Rotational positional error-corrected linear set-up margin calculation technique for lung stereotactic body radiotherapy in a dual imaging environment of 4-D cone beam CT and ExacTrac stereoscopic imaging.

OBJECTIVE: Accurate calculation of set-up margin is a prerequisite to arrive at the most optimal clinical to planning target volume margin. The aim of this study was to evaluate the compatibility of different on-board and in-room stereoscopic imaging modalities by calculating the set-up margins (SM) in stereotactic body radiotherapy technique accounting and unaccounting for rotational positional errors (PE). Further, we calculated separate SMs one based on residual positional errors and another based on residual + intrafraction positional errors from the imaging data obtained in a dual imaging environment. MATERIALS AND METHODS: A total of 22 lung cancer patients were included in this study. For primary image guidance, four-dimensional cone beam computed tomography (4-D CBCT) was used and stereoscopic ExacTrac was used as the auxiliary imaging. Following table position correction (TPC) based on the initial 4-D CBCT, another 4-D CBCT (post-TPC) and a pair of stereoscopic ExacTrac images were obtained. Further, during the treatment delivery, a series of ExacTrac images were acquired to identify the intrafraction PE. If a, b and c were the observed translational shifts in lateral (x-axis), longitudinal (y-axis) and vertical direction (z-axis) and α, ß and γ were the rotational shifts in radians about the same axes, respectively, then the resultant translational vectors (A, B and C) were calculated on the basis of translational and rotational values. Set-up margins were calculated using residual errors post-TPC only and also using intrafraction positional errors in addition to the residual errors. RESULTS: Residual and residual + intrafraction SM were calculated from a dataset of 82 CBCTs and 189 ExacTrac imaging sessions. CBCT-based mean ± SD shifts in translational and rotational directions were 0.3 ± 1.8 mm, 0.1 ± 1.8 mm, - 0.4 ± 1.6 mm, 0.1 ± 0.4°, 0.0 ± 1.0° and 0.3 ± 0.7°, respectively, and for ExacTrac - 0.1 ± 1.8 mm, 0.2 ± 2.4 mm, - 0.6 ± 1.8 mm, 0.1 ± 1.2°, - 0.2 ± 1.3° and - 0.1 ± 0.6°, respectively. Residual SM without considering the rotational correction in x, y and z directions were 5.0 mm, 4.5 mm and 4.4 mm; rotation-corrected SM were 4.4 mm, 4.0 mm and 5.5 mm, respectively. Residual plus intrafraction SM were 5.5 mm, 6.6 mm and 6.2 mm without considering the rotational corrections, whereas they were 5.0 mm, 6.3 mm and 6.2 mm with rotational errors accounted for. CONCLUSION: Accurate calculation of set-up margin is required to find the clinical to planning target volume margin. Primary and auxiliary imaging margins fall in the range of 4.0 to 5.5 mm and 5.0 to 7.0 mm, respectively, indicating a higher SM for X-ray-based planar imaging techniques over three-dimensional cone beam images. This study established the degree of mutual compatibility between two different kinds of widely used set-up imaging modalities, on-board CBCT and in-room stereoscopic imaging ExacTrac. It also describes the technique to calculate the residual and residual plus intrafraction SM and its variation in a dual imaging environment accounting for rotational PE in stereotactic body radiotherapy of lung.

Setup time analysis for stereotactic body radiotherapy in O-ring linear accelerator without rotational correction.

This study analyse setup time (ST) and frequency of on-board imaging for stereotactic abdomen (liver, stomach), lung, and spine radiotherapy in the absence of automatic rotational correction. Total 53 stereotactic body radiotherapy (SBRT) patients, 28 of abdomen, 19 lung, and 6 spine treated for 230 sessions in O-ring gantry accelerator were evaluated for ST analysis. The mean setup time for all patients, abdomen, lung, and spine cases were 7.7 ± 7.4 min, 9.2 ± 9.2 min, 6.3 ± 4.1 min, and 5.5 ± 3.3 min, respectively. Median number CBCT was 2. 96% of cases had a CBCT between 1 and 3, and 9 (4%) had ≥ 4 CBCTs. Overall, 38.1%, 35.5%, 22.1%, 2.2%, and 2.2% of setup time fall into window of 0-5 min, 5-10 min, 10-20 min, 20-30 min, and > 30 min. Most difficult challenge is to negotiate with unknown rotational errors. It will be easy to dealt with them without automatic rotational correction if values are known.

