To investigate the dosimetric advantage of quasi-continuous couch motion-enabled trajectory modulated arc radiotherapy therapy (TMAT) over the coplanar tangential partial arcs volumetric modulated arc radiotherapy (VMAT) for treating left breast and chest wall patients.

Treatment plans of 43 patients who received radiotherapy for left breast (17) or for left chest wall (26) using coplanar partial tangential arcs VMAT (reference plan) were considered for this study. For each patient, in addition to the treatment plan, a TMAT plan was also generated using quasi-continuous couch rotation. The TMAT plan consisted of original two 30° tangential arc beams and two supplementary beams having a couch rotation of ±10°, ±20° and ±30°, respectively. The difference in PTV volume coverage (PTV V95%) between TMAT plan and VMAT plan was calculated for all the cases and normalised to the plan’s prescription dose. Similarly, differences in PTV_V105% and several dose-volume parameters related to organs at risk (OAR) were also computed and tabulated.

TMAT shows an increment in the PTV dose coverage V95% with respect to reference plan by 4·7±2·5% when averaged overall prescription dose levels. Mean PTV dose (averaged overall prescription levels) for reference and TMAT plan was 4638·6±423·8 and 4793·5±447·2 cGy, respectively, and statistically insignificant (p=0·06). However mean PTV_V105% values for TMAT and for reference plans were 6·7±4·8 and 7·2±5·2%, respectively, and were not statistically different (p=0·85). Mean heart dose in TMAT was less than in VMAT plans, but not significantly. As regarding D1% to heart, TMAT plan was again found to be better with a mean difference of 137·1 cGy over VMAT plan. Other parameters evaluated were: mean dose and D1% to contralateral breast, and V20 Gy and V5 Gy for lung.

TMAT plans were found to be better than VMAT plans in terms of PTV coverage and D1% for heart. For evaluated dose parameters apart from PTV coverage and D1% to the heart, no significant differences were observed. Thus, TMAT plans yielded better dose distribution in terms of PTV dose coverage, hot spots and OAR doses.

The main objective of this research work is to compare the dosimertic effect on lower and upper oesophagus cancer treatment using 3D conformal radiotherapy as well as to evaluate the doses administered to the organs at risk.

In this study, a cohort of 30 oesophageal cancer patients between the ages of 45 and 67 years registered during March 2017 to February 2018 was considered. These patients were treated through 3D conformal radiotherapy using four-field technique. Beam energy of 15 MV from Varian DHX linear accelerator was used. The given 30 patients were divided into two groups. The 1st group of 15 patients with upper oesophagus cancer was prescribed 5000 cGy doses, and the 2nd group of remaining 15 patients with lower oesophagus cancer was prescribed 4500 cGy. Computed tomography scans of every patient were obtained and then transmitted to Eclipse TPS for generating treatment plans. All radiotherapy plans were evaluated through various dosimetric indices. Statistical analysis software SPSS was utilised to get the values of means standard error and standard deviation of these indices for the treatment plan evaluation.

Uniformity index (UI) calculated for first group of patients showed difference of 7·4% from ideal value. A difference of 7% between ideal and calculated UI value was observed in 2nd group of patients. The values of other dosimetric indices like coverage, homogeneity, moderate dose homogeneity index (mDHI) and radical dose homogeneity index (rDHI) were found in limits specified by the Radiation Therapy and Oncology Group. The maximum difference of 6% was observed between the coverage mean values of 1st and 2nd group treatment plans.

For oesophageal cancer, 3D conformal radiotherapy using four-field treatment plans shows homogeneous distribution of dose around the target and limits the dose to organ at risk.

This study evaluated the impact of patient set-up errors on the probability of pulmonary and cardiac complications in the irradiation of left-sided breast cancer.

Using the CMS XiO Version 4·6 radiotherapy planning system's normal tissue complication probability (NTCP) algorithm and the Lyman–Kutcher–Burman model, we calculated the dose–volume histograms (DVH) indices for the ipsilateral lung and heart and the resultant NTCP for radiation-induced pneumonitis and excess cardiac mortality in 12 left-sided breast cancer patients.

