External Beam Radiation Treatment Research Articles

Megavoltage Radiotherapy for the Treatment of Degenerative Joint Disease in Dogs: Results of a Preliminary Experience in an Italian Radiotherapy Centre.

The aim of the study was to evaluate the efficacy and toxicity of a low-dose radiotherapy treatment in dogs with osteoarthritis (OA). Inclusion criteria were dogs affected by OA of one or multiple joints, with lameness, previously treated with medical therapy and referred for radiotherapy because of chronic unresponsive pain. After suspension of medical therapy, dogs underwent external beam radiotherapy treatments delivered in three fractions of 2 Gy each. Four of these dogs had one (three dogs) to four (one dog) additional courses of radiation. Medical records were reviewed and follow-up information was collected by clinical recheck and owners interview. Twenty-five dogs matched the inclusion criteria; among them, 21 had one course of RT and 4 underwent multiple treatments, respectively 218, 266, 39, and 1,384 days after the first treatment. Clinical improvement was observed in 92% of patients with median benefit duration of 356 days after the first treatment, and 418 days after the second treatment. No side effects were recorded. In this group of patients, radiotherapy was effective, well tolerated, and repeatable, leading to an improvement of quality of life in dogs with degenerative joint disease unresponsive to medical treatments.

Multi-institutional evaluation of end-to-end protocol for IMRT/VMAT treatment chains utilizing conventional linacs

We conducted a multi-institutional assessment of a recently developed end-to-end monthly quality assurance (QA) protocol for external beam radiation therapy treatment chains. This protocol validates the entire treatment chain against a baseline to detect the presence of complex errors not easily found in standard component-based QA methods. Participating physicists from 3 institutions ran the end-to-end protocol on treatment chains that include Imaging and Radiation Oncology Core (IROC)-credentialed linacs. Results were analyzed in the form of American Association of Physicists in Medicine (AAPM) Task Group (TG)-119 so that they may be referenced by future test participants. Optically stimulated luminescent dosimeter (OSLD), EBT3 radiochromic film, and A1SL ion chamber readings were accumulated across 10 test runs. Confidence limits were calculated to determine where 95% of measurements should fall. From calculated confidence limits, 95% of measurements should be within 5% error for OSLDs, 4% error for ionization chambers, and 4% error for (96% relative gamma pass rate) radiochromic film at 3% agreement/3 mm distance to agreement. Data were separated by institution, model of linac, and treatment protocol (intensity-modulated radiation therapy [IMRT] vs volumetric modulated arc therapy [VMAT]). A total of 97% of OSLDs, 98% of ion chambers, and 93% of films were within the confidence limits; measurements were found outside these limits by a maximum of 4%, < 1%, and < 1%, respectively. Data were consistent despite institutional differences in OSLD reading equipment and radiochromic film calibration techniques. Results from this test may be used by clinics for data comparison. Areas of improvement were identified in the end-to-end protocol that can be implemented in an updated version. The consistency of our data demonstrates the reproducibility and ease-of-use of such tests and suggests a potential role for their use in broad end-to-end QA initiatives.

Ischaemic heart disease following conventional and hypofractionated radiation treatment in a contemporary breast cancer series.

We report the incidence of ischaemic cardiac toxicity in a contemporary cohort of patients receiving conventional (CFRT) or hypofractionated (HFRT) radiation after surgery for early breast cancer and investigate the interplay of cardiac risk factors and fractionation. Included were patients receiving external beam radiation treatment from 2002 to 2006 at the Christchurch public hospital. Hospital coding databases, oncology databases and medical records were reviewed for baseline characteristics, treatment details and outcomes. The primary outcome was cardiac toxicity (including myocardial infarction, admission for cardiac chest pain, coronary angiogram positivity and ischaemic cardiac death). Kaplan-Meier methods were used to derive ischaemic cardiac event free and overall survival. Predefined univariate and multivariate analysis was performed to investigate interaction with radiation fraction size, cardiac risk factors, age and side of cancer. Standardised mortality ratios were constructed. Five hundred and one patients were identified, 220 treated with CFRT and 281 with HFRT. The median age was 56 and median follow-up 10.33 years. The 10-year breast cancer specific survival was 81.8% (95% CI %.78.1-85.0). The 10-year freedom from cardiac death was 98.6% (95% CI 96.9-99.4). There were 27 post radiation cardiac events including 5 cardiac deaths and 19 cases of acute myocardial infarction. 265 (53%) had at least one cardiac risk factor. Twenty five of the 27 patients with a cardiac event had cardiac risk factors. On univariate and multivariate analysis, fractionation schedule was not significantly associated with a post radiation ischaemic event, however, there was a significant relationship with age and the presence of a cardiac risk factor. The standardised mortality ratio was 0.89 (95% CI: 0-3.13). Our study has shown a low rate of ischaemic cardiac disease for both CFRT and HFRT in women treated for breast cancer with no evidence of an effect with fractionation schedule. Coexisting cardiac risk factors are common in the population.

