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It has been shown that patients with a greater tumour volume have poorer outcomes following definitive radiotherapy but its exact role remains unclear. The purpose of this study is to investigate the role of tumour volume as a prognostic indicator in non-small cell lung cancer (NSCLC) patients treated with definitive radiotherapy in a single institution over 10 years.
In total, 167 patients with NSCLC treated by definitive (chemo)radiotherapy were retrospectively reviewed between 2006 and 2015. Patient demographics, disease characteristics and tumour volume parameters were collected. Univariate analyses were carried out using Kaplan–Meier survival curves to assess the association of potential prognostic factors with the primary endpoints of overall survival (OS) rates and locoregional recurrence rates. Multivariate analyses were carried out using a Cox regression method.
The median total tumour volume (TTV), defined as the gross tumour volume plus the volume of involved nodes, was 103 cm3. Patients were divided into small and large tumour groups based on this median. OS rates at 1, 3 and 5 years for smaller volumes were 69%, 24% and 13% and for larger volumes 48%, 14% and 8%, respectively. On univariate survival analyses larger TTV was significantly associated with poorer OS (p = 0·019). The concurrent use of chemotherapy significantly improved survival (p = 0·026). Nodal involvement (p = 0·03) and Eastern Cooperative Oncology Group performance status (p < 0·001) were also significant independent prognostic factors of OS. On multivariate analysis TTV was strongly predictive of survival (p = 0·03; hazard ratio 1·702, 95% confidence interval 1·198–2·415). There was no association between nodal volume, tumour stages, overall stage, age, histology and radiation dose with any of the primary endpoints.
TTV is a significant prognostic factor in patients with advanced NSCLC treated by radical radiotherapy. In this cohort of patients TTV is more reliable at predicting survival than T stage and overall stage.
The purpose of this study was to evaluate the dosimetric impact of multileaf collimator (MLC) positional errors on dynamic intensity-modulated radiotherapy (IMRT) treatments through planning simulation. Secondly the sensitivity of IMRT MatriXX device for detecting the MLC leaf positional errors was also evaluated.
Materials and methods
In this study five dynamic IMRT plans, each for brain and head–neck (HN), were retrospectively included. An in-house software was used to introduce random errors (uniform distribution between −2·0 and +2·0 mm) and systematic errors [±0·5, ±0·75, ±1·0 and ±2·0 mm (+: open MLC error and −: close MLC error)]. The error-introduced MLC files were imported into the treatment planning system and new dose distributions were calculated. Furthermore, the dose–volume histogram files of all plans were exported to in-house software for equivalent uniform dose (EUD), tumour control probability and normal tissue complication probability calculations. The error-introduced plans were also delivered on LINAC, and the planar fluences were measured by IMRT MatriXX. Further, 3%/3 mm and 2%/2 mm γ-criteria were used for analysis.
In planning simulation study, the impact of random errors was negligible and ΔEUD was <0·5±0·7%, for both brain and HN. The impact of systematic errors was substantial, and on average, the maximum change in EUD for systematic errors (close 2 mm) was −10·7±3·1% for brain and −15·5±2·6% for HN.
It can be concluded that the acceptable systematic error was 0·4 mm for brain and 0·3 mm for HN. Furthermore, IMRT MatriXX device was able to detect the MLC errors ≥2 mm in HN and >3 mm errors in brain with 2%/2 mm γ-criteria.
To quantify the relationship between the planning target volume (PTV) dose homogeneity and organs at risk (OARs) sparing in correlation with anatomical parameters in prostate intensity-modulated radiotherapy (IMRT).
Materials and methods
Nine IMRT plans with various target dose constraints’ priorities were created for 15 prostate cancer patients. Selected PTV and OARs parameters were calculated for the patients. A trade-off was assessed between homogeneity index (HI) and OAR sparing. Several anatomical parameters were evaluated to investigate their effects on the OAR sparing and HI.
Inverse exponential relationships were found between the OAR sparing and HI (average R2 of 0·983 and 0·994 for bladder and rectum, respectively). Decreasing the priority led to more OARs sparing (normal tissue complication probability reduction: 97·6 and 74·5%; mean dose reduction: 16·3 and 11·3% for bladder and rectum, respectively) and worsening of the HI (0·095–0·322) but with no significant effect on tumour control probability. Furthermore, OARs volumes, distances between OARs and PTV and their joint volumes had stronger correlations with OARs’ mean doses.
Enforcement of target dose constraints was more effective on the improvement of HIs for the patients with initial high HI values at low dose constraints’ priorities. Reducing the priority had more effects on the OARs sparing compared to HI, especially for the patients with high OAR doses in high priority plans. This can be attributed to smaller distances or greater joint volumes between the OARs and PTV.
