International Journal of Cancer Therapy and Oncology
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Investigating the dosimetric effect of inter-fraction deformation in lung cancer stereotactic body radiotherapy (SBRT)
Get PDFPurpose: We studied on the negative dosimetric effect of inter-fraction deformation in lung stereotactic body radiotherapy (SBRT), in order to see whether there is a need for adaptive re-planning of lung SBRT cases.Methods: Six lung cancer patients with different treatment fractions were retrospectively investigated. All the patients were immobilized and localized with a stereotactic body frame and were treated with cone-beam CT guidance for each fraction. We calculated the actual delivered dose of the treatment plan using the up-to-date patient geometry of each fraction, and compared the dose with the intended plan dose to investigate the dosimetric effect of the inter-fraction deformation. Due to the relatively poor image quality of CBCT, deformable registration was carried out between treatment planning CT and CBCT of each fraction to obtain deformed planning CT for more accurate dose calculation of delivered dose. The extent of the inter-fraction deformation was also evaluated by calculating the dice similarity coefficient between the contours on planning CT and those on deformed planning CT.Results: The average dice coefficients for PTV, spinal cord, esophagus were 0.87, 0.83 and 0.69, respectively. The volume of PTV covered by prescription dose was decreased by 23.78% on average for all fractions of all patients. For spinal cord and esophagus, the volumes covered by the constraint dose were increased by 4.57% and 3.83% in most fractions. The maximum dose was also increased by 4.11% for spinal cord and 4.29% for esophagus.Conclusion: Due to inter-fraction deformation, large deterioration was found in both PTV coverage and OAR sparing, which demonstrated the need for adaptive re-planning of lung SBRT cases to improve target coverage while reducing radiation dose to nearby normal tissues.----------------------------------------Cite this article as: Jia J, Tian Z, Gu X, Yan H, Jia X, Jiang S. Investigating the dosimetric effect of inter-fraction deformation in lung cancer stereotactic body radiotherapy (SBRT). Int J Cancer Ther Oncol 2014; 2(2):020225. DOI: 10.14319/ijcto.0202.2
Irradiation of lung and esophagus tumors: A comparison of dose distributions calculated by anisotropic analytical algorithm and pencil beam convolution algorithm, a retrospective dosimetric study
Get PDFPurpose: The aim of this study was to evaluate dosimetric differences between pencil beam convolution (PBC) algorithm and anisotropic analytical algorithm (AAA) calculations in patients with lung and esophageal cancers. Methods: The existing plans calculated with PBC for 60 patients treated in 2012 were recalculated with AAA maintaining the same beam geometry and dose monitor units. For these plans, dose prescription ranges were 41.4 Gy to 56.0 Gy for esophageal cancers and 50.0 Gy to 64.0 Gy for lung cancers. Dosimetric variables were the 95% PTV coverage, mean PTV dose, maximum spinal cord dose, lung V5Gy, and lung V20Gy. Results: The 95% PTV coverage’s for both lung and esophageal tumors were reduced when recalculated with AAA. Maximum spinal cord doses for lung cancer patients were reduced by 0.7 Gy and by 0.3 Gy for esophageal cancer patients on AAA. On the other hand, lung V5Gy had 3.5% increase for both lung and esophageal cancer patients on AAA, whereas lung V20Gy increased by 1.5% also on AAA for esophageal cancer patients.Conclusion: These clinical results confirm the differences between AAA and PBC algorithms as observed in phantom dosimetric studies, and give an indication of the clinical implications of changing from one calculation algorithm to another.---------------------------------------Cite this article as: Amankwaa-Frempong E, Vernimmen F, Blay S, Ezhilalan R. Irradiation of lung and esophagus tumors: A comparison of dose distributions calculated by anisotropic analytical algorithm and pencil beam convolution algorithm, a retrospective dosimetric study. Int J Cancer Ther Oncol 2014; 2(2):020210. DOI: 10.14319/ijcto.0202.1
Daily fraction dose recalculation based on rigid registration using Cone Beam CT