Complications of curative radiation treatment for early prostate cancer.

To report the incidence of urological complications following curative radiation treatment for early prostate cancer, including minimally invasive urological procedures (MUIP), hospital admissions and open surgical procedures. Second malignancies following radiation are also reported and compared with patients undergoing a prostatectomy. Included were patients receiving curative intent external beam radiation treatment for early prostate cancer between January 1, 2002, and December 31, 2009. Medical records were reviewed for baseline characteristics, treatment details and outcomes. Kaplan-Meier methods were used to derive the 5-year cumulative incidence of the urological outcomes and second malignancy. There were 439 patients identified. The median follow-up was 6.96 years. The median age was 69. A total of 56 patients developed a radiation related urological complication, 25 requiring hospital admission. The 5-year cumulative incidence for an MIUP and admission was 3.95% (95% confidence interval (CI), 2.47-6.28) and 2.24% (95% CI, 1.17-4.27), respectively. There were no open surgical procedures. Further malignancy developed in 27 patients during the 5- to 9-year posttreatment period with a cumulative incidence of 10.7% (95% CI, 7.31-15.51). Of the comparator prostatectomy group, of the 265 eligible patients analyzed, 19 patients developed a second malignancy with a cumulative incidence of 9.92% (95% CI, 6.28-15.48). On log-rank testing, there was no difference in the cumulative incidence rates of second malignancy between 5 and 9 years, following respective treatments (P=0.8554). The incidence of MUIP, hospital admissions and open surgical procedures following radiation is reassuringly low. The second malignancy rates are also low and similar to the rates in patients treated with a prostatectomy.

A comparison of early prostate-specific antigen decline between prostate brachytherapy and different fractionation of external beam radiation—Impact on biochemical failure

PurposeThe aim of this study was to compare early prostate-specific antigen (PSA) decline patterns and PSA nadirs between low-dose-rate seed prostate brachytherapy (LDR-PB) and different fractionations of external beam radiotherapy (EBRT) and their predictive importance for biochemical failure (bF). Methods and MaterialsPatients with D'Amico low- or intermediate-risk prostate cancer who underwent a single-modality treatment without androgen deprivation were included in this study. Three different treatment groups were compared: (1) normofractionation EBRT up to 70.2–79.2 Gy/1.8–2.0 Gy, (2) LDR-PB, and (3) EBRT with hypofractionation 60 Gy/3 Gy daily or 5–7.25 Gy once a week over 9–5 weeks, to a total dose of 45–36.25 Gy, respectively. The log-rank test, Cox regression analysis, and nonparametric tests were used. ResultsWe analyzed 892 patients: the median followup for patients without bF was 84 months (interquartile range 60–102 months), with 12% of patients experiencing bF. The PSA decline within the first 15 months was generally exponential. LDR-PB showed a faster early exponential decline compared with EBRT treatments, but whether decline was fast or slow had no influence on recurrence. The only factors that were positive predictive factors in univariate and multivariate analyses were the time to nadir >48 months (median), PSA nadir <0.5 ng/mL, and <0.2 ng/mL (all p < 0.001). ConclusionsAlthough there are significant differences in early exponential PSA decline between different treatments, only the PSA nadir and longer time to nadir were predictive factors for bF.

