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Skin care practices for radiotherapy patients are complicated by dosimetric concerns. This study measures the effect on skin dose of various topical agents and dressings.
Materials and methods
Superficial doses were measured under 17 topical agents and dressings and three clinical materials for reference. Dose was measured using a MOSFET detector under a 1 mm polymethyl methacrylate slab, with 6 MV photon beams at 100 cm source to surface distance.
Relative skin dose under reference materials was 128% (thermoplastic mask), 158% (5 mm bolus) and 171% (10 mm bolus). Under a realistic application of topical agent (0·5 mm), relative skin doses were 106–111%. All dry dressings yielded relative dose of ≤111%; two wet dressings yielded higher relative doses (133 and 141%).
Under clinically relevant conditions, no cream, gel or dry dressing increased the skin dose beyond that seen with a thermoplastic mask. Dressings soaked with water produced less skin dose than 5 mm bolus. This may be unacceptable if wet dressings are in place for the majority of the treatment course. Our results suggest that skin care practices should not be limited by dosimetric concerns when using a 6 MV photon beam.
To assess the feasibility of a randomised controlled trial (RCT) on patients receiving radical radiotherapy for carcinoma of the anus in order to compare the present skincare advice at the time of the study with an alternative product, Aveeno, used primarily for dermatological and chemotherapeutic-induced skin conditions.
Materials and method
Standardised Radiation Therapy Oncology Group (RTOG) grading and skincare assessments were used primarily to inform on physical reactions within a RCT. A pre-existing morbidity/quality-of-life instrument ‘the Head and Neck Radiotherapy Questionnaire’, which was validated for use with radiotherapy patients in preceding studies, was adapted for anus patients and formed the secondary basis for data collection. In all, 24 participants undergoing radical radiotherapy for anal cancer were randomised into two arms, Aveeno cream versus Aqueous Cream BP, and reviewed weekly to collect data and perform analysis and Mann–Whitney U non-parametric statistical tests.
RTOG gradings for skin reactions were comparable week by week across the cohorts, with a baseline 100% of participants exhibiting RTOG 0 at week 1 in all areas, through to week 6 where both cohorts had progressed to higher RTOG grades. The Aveeno cohort, however, indicated a p-value approaching significance in regards to epidermal regeneration at follow-up 1 (p=0·0543). Questionnaires yielded diminishing responses as treatment progressed correlating with advancing RTOG grades, and exhibited increasing negativity in responses in correlation with advancing RTOG grade exhibited.
The study was the first to recognise colloidal oatmeal as a skincare approach in the radiotherapy setting and recognises the potential benefits of Aveeno in radiation-induced skin reactions. The study determined the RTOG grading system to be robust as a method of evaluation of skin reactions and the questionnaires deemed the quality-of-life assessment to be a necessity in order to address patients’ psychological needs in addition to the physical needs.
It is unclear whether body mass index (BMI) is a useful measurement for examining prostate motion. Patient’s subcutaneous adipose tissue thickness (SAT) and weight has been shown to correlate with prostate shifts in the left/right direction. We sought to analyse the relationship between BMI and interfraction prostate movement in order to determine planning target volume (PTV) margins based on patient BMI.
Materials and methods
In all, 38 prostate cancer patients with three implanted gold fiducial markers in their prostate were recruited. Height, mass and SAT were measured, and the extent of interfraction prostate movement in the left/right, superior/inferior and anterior/posterior directions was recorded during each daily fiducial marker-based image-guided radiotherapy treatment. Mean corrective shift in each direction for each patient, along with BMI values, were calculated.
