Om Prakash Gurjar

Bio: Om Prakash Gurjar is an academic researcher from Mahatma Gandhi Memorial Medical College. The author has contributed to research in topics: Imaging phantom & Medicine. The author has an hindex of 6, co-authored 24 publications receiving 142 citations. Previous affiliations of Om Prakash Gurjar include Mewar University.

Comparison of dosimetric parameters and acute toxicity of intensity-modulated and three-dimensional radiotherapy in patients with cervix carcinoma: A randomized prospective study

Abstract: Purpose The use of intensity-modulated radiotherapy (IMRT) to treat cervix carcinoma has increased, however prospective randomized trials are still lacking. Aim To compare the dosimetric parameters and associated acute toxicity in patients with cervix carcinoma treated with three-dimensional (3D) conformal radiotherapy and IMRT. Patients and methods Forty patients were randomized in two arms each consisting of 20 patients. Patients in both arms received concurrent chemoradiation (cisplatin 40 mg/m 2 weekly; 50 Gy/25 fractions). Patients were treated with 3D conformal radiotherapy in one arm and with IMRT in another arm. After external beam radiotherapy, all patients received brachytherapy (21 Gy/3 fractions at weekly interval). For dosimetric comparison, both kinds of the plans were done for all the patients. All patients were assessed throughout and until 90 days after completion of treatment for acute gastrointestinal, genitourinary and hematologic toxicities. Results Both plans achieved adequate planning target volume coverage, while mean conformity index was found significantly better in IMRT plans ( P -value = 0.001). D 35 (dose to 35% volume) and D 50 for bladder was reduced by 14.62 and 32.57% and for rectum by 23.82 and 43.68% in IMRT. For IMRT, V 45 (volume receiving 45 Gy) of bowel were found significantly lesser ( P -value = 0.0001), non-tumour integral dose was found significantly higher ( P -value = 0.0240) and V 20 of bone marrow was found significantly reduced ( P -value = 0.019) in comparison to that in 3D conformal radiotherapy. Significant reduction of grade 2 or more (20 vs 45%; P -value = 0.058) and grade ≥ 3 (5 vs 15%, P -value = 0.004) acute genitourinary toxicity and grade 2 or more (20 vs 45%, P -value = 0.003) and grade 3 or more (5 vs. 20%, P -value = 0.004) acute gastrointestinal toxicity while no significant difference for grade 2 and 3 or more haematological toxicity was noted in patients treated with IMRT compared to 3D conformal radiotherapy. Conclusion IMRT provide a good alternative for treatment of cervix carcinoma with lower acute gastrointestinal and acute genitourinary toxicity with similar target coverage compared to 3D conformal radiotherapy.

Impact of repeat computerized tomography replans in the radiation therapy of head and neck cancers.

Abstract: Anatomical changes can occur during course of head-and-neck (H and N) radiotherapy like tumor shrinkage, decreased edema and/or weight loss. This can lead to discrepancies in planned and delivered dose increasing the dose to organs at risk. A study was conducted to determine the volumetric and dosimetric changes with the help of repeat computed tomography (CT) and replanning for selected H and N cancer patients treated with IMRT plans to see for these effects. In 15 patients with primary H and N cancer, a repeat CT scan after 3(rd) week of radiotherapy was done when it was clinically indicated and then two plans were generated on repeat CT scan, actual plan (AP) planned on repeat CT scan, and hybrid plan (HP), which was generated by applying the first intensity-modulated radiation therapy (IMRT) plan (including monitoring units) to the images of second CT scan. Both plans (AP and HP) on repeat CT scan were compared for volumetric and dosimetric parameter. The mean variation in volumes between CT and repeat CT were 44.32 cc, 82.2 cc, and 149.83 cc for gross tumor volume (GTV), clinical target volumes (CTV), and planning target volume (PTV), respectively. Mean conformity index and homogeneity index was 0.68 and 1.07, respectively for AP and 0.5 and 1.16, respectively for HP. Mean D95 and D99 of PTV was 97.92% (standard deviation, SD 2.32) and 93.4% (SD 3.75), respectively for AP and 92.8% (SD 3.83) and 82.8% (SD 8.0), respectively for HP. Increase in mean doses to right parotid, left parotid, spine, and brainstem were 5.56 Gy (Dmean), 3.28 Gy (Dmean), 1.25 Gy (Dmax), and 3.88 Gy (Dmax), respectively in HP compared to AP. Repeat CT and replanning reduces the chance of discrepancies in delivered dose due to volume changes and also improves coverage to target volume and further reduces dose to organ at risk.

Radiation dose verification using real tissue phantom in modern radiotherapy techniques.

