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The Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) reported that the risks of breast cancer treatment in woman smokers may outweigh the benefits. The data used doses from published reports using a variety of treatment techniques. In our study, the risks of lung cancer and heart disease were determined from a modern era tangential-only technique.
Methods and materials
Doses to the lung and heart were obtained for tangential radiotherapy to the breast or chest wall. The risk of lung cancer incidence and cardiac mortality were calculated by taking the ratio of our doses to those published by the EBCTG.
A total of 77 women were identified meeting our inclusion criteria. The mean combined whole lung dose was 2·0 Gy. The mean whole heart dose was 0·9 Gy. The estimated risk of lung cancer and cardiac mortality in a 50-year-old life-long smoker was estimated to be 1·5 and <1%, respectively.
Tangential only radiotherapy delivered substantially lower doses to the combined whole lung and whole heart than those reported by the EBCTCG. In this cohort, the risks of radiation induced lung cancer and heart disease are outweighed by the benefits of radiotherapy even in those that are smokers.
To evaluate the extent to which intensity-modulated arc therapy (IMAT) for high-grade gliomas is comparable with three-dimensional conformal radiotherapy (3DCRT) in relation to the dose delivered to normal brain tissue (NBT), planning target volume (PTV) conformity and the dose delivered to brainstem and optic chiasma.
A total of 16 randomly selected 3DCRT treatment plans of grade 3 gliomas were re-planned using an IMAT planning technique and dose–volume histograms were compared. Primary outcomes were maximum, mean, 1/3 and 2/3 doses to NBT outside the PTV. Also the maximum, mean, D50 and D20 doses to PTV. Secondary outcomes were maximum and mean doses to the brainstem and optic chiasm. Wilcoxon signed rank test was used to compare data.
IMAT led to a statistically significant increase in mean dose to NBT (34·4 versus 33·3 Gy, (p=0·047) but a statistically significant reduction in maximum dose to NBT (62·7 versus 63·8 Gy, p=0·004) compared with 3DCRT. IMAT led to statistically significant reductions in maximum, D50 and D20 doses to the PTV (63·3 versus 64·7 Gy, p=0·001; 60·0 versus 60·7 Gy, p=0·001 and 60·5 versus 61·8 Gy, p=0·002, respectively). No statistically significant differences were seen in doses to brainstem and optic chiasm.
IMAT is at least comparable with 3DCRT in relation to minimising dose to NBT and ensuring good PTV conformity. Doses delivered to organs at risk using IMAT were also comparable with 3DCRT. This study supports the continued use of IMAT for the treatment of high-grade gliomas.
This study compared the pattern of radiation induced parotid changes between conventional (ConRT) and intensity modulated radiotherapy (IMRT) in nasopharyngeal carcinoma patients.
56 adult NPC patients treated with IMRT (n=28) and conventional radiotherapy (n=28) were recruited. CT scans were acquired before radiotherapy, at 10th, 20th and 30th fractions, and 3 months after treatment. Parotid gland was delineated in the corresponding CT slices and its mean dose was calculated. The volumetric and geometric changes of the parotid gland at various time intervals were compared against the pre-treatment structure set. The pattern of changes was compared between the two techniques.
The mean parotid dose of IMRT (37.5±9.5 Gy) was significantly lower than ConRT (49.1±7.4 Gy). The parotid gland volume, DICE similarity coefficient and lateral dimension of patient head gradually decreased during the radiotherapy course and partially recovered in 3 months post-treatment. The differences between two groups were not significant until at 3 month after treatment, where IMRT showed significantly better volume recovery.
Similar parotid gland size and location changes were observed during the treatment course in both ConRT and IMRT. However IMRT demonstrated better parotid volume recovery after treatment.
The accuracy of two calculation algorithms of the Varian Eclipse treatment planning system (TPS), the electron Monte Carlo algorithm (eMC) and general Gaussian pencil beam algorithm (GGPB) for calculating peripheral dose distribution of electron beams was investigated.
Peripheral dose measurements were carried out for 6, 9, 12, 15, 18 and 22 MeV electron beams using parallel plate ionisation chamber and EBT3 film in the slab phantom. Measurements were performed for 6×6, 10×10 and 25×25 cm2 cone sizes at dmax of each energy up to 20 cm beyond the field edges. The measured and TPS calculated data were compared.
