Dosimetry of small fields (SF) is vital for the success of highly conformal techniques. IAEA along with AAPM recently published a code of practice TRS-483 for SF dosimetry. The scope of this paper is to investigate the performance of three different detectors with 10 MV with-flatting-filter (WFF) beam using TRS-483 for SF dosimetry and subsequent commissioning of the Eclipse treatment planning system (TPS version-13.6) for SF data. SF dosimetry data (beam-quality TPR 20,10(10), cross-calibration, beam-profile, and field-output-factor (F.O.F)) measurements were performed for PTW31006-pinpoint, IBA-CC01 and IBA-EFD-3G diode detectors in nominal field size (F.S) range 0.5 × 0.5cm2 to 10 × 10 cm2 with water and solid water medium using Varian Truebeam linac. However, Eclipse-TPS commissioning data was acquired using IBA-EFD-3G diode, and absolute dose calibration was performed with FC-65G detector. The dosimetric performance of the Eclipse-TPS was validated using TLD-LiF chips, IBA-PFD, and IBA-EFD-3G diodes. Dosimetric performance of the PTW31006-pinpoint, IBA-CC01, and IBA-EFD-3G detectors was successfully tested for SF dosimetry. The F.O.Fs were generated and found in close agreement for all F.S except 0.5 × 0.5cm2. It is also found that TPR20,10(10) value can be derived within 0.5% accuracy from a non-reference field using Palmans equation. Cross-calibration can be performed in F.S 6 × 6 cm2 with a maximum variation of 0.5% with respect to 10 × 10cm2. During profile measurement, the full-width half-maxima (FWHM) of F.S 0.5 × 0.5cm2 was found maximum deviated from the geometric F.S. In addition, Eclipse-TPS was commissioned along with some limitations: F.O.F below F.S 1 × 1cm2 was ignored by TPS, PDD and profiles were dropped from configuration below F.S 2 × 2 cm2, and F.O.F which does not satisfy the condition 0.7 < A/B < 1.4 (A and B are FWHM in cross-line and in-line direction) have higher uncertainty than specified in TRS-483. Validation tests for Eclipse-TPS generated plans were also performed. The measured dose was in close agreement (3%) with TPS calculated dose up to F.S 1.5 × 1.5cm2.

Purpose:The aim of this study was to quantify the discrepancies in geometrical and dosimetric impacts (in volumetric modulated arc therapy) between manually segmented (MS) contours and smart segmentation (SS) auto-contours (by Varian Eclipse Treatment Planning System SS v13.5) for prostate cancer patients. Methods:The automated segmentation was carried out by Eclipse Treatment Planning System (Varian, version 13.5) Smart Segmentation (SS) workspace of 10 prostate cancer patients for four regions of interest; such as, bladder, rectum, femoral head left, and femoral head right. The geometric and dosimetric deviation between SS and MS contours have been quantified in the form of different parameters. The organ-wise correlation between different validation parameters was addressed. Results:The organ-wise correlation analysis showed the good and consistent correlation between different geometric validation parameters for the bladder. The hypothesis test for checking compliance of different parameters with AAPM 132 tolerance was addressed and validated between MS and SS bladder with p-value = 0.01 and 0.05.There was no significant dosimetric difference between the dose-volume histogram (DVH) estimated for the SS bladder and standard DVH constraints protocol (as per the TMH PRIME trial) with p-value = 0.01 and 0.05. The difference between DVH estimated for MS and SS bladder was also not significant, with p-value = 0.05. Conclusion:This study shows that "well correlated validation parameters infer correctly about the matching or coincidence between auto and manually segmented contours," and the bladder contouring by Smart Segmentation and plan optimization can achieve acceptable DVH constraints.

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Purpose International Atomic Energy Agency published TRS-483 to address the issues of small field dosimetry. Our study calculates the output factor in the small fields of TomoTherapy using different detectors and dosimetric conditions. Furthermore, it estimates the various components of uncertainty and presents challenges faced during implementation. Materials and Methods Beam quality TPR20,10(10) at the hypothetical field size of 10 cm × 10 cm was calculated from TPR20,10(S). Two ionization chambers based on the minimum field width required to satisfy the lateral charge particle equilibrium and one unshielded electron field diode (EFD) were selected. Output factor measurements were performed in various dosimetric conditions. Results Beam quality TPR20,10(10) has a mean value of 0.627 ± 0.001. The maximum variation of output factor between CC01 chamber and EFD diode at the smallest field size was 11.80%. In source to surface setup, the difference between water and virtual water was up to 9.68% and 8.13%, respectively, for the CC01 chamber and EFD diode. The total uncertainty in the ionization chamber was 2.43 times higher compared to the unshielded EFD diode at the smallest field size. Conclusions Beam quality measurements, chamber selection procedure, and output factors were successfully carried out. A difference of up to 10% in output factor can occur if density scaling for electron density in virtual water is not considered. The uncertainty in output correction factors dominates, while positional and meter reading uncertainty makes a minor contribution to total uncertainty. An unshielded EFD diode is a preferred detector in small fields because of lower uncertainty in measurements compared to ionization chambers.

The Covid-19 onset was very pandemic for all of society all over the world. To overcome this state of affairs, the country’s government had done the lockdown in their respective countries. The lockdown helped the people from spreading the Covid-19 virus among people, however, it affected another part of life such as people becoming unemployed. The health care sector was affected a lot by the lockdown as the patient faced lots of problems such as reaching the hospital, meeting the concerned staff, getting the treatment on time, etc. Covid-19 affected the cancer patients most, during the lockdown. After awareness of Covid-19, when the world has started towards the unlock down. With the little negligence of people, the world has started facing the peak of Covid-19. And, there was more crowd in the health care sectors, therefore the hospital staff got infected a lot, as the patient treatment cannot be carried out from home. Cancer patient treatment, which comes under radiotherapy, has already existed in chronic medical conditions, such as lung cancer patients, esophagus cancer patients, heart disease patients, etc, has a higher risk of Covid-19 infection. During treatment, when such a patient comes in contact with a radiation oncologist, medical physicist, and radiation technologist, then some of the staff get infected through patients. To prevent such spread, all the medical staff should strictly follow the rules made for staff. In this article, we are sharing the challenges for the medical physics team and some suggestions during patient care.