Isocentric shifts in the posterior direction had the greatest effect on the lung V20, heart V25, and mean and maximum doses to the lung and the heart. DVH results show that the ipsilateral lung V20 tolerance was exceeded in 58% of the patients after 1 cm posterior shifts. Similarly, the heart V25 tolerance was exceeded after 1 cm antero-posterior and left–right isocentric shifts in 70% of the patients. The baseline NTCPs for radiation-induced pneumonitis ranged from 0·73% to 3·4%, with a mean value of 1·7%. The maximum reported NTCP for radiation-induced pneumonitis was 5·8% (mean 2·6%) after 1 cm posterior isocentric shift. The NTCP for excess cardiac mortality were 0% in 100% of the patients (n = 12) before and after set-up error simulations.

Set-up errors in left-sided breast cancer patients have a statistically significant impact on the Lung NTCPs and DVH indices. However, with a central lung distance of 3 cm or less (CLD < 3 cm), and a maximum heart distance of 1·5 cm or less (MHD < 1·5 cm), the treatment plans could tolerate set-up errors of up to 1 cm without any change in the NTCP to the heart.

To assess the accuracy of the Varian PerfectPitch six-degree-of-freedom (6DOF) robotic couch by using a Varian SRS QA phantom.

The stereotactic radiosurgery (SRS) phantom has five tungsten carbide BBs each with 7·5 mm in diameter arranged with the known geometry. Optical surface images and cone beam CT (CBCT) images of the phantom were taken at different pitch, roll and rotation angles. The pitch, roll, and rotation angles were varied from −3 to 3 degrees by inputs from the linac console. A total of 39 Vision RT images with different rotation angle combinations were collected, and the Vision RT software was used to determine the rotation angles and translational shifts from those images. Eight CBCT images at most allowed rotational angles were analysed by in-house software. The software took the coordinates of the voxel of the maximum CT number inside a 7·5-mm sphere surrounding one BB to be the measured position of this BB. Expected BB positions at different rotation angles were determined by multiplying measured BB positions at zero pitch and roll values by a rotation matrix. Applying the rotation matrix to 5 BB positions yielded 15 equations. A linear least square method was used for regression analysis to approximate the solutions of those equations.

Of the eight calculations from CBCT images, the maximum rotation angle differences (degree) were 0·10 for pitch, 0·15 for roll and 0·09 for yaw. The maximum translation differences were 0·3 mm in the left–right direction, 0·5 mm in the anterior–posterior direction and 0·4 mm in the superior–inferior direction.

The uncertainties of the 6-DOF couch were examined with the methods of optical surface imaging and CBCT imaging of the SRS QA phantom. The rotational errors were less than 0·2 degree, and the isocentre shifts were less than 0·8 mm.

The purpose of this study was to determine the dose enhancement factor (DEF) of gold nanoparticles in a dosimeter gel and construct percentage depth dose curves, using the Optical CT system and the Monte Carlo simulation model, to determine the effect of increasing the dose caused by increasing the concentration of gold nanoparticles at depths in the gel.

The Magic-f Gel was made based on the relevant protocol in the physics lab. To determine the amount of the increase in the absorbed dose, the gold nanoparticles were added to the gel and irradiated. An increase in the dose after adding nanoparticles to the gel vials was estimated both with the Optical CT system and by the Monte Carlo simulation method.

Dose enhancement curves for doses of 2, 4 and 6 Gy were prepared for gel vials without adding nanoparticles, and nanoparticle gels at concentrations 0·17, 3 and 6 mM. Also, the DEF was estimated. For the 0·17 mM molar gel, the DEF for 2, 4 and 6 Gy was 0·7, 0·743 and 0·801, respectively. For the 3 mM gel, it was 1·98, 2·5 and 2·2, and for the 6 mM gel, it was 37·4, 4·24 and 4·71, respectively.

The enhancement of the dose after adding gold nanoparticles was confirmed both by experimental data and by simulation data.

The aim of this study was to evaluate clinical efficacy and radiobiological outcome of intensity-modulated radiation therapy (IMRT) modalities using various collimator angles and non-coplanar fields for nasopharyngeal cancer (NPC).