Efficacy and the toxicity of the interstitial high-dose-rate brachytherapy in the management of recurrent keloids: 5-year outcomes

PurposeRecurring keloids are a clinical challenge. Interdisciplinary treatments are required in most cases. Owing to the wide variety of concepts, the optimal treatment regime remains unclear. Our clinic established a protocol of perioperative interstitial high-dose-rate brachytherapy with three fractions of 6 Gy and achieved an excellent 2-year local control rate of 94% (In search of the optimal treatment of keloids: Report of a series and a review of the literature). This report is an update on our long-term results of prospective study. Twenty-nine patients were included with a median followup of 5 years. Methods and MaterialsFrom 2009 to 2015, 29 patients with 37 recurrent keloids were treated with perioperative interstitial high-dose-rate brachytherapy; 3 patients had been previously treated with adjuvant external beam radiotherapy and presented with recurrences in the pretreated area. Brachytherapy was given in three fractions with a single dose of 6 Gy in 5-mm tissue depth and covered the scar in total length. Followup visits were scheduled at 6 weeks, 3 months, 6 months, 1 year, and annually thereafter. Therapeutic outcome was assessed in terms of recurrence, acute and late complications, and cosmetic results. ResultsNo procedure-related complications occurred. Improvement of keloid-related symptoms was noticed in all patients after treatment. After a median followup of 49.7 months (range: 7.9–91.9 months), three keloid recurrences and two hypertrophied scars were observed. ConclusionsOur results suggest that brachytherapy may be advantageous in the management of high-risk keloids, even after failure of external beam radiotherapy and other treatment procedures. Our three-fraction treatment schedule reduces the treatment period to 2 days and is therefore convenient for the patients.

Role of deformable image registration for delivered dose accumulation of adaptive external beam radiation therapy and brachytherapy in cervical cancer.

PurposeDeformable image registration (DIR) can be used to accumulate the absorbed dose distribution of daily image-guided adaptive external beam radiation treatment (EBRT) and brachytherapy (BT). Since dose-volume parameter addition assumes a uniform delivered EBRT dose around the planned BT boost, the added value of DIR over direct addition was investigated for dose accumulation in bladder and rectum.Material and methodsFor 10 patients (EBRT 46/46.2 GyEQD2, EBRT + BT: D90 85-90 GyEQD2, in equivalent dose in 2 Gy fractions), the actually delivered dose from adaptive volumetric-modulated arc therapy (VMAT)/intensity-modulated radiotherapy (IMRT) EBRT was calculated using the daily anatomy from the cone-beam computed tomography (CBCT) scans acquired prior to irradiation. The CBCT of the first EBRT fraction and the BT planning MRI were registered using DIR. The cumulative dose to the 2 cm3 with the highest dose (D2cm3) from EBRT and BT to the bladder and rectum was calculated and compared to direct addition assuming a uniform EBRT dose (UD).ResultsDifferences (DIR-UD) in the total EBRT + BT dose ranged between –0.2-3.9 GyEQD2 (bladder) and –1.0-3.7 GyEQD2 (rectum). The total EBRT + BT dose calculated with DIR was at most 104% of the dose calculated with the UD method.ConclusionsDifferences between UD and DIR were small (< 3.9 GyEQD2). The dose delivered with adaptive VMAT/IMRT EBRT to bladder and rectum near the planned BT boost can be considered uniform for the evaluation of bladder/rectum D2cm3.

Surgery Versus Radiation Treatment for High-Grade Neuroendocrine Cancer of Uterine Cervix: A Surveillance Epidemiology and End Results Database Analysis.

The objective of this study was to assess treatment and other factors impacting survival in cervical high-grade neuroendocrine carcinoma (HGNEC). We identified patients with cervical HGNECs diagnosed during 1988 to 2012 in the Surveillance Epidemiology and End Results database. We determined overall survival by International Federation of Gynecology and Obstetrics stages and by local treatment modalities, that is, radical surgery versus external beam radiation treatment (EBRT) plus brachytherapy using Kaplan-Meier analysis with log-rank test. We also determined factors of age, stage, and treatment modality impacting survival using proportional hazard analysis. We identified 832 cases of cervical HGNECs in the database. After excluding cases with incomplete stage data, the International Federation of Gynecology and Obstetrics stages I to IV distributions were 196 (28.0%), 69 (9.9%), 175 (25.0%), and 260 patients (37.1%), respectively. Radical surgery and primary radiotherapy yielded similar 5-year overall survival for stages I (61% vs 53%, P = 0.27), II (48% vs 28%, P = 0.308), and III (33% vs 28%, P = 0.408) patients. External beam radiation treatment plus brachytherapy did not yield superior survival than EBRT alone in stage I (48% vs 49%, P = 0.799), II (37% vs 20%, P = 0.112), or III (25% vs 32%, P = 0.636) patients. Age (P = 0.004) and stage (stage II: hazard ratio [HR], 1.78, P = 0.013; stage III: HR, 2.42; P < 0.001) were independent factors impacting survival but not local treatment modality (EBRT: HR, 1.30, P = 0.17; EBRT plus brachytherapy: HR, 1.16; P = 0.417). Patients with cervical HGNECs had poor prognosis. Primary treatment by radical surgery or external beam radiotherapy with or without brachytherapy yielded equally poor survival.