The TPS underestimated the out-of-field doses. The difference between measured and calculated doses increase with the cone size. For ionisation chamber measurement, the largest deviation between calculated and measured doses is <4·29% using the eMC, but can increase up to 8·72% of the distribution using GGPB. For film measurement, the minimum gamma analysis passing rates between measured and calculated dose distributions for all field sizes and energies used in this study were 91·2 and 74·7% for eMC and GGPB, respectively.
The use of GGPB for planning large field treatments with 6 MeV could lead to inaccuracies of clinical significance.
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.
Materials and methods
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.
Small field dosimetry is complicated and accuracy in the measurement of total scatter factor (TSF) is crucial for dosimetric calculations, in making optimum intensity-modulated radiotherapy plans for treating small target volumes. In this study, we intended to determine the TSF measuring properties of CC01 and CC04 detectors for field sizes ranging from sub-centimetre to the centimetre fields.
Material and methods
CC01 and CC04 chamber detectors were used to measure TSF for 6 and 18 MV photon beam delivered from the linear accelerator, through small fields in a water phantom. Small fields were created by collimator jaws and multi-leaf collimators separately, with field sizes ranging from 0·6 to 10 cm2 and 0·5 to 20 cm2, respectively.
CC01 measured TSF at all the given field sizes created by jaws and multi-leaf collimators for both 6 and 18 MV beams whereas CC04 could not measure TSF for field sizes <1 cm2 due to volume averaging and perturbation effects.
CC01 was shown to be effective for measurement of TSF in sub-centimetre field sizes. CC01 can be employed to measure other dosimetric quantities in small fields using different energy beams.
This is a retrospective study to evaluate the efficacy and safety of routine use of electronic portal imaging device (EPID) in intensity-modulated radiation therapy for localised prostate cancer.
Materials and methods
Data from 20 patients with localised prostate cancer treated by radical radiotherapy using intensity-modulated technique in Habib Bourguiba Hospital were analysed to define the action levels for pretreatment planer dose distribution of 100 treatment fields and the set-up errors of 418 portal imaging. Pretreatment planar dose distribution was measured with the EPID. The additional dose from repeated portal imaging was determined with treatment planning system.
For all 100 fields, the predicted and the measured planar dose distribution agrees well with mean±standard deviation value for γmax=2·31±0·57, γavg=0·36±0·07 and γ%≤1=98·94%±0·71%, respectively. For the evaluation of set-up errors, the mean total errors with 1 SD in the lateral, longitudinal and vertical directions were 0·11±0·44 cm; 0·02±0·37 cm and −0·02±0·21 cm, respectively. The imaging additional dose was evaluated as 1 cGy per monitor unit.
EPID is a useful tool to verify pretreatment dose distribution and to assess the correct field position without a significant increase in the absorbed dose due to the repetition of portal imaging.
Monte Carlo calculation method is considered to be the most accurate method for dose calculation in radiotherapy. The purpose of this research is comparison between 6 MV Primus LINAC simulation output with commissioning data using EGSnrc and build a Monte Carlo geometry of 6 MV Primus LINAC as realistically as possible. The BEAMnrc and DOSXYZnrc (EGSnrc package) Monte Carlo model of the LINAC head was used as a benchmark.
In the first part, the BEAMnrc was used for the designing of the LINAC treatment head. In the second part, dose calculation and for the design of 3D dose file were produced by DOSXYZnrc. The simulated PDD and beam profile obtained were compared with that calculated using commissioning data. Good agreement was found between calculated PDD (1·1%) and beam profile using Monte Carlo simulation and commissioning data. After validation, TPR20,10, TMR and Sp values were calculated in five different field.
Good agreement was found between calculated values by using Monte Carlo simulation and commissioning data. Average differences for five field sizes in this approach is about 0·83% for Sp. for TPR20,10 differences for field sizes 10×10 cm2 is 0·29% and for TMR in five field sizes, the average value is ~1·6%.