A 70-Gy planning target volume dose was administered for 30 NPC patients referred for IMRT. Standard IMRT plans were constructed based on the target and organs at risk (OARs) volume; and dose constraints recommended by Radiation Therapy Oncology Group (RTOG). Using various collimator angles and non-coplanar fields, 11 different additional IMRT protocols were investigated. Homogeneity indexes (HIs) and conformation numbers (CNs) were calculated. Poisson and relative seriality models were utilised for estimating tumour control probability (TCP) and normal tissue complication probabilities (NTCPs), respectively.

Various collimator angles and non-coplanar fields had no significant effect on HI, CN and TCP, while significant effects were noted for some OARs, with a maximum mean dose (Dmax). No significant differences were observed among the calculated NTCPs of all the IMRT protocols. However, the protocol with 10° collimator angle (for five fields out of seven) and 8° couch angle had the lowest NTCP. Furthermore, the standard and some of non-coplanar IMRT protocols led to the reduction in OARs Dmax.

Using appropriate standard/non-coplanar IMRT protocols for NPC treatment could potentially reduce the dose to the OARs and the probability of inducing secondary cancer in patients.

Total body irradiation (TBI) is an external radiotherapy technique in which the whole body including the superficial regions is required to receive the therapeutic dose. The purpose of this study is to evaluate the received surface dose during TBI technique.

The anterior/posterior (AP/PA) TBI was implemented with 18-MV photon beam at 312-cm treatment distance for human-like phantom. The GAFCHROMIC-EBT3 films were used for superficial dose measurements.

The percentage of surface-absorbed dose relative to the prescription point for 8 points of measurements was between 102·78–121·48% and 104·51–127·43% at 5 and 10 mm depth, respectively. In the chest wall region due to the presence of lung blocks, the absorbed dose was below the acceptable level, so an electron boost was required to increase the chest wall absorbed dose.

According to the results, the implemented technique was able to deliver sufficient dose to the shallow surface of phantom’s body.

This study investigates the dose escalation to dominant intra-prostatic lesions (DILs) that is achievable using single-source-strength (SSS) and dual-source-strength (DSS) low-dose-rate (LDR) prostate brachytherapy and a sector-based plan approach.

Twenty patients were retrospectively analysed. Image registration and planning were undertaken using VariSeed v9·0. SSS and DSS boost plans were produced and compared to clinical plans. Dosimetric robustness to seed displacement for SSS and DSS plans was compared to clinical plans using Monte Carlo simulations.

Fourteen out of 20 patients had DIL identifiable on magnetic resonance imaging. Median increase in sector D90 of 27% (p < 0·0001) and sector V150 of 31% (p < 0·0001) was achieved with SSS planning without exceeding local rectum and urethra dose constraints. DSS plans achieved dose distributions not statistically significantly different from the SSS plans with a median of eight fewer seeds and two fewer needles. SSS and DSS plan sensitivity to random seed displacement was similar to the clinical plans.

Treatment planning using VariSeed to produce SSS and DSS focal boost plans is feasible for LDR prostate brachytherapy to achieve a median escalation in sector D90 of 27% without exceeding local urethral and rectal constraints. SSS and DSS plan dosimetric robustness was similar to clinical plan dosimetric robustness.

Treatment of metachronous second primary non-small cell lung cancer (NSCLC) in patients already treated with definitive radiotherapy is a matter of debate, since most patients are excluded from surgical treatment, which remains a therapeutic standard for patients with isolated lung masses. Salvage chemotherapy or immunotherapy alone offers a low probability of disease control. The option of re-irradiation often remains the only viable, but the risks of severe acute or late toxicities affecting the surrounding normal tissues make this a real clinical challenge.

From January 2015 to April 2018, five patients (male/female: 4/1; age 54–81 years, median 68) with previously irradiated NSCLC presented with a second primary lung tumour.

A partial response was seen in four patients, one complete responses in the fifth. The toxicity was low: two patients experienced a grade 2 asymptomatic radiation pneumonitis after 6 and 12 months from the end of stereotactic body radiation therapy, resolved with cortisone therapy. No acute or late oesophageal or cardiac toxicity was found.