Planning System-dependent Recommendations of Intensity-modulated Technique for Breast Radiotherapy: A Literature Review-based Adaptation and Institutional Dosimetric Experience from a Large-volume Tertiary Cancer Care Hospital.

This article aims to identify, through a literature review, the best intensity-modulated technique (IMRT)/volumetric-modulated arc therapy (VMAT) for the breast/chest wall (Br/CW) as a function of the treatment planning system (TPS) and present the institutional dosimetric data for the same. A PubMed search was conducted following intensity-modulated irradiation techniques (IMRT) presented in the study: field-in-field (FiF), tangential IMRT (t-IMRT), multi-field IMRT, tangential VMAT (t-VMAT), half-arc VMAT (HA-VMAT), and large arc VMAT (LA-VMAT). The literature with at least one arm VMAT is included in this study. A total of 370 articles were identified between 2010 and 2022, out of which 19 articles were found to be unique. These articles were classified in terms of the TPS used: Eclipse (9), Monaco (6), RayStation (2), Pinnacle (1), and one unidentified TPS. Based on the literature review, dosimetric attributes, and second cancer risk analysis (SCRA), t-IMRT was found to be the most preferable technique in Eclipse, Pinnacle, and RayStation TPS. However, for Monaco TPS, t-VMAT (approximately 30° tangential arc) offers better dose coverage with lower organ-at-risk (OAR) doses. In terms of OAR doses and SCRA, LA-VMAT (≥210°) and HA-VMAT (180°) are avoidable techniques in any TPS, and FiF should be preferred over these two techniques. In our present institution, which uses the Eclipse TPS, data for 300 patients treated with t-IMRT were collected. The data included beam angle, monitor unit [MU], target coverage (D95% and V105% [cc]), and analysis of the maximum (%), and mean dose (%) of the OAR. t-IMRT utilizes two medial and three lateral tangential beams placed at a spread of approximately 10° and 20°, respectively. The results showed a D95% of 96.3 ± 1.2% and a V105% of 4.9 ± 7.0 cc. The mean doses to the heart and ipsilateral lung were 10.1 ± 20.9% and 11.4 ± 10.2%, respectively. The mean MU was 1282.7 ± 453.4. Based on the findings, the most preferred intensity-modulated technique for Eclipse, Pinnacle, and RayStation is t-IMRT, while for Monaco, it is t-VMAT. The data from the Eclipse planning system demonstrate a satisfactory dosimetric outcome for t-IMRT. However, the use of VMAT techniques employing an arc angle between 180° and 210° or higher is strongly discouraged.

Gender Parity in Healthcare: A Chronicle of Escalating Success Rate of Female Radiation Oncologists in India.

Biplab SarkarObjectives This editorial describes the growth pattern of female radiation oncologists (FRO) in India and the prediction of gender equality through a mathematical formulation. Materials and Methods Among the countries in South Asia, India has the largest population of radiation oncologists (RO), a total of 3,763: 1,286 female and 2,477 male radiation oncologists (MROs), and they are registered with the Association of Radiation Oncologists of India (AROI). The data were analyzed to find the differential and cumulative growth pattern of the FROs and MROs and predict gender equality in radiation oncology. The cumulative growth rate indicates the total number of FROs and MROs by end of every year. Differential growth rate indicates the differential increase in the number of FROs and MROs for a particular year. Annual cumulative and differential growth patterns were plotted as a function of the time, and an analytical functional form was fitted to predict the future growth pattern and achievement of gender equality. Results AROI registration of FROs and MROs for 2013-2020 were as follows: FRO: MRO 2013-54: 102, 2014-99: 162, 2015-77: 148; 2016-86: 143, 2017-110: 110, 2018-116: 151, 2019-121: 152, 2020 (October)-129: 110. Differential growth pattern between 2013 and 2020 with the average incremental growth rate for FROs and MROs were 12.7 ± 14.8% and 2.1 ± 32.0%. Differential growth rate FRO fits in a power-law exponent 58.6 ×(Power0.3695), where MRO growth pattern showed a saturation [4.7ln(×) + 128.5] . Gender parity among Indian radiation oncologists is likely to be achieved by end of 2027. Conclusions The present density of FRO in India 34.1% is high compared to developed countries such as the United States (≈26%). It is a big leap for the Indian radiation oncology society tending toward gender parity.

EVALUATION OF PATIENT-SPECIFIC IMRT QUALITY ASSURANCE AND POINT DOSE MEASUREMENT FOR COMPLEX HEAD AND NECK AND BRAIN CANCER USING GAFCHROMIC EBT3 FILM.