The purpose of this study is the verification of intensity modulated radiation therapy (IMRT) head neck treatment planning with one-dimensional and two-dimensional (2D) dosimeters using imaging and radiation oncology core (IROC) Houston head & neck (H&N) phantom.
The image of the H&N phantom was obtained by computed tomography scan which was then transferred to Pinnacle@3 treatment planning system (TPS) for treatment planning. The contouring of the target volumes and critical organ were done manually and dose constraints were set for each organ according to IROC prescription. The plan was optimised by adoptive convolution algorithm to meet the IROC criteria and collapse cone convolution algorithm calculated the delivered doses for treatment. Varian Clinac 2110 was used to deliver the treatment plan to the phantom, the process of irradiation and measurement were repeated three times for reproducibility and reliability. The treatment plan was verified by measuring the doses from thermoluminescent dosimeters (TLDs) and GafChromic external beam therapy 2 films. The agreement between the planned and delivered doses were checked by calculating the percentage dose differences, analysing their isodose line profiles and 2D gamma maps.
The average percent dose difference of 1·8% was obtained between computed doses by TPS and measured doses from TLDs, however these differences were found to be higher for organ at risk. The film dose profile was well in agreement with the planned dose distribution with distance to agreement of 1·5 mm. The gamma analysis of the computed and recorded doses passed the criteria of 3%/3 mm with passing percentages of >96%, which shows successful authentication of delivered doses for IMRT.
IMRT pre-treatment validation can be done with IROC anthropomorphic phantoms, which is essential for the delivery of modulated radiotherapies. It was concluded that films and TLDs can be used as quality assurance tools for IMRT.
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.
Materials and methods
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.
The treatment planning system (TPS) plays a key role in radiotherapy treatments; it is responsible for the accurate determination of the monitor unit (MU) needed to be delivered to treat a patient with cancer. The main goal of radiotherapy is to sterilise the tumour; however, any imprecise dose delivered could lead to deadly consequences. The TPS has a quality assurance tool, an independent program to double check the MU, evaluate patient plan correctness and search for any potential error.
Materials and methods
In this work, a comparison was carried out between a MU calculated by TPS and an independent in-house-developed monitor unit calculation program (MUCP). The program, written in Cplusplus (C++ Object-Oriented), requires a database of several measured quantities and uses a recently developed physically based method for field equivalence calculation. The ROOT CERN data analysis library has been used to establish fit functions, to extend MUCP use to a variety of photon beams. This study presents a new approach to checking MU correctness calculated by the TPS for a water-like tissue equivalent medium, using our MUCP, as the majority of previous studies on the MU independent checks were based on the Clarkson method. To evaluate each irradiated region, four calculation points corresponding to relative depths under the water phantom were tested for several symmetric, asymmetric, irregular symmetric and asymmetric field cases. A comparison of MU for each radiation fields from readings of the TPS and the MUCP was undertaken.
A satisfactory agreement has been obtained and within the required standards (3%). Additional experimental measurements of dose deposited in a water phantom showed a deviation of <1·6%.
The MUCP is a useful tool for basic and complex MU verification for 3D conformal radiation therapy plans.
The purpose of this study is to evaluate variation in the treatment hold pattern and quantify its dosimetric impact in breath-hold radiotherapy, using fraction-specific post-treatment quality assurance.
Material and Methods
A patient with lung mets treated using intensity-modulated radiation therapy (IMRT) with active breath coordinator (ABC) was recruited for the study. Treatment beam hold conditions were recorded for all the 25 fractions. The linearity and reproducibility of the dosimetric system were measured. Variation in the dose output of unmodulated open beam with beam hold was studied. Patient-specific quality assurance (PSQA) was performed with and without beam hold, and the results were compared to quantify the dosimetric impact of beam hold.
There was a considerable amount of variation observed in the number of beam hold for the given field and the monitor unit at which the beam held. Linearity and reproducibility of the dosimetric system were found within the acceptable limits. The average difference over the 25 measurements was 0·044% (0·557 to −0·318%) with standard deviation of 0·248.
Patient comfort with the ABC system and responsiveness to the therapist communication help to maintain consistent breathing pattern, in turn consistent treatment delivery pattern. However, the magnitude of dosimetric error is much less than the acceptable limits recommended by IROC. The dosimetric error induced by the beam hold is over and above the dose difference observed in conventional PSQA.
This is a prospective study to evaluate the dosimetric benefits of treatment plan adaptation for patients who had undergone repeat computed tomography (ReCT)and re-planning due to treatment-induced anatomical changes during radiotherapy.
