Near complete resolution of COVID-19 pneumonia lesions in a patient of carcinoma lung treated with volumetric modulated arc therapy.

A 49-year-old male presented with non-small cell lung cancer in right upper lobe lung with solitary brain metastasis. He developed COVID-19 infection and received domiciliary treatment for 3 weeks. Three weeks after testing negative for RT-PCR test, he received stereotactic radiosurgery (SRS) to brain metastasis. He then presented in emergency with pain in the epigastrium and was detected with amoebic liver abscess. Subsequently, he developed recurrent hemoptysis for which he was planned for palliative radiation to right lung mass. Planning CT scan showed COVID-19 pneumonia lesions involving bilateral lungs in addition to right upper lobe tumour. Palliative radiation 8 Gy/1 fraction was delivered to lung tumour with VMAT technique. He showed near total resolution of COVID-19 lesions with low-dose scatter radiation and relief of haemoptysis.

Stereotactic ablative radiotherapy (SABR) for recurrent and previously irradiated head and neck cancers.

OBJECTIVE: To assess the response and toxicity of stereotactic ablative radiotherapy (SABR) in patients with recurrent head and neck cancer (HNC), who had previously received radiation for their primary tumor. METHODS: Between 2014 and 2018, patients who received SABR to recurrent HNC within the previously irradiated region were retrospectively reviewed. Mean age was 60 years (range 30-78 Years). Histology was confirmed in all patients. MRI and /or CT-positron emission tomography were done to evaluate local extent and to rule out metastasis. Response was assessed as per RECIST/PERCIST Criteria. Cox proportional hazards regression and the Kaplan-Meier methods were used for statistical analysis. RESULTS: 32 patients received SABR. RPA Class II, III patients were 20 and 12 respectively. 87% patients received a dose of ≥30 Gy/5 fractions. Median follow-up was 12 months. Estimated 1 year and 2 years local control was 64.2 and 32% and 1 year and 2 years overall survival was 67.5 and 39.5% respectively. Acute Grade 2 skin and Grade 3 mucosal toxicity was seen in 31.3 and 28% patients respectively. Late Grade 3 toxicity was seen in 9.3% patients. CONCLUSION: Re-irradiation with SABR yields high local control rates and is well tolerated. It compares favorably with other treatment modalities offered to patients with recurrent HNC. It is also suitable for patients of RPA Class II and III. There is need for novel systemic agents to further improve the survival. ADVANCES IN KNOWLEDGE: Treatment of patients with recurrent HNC is challenging and is more difficult in previously radiated patient. More than 50% patients are unresectable. Other options of salvage treatment like re-irradiation and chemotherapy are associated with poor response rates and high incidence of acute and late toxicity (Gr ≥3 toxicity 50-70%). SABR is a novel technology to deliver high dose of radiation to recurrent tumor with high precision. It yields high local control rates with less toxicity compared to conventionally fractionated radiation.

Development and Validation of a MATLAB Software Program for Decoding the Treatment Errors in Real-time Position Management™ Gating-generated Breathing Trace.

INTRODUCTION: The Real-time Position Management™ (RPM) is used as a motion management tool to reduce normal tissue complication. However, no commercial software is available to quantify the "beam-on" errors in RPM-generated breathing traces. This study aimed to develop and validate an in-house-coded MATLAB program to quantify the "beam-on" errors in the breathing trace. MATERIALS AND METHODS: A graphical user interface (GUI) was developed using MATLAB (Matrix Laboratory Ra2016) software. The GUI was validated using two phantoms (Varian-gated phantom and Brainlab ET gating phantom) with three regular motion profiles. Treatment time delay was calculated using regular sinusoidal motion profile. Ten patient's irregular breathing profiles were also analyzed using this GUI. RESULTS: The beam-on comparison between the recorded reference trace and irradiated trace profile was done in two ways: (1) beam-on time error and (2) beam-on displacement error. These errors were ≤1.5% with no statistical difference for phase- and amplitude-based treatments. The predicated amplitude levels of reference phase-based profiles, and the actual amplitude levels of amplitude-based irradiated profiles were almost equal. The average treatment time delay was 47 ± 0.003 ms. The irregular breathing profile analysis showed that the amplitude-based gating treatment was more accurate than phase based. CONCLUSION: The developed GUI gave the same and acceptable results for all regular profiles. These errors were due to the lag time of the linear accelerator with gating treatment. This program can be used as to quantifying the intrafraction "beam-on" errors in breathing trace with both mode of gating techniques for irregular breathing trace, and in addition, it is capable to convert phase-based gating parameters to amplitude-based gating parameters for treatment.