Patient-specific intensity-modulated radiation therapy (IMRT) quality assurance (QA) is essential for complex radiotherapy treatment as it involves complex intensity modulation and high-dose gradient regions. IMRT QA was performed by point dose verification and two-dimensional (2D) dose distribution measurement using gamma method. Calibrated External Beam Therapy 3 (EBT3) film was used for point dose and pre-treatment verification of 10 IMRT plans, five complex Head and Neck (HN) and five brain cases. The gamma passing rate (GPR) was evaluated for 3%/3 mm gamma criteria and compared with 2D array. Isocentre dose was measured for all 10 IMRT plans on EBT3 film. Percentage deviation of point dose measurement from TPS calculated was found 0.4% for brain cases and 2.9% for HN cases. The GPR for 3%/3 mm criteria was obtained higher than 95% for brain and HN cases. Results suggest that film dosimetry is also a reliable verification system for patient-specific IMRT QA as the 2D array.

Application of a Comprehensive Treatment Planning Test for Credentialing Intensity-Modulated Radiotherapy and RapidArc in a TrueBeam Linear Accelerator Setup.

An extended version of task group report (TG)-119 dosimetric tests was introduced and tested on the TrueBeam linear accelerator setup. Treatment plan results and quality assurance (QA) results of RapidArc (RA) and intensity-modulated radiotherapy (IMRT) were compared to understand the limitation and efficacy of the RA and IMRT system of the linear accelerator. Test structure sets were drawn on OCTAVIUS four-dimensional (4D) phantom computed tomography scan data for this study. We generated treatment plans based on the specified goal in the Eclipse™ treatment planning system using RA and IMRT in the study phantom. We used the same planning objectives for RA and IMRT techniques. Planar dose verification was performed using electronic portal imaging device and OCTAVIUS 4D phantom. The treatment log file was further analyzed using Pylinac (V2.4.0 (Open Source Code library available on Github, runs under Python programming language)) to compare the dosimetric outcome of RA and IMRT. Dose to the planning target volume (PTV) 1-5 and organ at risk (OAR) were analyzed in this study for the efficiency comparison of RA and IMRT. The primary objective was accomplished by adhering to the dose constraints associated with PTV 2 and the OAR. RA and IMRT also met the secondary objective. The tertiary goal of dose delivery to PTV 4 was met with RA but not IMRT. This study can be utilized to compare different institutions' planning and patient-specific QA (PSQA) procedures. The findings of this study were in line with the published works of the literature. A multi-institutional planning and delivery accuracy audit can be built using this structure and set of planning objectives having similar PSQA phantom. The TG-119 report incorporated test challenges that were combined in a single study set and a single plan. This reduces the complexity of performing the original TG-119 tests, whereas keeping the challenges as introduced in the TG-119 report. This study's planning and dosimetric results could be further utilized for dosimetry audit with any institute having a linear accelerator and OCTAVIUS 4D phantom for PSQA.

Customizing Treatment Scheduling Windows with a Time Margin Recipe: A Single-institutional Study.

Purpose: Rising cancer incidences, complex treatment techniques, and workflows have all impacted the radiotherapy scheduling process. Intelligent appointment scheduling is needed to help radiotherapy users adapt to new practices. Materials and Methods: We utilized van Herk's safety margin formula to determine the radiotherapy department's treatment scheduling window (TSW). In addition, we examined the influence of in-room imaging on linac occupancy time (LOT). Varian Aria™ software version 15.1 was used to collect retrospective data on LOT, treatment site, intent, techniques, special protocol, and in-room imaging. Results: Treatment scheduling windows varied across treatment sites. The mean TSW using van Herk's formalism was 31.5 min, significantly longer than the current TSW of 15 min (P = 0.036), with the pelvic site having the longest (43.8 min) and the brain site having the shortest (12 min). 28% of patients exceeded the in-practice TSW of 15 min. 46.2% of patients had multiple images per fraction, with the proportion being highest in pelvic patients (33%). Patients treated with palliative intent, intensity-modulated radiotherapy, special protocols (bladder protocol and gating), and multiple in-room images per fraction had significantly higher LOT. High treatment time uncertainty was observed in the pelvic and thorax sites, indicating the impact of in-room imaging frequency and on-couch treatment decisions on overall treatment time and indicating that current treatment practices should be reviewed and modified if necessary. Conclusions: The time margin recipe can customize the treatment scheduling window and improve treatment practices. This formalism can help manage the radiotherapy department's workload and reduce patient wait times.

Efficient and Reliable Data Extraction in Radiation Oncology using Python Programming Language: A Pilot Study.