Prognostic factors of axillary lymph node-positive patients in clinical stage II and III breast cancer after neoadjuvant chemotherapy

Background: Surgery following neoadjuvant chemotherapy (NAC) is increasingly utilized for breast cancer treatment with respect to downstage and recurrent risk reduction. However, there are some uncertainties about the solutions of adjuvant radiotherapy (design of RT field and indication in low-risk patients) in patients after NAC, especially in clinically node-positive patients. The objective of this study is to identify the risk factors of loco-regional recurrence (LRR), relapse and overall survival (OS) regarding tumor response post-NAC in this institution. Methods: From 2007 to 2015, 90 patients with newly diagnosed clinical stage II (n=44) or III (n=46) breast cancer and pathological positive lymph nodes who received chemotherapy followed by breast conserving surgery or mastectomy, adjuvant radiotherapy, and some with adjuvant systemic therapy were identified. All of them received anthracycline-based or taxane-based chemotherapy, external beam radiotherapy and systemic treatment including target or hormone therapy if indicated. Methods: The patient characteristics included clinical T/N stage, pathologic T/N stage, response after NAC, tumor grade, surgical margin, the presence or absence of lymphovascular invasion and extracapsular extension, the total number of lymph nodes dissection, the positive lymph nodes ratio (pLNR), tumor biomarker status [estrogen receptor (ER)/progesterone receptor (PR)/human epidermal growth factor receptor 2 (HER-2)], and adjuvant chemotherapy/target therapy or not. Univariate and multivariate analyses for risks of loco-regional recurrence (LRR), relapse (any local, regional or distant recurrence), and overall survival (OS) and the survival curves of LRR and relapse were performed. Results: After a median follow-up duration of 62 months (7–125 months), the multivariate analysis for risks of LRR showed that the status of clinical lymph nodes (cN2: HR =6.07, P=0.046; cN3: HR =30.22, P=0.001), response subgroups (stable disease: HR =3.01, P=0.047; progressive disease: HR =10.76, P&lt;0.001), and pLNR (67–100%: HR =4.32, P=0.025) have statistical significance. The multivariate analysis for risks of relapse also showed that the status of clinical lymph nodes (cN1 micro/N1: HR =3.97, P=0.037; cN2: HR =4.06, P=0.053; cN3: HR =10.39, P=0.005), response subgroups (progressive disease: HR =3.73, P=0.008) and pLNR (67–100%: HR =3.02, P=0.032) have statistical significance. The multivariate analysis of OS only showed the tumor biomarker status of triple-negative breast cancer (TNBC) (HR =3.04, P=0.048) has statistical significance. Conclusions: In this study, we recorded poor therapeutic response, advanced clinically positive lymph nodes, and higher proportional positivity of dissected lymph nodes showing poor outcome regarding the loco-regional control and relapse-free survival among patients with positive axillary lymph nodes after NAC.

The Use of Ultrasound Imaging in the External Beam Radiotherapy Workflow of Prostate Cancer Patients.