Get PDFPurpose: To calculate the daily fraction dose for CBCT recalculations based on rigid registration and compare it to the planned CT doses.Methods: For this study, 30 patients that were previously treated (10 SBRT lung, 10 prostate and 10 abdomen) were considered. The daily CBCT images were imported into the Pinnacle treatment planning system from Mosaic. Pinnacle was used to re-contour the regions of interest (ROI) for the specific CBCT by copying the contours from the original CT plan, planned by the prescribing physician, onto each daily CBCT and then manually reshaping contours to match the ROIs. A new plan is then created with the re-contoured CBCT as primary image in order to calculate the daily dose delivered to each ROI. The DVH values are then exported into Excel and overlaid onto the original CT DVH to produce a graph.Results: For the SBRT lung patients, we found that there were small daily volume changes in the lungs, trachea and esophagus. For almost all regions of interest we found that the dose received each day was less than the predicted dose of the planned CT while the PTV dose was relatively the same each day. The results for the prostate patients were similar, showing slight differences in the DVH values for different days in the rectum and bladder but similar PTV.Conclusion: By comparing daily fraction dose between the re-contoured CBCT images and the original planned CT show that PTV coverage for both prostate and SBRT, it has been shown that for PTV coverage, a planned CT is adequate. However, there are differences between the dose for the organs surrounding the PTV. The dose difference is less than the planned in most instances.-----------------------Cite this article as: Bosse C, Tuohy R, Mavroidis P, Shi Z, Crownover R, Gutierrez A, Papanikolaou N, Stathakis S. Daily fraction dose recalculation based on rigid registration using Cone Beam CT. Int J Cancer Ther Oncol 2014; 2(2):020217. DOI: 10.14319/ijcto.0202.1
The results of 2013 survey to evaluate Laparoscopic and Partial nephrectomy practice in the United Kingdom
Get PDFThis article is an editorial, and it doesn't include an abstract. Full text of this article is available in HTML and PDF.Cite this article as: Vasdev N, Mafeld S, Fuge O, Lane T, Boustead G, Adshead JM, Soomro NA. The results of 2013 survey to evaluate laparoscopic and partial nephrectomy practice in the United Kingdom. Int J Cancer Ther Oncol 2014; 2(2):02022.DOI: http://dx.doi.org/10.14319/ijcto.0202.
A new calculation formula of the nuclear cross-section of therapeutic protons
Get PDFPurpose: We have previously developed for nuclear cross-sections of therapeutic protons a calculation model, which is founded on the collective model as well as a quantum mechanical many particle problem to derive the S matrix and transition probabilities. In this communication, we show that the resonances can be derived by shifted Gaussian functions, whereas the unspecific nuclear interaction compounds can be represented by an error function, which also provides the asymptotic behavior. Method: The energy shifts can be interpreted in terms of necessary domains of energy to excite typical nuclear processes. Thus the necessary formulas referring to previous calculations of nuclear cross-sections will be represented. The mass number AN determines the strong interaction range, i.e. RStrong = 1.2·10-13·AN1/3cm. The threshold energy ETh of the energy barrier is determined by the condition Estrong = ECoulomb. Results and Conclusion: A linear combination of Gaussians, which contain additional energy shifts, and an error function incorporate a possible representation of Fermi-Dirac statistics, which is applied here to nuclear excitations and reaction with release of secondary particles. The new calculation formula provides a better understanding of different types of resonances occurring in nuclear interactions with protons. The present study is mainly a continuation of published papers.1-3--------------------------------Cite this article as: Ulmer W. A new calculation formula of the nuclear cross-section of therapeutic protons. Int J Cancer Ther Oncol 2014; 2(2):020211. DOI: 10.14319/ijcto.0202.1
Characterization of tumor dose heterogeneity for 90Y microsphere therapies using voxel- based dosimetry