In this work, we present our initial experience about the use of stereotactic radiotherapy technique in already irradiated patients. We reported a local disease control in all cases with an acceptable toxicity.

Previous studies showed that replacing conventional flattened beams (FF) with flattening filter-free (FFF) beams improves the therapeutic ratio in lung stereotactic body radiation therapy (SBRT), but these findings could have been impacted by dose calculation uncertainties caused by the heterogeneity of the thoracic anatomy and by respiratory motion, which were particularly high for target coverage. In this study, we minimised such uncertainties by calculating doses using high-spatial-resolution Monte Carlo and four-dimensional computed tomography (4DCT) images. We aimed to evaluate more reliably the benefits of using FFF beams for lung SBRT.

For a cohort of 15 patients with early-stage lung cancer that we investigated in a previous treatment planning study, we recalculated dose distributions with Monte Carlo using 4DCT images. This included 15 FF and 15 FFF treatment plans.

Compared to Monte Carlo, the treatment planning system (TPS) over-predicted doses in low-dose regions of the planning target volume (PTV). For most patients, replacing FF beams with FFF beams improved target coverage, tumour control, and uncomplicated tumour control probabilities.

Monte Carlo tends to reveal deficiencies in target coverage compared to coverage predicted by the TPS. Our data support previously reported benefits of using FFF beams for lung SBRT.

The aim of this study is to investigate the impact of anatomical changes in prostate cancer patients on the target coverage when using 6 MV beams-VMAT therapy and to propose strategies that allow us to evaluate the dose or correct it by normalization without having to perform a new simulation.

Ten patients of high-risk prostate cancer were chosen for the study. All test plans were delivered using the same isocenter and monitor units as the original plan and compared against the original unedited plan. The expansion and contraction of body contours due to size changes was mimicked by increasing and decreasing the body contour with depths of −2, −1·5, …, 1·5, 2 cm, in the anterior, and both lateral directions of the patient. A total of 90 plans were evaluated, 9 for each patient. Dose-volume histogram statistics were extracted from each plan and normalized to prescription dose.

Weight changes resulted in considerable dose modifications to the target and critical structures. Plans were found to be varied with 2·9% ± 0·3% per cm SSD change for VMAT treatment with a correlation index close to one. Therefore, doses variations were linear to the changes of depth. Gamma index evaluation was performed for the 10 renormalized plans. All of them passed criteria of 3%/3 mm in at least 98.2% of points. Eight of them passed criteria in 99% points. Gamma index 4%/4 mm passed 100% points in all patients for the chosen region of interest.

The dosimetry estimation presented in this study shows important data for the radiation oncology staff to justify whether a CT rescan is necessary or not when a patient experiences weight changes during treatment. Based on the results of our study, discrepancies between real dose and planned dose were >5% for 1·7 cm of difference in external contour in the anterior and both lateral directions of the patient.

CyberKnife is the most advanced form of stereotactic body radiotherapy (SBRT) system that uses a robotic arm to deliver highly focused beams of radiation; however, a limitation is that it only irradiates from ceiling to floor direction. In patients with posterior lungs tumour who are positioned supine, normal lung tissue may suffer undesirable radiation injuries. This study compares the treatment planning between the prone set-up and the supine set-up for lung cancer in CyberKnife SBRT to decrease normal lung dose to avoid radiation side effects.

A human phantom was used to generate 108 plans (54 for prone and 54 for supine) using the CyberKnife planning platform. The supine and prone plans were compared in terms of the dosimetric characteristics, delivery efficiency and plan efficiency.

For posterior targets, the area of low-dose exposure to normal lungs was smaller in the prone set-up than in the supine set-up. V10 of the lungs was 7·53% and 10·47% (p < 0·001) in the anterior region, and 10·78% and 8·03% (p < 0·001) in the posterior region in the supine and prone set-up plans, respectively.

The comparison between the prone set-up and the supine set-up was investigated with regard to target coverage and dose to organs at risk. Our results may be deployed in CyberKnife treatment planning to monitor normal tissue dose by considering patient positioning. This may assist in the design of better treatment plans and prevention of symptomatic radiation pneumonitis in lung cancer patients.

Orbital metastases lead to many distressful symptoms.