In conclusion, the BEAMnrc and DOSXYZnrc codes package have very good accuracy in calculating dose distribution for 6 MV photon beam and it can be considered as a promising method for patient dose calculations and also the Monte Carlo model of primus linear accelerator built in this study can be used as method to calculate the dose distribution for cancer patients.
Across the history of radiotherapy, with gradual technological progress and various methods of irradiation, the purpose has always been to deliver homogeneously 100% of the prescribed dose to 100% of the target volume containing the identifiable tumour and/or tumour cells potentially present while limiting the dose to adjacent normal tissues.
Material and methods
The formula for triple point conformity scale is: CS3=(V95+V100+V105)/3VT. (a) Lower limit determination: CS3=(VT+0·93 VT+0·0)/3VT=0·643; (b) Upper limit determination: in order to find out an empirical relation in between V105 and VT, we studied over 593 cancer patients of various sites by taking planning target volume as target, and an empirical relation is derived out as: V105/VT=0·0007. Hence, CS3=(VT+VT+0·0007 VT)/3VT=0·6667~0·667.
Upper and lower limits of CS3 have been calculated at 0·643 and 0·667, respectively. Maximum value of CS3 index is recorded 0·656 while minimum value is 0·478.
The CS3 scale constitutes an attractive tool because it could facilitate decisions during analysis of various treatment plans proposed for conformal radiotherapy. Its major advantages are its simplicity and integration of multiple parameters.
The triple point conformity scale (CS3) provides better qualitative information about radiotherapy plans as compared to other conformity indices. This study advises the users to use the CS3 scale to evaluate a conformal radiotherapy plan which encompasses a wide range of relevant clinical volumes, and is able to extract qualitative dosimetric information.
To compare the dosimetric outcomes of linear accelerator-based stereotactic radiotherapy (SRT) techniques—static conformal field (SCF), static conformal arc (SCA) and dynamic conformal arc (DCA), for treating pituitary adenoma and craniopharyngioma.
Materials and methods
Computer image sets of 20 patients with pituitary adenoma or craniopharyngioma and treated with post-operative SRT were selected for this study. For each dataset, three SRT plans, with SCF, SCA and DCA techniques were generated using Brain LAB, iPlan RT V.4.5.3, TPS software. The conformity index (CI), homogeneity index (HI), quality of coverage of the target, dose–volume histograms for the target and organs at risk (OARs) and the time taken to deliver treatment was compared across three sets of plan.
There were 12 patients with pituitary adenoma and eight with craniopharyngioma. The CI and HI were comparable across three techniques. The quality of coverage was superior in DCA technique. OARs were better spared in SCF and DCA techniques. Time taken to deliver treatment was least in SCF technique.
The linac-based SRT techniques SCF, SCA and DCA are efficient in delivering highly conformal and homogenous dose to the target in pituitary adenoma and craniopharyngioma. Among these three techniques, SCF and DCA had acceptable quality of coverage. The dose received by OARs was least in the SCF technique.
This study deals with the characteristics of simultaneous photon and electron beams in homogenous and inhomogeneous phantoms by experimental and Monte Carlo dosimetry, for therapeutic purposes. Materials and methods: Both 16 and 20 MeV high-energy electron beams were used as the original beam to strike perforated lead sheets to produce the mixed beam. The dosimetry results were achieved by measurement in an ion chamber in a water phantom and film dosimetry in a Perspex nasal phantom, and then compared with those calculated through a simulation approach. To evaluate two-dimensional dose distribution in the inhomogeneous medium, the dose–area histogram was obtained.
The highest percentage of photon contribution in mixed beam was found to be 36% for 2-mm thickness of lead layer with holes diameter of 0·2 cm for a 20 MeV primary electron energy. For small fields, the percentage depth dose parameters variations were found to be similar to pure electron beam within ±2%. The most feasible flatness in beam profile was 11% for pure electron and 7% for the mixed beam. Penumbra changes as function of depth was about ten times better than in pure electron field.
The results present some dosimetric advantages that can make this study a platform for the production of simultaneous mixed beams in future linear accelerators (LINACs), which through redesign of the LINAC head, which could lead to setup error reduction and a decrease of intra-fractional tumour cells repair.