Get PDFPurpose: Dosimetry for 90Y microsphere therapies (YMT) with Standard (SM) and Partition (PM) models provide only uniform dose estimates to tumor and liver. Our objective is to calculate tumor dose heterogeneity, known to effect response, using voxel-based dosimetry and investigate the limitations of SM and PM.Methods: Voxel-based dosimetry was performed on 17 YMT patients using Monte Carlo DOSXYZnrc. 90Y activity and tissue/density distributions were based on quantitative 90Y bremsstrahlung SPECT/CT. Tumors (n=31), liver, and treatment lobe/segments were segmented on diagnostic CT or MR. Dose volume histograms (DVH) were created for tumors and normal liver. Bland-Altman analysis compared voxel-based mean absorbed doses to tumor and liver with SM and PM. Tumor and normal liver absorbed dose heterogeneity were investigated through metrics: integral uniformity (IU), D10/D90, COV. Correlations of heterogeneity with voxel-based mean doses and volumes were evaluated.Results: Heterogeneity metrics (mean ± 1σ) for tumor dose were COV = 0.48 ± 0.28, D10/D90 = 4.7 ± 3.9, and IU = 0.8 ± 0.18. Heterogeneity metrics correlated with tumor volume (r > 0.58) but not tumor mean doses (r < 0.20). Voxel-based tumor mean doses correlated with PM (r = 0.84) but not SM (r = 0.08). Both yielded poor limits of agreement with of 83 ± 174 and -28 ± 181 Gy, respectively. Normal liver heterogeneity metrics (mean ± 1σ) were COV = 0.83 ± 0.29, D10/D90 = 12 ± 15, and IU = 0.97 ± 0.03. Only D10/D90 (r = 0.49) correlated with mean normal liver absorbed dose. Voxel-based normal liver/lobe mean doses correlated with PM (r = 0.96), but had poor limits of agreement (26 ± 29 Gy).Conclusion: Tumor doses have high levels of heterogeneity that increase with volume but are independent of dose. Voxel-based DVH and dose heterogeneity metrics will promote accurate characterization of tumor response following YMT.--------------------------------------Cite this article as: Mikell J, Mourtada F, Mahvash A, Kappadath SC. Characterization of tumor dose heterogeneity for 90Y microsphere therapies using voxel- based dosimetry. Int J Cancer Ther Oncol 2014; 2(2):020228. DOI: 10.14319/ijcto.0202.2
The use of gold markers and electronic portal imaging for radiotherapy verification in prostate cancer patients: Sweden Ghana Medical Centre experience
Get PDFThe success of radiotherapy cancer treatment delivery depends on the accuracy of patient setup for each fraction. A significant problem arises from reproducing the same patient position and prostate location during treatment planning for every fraction of the treatment process. To analyze the daily movements of the prostate, gold markers are implanted in the prostate and portal images taken and manually matched with reference images to locate the prostate. Geometrical and fiducial markers are annotated onto a highly quality generated digitally reconstructed radiographs, that are compared with portal images acquired right before treatment dose delivery. A 0 and 270 degree treatment fields are used to calculate prostate shifts for all prostate cancer patients undergoing treatment at the Sweden Ghana Medical Centre, using an iViewGT portal imaging device. After aligning of the marker positions onto the reference images, the set-up deviations corrections are displayed and an on-line correction procedure applied. The measured migrations of the prostate markers are below the threshold of 3 mm for the main plans and 2 mm for the boost plans. With daily electronic portal imaging combined with gold markers, provides an objective method for verifying and correcting the position of the prostate immediately prior to radiation delivery.--------------------------------------------Cite this article as: Acquah GF. The use of gold markers and electronic portal imaging for radiotherapy verification in prostate cancer patients: Sweden Ghana Medical Centre experience. Int J Cancer Ther Oncol 2014; 2(1):020112.DOI: http://dx.doi.org/10.14319/ijcto.0201.1
A decision tool to adjust the prescribed dose after change in the dose calculation algorithm
