International Journal of Cancer Therapy and Oncology
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Mathematical analysis of approximate biological effective dose (BED) calculation for multi-phase radiotherapy treatment plans
Get PDFPurpose: There is growing interest about biological effective dose (BED) and its application in treatment plan evaluation due to its stronger correlation with treatment outcome. An approximate biological effective dose (BEDA) equation was introduced in order to simplify BED calculations by treatment planning systems in multi-phase treatments. The purpose of this work is to reveal its mathematical properties relative to the true, multi-phase BED (BEDT) equation.Methods: The BEDT equation was derived and used to reveal the mathematical properties of BEDA. MATLAB (MathWorks, Natick, MA) was used to simulate and analyze common and extreme clinical multi-phase cases. In those cases, percent error and Bland-Altman analysis were used to study the significance of the inaccuracies of BEDA for different combinations of total doses, numbers of fractions, doses per fractions and α/β values. All the calculations were performed on a voxel-basis in order to study how dose distributions would affect the accuracy of BEDA.Results: When the voxel dose-per-fractions (DPF) delivered by both phases are equal, BEDA and BEDT are equal (0% error). In heterogeneous dose distributions, which significantly vary between the phases, there are fewer occurrences of equal DPFs and hence the imprecision of BEDA is greater. It was shown that as the α/β ratio increased the accuracy of BEDA would improve. Examining twenty-four cases, it was shown that the range of DPF ratios for 3% Perror varied from 0.32 to 7.50Gy, whereas for Perror of 1% the range varied from 0.50 to 2.96Gy.Conclusion: The DPF between the different phases should be equal in order to render BEDA accurate. OARs typically receive heterogeneous dose distributions hence the probability of equal DPFs is low. Consequently, the BEDA equation should only be used for targets or OARs that receive uniform or very similar dose distributions by the different treatment phases.---------------------------Cite this article as: Kauweloa KI, Gutierrez AN, Bergamo A, Stathakis S, Papaniko-laou N, Mavroidis P. Mathematical analysis of approximate biological effective dose (BED) calculation for multi-phase radiotherapy treatment plans. Int J Cancer Ther Oncol 2014; 2(2):020226. DOI: 10.14319/ijcto.0202.2
SPECT deadtime count loss correction using monitor source method
Get PDFPurpose: Deadtime-count-loss (DTloss) correction using monitor source (MS) requires: 1) uniform fractional DTloss across FOV, 2) high statistics MS images both with & without the object. The aims are validating condition 1 and developing a practical protocol that satisfies conditions 2 with minimal additional study duration.Methods and Materials: SPECT images of non-uniform phantoms (4GBq 99mTc) along with MS (20MBq 99mTc) attached to each detector were acquired multiple times over 48 hours in photopeak and scatter energy window (EW) using Siemens-SymbiaS and GE-D670. Planar images of the MS alone were acquired. Photopeak counts for the MS ROIs were > 100kcts. Fractional DTloss uniformity across the FOV was evaluated by correlating count rates in different ROIs on projection images at different DTloss levels. The correction factor for each SPECT projection at every time point was calculated as the ratio of time-corrected MS count rates with & without the phantom.The DTloss-corrected projections for each SPECT acquisition were decay corrected to one time point. The correction accuracy was assessed against DTloss estimated by paralyzable model. The accuracy of projection-based DTloss correction for SPECT was evaluated. A method to model projection DTloss based on a subset of measured projection DTloss was investigated. The relation of DTloss between photopeak and scatter EW was explored.Results: The fractional DTloss was uniform across the FOV (r > 0.99), validating condition 1. The MS method was accurate to > 99% for planar and SPECT. Measured DTloss from 3-to-5 projections/detector may be used to estimate DTloss with accuracy > 98% for all SPECT projections by modeling DTloss with measured projection rate. The correction factor in photopeak and scatter EW are equivalent with > 99% agreement.Conclusion: MS method can accurately correct planar and SPECT DTloss. Sparse sampling of the projection DTloss allows acquiring MS counts with high statistics with minimal additional study duration making it clinically practical.--------------------------------------Cite this article as: Siman W, Kappadath SC. SPECT deadtime count loss correction using monitor source method. Int J Cancer Ther Oncol 2014; 2(2):020234. DOI: 10.14319/ijcto.0202.3
Presentation and outcome of twenty patients with synchronous stage IV rectal carcinoma
Get PDFPurpose: Palliative treatment techniques for advanced stage rectal cancer should be designed according to the patients’ major symptoms. Combined chemo-radiation therapy is effective choice for symptomatic patients with good performance status. In this study, we reviewed our patients' stage IV rectal carcinoma in regard to most common presentation, outcome and possible prognostic features.Methods Medical chart of twenty patients who were diagnosed with stage IV rectal carcinoma, were reviewed based on the hospital database information, which included images, radiotherapy charts, and their follow up notes. Results: All patients were young with age less than 40 years. Bleeding per rectum, pain, and symptoms of obstruction were the most common presentation. Seven patients had solitary lesion and 13 patients had multiple lesions. Eleven patients with multiple metastases were treated with palliative chemotherapy and radiotherapy. Patients who had solitary metastases to liver had a median survival time of 49 months versus 13.5 months for other patients (p = 0.001). Conclusion: Patients who presented with solitary liver metastases could be treated with a course of neoadjuvant chemo-radiotherapy similar to the curative one.-----------------------------------Cite this article as: Aboziada MA, Attia AM, Alhamad AA. Presentation and outcome of twenty patients with synchronous stage IV rectal carcinoma. Int J Cancer Ther Oncol 2014; 2(3):020313. DOI:10.14319/ijcto.0203.1