External beam radiotherapy (EBRT) is one of the curative treatment options for prostate cancer patients. The aim of this treatment option is to irradiate tumor tissue, while sparing normal tissue as much as possible. Frequent imaging during the course of the treatment (image guided radiotherapy) allows for determination of the location and shape of the prostate (target) and of the organs at risk. This information is used to increase accuracy in radiation dose delivery resulting in better tumor control and lower toxicity. Ultrasound imaging is harmless for the patient, it is cost-effective, and it allows for real-time volumetric organ tracking. For these reasons, it is an ideal technique for image guidance during EBRT workflows. Review papers have been published in which the use of ultrasound imaging in EBRT workflows for different cancer sites (prostate, breast, etc.) was extensively covered. This new review paper aims at providing the readers with an update on the current status for prostate cancer ultrasound guided EBRT treatments.

Non-rigid CT/CBCT to CBCT registration for online external beam radiotherapy guidance

Image-guided external beam radiotherapy (EBRT) allows radiation dose deposition with a high degree of accuracy and precision. Guidance is usually achieved by estimating the displacements, via image registration, between cone beam computed tomography (CBCT) and computed tomography (CT) images acquired at different stages of the therapy. The resulting displacements are then used to reposition the patient such that the location of the tumor at the time of treatment matches its position during planning. Moreover, ongoing research aims to use CBCT–CT image registration for online plan adaptation.However, CBCT images are usually acquired using a small number of x-ray projections and/or low beam intensities. This often leads to the images being subject to low contrast, low signal-to-noise ratio and artifacts, which ends-up hampering the image registration process. Previous studies addressed this by integrating additional image processing steps into the registration procedure. However, these steps are usually designed for particular image acquisition schemes, therefore limiting their use on a case-by-case basis.In the current study we address CT to CBCT and CBCT to CBCT registration by the means of the recently proposed EVolution registration algorithm. Contrary to previous approaches, EVolution does not require the integration of additional image processing steps in the registration scheme. Moreover, the algorithm requires a low number of input parameters, is easily parallelizable and provides an elastic deformation on a point-by-point basis. Results have shown that relative to a pure CT-based registration, the intrinsic artifacts present in typical CBCT images only have a sub-millimeter impact on the accuracy and precision of the estimated deformation. In addition, the algorithm has low computational requirements, which are compatible with online image-based guidance of EBRT treatments.

Improved rectal dosimetry with the use of SpaceOAR during high-dose-rate brachytherapy

PurposeHydrogel spacers have been suggested to limit rectal radiation dose with improvements in clinical outcomes in patients undergoing external beam radiation treatment for prostate cancer. No studies to date have assessed the utility and dosimetric effect of SpaceOAR (Augmenix, Inc, Waltham, MA), the only Food and Drug Administration–approved hydrogel rectal spacer, for high-dose-rate (HDR) brachytherapy. MethodsEighteen consecutive patients scheduled for HDR brachytherapy in the treatment of prostate cancer underwent transperineal ultrasound-guided placement of 10 cc of SpaceOAR hydrogel following catheter implantation. Treatment plans were generated using an inverse planning simulated annealing algorithm. Rectal dosimetry for these 18 patients was compared with the 36 preceding patients treated with HDR brachytherapy without SpaceOAR. ResultsFifty-four plans were analyzed. There was no difference in age, pretreatment prostate-specific antigen, Gleason score, clinical stage, prostate volume, or contoured rectal volume between those who received SpaceOAR and those who did not. Patients who received SpaceOAR hydrogel had significantly lower dose to the rectum as measured by percent of contoured organ at risk (median, V80 < 0.005% vs. 0.010%, p = 0.003; V75 < 0.005% vs. 0.14%, p < 0.0005; V70 0.09% vs. 0.88%, p < 0.0005; V60 = 1.16% vs. 3.08%, p < 0.0005); similar results were seen for rectal volume in cubic centimeters. One patient who received SpaceOAR developed a perineal abscess 1 month after treatment. ConclusionsTransperineal insertion of SpaceOAR hydrogel at the time of HDR brachytherapy is feasible and decreases rectal radiation dose. Further investigation is needed to assess the clinical impact of this dosimetric improvement and potential toxicity reduction.

Updates on the Management of Advanced, Metastatic, and Radioiodine Refractory Differentiated Thyroid Cancer.