Get PDFPurpose: This work aims to introduce a method to quantify and assess the differences in monitor unites MUs when changing to new dose calculation software that uses a different algorithm, and to evaluate the need and extent of adjustment of the prescribed dose to maintain the same clinical results. Methods: Doses were calculated using two classical algorithms based on the Pencil Beam Convolution PBC model, using 6 patients presenting lung cancers. For each patient, 3 treatment plans were generated: Plan 1 was calculated using reference algorithm PBC without heterogeneity correction, Plan 2 was calculated using test algorithm with heterogeneity correction, and in plan 3 the dose was recalculated using test algorithm and monitor unites MUs obtained from plan 1 as input. To assess the differences in the calculated MUs, isocenter dose, and spatial dose distributions using a gamma index were compared. Statistical analysis was based on a Wilcoxon signed rank test. Results: The test algorithm in plan 2 calculated significantly less MUs than reference algorithm in plan 1 by on average 5%, (p < 0.001). We also found underestimating dose for target volumes using 3D gamma index analysis. In this example, in order to obtain the same clinical outcomes with the two algorithms the prescribed dose should be adjusted by 5%.Conclusion: This method provides a quantitative evaluation of the differences between two dose calculation algorithms and the consequences on the prescribed dose. It could be used to adjust the prescribed dose when changing calculation software to maintain the same clinical results as obtained with the former software. In particular, the gamma evaluation could be applied to any situation where changes in the dose calculation occur in radiotherapy
Secondary neutrons issue in proton radiotherapy—a brief report
Get PDFSecondary neutrons are unwanted byproduct in proton radiotherapy. Exposure due to secondary neutrons in proton radiotherapy could cause a significant risk for developing a secondary cancer later in the patient lifetime. The level of exposure due to secondary neutrons primarily depends on the type of beam delivery system used to deliver the primary proton dose. Although the patient body can produce significant neutrons but since these neutron are created inside the human body, their exposure is unavoidable. This report briefly discusses the type of beam delivery systems currently in use in proton radiotherapy, a relative comparison of neutron exposure in each case, and the importance of neutron study in proton radiotherapy.------------------------------------Cite this article as: Islam MR. Secondary neutrons issue in proton radiotherapy-a brief report. Int J Cancer Ther Oncol 2014; 2(1):02017.DOI: http://dx.doi.org/10.14319/ijcto.0201.
Cyberknife fractionated radiotherapy for adrenal metastases: Preliminary report from a multispecialty Indian cancer care center
Get PDFPurpose: Metastasis to adrenal gland from lung, breast, and kidney malignancies are quite common. Historically radiotherapy was intended for pain palliation. Recent studies with stereotactic body radiotherapy (SBRT) including Cyberknife robotic radiosurgery aiming at disease control brings about encouraging results. Here we represent the early clinical experience with Cyberknife stereotactic system from an Indian cancer care center. The main purpose of this retrospective review is to serve as a stepping stone for future prospective studies with non- invasive yet effective technique compared to surgery. Methods: We retrospectively reviewed four cases of adrenal metastases (three: lung and one: renal cell carcinoma) treated with Cyberknife SBRT. X sight spine tracking was employed for planning and treatment delivery. Patients were evaluated for local response clinically as well as with PETCT based response criteria.Results: With a median gross tumor volume of 20.5 cc and median dose per fraction of 10 Gy, two patients had complete response (CR) and two had partial response (PR) when assessed 8-12 weeks post treatment as per RECIST. There was no RTOG grade 2 or more acute adverse events and organs at risk dosage were acceptable. Till last follow up all the patients were locally controlled and alive. Conclusion: Cyberknife SBRT with its unique advantages like non- invasive, short duration outpatient treatment technique culminating in similar local control rates in comparison to surgery is an attractive option. World literature of linear accelerator based SBRT and our data with Cyberknife SBRT with small sample size and early follow up are similar in terms of local control in adrenal metastases. Future prospective data would reveal more information on the management of adrenal metastases