The median BMI value was 28·4 kg/m2 (range 21·4–44·7). Pearson’s product-moment correlation analysis showed no significant relationship between BMI, mass or SAT and the extent of prostate movement in any direction. Linear regression analysis also showed no relationship between any of the patient variables and the extent of prostate movement in any direction (BMI: R2=0·006 (ρ=0·65), 0·002 (ρ=0·80) and 0·001 (ρ=0·86); mass: R2=0·001 (ρ=0·87), 0·010 (ρ=0·54) and 0·000 (ρ=0·99); SAT: R2=0·012 (ρ=0·51), 0·013 (ρ=0·50) and 0·047 (ρ=0·19) for shifts in the X, Y and Z axis, respectively). Patients were grouped according to BMI, as BMI<30 (n=25, 65·8%) and BMI≥30 (n=13, 34·2%). A two-tailed t-test showed no significant difference between the mean prostate shifts for the two groups in any direction (ρ=0·320, 0·839 and 0·325 for shifts in the X, Y and Z axis, respectively).
BMI is not a useful parameter for determining individualised PTV margins. Gold fiducial marker insertion should be used as standard to improve treatment accuracy.
To evaluate the impact of leg position on the dose distribution during intracavitary brachytherapy for cervical cancer.
Patients and methods
This prospective study was performed on 11 women with cervical cancer who underwent intracavitary brachytherapy. After insertion of the brachytherapy applicator, two sets of computed tomography slices were taken including pelvis, one with straight leg and one with leg flexion position with knee support. The dose (7 Gy) was prescribed to point A. The radiotherapy plan was run on the Plato Planning Software System V14·1 to get the dose distributions. Also, rectum and bladder doses were measured for both leg positions during the treatment. The doses and volumes of organs were compared via the Wilcoxon signed-rank test by using Statistical Package for the Social Sciences 11·5 statistical software.
No significant difference regarding the dose distributions and volumes of target, sigmoid and bladder due to leg position was observed, either on 3D planning or on in vivo dose measurements. However, there were significant differences for 25 and 50% isodose coverage of rectum in favour of straight leg position (p=0·026). There were no significant differences regarding maximum doses in any critical organ.
Difference in leg position caused only a small change in rectum dose distribution and did not cause any other change in either dose distributions or in vivo measured doses of both target and critical organs during cervical brachytherapy. Straight leg position appears better with regard to rectum dose.
Treatment tabletops are usually made of carbon fibre due to its high mechanical strength and rigidity, low specific density, extremely light and regularly considered radiotranslucent. Our clinic acquired a Calypso 4D Localization System where electromagnetic (EM) frequencies to detect implanted transponders in the patient are used. Carbon fibre is an electrical conductive material which interferes with EM frequencies. Therefore, in order to be able to use the Calypso System the carbon fibre tabletop in the treatment room must be replaced. It is our goal to determine the attenuation of the new, non-carbon fibre, tabletop in treatment delivery.
Materials and Methods
Measurements were performed using an ionisation chamber inserted in a slab phantom positioned at the isocenter for 6, 10 MV, 6 and 10 flattening filter free (FFF) MV photon beams. These measurements were performed with and without tabletop for 0°, 30° and 60° beam angle for a True Beam STx linac, for 5×5 cm2 and 10×10 cm2 field size beams. The attenuation was calculated for each measurement for each tabletop.
At 0° incidence on the Exact IGRT Couch, the measured attenuation for 10×10 cm2 was 2·8 and 2·1% for 6 and 10 MV beams, respectively. For the same field size was measured 3·3 and 2·6% attenuation for 6 and 10 FFF MV beams, respectively. At the same incidence and regarding the other tabletops, the calculated attenuation is lower. For 10×10 cm2 field, there is 2·0, 1·4, 2·1 and 2·6% attenuation for 6, 10 MV, 6 and 10 FFF MV energy beams on the kVueTM Universal Couch. For the KvueTM Calypso® Couch 10×10 cm2 irradiation field, the measurements were 1·6, 1·3, 1·9 and 1·5%, respectively. This tendency is observed for all gantry angles.
The attenuation outputs were definitely higher for the Varian Exact IGRT Couch when compared with the kVue tabletops. The attenuation measurements for the kVue tabletops were closer to each other. Nevertheless kVueTM Calypso® Varian tabletop showed smaller mean attenuation of the beams than kVueTM Universal Tip Insert for all measurements.