A case-report of a 44-year-old woman with a melanoma metastasis in the orbital cavity, is reported. A patient presented with headache, proptosis and diplopia. The stereotactic radiotherapy of 19.5 Gy in three fractions using CyberKnife was performed. Follow-up examination 7 months later revealed satisfactory local control of the tumour, alleviation of orbital symptoms with no negative impact on visual function.

Stereotactic radiotherapy seems to be a safe and effective treatment of orbital metastases from melanoma.

This exploration is intended to measure tissue maximum ratios (TMRs) in smaller fields through CC01 detector and to compare CC01 measured TMRs with Pinnacle treatment planning software (TPS) calculated TMRs.

CC01 compact chamber detector was used to measure TMR in water phantom for 6 and 18 MV beam delivered from Varian linear accelerator. Pinnacle TPS was employed in this study to calculate TMR from the measured percentage depth doses data. CC01 measured TMR data was compared with the calculated TMR data at depths from 5 to 20 cm for field sizes varying from 1 to 10 cm2.

For the smallest given field size of 1 cm2, CCO1 measured 13·95% higher TMR value for 18 MV beam than that for 6 MV beam. At 20 cm depth for 1 cm2 field size, TMR due to 18 MV beam was 52·4% higher than the TMR due to 6 MV beam. For 6 MV beam, the maximum difference appeared between the measured TMR and pinnacle calculated TMR was 2·8% and for 18 MV beam, the maximum difference was 4%.

For both 6 and 18 MV beam, there was good agreement between CC01 measured and Pinnacle calculated TMRs for the field sizes ranging from 1 to 10 cm2. This exploration can be extended to the determination of other dosimetric parameters like TARs, TPRs in small fields.

To analyse the dosimetric benefit of the hybrid inverse planning optimisation (HIPO) planning method over the graphical optimisation (GrO) planning method for 3D volume-based intravaginal brachytherapy (IVBT) in a mono-centre patient cohort.

Twenty-five patients surgically staged with endometrial cancer were considered for the study. All the patients had received adjuvant IVBT for three fractions with one-time computed tomography image-based planning. The data on the patient, tumour, plan, and treatment characteristics were retrieved from the database. All the plans were re-optimised with GrO and HIPO techniques for this comparison study. The different dosimetric parameters were compared between the two methods, and the collected data were tabulated and shown graphically. The statistical evaluation was performed with IBM SPSS version 26, and Origin Pro 8.5 was employed for plots.

HIPO plans show similar target coverage in terms of D 90(%), V 95(%) and conformity index with no significant statistical difference from the GrO plans with an acceptable increase in homogeneity index (0·087 ± 0·062%). It succeeds in achieving a statistically significant reduction of dose to organs at risk such as D0·1 cc, D1·0 cc and D2·0 cc for the bladder (11·59%, 4·8% and 3·99%), rectum (41·33%, 16·9% and 16·05%) and sigmoid (20·97%, 13·53% and 11·21%), respectively, in comparison with GrO optimisation.

Considering the dosimetric outcome of 3D-based IVBT, it is suggested to adopt inverse optimisation techniques like HIPO over GrO to achieve higher quality treatment plan in terms of adequate target dose and lesser dose to OARs.

The purpose of this study is to investigate the feasibility of proton arc therapy (PAT) using the double-scattering MEVION-S250 proton system. The treatment planning and dose delivery parameters from PAT were compared with conventional treatment planning techniques.

PAT was simulated with multiple conformal and fixed-aperture beams (5–15) using the MEVION-S250-double-scattering proton system. Conformal apertures were simulated with the Eclipse-treatment-planning system: (a) using a static single aperture that provides the best average conformal circular or rectangular apertures to cover the tumour from different angular views (SPAT), and (b) dynamic conformal apertures of the tumour shape at each irradiation angle that can be obtained from a multi-leaf-collimator system (DPAT).