Abstract: In vitro dosimetric verification prior to patient treatment has a key role in accurate and precision radiotherapy treatment delivery. Most of commercially available dosimetric phantoms have almost homogeneous density throughout their volume, while real interior of patient body has variable and varying densities inside. In this study an attempt has been made to verify the physical dosimetry in actual human body scenario by using goat head as "head phantom" and goat meat as "tissue phantom". The mean percentage variation between planned and measured doses was found to be 2.48 (standard deviation (SD): 0.74), 2.36 (SD: 0.77), 3.62 (SD: 1.05), and 3.31 (SD: 0.78) for three-dimensional conformal radiotherapy (3DCRT) (head phantom), intensity modulated radiotherapy (IMRT; head phantom), 3DCRT (tissue phantom), and IMRT (tissue phantom), respectively. Although percentage variations in case of head phantom were within tolerance limit (< ± 3%), but still it is higher than the results obtained by using commercially available phantoms. And the percentage variations in most of cases of tissue phantom were out of tolerance limit. On the basis of these preliminary results it is logical and rational to develop radiation dosimetry methods based on real human body and also to develop an artificial phantom which should truly represent the interior of human body.

Demineralization of tooth enamel following radiation therapy; An in vitro microstructure and microhardness analysis.

Abstract: Objective: The objective of this study is to evaluate the effects of radiotherapy doses on mineral density and percentage mineral volume of human permanent tooth enamel. Materials and Methods: Synchrotron radiation Xray microcomputed tomography (SRμCT) and microhardness testing were carried out on 8 and 20 tooth samples, respectively. Enamel mineral density was derived from SRμCT technique using ImageJ software. Microhardness samples were subjected to Vickers indentations followed by calculation of microhardness and percentage mineral volume values using respective mathematical measures. Data were analyzed using paired t-test at a significance level of 5%. Qualitative analysis of the enamel microstructure was done with two-dimensional projection images and scanned electron micrographs using μCT and field emission scanning electron microscopy, respectively. Results: Vickers microhardness and SRμCT techniques showed a decrease in microhardness and an increase in mineral density, respectively, in postirradiated samples. These changes were related to mineral density variation and alteration of hydroxyapatite crystal lattice in enamel surface. Enamel microstructure showed key features such as microporosities and loss of smooth homogeneous surface. These indicate tribological loss and delamination of enamel which might lead to radiation caries. Conclusions: Tooth surface loss might be a major contributing factor for radiation caries in head-and-neck cancer patients prescribed to radiotherapy. Such direct effects of radiotherapy cause enamel abrasion, delamination, and damage to the dentinoenamel junction. Suitable measures should, therefore, be worked out to protect nontarget oral tissues such as teeth while delivering effective dosages to target regions.

A study on the necessity of kV-CBCT imaging compared to kV-orthogonal portal imaging based on setup errors: considering other socioeconomical factors.

Abstract: Purpose: Evaluation of setup accuracy in kV-orthogonal portal imaging (OPI)-based and kV-CBCT-based radiotherapy treatment and to find out the necessity of cone-beam computed tomography (CBCT) compared to OPI. Materials and Methods: A retrospective study was carried out on 30 patients, who received radiotherapy to the Brain, Head and Neck, and Pelvis. In the OPI technique, anterior-posterior and right-lateral portal images were taken by the On Board Imaging (OBI) system and were superimposed on the reference images. Similarly, in the kV-CBCT technique, CBCT was performed by the OBI system and CBCT images were superimposed on the reference CT images. A total of 150 comparison sets of kV-OPI and kV-CBCT images were analyzed and evaluated. Shifts in the Lateral, Longitudinal, and Vertical directions were noted in both techniques. The iso displacement vector (IDV) was calculated for all imaging. Results: The mean IDV (in cm) are found to be 0.3395 (SD: 0.1477) and 0.3088 (SD: 0.1593) in cases of the brain, 0.4266 (SD: 0.1511) and 0.3666 (SD: 0.1533) in cases of the head and neck, and 1.0339 (SD: 0.5893) and 0.9498 (SD: 0.6047) in cases of the pelvis for the CBCT and OPI techniques, respectively. The P values were 0.3201, 0.0515, and 0.4829 for the brain, head and neck, and pelvic cases, respectively. Conclusions: There is statistically no significant difference between both the imaging techniques. As the dose delivered by the CBCT technique is higher than that by the OPI technique, from the socioeconomical and radiation safety point of view, the OPI technique is possibly better than the CBCT technique. Hence, it can be concluded that CBCT is not a mandatory technique compared to the OPI technique in routine brain, head and neck, and pelvic cases, except in those cases where better information about interfraction movements of soft tissue is necessarily required for positioning of the target, as is the case in prostate carcinoma.