Differentiated thyroid cancer (DTC) accounts for 95% of all thyroid cancers and is generally an indolent tumor, treated effectively with surgery, radioactive iodine, and thyroid-stimulating hormone suppressive therapy. However, 5–10% of patients have advanced disease, with aerodigestive tract invasion, distant metastases, or radioiodine refractory disease, with poor prognosis. This review focuses on the approaches for treating advanced DTC, including management of gross extra-thyroidal extension, recurrent loco-regional or distant metastatic disease, the role of external beam radiation therapy and systemic treatment. Locally ablative treatment modalities, including surgery, radiation therapy, and thermal ablation are evolving and can be used in selected patients. In recent years, new therapeutic agents with molecular targets have become available and two multi-kinase inhibitors, Sorafenib and Lenvatinib, have been licensed for iodine refractory DTC showing an advantage in terms of progression-free survival, although an impact on overall survival has not been proven yet. Management of advanced thyroid cancer can be challenging but a multidisciplinary approach can significantly improve outcomes for this patient population.

Evaluation of an automatic MR-based gold fiducial marker localisation method for MR-only prostate radiotherapy

An MR-only radiotherapy planning (RTP) workflow would reduce the cost, radiation exposure and uncertainties introduced by CT-MRI registrations. In the case of prostate treatment, one of the remaining challenges currently holding back the implementation of an RTP workflow is the MR-based localisation of intraprostatic gold fiducial markers (FMs), which is crucial for accurate patient positioning.Currently, MR-based FM localisation is clinically performed manually. This is sub-optimal, as manual interaction increases the workload. Attempts to perform automatic FM detection often rely on being able to detect signal voids induced by the FMs in magnitude images. However, signal voids may not always be sufficiently specific, hampering accurate and robust automatic FM localisation.Here, we present an approach that aims at automatic MR-based FM localisation. This method is based on template matching using a library of simulated complex-valued templates, and exploiting the behaviour of the complex MR signal in the vicinity of the FM. Clinical evaluation was performed on seventeen prostate cancer patients undergoing external beam radiotherapy treatment. Automatic MR-based FM localisation was compared to manual MR-based and semi-automatic CT-based localisation (the current gold standard) in terms of detection rate and the spatial accuracy and precision of localisation. The proposed method correctly detected all three FMs in 15/17 patients. The spatial accuracy (mean) and precision (STD) were 0.9 mm and 0.5 mm respectively, which is below the voxel size of mm3 and comparable to MR-based manual localisation. FM localisation failed (3/51 FMs) in the presence of bleeding or calcifications in the direct vicinity of the FM.The method was found to be spatially accurate and precise, which is essential for clinical use. To overcome any missed detection, we envision the use of the proposed method along with verification by an observer. This will result in a semi-automatic workflow facilitating the introduction of an MR-only workflow.

Quality of Life in Patients With Localized Prostate Cancer: High-Dose Rate Brachytherapy Versus Laparoscopic Prostatectomy

Prostate cancer is a disease with a significant impact on quality of life both during and after the cancer treatment. This study describes and compares health-related quality of life (QoL) of prostate cancer patients who received either radical laparoscopic prostatectomy or high-dose rate brachytherapy combined with external beam radiotherapy for treatment of localized prostate cancer. We conducted a prospective, two-center, observational study that included 99 prostate cancer patients. 50 patients underwent laparoscopic prostatectomy and 49 patients received brachytherapy with external beam radiotherapy. Quality of life was routinely evaluated with validated questionnaires: The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire EORTC-QLQ-Prostate Module (PR)25, International Index of Erectile Function (IIEF)-15, International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF) and International Prostate Symptom Score (I-PSS). Patients completed questionnaires before treatment, six months and one year after completion of treatment. Statistical analysis was performed with the use of analysis of variance (ANOVA) and chi-squared test. Median age was 61 years in the laparoscopic prostatectomy group and 64 years in the brachytherapy group. Patients treated with high-dose rate brachytherapy had significantly better urinary function than patients treated with radical prostatectomy (p<0.0482). Patients after radical prostatectomy had significantly worse urinary incontinence than those from brachytherapy group 6 and 12 months after treatment (p <0.0133 and <0.0361, respectively). Radical prostatectomy patients experienced considerable impairment in sexual functioning 6 months after the surgery (p<0.0069). No significant differences were observed among the groups in measures of bowel function. Both treatment methods showed a unique pattern of changes in quality of life related to urinary symptoms and sexual function. These results provide relevant information for clinical decision making which is often influenced by quality of life. However, additional research is needed to understand how different approaches may impact quality of life.