The Composite Planning Technique in Left Sided Breast Cancer Radiotherapy: A Dosimetric Study.

OBJECTIVE: The aim of this retrospective study is to reduce the dose of heart, both lung and opposite breast and left anterior descending artery (LAD) and avoid long term complication and radiation induced secondary malignancies in radiotherapy left breast/chest wall without losing homogeneity and conformity of the Planning Target Volume (PTV), contoured using Radiotherapy Oncology Group (RTOG 1005) guideline. MATERIALS AND METHODS: The treatment plans were generated retrospectively by TFIF, VMAT and Composite techniques for 30 patients. Dose-Volume Histograms (DVHs) were evaluated for PTV and organs at risk (OAR's) and analyzed in two groups BCS and MRM using Wilcoxon signed rank test. RESULTS: The homogeneity index (HI) was improved in Composite technique by 32.72% and 21.81% of VMAT, 50.66% and 49.41% of TFIF in BCS and MRM group respectively. The Conformity Index (CI) for composite plan was statistically same as VMAT and superior by 27.94% and 41.37% of TFIF in BCS and MRM group respectively. The low dose volume V5Gy and V10Gy of the heart were improved in Composite plan by 47.9% and 26.1% of VMAT respectively in BCS group and in MRM group, improved by 21.2% and 45.6% of VMAT. The V5Gy and V10Gy of ipsilateral lung were improved in Composite plan by 16% and 13.7% of VMAT respectively in BCS and 8.4% and 3% of VMAT respectively in MRM group. CONCLUSION: The Composite plan consisting of VMAT and TFIF plan with an optimum selection of fractions can achieve lower low dose exposure to the OAR's without compromising coverage compared to VMAT.

Evaluation of automated image registration algorithm for image-guided radiotherapy (IGRT).

The performance of an image registration (IR) software was evaluated for automatically detecting known errors simulated through the movement of ExactCouch using an onboard imager. Twenty-seven set-up errors (11 translations, 10 rotations, 6 translation and rotation) were simulated by introducing offset up to ± 15 mm in three principal axes and 0° to ± 1° in yaw. For every simulated error, orthogonal kV radiograph and cone beam CT were acquired in half-fan (CBCT_HF) and full-fan (CBCT_FF) mode. The orthogonal radiographs and CBCTs were automatically co-registered to reference digitally reconstructed radiographs (DRRs) and planning CT using 2D-2D and 3D-3D matching software based on mutual information transformation. A total of 79 image sets (ten pairs of kV X-rays and 69 session of CBCT) were analyzed to determine the (a) reproducibility of IR outcome and (b) residual error, defined as the deviation between the known and IR software detected displacement in translation and rotation. The reproducibility of automatic IR of planning CT and repeat CBCTs taken with and without kilovoltage detector and kilovoltage X-ray source arm movement was excellent with mean SD of 0.1 mm in the translation and 0.0° in rotation. The average residual errors in translation and rotation were within ± 0.5 mm and ± 0.2°, ± 0.9 mm and ± 0.3°, and ± 0.4 mm and ± 0.2° for setup simulated only in translation, rotation, and both translation and rotation. The mean (SD) 3D vector was largest when only translational error was simulated and was 1.7 (1.1) mm for 2D-2D match of reference DRR with radiograph, 1.4 (0.6) and 1.3 (0.5) mm for 3D-3D match of reference CT and CBCT with full fan and half fan, respectively. In conclusion, the image-guided radiation therapy (IGRT) system is accurate within 1.8 mm and 0.4° and reproducible under control condition. Inherent error from any IGRT process should be taken into account while setting clinical IGRT protocol.

Physical and dosimetric characteristic of high-definition multileaf collimator (HDMLC) for SRS and IMRT.