Prediction of outcome using pretreatment 18 F-FDG PET/CT and MRI radiomics in locally advanced cervical cancer treated with chemoradiotherapy

Abstract: The aim of this study is to determine if radiomics features from 18fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) images could contribute to prognoses in cervical cancer. One hundred and two patients (69 for training and 33 for testing) with locally advanced cervical cancer (LACC) receiving chemoradiotherapy (CRT) from 08/2010 to 12/2016 were enrolled in this study. 18F-FDG PET/CT and MRI examination [T1, T2, T1C, diffusion-weighted imaging (DWI)] were performed for each patient before CRT. Primary tumor volumes were delineated with the fuzzy locally adaptive Bayesian algorithm in the PET images and with 3D Slicer™ in the MRI images. Radiomics features (intensity, shape, and texture) were extracted and their prognostic value was compared with clinical parameters for recurrence-free and locoregional control. In the training cohort, median follow-up was 3.0 years (range, 0.43–6.56 years) and relapse occurred in 36% of patients. In univariate analysis, FIGO stage (I–II vs. III–IV) and metabolic response (complete vs. non-complete) were probably associated with outcome without reaching statistical significance, contrary to several radiomics features from both PET and MRI sequences. Multivariate analysis in training test identified Grey Level Non UniformityGLRLM in PET and EntropyGLCM in ADC maps from DWI MRI as independent prognostic factors. These had significantly higher prognostic power than clinical parameters, as evaluated in the testing cohort with accuracy of 94% for predicting recurrence and 100% for predicting lack of loco-regional control (versus ~50–60% for clinical parameters). In LACC treated with CRT, radiomics features such as EntropyGLCM and GLNUGLRLM from functional imaging DWI-MRI and PET, respectively, are independent predictors of recurrence and loco-regional control with significantly higher prognostic power than usual clinical parameters. Further research is warranted for their validation, which may justify more aggressive treatment in patients identified with high probability of recurrence.

Radiation Therapy for Cervical Cancer: Executive Summary of an ASTRO Clinical Practice Guideline

Abstract: Purpose This guideline reviews the evidence and provides recommendations for the indications and appropriate techniques of radiation therapy (RT) in the treatment of nonmetastatic cervical cancer. Methods The American Society for Radiation Oncology convened a task force to address 5 key questions focused on the use of RT in definitive and postoperative management of cervical cancer. These questions included the indications for postoperative and definitive RT, the use of chemotherapy in sequence or concurrent with RT, the use of intensity modulated radiation therapy (IMRT), and the indications and techniques of brachytherapy. Recommendations were based on a systematic literature review and created using a predefined consensus-building methodology and system for grading evidence quality and recommendation strength. Results The guideline recommends postoperative RT for those with intermediate risk factors, and chemoradiation for those with high-risk factors. In the definitive setting, chemoradiation is recommended for stages IB3-IVA, and RT or chemoradiation is conditionally recommended for stages IA1-IB2 if medically inoperable. IMRT is recommended for postoperative RT and conditionally recommended for definitive RT, for the purposes of reducing acute and late toxicity. Brachytherapy is strongly recommended for all women receiving definitive RT, and several recommendations are made for target dose and fractionation, the use of intraoperative imaging, volume-based planning, and recommendations for doses limits for organs at risk. Conclusions There is strong evidence supporting the use of RT with or without chemotherapy in both definitive and postoperative settings. Brachytherapy is an essential part of definitive management and volumetric planning is recommended. IMRT may be used for the reduction of acute and late toxicity. The use of radiation remains an essential component for women with cervical cancer to achieve cure.

External validation of a combined PET and MRI radiomics model for prediction of recurrence in cervical cancer patients treated with chemoradiotherapy

Abstract: The aim of this study was to validate previously developed radiomics models relying on just two radiomics features from 18F-fluorodeoxyglucose positron emission tomography (PET) and magnetic resonance imaging (MRI) images for prediction of disease free survival (DFS) and locoregional control (LRC) in locally advanced cervical cancer (LACC). Patients with LACC receiving chemoradiotherapy were enrolled in two French and one Canadian center. Pre-treatment imaging was performed for each patient. Multicentric harmonization of the two radiomics features was performed with the ComBat method. The models for DFS (using the feature from apparent diffusion coefficient (ADC) MRI) and LRC (adding one PET feature to the DFS model) were tuned using one of the French cohorts (n = 112) and applied to the other French (n = 50) and the Canadian (n = 28) external validation cohorts. The DFS model reached an accuracy of 90% (95% CI [79–98%]) (sensitivity 92–93%, specificity 87–89%) in both the French and the Canadian cohorts. The LRC model reached an accuracy of 98% (95% CI [90–99%]) (sensitivity 86%, specificity 100%) in the French cohort and 96% (95% CI [80–99%]) (sensitivity 83%, specificity 100%) in the Canadian cohort. Accuracy was significantly lower without ComBat harmonization (82–85% and 71–86% for DFS and LRC, respectively). The best prediction using standard clinical variables was 56–60% only. The previously developed PET/MRI radiomics predictive models were successfully validated in two independent external cohorts. A proposed flowchart for improved management of patients based on these models should now be confirmed in future larger prospective studies.