There was no loss in treatment quality administration due to beam attenuation in the tabletop when tabletops were exchanged because of Calypso system integration. There is no need to change between kVue tabletops whenever there is a regular treatment or a Calypso System guided treatment.
To determine if a patient’s breast size accurately correlates with the breast volume measured in the computed tomography (CT) scan, and to determine which sizes correspond to a volume >750 cc; in order to predict which patients will benefit from breast irradiation in the prone position.
Breast size was calculated as the difference between the thoracic (band) and breast (bust) circumferences. Breast volume was contoured by a radiation oncologist and measured on the simulation CT scan. Pearson’s coefficient was used to evaluate the correlation between both variables. A receiver operating characteristic (ROC) analysis was performed to determine the optimal cut-off point to predict which differences between band and bust would be associated with a volume ≥750 cc.
Fifty-nine patients were included in this study. Mean breast volume was 851·8 cc and mean size difference was 4·7 inches. Pearson’s correlation coefficient was 0·61 (p<0·001). The ROC analysis determined that a difference of 5 inches between the band and bust circumferences was the optimal cut-off point to determine a breast volume of 750 cc.
A significant correlation between breast size as measured in the clinical practice and breast volume measured in the CT scan was found. Among other characteristics, a 5-inch difference between breast band and bust will be the cut-off point to decide if a patient will be treated prone at our institution.
Indeterminate pulmonary nodules incidentally detected during radiological imaging completed for radiotherapy planning always creates dilemma for the oncologist. The purpose of this study is to evaluate the clinical significance of pulmonary nodules incidentally detected in patients undergoing locoregional radiotherapy for breast cancer and present a retrospective analysis of the natural progression of such nodules.
A retrospective review of computed tomography scans of breast cancer patients who underwent radiotherapy over a period of 3 years to screen out patients with indeterminate lung nodules was undertaken. This was correlated with the patient and tumour characteristics and the status of the disease at last follow-up.
Of the 132 patients reviewed 28 had indeterminate lung nodules. Of the 28 patients, four had progressive lung nodules on follow-up. Subgroup analyses did not show any significant correlation.
Discussion and conclusion
One fifth of patients may present with incidentally detected lung nodules. Multiple nodules, ER negative status and locally advanced breast cancer may point to a higher risk of these nodules progressing to metastatic cancer. There is no indication to stop locoregional therapy in the presence of indeterminate nodules, but close follow-up of high-risk group is recommended.
The aim of this study is the dosimetric verification and comparative analysis of two different treatment planning systems (TPS) using collapsed cone convolution (CCC) and pencil beam (PB) algorithms for treatment sites of head and neck, chest wall–supraclavicular region, lung and prostate.
Methods and materials
Target volumes and critical organs for treatment sites mentioned above were delineated according to relevant The Radiation Therapy Oncology Group protocols. Treatment plans were generated using 6 MV photon energy with medical linear accelerator and Thermoluminescent Dosimeter-100 dosimeters were used to perform dosimetric verification, which were placed at appropriate locations in the Alderson Rando phantom.
Results and conclusions
Comparative analysis of CCC and PB algorithms for treatment sites revealed that point dose measurement values were higher with the PB algorithm compared with CCC algorithm, in both head and neck and chest wall–supraclavicular region plans. The most significant difference between two algorithms were found at the supraclavicular region which includes the lung point dose within the treatment field and 7–12 mm depth from the skin, respectively. Unlike the head and neck and chest wall–supraclavicular region plans, CCC and PB algorithms show overall comparable results in lung and prostate plans in terms of point dose measurement values; however, the most prominent difference was found in 7 mm and 6 cm depth from skin, respectively. The CCC algorithm values were higher. Our study confirms that the main reason of PB algorithm calculates less absorbed dose than CCC algorithm in medium transitions, skin entrance and irregular treatment regions is the underestimation of lateral equilibrium’s contribution to the total absorbed dose.
Intraoperative radiotherapy is a method of choice to deliver a critical radiation dose to the tumour bed immediately after surgical excision.
The purpose of this work is to check the dose delivered to the patients during intraoperative electron beam radiation therapy (IOERT) in the conservative treatment of breast cancer, by means of reference dose measurement using radiochromic (EBT-2) films.