Nodal dose estimation for individualised brachytherapy planning for patients with cervical cancer

Introduction Radiotherapy for locally advanced cervical cancers involves External Beam Radiotherapy (EBRT) and a High Dose Rate Brachytherapy (HDR-BT) boost. 50% of these patients present with Pelvic Lymph Nodes (PLN) metastases therefore total dose delivered to PLN is an important consideration. This study estimates differences between dose at point B (Manchester system): for plans prescribed to point A and plans optimised to cover a High Risk Clinical Tumour Volume (HR-CTV). Methods Retrospective analysis was completed for 14 consecutive patients. EBRT standard 4-field box technique 50.4 Gy in 28 fractions was delivered followed by HDR-BT 6–7 Gy in 3 fractions using Varian ring and tandem applicators. Standard plans were normalised to point A and, if necessary, dwell times manually adjusted to optimise HR-CTV coverage D90 ⩾ 100%. Doses at points B were calculated in 2 Gy Equivalent Dose (EQD2) using radiobiology Linear Quadratic model (LQm) using α / β = 10 for all HDR-BT fractions. Results and conclusions The average EQD2 for EBRT and HDR-BT combined treatment was 55.1 Gy for standard plans and ranged between 52.8 Gy and 56.5 Gy for optimised plans. Dose at points B for HDR cervix treatment depends on the intended dose to the HR-CTV, HR-CTV volume and loading pattern. For standard plans the dose is predictable, approximately 1.8 Gy per fraction, however for individualised plans there is much greater variation. As we move towards more individualised planning it is important to be aware of these differences in dose delivered to PLN and the relationship between dose to PLN and risk of metastases.

Real-Time External Respiratory Motion Measuring Technique Using an RGB-D Camera and Principal Component Analysis.

Accurate tracking and modeling of internal and external respiratory motion in the thoracic and abdominal regions of a human body is a highly discussed topic in external beam radiotherapy treatment. Errors in target/normal tissue delineation and dose calculation and the increment of the healthy tissues being exposed to high radiation doses are some of the unsolicited problems caused due to inaccurate tracking of the respiratory motion. Many related works have been introduced for respiratory motion modeling, but a majority of them highly depend on radiography/fluoroscopy imaging, wearable markers or surgical node implanting techniques. We, in this article, propose a new respiratory motion tracking approach by exploiting the advantages of an RGB-D camera. First, we create a patient-specific respiratory motion model using principal component analysis (PCA) removing the spatial and temporal noise of the input depth data. Then, this model is utilized for real-time external respiratory motion measurement with high accuracy. Additionally, we introduce a marker-based depth frame registration technique to limit the measuring area into an anatomically consistent region that helps to handle the patient movements during the treatment. We achieved a 0.97 correlation comparing to a spirometer and 0.53 mm average error considering a laser line scanning result as the ground truth. As future work, we will use this accurate measurement of external respiratory motion to generate a correlated motion model that describes the movements of internal tumors.

Experimental verification of EGSnrc Monte Carlo calculated depth doses within a realistic parallel magnetic field in a polystyrene phantom.