Materials and Methods
This study involved five head and neck cancer patients who had their treatment plan modified, based on weekly thrice imaging protocol. Impact of mid-course imaging was assessed in patients using ReCT and cone beam computed tomography (CBCT)-based dose verification. Patients were imaged, apart from their initial CT, during the course of their radiation therapy with a ReCT and on board imager CBCT (Varian Medical Systems Inc., Palo Alto, CA, USA). Each CBCT/CT series was rigidly registered to the initial CT in the treatment planning system Eclipse (Varian Medical Systems Inc.) using bony landmarks. The structures were copied to the current CBCT/CT series and, where needed, manually edited slicewise. The dose distribution from the treatment plan was viewed as of the current anatomy by applying the treatment plan the CBCT/CT series, and studying the corresponding dose–volume histograms for organs at risk doses.
The reduction of parotid volumes due to weight loss was observed in all patients, which means an increase in predicted mean doses of parotid when initial CT plan was re-calculated on ReCT and CBCT (Table 1). This explains the necessity of adaptive planning. The predicted mean dose of parotid glands was increased and constraints to spinal cord and skin were exceeded, so re-planning was performed.
The CBCT is a useful tool to view anatomic changes in patients and get an estimate of their impact on dose distribution. Re-planning based on imaging in head and neck patients during the course of radiotherapy is mandatory to reduce side effects.
The aim of this study is to compare three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and tomotherapy techniques used in the treatment of prostate cancer with target and critical organ doses to be included.
Materials and Methods
The target dose was studied with 4-and 6-field 3D-CRT, 7-field IMRT and tomotherapy techniques used to treat ten patients for prostate cancer and the dose volume histograms of critical organs were analyzed. The same target volumes, critical organs doses prescribed and treatment times for the three techniques were compared. Total dose of 76 Gy was given using 6 MV and 18 MV for 3D-CRT, 6 MV for IMRT and tomotherapy techniques.
When we compare the three techniques, for rectum V35(p:0·001), V65(p:0·001), D50(p:0·020) and D25(p:0·002), for bladder V50(p:0·027), V65(p:0·006), V100(p:0·006) and for femoral head, the V50(p:0·001) dose was found to be significantly different and more favourable in the tomotherapy technique. Significant differences were found with IMRT planning in 50% of bladder volume (p:0·002). There is no significant difference between the three techniques for doses of 100% volume of rectum and 25% of volume of bladder. The minimum dose that healthy tissue received which was outside the tumour volume was investigated.
Doses to critical organs were lower using the tomotherapy technique. However, the minimum doses that healthy tissue received were higher for the tomotherapy technique. When the beam on times were compared for all three techniques, a significant difference was found in favor of tomotherapy.
The purpose of this study is to introduce a new approach to assess the dosimetry quality of photon beam with energy and irradiation field size. This approach is based on percentage depth dose (PDD) fragmentation for investigating the dosimetry quality.
Materials and methods
For the investigation of the dosimetry quality of 6 and 18 MV photon beams, we have proceeded to fragment the PDD at different field sizes. This approach checks the overall PDD and is not restricted to the exponential decay regions, as per the International Atomic Energy Agency Technical Reports Series No 398 and the American Association of Physicist in Medicine Task Group 51 recommendations.
Results and discussion
The 6 MV photon beam deposited more energy in the target volume than the 18 MV photon beam. The dose delivered by the 6 MV beam is greater by a factor of 1·5 than that delivered by the 18 MV beam in the build-up region and the dose delivered by the 6 MV beam is greater by a factor of 2·6 than that delivered by the 18 MV beam in the electronic equilibrium and the exponential decay regions.
The dose measured at different points of the beam is higher for 6 MV than for 18 MV photon beam. Therefore, the 6 MV beam is more dosimetrically efficient than the 18 MV beam. Using the proposed approach, we can assess the dosimetry quality by taking into account overall PDD not only in the exponential decay region but also in the field.
The main aim was to examine the effect of bit depth on computed tomography (CT) number for high-density materials. Analysis of the CT number for high-density materials using 16-bit scanners will extend the CT scale that currently exists for 12-bit scanners and thus will be beneficial for use in CT–electron density (ED) curve in radiotherapy treatment planning system (TPS). Implementation of this extended CT scale will compensate for tissue heterogeneity during CT–ED conversion in treatment planning.
Materials and methods
An in-house built phantom with 10 different metal samples was scanned using 80, 100 and 120 kVp in two different CT scanners. A region of interest was set at the centre of the material and the mean CT numbers together with data deviation were determined. Dosimetry calculation was performed by applying a direct anterior beam on 12-bit, 12-bit extended and 16-bit.