Physical and dosimetric characteristics of HDMLC were studied for SRS6, 6, and 10 MV X-rays from Novalis Tx. This in-built tertiary collimator consists of 60 pairs (32 × 0.25 cm; 26 × 0.5 cm and 2 × 0.7 cm) of leaves. Properties of HDMLC studied included alignment, readout and radiation field congruence, radiation penumbra, accuracy and reproducibility of leaf position and gap width, static and dynamic leaf shift, tongue-and-groove effect, leaf transmission and leakage, leaf travel speed, and delivery of dynamic conformal arc and IMRT. All tests were performed using a calibrated ionization chamber, film dosimetry and DynaLog file analysis. Alignment of leaves with isocenter plane was better than 0.03 cm at all gantry and collimator positions. The congruence of HDMLC readout and radiation field agreed to within ± 0.03 cm for filed sizes ranging from 1 × 1 to 20 × 20 cm2. Mean 80% to 20% penumbra width parallel (perpendicular) to leaf motion was 0.24 ± 0.05 (0.21 ± 0.02) cm, 0.37 ± 0.12 (0.29 ± 0.07) cm, and 0.51 ± 0.13 (0.43± 0.07) cm for SRS6, 6, and 10 MV X-rays, respectively. Circular field penumbra was comparable to corresponding square field. Average penumbra of 1 × 20 cm2 field was effectively constant over off-axis positions of up to 12 cm with mean value of 0.16 (± 0.01) cm at 1.5 cm depth and 0.38 (± 0.04) cm at 10 cm depth. Minimum and maximum effective penumbra along the straight diagonal edge of irregular fields increased from 0.3 and 0.32 cm at 70° steep angle to 0.35 and 0.56 cm at 20° steep angle. Modified Picket Fence test showed average FWHM of 0.18 cm and peak-to-peak distance of 1.99 cm for 0.1 cm band and 2 cm interband separation. Dynamic multileaf collimation (DMLC) output factor remained within ± 1% for 6 MV and ± 0.5% for 10 MV X-rays at all gantry positions, and was reproducible within ± 0.5% over a period of 14 months. The static leaf shift was 0.03 cm for all energies, while dynamic leaf shift was 0.044 cm for 10 MV and 0.039 cm for both SRS6 and 6 MV X-rays. The dose depression and corresponding tongue-and-groove size were 24% and 0.17 cm for 6 MV and 19% and 0.20 cm for 10 MV X-rays. Average transmission through HDMLC was 1.09%, 1.14% and 1.34% for SRS6, 6 and 10 MV X-rays. Analysis of DynaLog files for leaf speed test in arc dynamic mode, delivery test of dynamic conformal arc, and step-and-shoot and sliding window IMRT showed at least 95% or more of the error counts had misplacements < 0.2 cm, with maximum root mean square (RMS) error value calculated at 0.13cm. Accurate and reproducible leaf position and gap width, and less leakage and small consistent penumbra over the fields demonstrate HDMLC suitable for high-dose resolution SRS and IMRT.

Portal dosimetry for pretreatment verification of IMRT plan: a comparison with 2D ion chamber array.

Portal dosimetry (PD) was performed for 181 fields from 14 IMRT plans of various clinical sites at gantry zero and source-to-detector distance (SDD) of 100 cm. PD was realized using aSi1000 electronic portal imaging device (EPID) and portal dose prediction (PDP) algorithm implemented in Eclipse treatment planning system (TPS). Agreement of PDP predicted and EPID measured photon fluence/dose distribution were evaluated using gamma (γ) index set at 3% at 3 mm distance to point agreement (DTA). Three gamma scaling parameters, maximum γ (γ(max)), average γ (γ(avg)) and percentage of points with γ ≤ 1 (γ% ≤ 1) were estimated for each field. An independent measurement was carried out using MatriXX 2D ion chamber array with detector plane at 100 cm and γ(max), γ(avg) and γ% ≤ 1 were estimated using OmniPro IMRT analyzing software. Effect of extended SDD and gantry rotation on portal dosimetry outcome was also investigated for another 45 IMRT fields. PDP predicted and EPID measured photon fluence agrees well with overall mean values of γ(max), γ(avg) and γ% ≤ 1 at 2.02, 0.24 and 99.43%, respectively. γ(max) value was lower in 15 MV compared to 6 MV IMRT plan. Independent verification using MatriXX showed comparable overall mean values of γ(avg) and γ% ≤ 1 at 0.25 and 99.80%. However, in all plans, MatriXX showed significantly lower γ(max) (p < 0.05) with an overall mean value of 1.35. In portal dosimetry, compared to gamma values at 100 cm SDD, γ(max), γ(avg) and γ% ≤ 1 values improve from a mean of 0.16, 0.03 and 0.26 at 110 cm SDD to 0.35, 0.05 and 0.29 at 140 cm SDD. PD outcome was independent of gantry rotation. In conclusion, both MatriXX 2D ion chamber array and portal dosimetry showed comparable results and can be use as an alternative to each other for relative photon fluence verification.