Material and methods
Ninety patients with early-stage breast cancer underwent exclusive IOERT to the tumour bed using a LIAC linear accelerator. Absolute dose measurements were done with film pieces. After irradiation, the pixel values of the films were obtained via MATLAB and ImageJ softwares. Calibration curve was also used for calculating net optical density. Expected dose was compared to the patient delivered dose.
The mean deviation of the delivered dose from the expected one was 2·56% that is well in the accepted criteria. Only in one case, there was a larger deviation due to barometer miscalibration.
EBT-2 film response is independent from dose-per-pulse and as it was shown in this study it can be robustly used during breast IOERT for dosimetric and also positioning verifications.
Pre-registration teaching of radiotherapy planning in a non-clinical setting should allow students the opportunity to develop clinical decision-making skills. Students frequently struggle with their ability to prioritise and optimise multiple objectives when producing a clinically acceptable plan. Emerging software applications providing quantitative assessment of plan quality are designed for clinical use but may have value for teaching these skills. This project aimed to evaluate the potential value of automated feedback to second year BSc (Hons) Radiotherapy students.
Materials and methods
All 26 students studying a pre-registration radiotherapy planning module were provided with automated prediction of relative feasibility for left lung tumour planning targets by planning metrics software. Students were also provided with interim quantitative reports during the development of their plan. Student perceptions of the software were gathered using an anonymous questionnaire. Independent blinded marking of plans was performed after module completion and analysed for correlation with software-assigned marks.
In total, 25 plans were utilised for marking comparison and 16 students submitted feedback relating to the software. Overall, student feedback was positive regarding the software. A ‘strong’ Spearman’s rank-order correlation (rs=0·7165) was evident between human and computer marks (p=0·000055).
Automated software is capable of providing useful feedback to students as a teaching aid, in particular with regard to relative feasibility of goals. The strong correlation between human and computer marks suggests a role in benchmarking or moderation; however, the narrow scope of assessment parameters suggests value as an adjunct and not a replacement to human marking.
In our study basic dosimetric properties of a flattening filter free 6 MV photon beam shaped by multileaf collimators (MLC) is examined using the Monte Carlo (MC) method.
Methods and Materials
BEAMnrc code was used to make a MC simulation model for 6 MV photon beam based on Varian Clinic 600 unique performance linac, operated with and without a flattening filter in beam line. Dosimetric features including central axis depth dose, beam profiles, photon and electron spectra were calculated and compared for flattened and unflattened cases.
Dosimetric field size and penumbra were found to be smaller for unflattened beam, and the decrease in field size was less for MLC shaped in comparison with jaw-shaped unflattened beam. Increase in dose rate of >2·4 times was observed for unflattened beam indicating a shorter beam delivery time for treatment. MLC leakage was found to decrease significantly when the flattening filter was removed from the beam line. The total scatter factor showed slower deviation with field sizes for unflattened beam indicating a reduced head scatter.
Our study demonstrated that improved accelerator characteristics can be achieved by removing flattening filter from beam line.
Jugulotympanic glomus tumours (JTGT) are highly vascular neoplasms composed of paraganglionic tissue of neural crest origin. Because of the neoplasm’s slow growth potential, any claimed efficacy associated with applied treatment must be supported by long-term effects observed in patients.
This report presents a case of advanced stage JTGT in a 66-year-old woman treated by γ knife radiosurgery (GKRS).
Sustained tumour control with preservation of lower cranial nerve function was observed for more than 10 years after completion of treatment.
GKRS even with large intracranial extension of JTGT in patients may help to achieve long-term disease control with minimal morbidity.
We report a unique presentation of a late side effect associated with stereotactic body radiation therapy (SBRT) of the lung.
The case of a 65-year-old male who developed left-sided vocal cord paralysis after two courses of SBRT for squamous cell lung carcinoma is presented. The patient developed this late toxicity 15 months after his second treatment, which was to address a recurrence in the perihilar region of the left upper lobe.