outcomes.

Results: Median age was 46 years with male; female ratio of 110:6. The edition of the American Joint Committee on Cancer stage distributions were I (3.4%), II (34.4%), III (24.1%), and IV (37.9%). At a median follow-up of 22 months, crude rates of local failure, regional failure, and contralateral neck failure were 9.4%, 10.3%, and 3.4%, respectively. The 2-year contralateral neck control rate was 94.9%. Pathological positive node portended poorer OS (86.6% vs. 68.6%; p = 0.015) and DFS (86.5% vs. 74.9%; p = 0.01).

Conclusion: Incidence of contralateral recurrence with ipsilateral irradiation in buccal mucosa cancers is low with descent survival outcomes, particularly in node negative cases.
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http://dx.doi.org/10.3857/roj.2020.00458DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7533397PMC
September 2020

Development of a Method to Determine Electron Density and Effective Atomic Number of High Atomic Number Solid Materials Using Dual-Energy Computed Tomography.

J Med Phys 2019 Jan-Mar;44(1):49-56

Department of Medical Physics Unit, IRCH, AIIMS, New Delhi, India.

Aim: This study aims to develop a method using dual-energy computed tomography (DECT) to determine the effective atomic number and electron density of substances.

Materials And Methods: Ten chemical substances of pure analytical grade were obtained from various manufacturers. These chemicals were pelletized using a hydraulic press. These pellets were scanned using DECT. A relation was obtained for the pellet's atomic number and electron density with their CT number or Hounsfield unit (HU) values. Calibration coefficients were determined. Five new chemical pellets were scanned, and their effective atomic number and electron densities were determined using the calibration coefficients to test the efficacy of the calibration method.

Results: The results obtained for effective atomic number and electron density from the HU number of DECT images were within ±5% and ±3%, respectively, of their actual values.

Conclusions: DECT can be used as an effective tool for determining the effective atomic number and electron density of high atomic number substance.
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http://dx.doi.org/10.4103/jmp.JMP_125_18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6438052PMC
April 2019

Non-invasive characterization of coronary artery atherosclerotic plaque using dual energy CT: Explanation in ex-vivo samples.

Phys Med 2018 Jan 19;45:52-58. Epub 2017 Dec 19.

Medical Physics Unit, Dr. B.R.A. Institute Rotary Cancer Hospital (IRCH), All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India. Electronic address:

Purpose: In this study non-calcified plaque composition is evaluated by Dual Energy CT (DECT). Energy Dispersive X-ray Spectroscopy (EDS) has been used to study the Plaque composition. An attempt has been made to explain the DECT results with EDS analysis.

Methods: Thirty-two ex-vivo human cadaver coronary artery samples were scanned by DECT and data was evaluated to calculate their effective atomic number and electron density (Z & ρ) by inversion method. Result of DECT was compared with pathology to assess their differentiating capability. The EDS study was used to explain DECT outcome.

Results: DECT study was able to differentiate vulnerable plaque from stable with 87% accuracy (area under the curve (AUC):0.85 [95% confidence interval {CI}:0.73-0.98}] and Kappa Coefficient (KC):0.75 with respect to pathology. EDS revealed significant compositional difference in vulnerable and stable plaque at p < .05. The weight percentage of higher atomic number elements like F, Na, Mg, S, Si, P, Cl, K and Ca was found to be slightly more in vulnerable plaques as compared to a stable plaque. EDS also revealed a significantly increased weight percentage of nitrogen in stable plaques.

Conclusions: The EDS results were able to explain the outcomes of DECT study. This study conclusively explains the physics of DECT as a tool to assess the nature of non-calcified plaques as vulnerable and stable. The method proposed in this study allows for differentiation between vulnerable and stable plaque using DECT.
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http://dx.doi.org/10.1016/j.ejmp.2017.12.006DOI Listing
January 2018
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