Integrating a linac with a magnetic resonance imager (MRI) will revolutionize the accuracy of external beam radiation treatments. Irradiating in the presence of a strong magnetic field, however, will modify the dose distribution. These dose modifications have been investigated previously, mainly using Monte Carlo simulations. The purpose of this work is to experimentally verify the use of the EGSnrc Monte Carlo (MC) package for calculating percent depth doses (PDDs) in a homogeneous phantom, in the presence of a realistic parallel magnetic field. Two cylindrical electromagnets were used to produce a 0.207T magnetic field parallel to the central axis of a 6MV photon beam from a clinical linac. The magnetic field was measured at discrete points along orthogonal axes, and these measurements were used to validate a full 3D magnetic field map generated using COMSOL Multiphysics. Using a small parallel plate ion chamber, the depth dose was measured in a polystyrene phantom placed inside the electromagnet bore at two separate locations: phantom top surface coinciding with top of bore, and phantom top surface coinciding with center of bore. BEAMnrc MC was used to model the linac head which was benchmarked against the linac's commissioning measurements. The depth dose in polystyrene was simulated using DOSXYZnrc MC. For the magnetic field case, the DOSXYZnrc code was slightly modified to implement the previously calculated 3D magnetic field map to be used in the standard electromagnetic macros. The calculated magnetic field matched the measurements within 2% of the maximum central field (0.207T) with most points within the experimental uncertainty (1.5%). For the MC linac head model, over 93% of all simulated points passed the 2%, 2mm γ acceptance criterion, when comparing measured and simulated lateral beam and depth dose profiles. The parallel magnetic field caused a surface dose increase, compared to the no magnetic field case, due to the Lorentz force confining contaminant electrons within the beam. The surface dose increase was measured to be approximately 10% (relative to no field Dmax ) when the phantom surface coincided with the top of the electromagnet's bore. This effect was enhanced by moving the phantom surface to the center of the magnet's bore in relatively high magnetic field (>0.13T). The surface dose for this setup increased by 30% and the entire buildup region was affected. When the dimensions and composition of the ion chamber air cavity and entrance window were included, EGSnrc was able to accurately simulate these dose increases, both at the surface and in the buildup region. All the simulated points were within 1% of the measurements for both setups. The ferromagnetic linac head was determined to have a negligible effect on the final PDD comparison. Irradiating in the presence of a parallel magnetic field causes measurable surface and buildup depth dose increases. We have experimentally verified that the EGSnrc Monte Carlo package is able to accurately calculate the PDDs with these surface and buildup dose modifications in a homogeneous phantom.

Improving efficiency and safety in external beam radiation therapy treatment delivery using a Kaizen approach

IntroductionModern external beam radiation therapy treatment delivery processes potentially increase the number of tasks to be performed by therapists and thus opportunities for errors, yet the need to treat a large number of patients daily requires a balanced allocation of time per treatment slot. The goal of this work was to streamline the underlying workflow in such time-interval constrained processes to enhance both execution efficiency and active safety surveillance using a Kaizen approach. Methods and materialsA Kaizen project was initiated by mapping the workflow within each treatment slot for 3 Varian TrueBeam linear accelerators. More than 90 steps were identified, and average execution times for each were measured. The time-consuming steps were stratified into a 2 × 2 matrix arranged by potential workflow improvement versus the level of corrective effort required. A work plan was created to launch initiatives with high potential for workflow improvement but modest effort to implement. Time spent on safety surveillance and average durations of treatment slots were used to assess corresponding workflow improvements. ResultsThree initiatives were implemented to mitigate unnecessary therapist motion, overprocessing of data, and wait time for data transfer defects, respectively. A fourth initiative was implemented to make the division of labor by treating therapists as well as peer review more explicit. The average duration of treatment slots reduced by 6.7% in the 9 months following implementation of the initiatives (P = .001). A reduction of 21% in duration of treatment slots was observed on 1 of the machines (P < .001). Time spent on safety reviews remained the same (20% of the allocated interval), but the peer review component increased. ConclusionsThe Kaizen approach has the potential to improve operational efficiency and safety with quick turnaround in radiation therapy practice by addressing non–value-adding steps characteristic of individual department workflows. Higher effort opportunities are identified to guide continual downstream quality improvements.

A descriptive and broadly applicable model of therapeutic and stray absorbed dose from 6 to 25 MV photon beams.

To develop a simple model of therapeutic and stray absorbed dose for a variety of treatment machines and techniques without relying on proprietary machine-specific parameters. Dosimetry measurements conducted in this study and from the literature were used to develop an analytical model of absorbed dose from a variety of treatment machines and techniques in the 6 to 25MV interval. A modified one-dimensional gamma-index analysis was performed to evaluate dosimetric accuracy of the model on an independent dataset consisting of measured dose profiles from seven treatment units spanning four manufacturers. The average difference between the calculated and measured absorbed dose values was 9.9% for those datasets on which the model was trained. Additionally, these results indicate that the model can provide accurate calculations of both therapeutic and stray radiation dose from a wide variety of radiotherapy units and techniques. We have developed a simple analytical model of absorbed dose from external beam radiotherapy treatments in the 6 to 25MV beam energy range. The model has been tested on measured data from multiple treatment machines and techniques, and is broadly applicable to contemporary external beam radiation therapy.