Background and Purpose: In recent years, data science approaches have entered health-care systems such as radiology, pathology, and radiation oncology. In our pilot study, we developed an automated data mining approach to extract data from a treatment planning system (TPS) with high speed, maximum accuracy, and little human interaction. We compared the amount of time required for manual data extraction versus the automated data mining technique. Materials and Methods: A Python programming script was created to extract specified parameters and features pertaining to patients and treatment (a total of 25 features) from TPS. We successfully implemented automation in data mining, utilizing the application programming interface environment provided by the external beam radiation therapy equipment provider for the whole group of patients who were accepted for treatment. Results: This in-house Python-based script extracted selected features for 427 patients in 0.28 ± 0.03 min with 100% accuracy at an astonishing rate of 0.04 s/plan. Comparatively, manual extraction of 25 parameters took an average of 4.5 ± 0.33 min/plan, along with associated transcriptional and transpositional errors and missing data information. This new approach turned out to be 6850 times faster than the conventional approach. Manual feature extraction time increased by a factor of nearly 2.5 if we doubled the number of features extracted, whereas for the Python script, it increased by a factor of just 1.15. Conclusion: We conclude that our in-house developed Python script can extract plan data from TPS at a far higher speed (>6000 times) and with the best possible accuracy compared to manual data extraction.

Challenges faced by female radiation oncologists (FRO) in South Asia.

AIM: This study was designed to evaluate the personal challenges, work environment, and financial satisfaction of female radiation oncologists (FRO) in South Asia. MATERIAL AND METHOD: A 28-point online survey was answered by 296 FRO from south Asia. The study comprised of seven sections: personal, professional, family, economic, workplace burnout, research/academic components, and challenges exclusive to being a working woman. RESULTS: The distribution of the participants was 73.4%, 14.8%, 7.9%, and 3.9% from India, Bangladesh, Nepal, and Pakistan, respectively. Age distribution was>50 y 12.1%, 30-50 y 61.1%, and<30 y 26.8%. Out of 296 respondents 206 (69.6%) and 176 (59.5%) were married and mothers respectively. 43.8% (77) of all mothers were denied maternity leave partially.45.9% (136) of all respondents and 68.7% (121) of all mothers found motherhood the principal obstacle to career growth. Total 60.1% encounter a gender bias in the department, and 34.8% reported they were either gained or lost a job/training because of their gender. 43.3%, 36.9%, 30.6%, and 25.5% of responders felt they could have done well in professional, financial, social, and academic perspectives, respectively, had they been of the opposite gender. 28.5%, 31%, and 16.4% FRO have income ½, equal and>1.5 times than their partners. 58.9% of FRO have a similar income to male colleagues in the city, and 43% of participants are financially satisfied. CONCLUSION: This study shows a fraction of FRO in south Asia faces a substantial gender disparity in the workplace. They are partially satisfied as a woman, as RO, as mother, and as lone-earner in the family. FROs need well deserved support for optimum delivery in their professional and personal lives.

Determination of Multileaf Collimator Positional Errors as a Function of Dose Rate, Speed, and Delivery Interruption for Volumetric-Modulated Arc Therapy Delivery.

Aim: To determine the multileaf collimator positional error (MLC-PE) during volumetric modulated arc therapy (VMAT) delivery by studying the time-dependent MLC velocity in mathematically derivable trajectories such as straight line and conic sections. Materials and Methods: VMAT delivery is planned in a way that MLCs are moving in a locus which can be defined by mathematical functions such as linear, parabolic, or circular velocity (PV or CV). The VMAT delivery was interrupted either once or multiple times during the delivery and projection images of the same were acquired in electronic portal imaging device. MLC-PE was then analyzed as a function of dose rate (DR), and MLC speed (SP) and number of interruptions in treatment delivery. In VMAT delivery with linear MLC motion, the delivery was interrupted either once (linear motion single interruption) or multiple (three) times (linear motion multiple interruptions). For PV and CV MLC velocity, the MLC motions are interrupted multiple times. Results: The maximum individual error obtained (DR of 35 MU/min, SP of 2.0 cm/s) was 1.96 ± 0.1 mm. Only 4.4% of MLCs showed ≥ ±1 mm positional error. When the treatment delivery is interrupted multiple times in VMAT delivery, the influence of interruption in MLC-PE overwhelmed the influence by DR and SP. For a sub-group analysis of independent and dependent variables, the mean MLC-PE was 0.18 ± 0.4 mm 0.19 ± 0.42 mm, respectively. Conclusion: Determination of MLC-PEs using a mathematical function without approximation indicates that MLC-PE is not a function of MLC speed. In less than 5% of the studied scenarios, the MLC-PE exceeds its tolerance value (±1 mm). The MLC-PE is significantly less in modern machines due to advancements in the delivery mechanism.