Cervical cancer is considered to be the fourth most frequent cancer among women. Postoperative treatment is indicated depending up on surgical findings and disease stage.
The objective of this study was to assess the long-term postoperative outcomes of cervical cancer patients with intermediate risk factors who have received pelvic external beam radiotherapy with or without vaginal brachytherapy, and treatment-related toxicities.
Patients and methods
In this retrospective study, the records were collected for all patients with cervical cancer who received postoperative radiotherapy at the National Cancer Institute between the years 2008 and 2013. The end points of the study were local control, progression-free survival, overall survival (OS) and delayed complications.
Out of 248 patients, the median age of patients who did not receive brachytherapy was 53 years and the median age of patients who received brachytherapy was 52 years. A statistically significant difference was found in OS, progression-free survival and recurrence-free survival for those who received brachytherapy, with a p value<0·001, 0·01 and 0·004, respectively.
The addition of brachytherapy to postoperative external beam radiotherapy improves OS, progression-free survival and local control for patients with intermediate-risk cervical cancer.
The aim of this study is to establish clinical evidence regarding the use of magnetic resonance imaging (MRI) in target volume definition for radiotherapy treatment planning of brain tumours.
Primary studies were systematically retrieved from six electronic databases and other sources. Studies included were only those that quantitatively compared computed tomography (CT) and MRI in target volume definition for radiotherapy of brain tumours. Study characteristics and quality were assessed and the data were extracted from eligible studies. Effect estimates for each study was computed as mean percentage difference based on individual patient data where available. The included studies were then combined in meta-analysis using Review Manager (RevMan) software version 5.0.
Five studies with a total number of 72 patients were included in this review. The quality of the studies was rated strong. The percentages mean differences of the studies were 7·47, 11·36, 30·70, 41·69 and −24·6% using CT as the baseline. The result of statistical analysis showed small-to-moderate heterogeneity; τ2=36·8; χ2=6·23; df=4 (p=0·18); I2=36%. The overall effect estimate was −1·85 [95% confidence interval (CI); −7·24, 10·94], Z=0·40 (p=0·069>0·5).
Brain tumour volumes measured using MRI-based method for radiotherapy treatment planning were larger compared with CT defined volumes but the difference lacks statistical significance.
In radiotherapy, electron beam irradiation is an effective modality for superficial tumours. Electron beams have good coverage of tumours which involve the skin, however there is an issue about electron scattering and tissue heterogeneity. This subsequently demands dosimetric analysis of electron beam behaviour, particularly in the treatment of lesions on the scalp requiring the application of treatment to scalp curvatures. There are various methods which are used to treat scalp malignancies including photons and electrons, but, the later needs precise dosimetry before each session of treatment. The purpose of the study was to undertake a detailed analysis of the dosimetry of electron beams when applied to the curved surface of the scalp using Gafchromic® EBT2 films.
Methods and materials
A rando phantom and Gafchromic® EBT2 films were used for dosimetric analysis. A gafchromic calibration curve was plotted and an in-treatment beam dosimetric analysis was carried out using dosimetry films placed on the scalp. Electron behaviour was assessed by introducing five electron fields in particular curvature regions of scalp.
There was an acceptable dose range through all five fields and hotspots occurred in the curved borders. In our study, skin doses and doses at the field junctions, with no gaps, were between 78–97% and 80–97%, respectively.
Electron beams are a good modality for treating one flat field, but in the special topography of the scalp, whole scalp treatment requires precise field matching and dosimetry. In undertaking this detailed dosimetric analysis using a rando phantom and Gafchromic® EBT2 films, it is concluded that this method requires further detailed analysis before using in clinics.
Nasopharyngeal carcinoma with local extension to the external auditory meatus is rarely reported.
We present two cases of nasopharyngeal carcinoma with invasion to the external auditory meatus. First case at initial presentation; and the second at disease recurrence. Both patients presented with unilateral otologic symptoms corresponding to the affected site; as well as being heavily node positive. Otoscopic examination and 18F-fluorodeoxyglucose positron-emission topography demonstrated the involvement of external auditory meatus.
These two cases highlight the need of careful otoscopic examination and functional imaging to diagnose such cases.