The DPAT and SPAT plans provided superior dose coverage and sparing of normal tissues in comparison with conventional plans (CPT). The entrance normal tissue and skin doses (<40%) were lowered significantly by delivering dose from different directions over a wider angular view compared to conventional plans that have large entrance dose from only two fields. While the mean and minimum doses from PAT and CPT were comparable, the maximum doses from arc plans were lower than the maximum doses in conventional plans. The SPAT and DPAT plans had comparable dose parameters for regularly shaped targets. The heterogeneity index (HI) was superior in PAT plans which improved with increasing number of beams in arc plans for the different treatment sites. The conformality index (CI) depends on the treatment site and complexity of the shape of the planning target volume where for brain, pancreatic and lung tumours, PAT plans conformality was comparable and sometimes superior to CPT; and HI and CI were generally better in DPAT compared to SPAT.

PAT plans have superior dose coverage and sparing of normal tissues compared to CPT plans using the MEVION double-scattering system as shown in this simulation study. Ideally, conformal proton arcs require beam shaping and dose delivery with the gantry moving; however, the MEVION double-scattering system lacks a multi-leaf collimator system and cannot deliver dose during gantry rotation. The single aperture conformal proton therapy technique is more time and cost effective compared with conventional techniques that are used currently with the MEVION proton therapy system because of the elimination of the need for patient-specific compensators. In present study, PAT was simulated with the MEVION double-scattering proton therapy system; however, it can be performed also with other proton therapy systems.

To analyse the presentation, diagnosis and patterns of care of extraosseous Ewing sarcoma treated at our institution between 2008 and 2018.

Electronic medical records of extraosseous Ewing sarcoma patients treated at our institution between January 2008 and April 2018 were reviewed. Kaplan–Meier curves were plotted to assess the overall and disease-free survival with 95% confidence intervals. A univariate analysis was carried out to assess the impact of variables such as surgical excision, completeness of surgery, completeness of chemotherapy and addition of radiation therapy on the survivorship.

The records of 65 patients treated at our institution were available for review. The mean age was 26·4 years. The most frequent sites of extraosseous Ewing tumour were kidney—9/65 (13·8%) and brain—10/65 (15·4%). Sixteen (24·6%) patients presented with inoperable/metastatic disease at diagnosis. The other 49 (75·4%) had localised disease at presentation. The median overall survival of the 49 non-metastatic patients was 46 months, and the disease-free survival was 45 months.

Extraosseous Ewing sarcoma is a rare and aggressive tumour diagnosed by molecular techniques. Multi-modality treatment including surgical resection with wide margins, adjuvant radiation when indicated and completion of systemic chemotherapy results in optimum outcomes.

Head and neck cancer (HNC) accounts for 5% of all new cancer cases and most were locally advanced. Positron emission tomography/computed tomography (PET/CT) in radiotherapy practice in locally advanced head and neck squamous cell carcinoma (HNSCC) is being used in staging and proper contouring. Proper staging is essential for accurate treatment decision.

This is a prospective phase II study conducted as a single institute centre to evaluate the role of PET/CT-treatment in staging, contouring and response evaluation of 30 patients with locally advanced HNSCC in contrast to CT scan. Our cases did not undergo radical surgery for the primary tumour, and biopsy was taken with PET/CT post-treatment to evaluate response.

Median age of patients was 49·4 years (minimum age of 32 years and maximum of 68 years). Males were predominant 22 (73·3%). Nasopharynx was the predominant site 16/30 (53·3%). PET/CT changed the overall staging in 40% of the patients (upstaged in 36·7% and downstaged in 3·3%). Gross tumour volume (GTV) of PET/CT was smaller in 23 patients (76·7%) and larger in 5 (16·7%) than the GTV of conventional CT, whereas GTV of lymph nodes of PET/CT was larger in 20 patients (67·7%) and smaller in 4 (13·3%). PET/CT study detected bone metastasis in two nasopharyngeal carcinoma patients and two cases of 2nd primary tumours which were not detected using conventional CT. The Cox-regression model showed that the median standardised uptake volume (SUV) of the initial tumour had been a dependent predictor of death in patients with HNSCC (p-value = 0·033) where the risk of death was 0·725 times among patients with high SUV of the initial tumour. Consequently, the size of GTV of the tumour was significant in the prediction of death (p = 0·018).

18F-FDG-PET/CT is useful for staging, radiotherapy delineation as well as aiding proper decision making, in addition to assessment of treatment response in HNSCC patients.