Technical Note: Rotational positional error corrected intrafraction set-up margins in stereotactic radiotherapy: A spatial assessment for coplanar and noncoplanar geometry.

PURPOSE: The aim of this study is to calculate setup margin based on six-dimensional (6D) corrected residual positional errors from kV cone beam computed tomography (CBCT) and from intrafraction projection kV imaging in coplanar and in noncoplanar couch positions in stereotactic radiotherapy. METHODS: Six dimensional positional corrections were carried out before patient treatments, using a robotic couch and CBCT matching. A CBCT and stereoscopic ExacTrac image were acquired post-table position correction. Further, a series of intrafraction ExacTrac images were obtained for the variable couch position. Translational and rotational errors were identified as lateral (X), longitudinal (Y), vertical (Z); roll (Ɵ°), pitch (Φ°) and yaw (Ψ°). A total of 699 intrafraction image sets (361 coplanar and 338 noncoplanar) for 51 SRS/SRT patients were analysed. Rotational errors were corrected in terms of translational coordinates. Residual set-up margins were calculated from CBCT shifts. ExacTrac shifts give residual + intrafraction setup margins as a function of coplanar and noncoplanar couch positions. RESULTS: The average residual positional error obtained from CBCT in X, Y, Z, Ɵ, Φ, Ψ were 0.1 ± 0.4 mm, 0.0 ± 0.6 mm, 0.0 ± 0.5 mm, 0.2 ± 0.8°, 0.1 ± 0.6° and -0.1 ± 0.7° respectively. For ExacTrac, the shits were -0.5 ± 0.9 mm, -0.0 ± 1mm, -0.6 ± 1.0mm, 0.4 ± 0.9°, -0.2 ± 0.6°, and -0.0 ± 0.8°. CBCT calculated linear setup margins in X, Y, Z direction were 0.5, 1.2, and 1 mm respectively. ExacTrac yielded coplanar and noncoplanar linear setup margins were 1.2, 1.3, 1.5, 1.4, 1.5, and 2.1 mm respectively. CONCLUSION: CBCT-based gross residual set-up margin is equal to 1 mm. ExacTrac calculated residual plus intrafraction setup margin falls within a 2 mm range; attributed to intrafraction patient movement, table position inaccuracies, and poor image fusion in noncoplanar geometry. There could be variations in the required additional margin between centers and between machines, which require further studies.

Derivative based sensitivity analysis of gamma index.

Originally developed as a tool for patient-specific quality assurance in advanced treatment delivery methods to compare between measured and calculated dose distributions, the gamma index (γ) concept was later extended to compare between any two dose distributions. It takes into effect both the dose difference (DD) and distance-to-agreement (DTA) measurements in the comparison. Its strength lies in its capability to give a quantitative value for the analysis, unlike other methods. For every point on the reference curve, if there is at least one point in the evaluated curve that satisfies the pass criteria (e.g., δDD = 1%, δDTA = 1 mm), the point is included in the quantitative score as "pass." Gamma analysis does not account for the gradient of the evaluated curve - it looks at only the minimum gamma value, and if it is <1, then the point passes, no matter what the gradient of evaluated curve is. In this work, an attempt has been made to present a derivative-based method for the identification of dose gradient. A mathematically derived reference profile (RP) representing the penumbral region of 6 MV 10 cm × 10 cm field was generated from an error function. A general test profile (GTP) was created from this RP by introducing 1 mm distance error and 1% dose error at each point. This was considered as the first of the two evaluated curves. By its nature, this curve is a smooth curve and would satisfy the pass criteria for all points in it. The second evaluated profile was generated as a sawtooth test profile (STTP) which again would satisfy the pass criteria for every point on the RP. However, being a sawtooth curve, it is not a smooth one and would be obviously poor when compared with the smooth profile. Considering the smooth GTP as an acceptable profile when it passed the gamma pass criteria (1% DD and 1 mm DTA) against the RP, the first and second order derivatives of the DDs (δD', δD") between these two curves were derived and used as the boundary values for evaluating the STTP against the RP. Even though the STTP passed the simple gamma pass criteria, it was found failing at many locations when the derivatives were used as the boundary values. The proposed derivative-based method can identify a noisy curve and can prove to be a useful tool for improving the sensitivity of the gamma index.