High-density materials (>4·34 g cm−3) in 16-bit depth provide disparities up to 44% compared to Siemens’ 12-bit extended. Influence of tube voltage showed a significant difference (p<0·05) in both bit depth and CT number of the gold and amalgam saturated in 16-bit depth. A 120 kVp energy illustrated a low variation on CT number for different scanners, but dosimetry calculation showed significant disparities at the metal interface in 12-bit, 12-bit extended and 16-bit.
High-density materials require 16-bit scanners to obtain CT number to be implemented in treatment planning in radiotherapy. This also suggests that proper tube voltage together with correct CT–ED resulted in accurate TPS algorithm calculation.
To evaluate the use of exercise in managing fatigue in breast cancer patients undergoing adjuvant radiotherapy. To explore the effectiveness of different exercise practices and explore how optimum management of fatigue might be achieved.
A CINAHL (Cumulative Index to Nursing and Allied Health Literature) database search of literature was undertaken and publications screened for retrieval with 24 qualifying for inclusion in the review.
There is evidence to support various forms of exercise including aerobic, resistance, alternative and combination exercise in the management of fatigue in early stage breast cancer patients undergoing adjuvant radiotherapy. The benefits of exercise for patients with later stage and metastatic disease is less clear and there is a lack of published research related to this category of patient.
Exercise is considered a safe, non-pharmacological intervention for early stage breast cancer patients receiving adjuvant radiotherapy. Further investigation is required into optimum exercise interventions and the effectiveness and viability of supervised and unsupervised models. Patient centred tailored advice and guidance needs to be developed and effectively promoted by therapeutic radiographers in order for patients to fully realise the benefit.
In this study, we undertake a dosimetric comparison of whole abdominal treatment plans of patients diagnosed with stage 3 Wilms tumour, to assess the benefits of treating these patients with volumetric arch therapy (VMAT) versus 3D conformal radiotherapy.
Material and methods
A retrospective study was undertaken on 23 patients receiving either VMAT or 3D conformal radiotherapy during 2013–2017. A dosimetric comparison was undertaken for both techniques, measuring planning target volume (PTV), conformity index (CI), homogeneity index (HI) and organs at risk (OAR).
The dosimetric parameters for the PTV dose in the VMAT and 3D conformal technique showed no statistical difference (1,289·17 cGy versus 1,357·13 cGy, respectively, p=0·404). However, the VMAT technique had a better CI (1·04 VMAT versus 1·26 3D, p=0·004), and there was little difference in the HI (1·13 VMAT versus 1·15 3D, p=0·1606). In the statistical analysis, the decrease in dose to OAR for the VMAT technique is statistically significant for doses to lung and kidney (p=0·011 and p=0·002, respectively). Between the two techniques, there was no statistical significance in dose difference to the other OAR.
This work proposes using the VMAT technique in whole abdominal irradiation to improve conformity, without affecting the quality of the PTV coverage, when compared with the 3D conformal technique. In addition, VMAT reduces the doses to OAR such as the remaining kidney and lungs that are important to preserve to reduce the probability of radiation toxicity in these patients.
To verify dose delivery and quality assurance of volumetric-modulated arc therapy (VMAT) for head and neck (H&N) cancer.
The Imaging and Radiation Oncology Core Houston (IROC-H) H&N phantom with thermoluminescent dosimeters (TLDs) and films, were imaged with computed tomography scan and the reconstructed image was transferred to pinnacle treatment planning system (TPS). On TPS, the planning target volume (PTV), secondary target volume (STV) and organ at risk (OAR) were delineated manually and a treatment plan was made. The dose constraints were determined for the concerned organs according to IROC-H prescription. The treatment plan was optimised using adoptive convolution algorithm to improve dose homogeneity and conformity. The dose calculation was performed using C.C Convolution algorithm and a Varian True Beam linear accelerator was used to deliver the treatment plan to the H&N phantom. The delivered radiation dose to the phantom was measured through TLDs and GafChromic external beam radiotherapy 2 (EBT2) films. The dosimetric performance of the VMAT delivery was studied by analysing percent dose difference, isodose line profile and gamma analysis of the TPS-computed dose and linac-delivered doses.
The percent dose difference of 3.8% was observed between the planned and measured doses of TLDs and a 1.5-mm distance to agreement (DTA) was observed by comparing isodose line profiles. Passed the gamma criteria of 3%/3 mm was with good percentages.
The dosimetric performance of VMAT delivery for a challenging H&N radiotherapy can be verified using TLDs and films embedded in an anthropomorphic H&N phantom.