The efficacy and safety of Oxaliplatin-Vinorelbine as a second-line chemotherapy combination in patients with platinum-resistant pretreated epithelial ovarian cancer: A retrospective study
Get PDFPurpose: The main purpose of this study was to analyze the effects and tolerability of Oxaliplatin-Vinorelbine combination on Platinum-resistant epithelial ovarian carcinoma (EOC) patients.Methods: A single centered retrospective study comprising of 34 patients was conducted, and all 34 patients were treated with Vinorelbine 30 mg/m2 on day 1 and 8 along with Oxaliplatin 100 mg/m2 on day 1 of 3 weeks treatment cycle following progressive platinum-resistant EOC. Results: The combination showed an overall response rate (ORR) of 18% (95% CI, 4.4 - 31.6) where 2 (6%) patients had complete response and 4 (12%) patients had partial response. Stable disease was observed in 9 (26%) patients and progressive disease in 19 (56%) patients. Median diseases free survival, median relapse free survival and median time to progression was 17.05 months, 4.4 months, and 1.25 months, respectively. Hematological toxicities were mild; only 1 (2.9%) patient had G3 anemia and major non-hematological toxicities include nausea-vomiting, diarrhea, constipation, hepatotoxicity, fatigueness and alopecia, which are mainly limited to G1-G2 and reversible. Conclusion: The effect of this combination is moderate as a second line treatment of platinum resistant EOC; however, in comparison with other regimens of Vinorelbine and Oxaliplatin, the activity is substandard but the toxicity profile is well tolerable. Further multicenter evaluation is needed for the better understanding of the therapeutic efficacy of the combination
Doppler string phantom for assessment of clinical doppler ultrasound velocity measurement
Get PDFPurpose: The Doppler string phantom provides accurate velocity of the string motion; it can be used to calibrate Doppler ultrasound (US) velocity measurements and to evaluate variations due to intrinsic spectral broadening. We developed a semi‐automated method to estimate the mode velocity (Vmode) and peak velocity (Vmax) based on duplex US images from a string phantom, and use them to assess clinical Doppler US velocity measurement.Methods: Steady motion of a rubber O‐ring (20 – 110 cm/s) in a CIRS Doppler String phantom (Model 043) was studied using GE LOGIQ E9 system with a 9L probe. 5 s of Doppler spectral data was averaged to generate a mean spectral profile. It was fitted by a Gaussian function and Vmode was defined as the velocity of the Gaussian peak, while Vmax is defined as the velocity at which the spectral profile falls to within 1 SD of the background. Vmode and Vmax were evaluated against the prescribed motor velocity. Repeatability and variation to scanning parameters were analyzed and reported in % range, i.e. (max – min) / mean.Results: Vmode and Vmax had good repeatability over six days (6.0% for Vmode, 2.9% for Vmax). Gain, compression, scale, sample volume (SV) depth and length, frequency and beam steering all had minimal impact on Vmode and Vmax (variations ≤ 4.4%). Doppler angle θ had minimal effect on Vmode (2.2%) but a strong effect on Vmax (26% increase as θ increased from 10° to 60°). Vmode was linearly correlated with but overestimated the motor velocity (Pearson’s r = 1.05, R2 = 1).Conclusion: This study developed a simple yet robust Vmode and Vmax estimation method. Combined with a string phantom, these velocity estimators are shown to be a useful tool to evaluate clinical Doppler US system performance. For the tested system, only Doppler angle has an appreciable impact on Vmax estimation.--------------------------------------------Cite this article as: Zhang Y, Lynch T, Hangiandreou NJ. Doppler string phantom for assessment of clinical doppler ultrasound velocity measurement. Int J Cancer Ther Oncol 2014; 2(2):020246. DOI:10.14319/ijcto.0202.4
The accuracy of the Acuros XB algorithm in external beam radiotherapy – a comprehensive review
Get PDFThe accuracy of dose calculation algorithms has been a topic of interest among the radiotherapy community throughout last decades. On one hand the advancements in computers and algorithms has improved the accuracy, but on the other hand the developments in other parts of treatment process, in treatment delivery techniques and in treatment devices have always pushed the requirements to the next level. In this review article a comprehensive overview on the accuracy of a new type ‘c’ dose calculation algorithm, the Acuros XB (AXB) algorithm (Varian Medical Systems, Inc., Palo Alto, CA, USA), is provided. All the articles that have applied the AXB algorithm in terms of external beam radiotherapy are included and the research frames with reported deviations to reference methods are described. For the homogeneous water phantoms the reported accuracy was from 1% to 2%, being of similar level for heterogeneous phantoms, in rare occasions lower. In anthropometric and anthropomorphic phantoms the mean deviations were about 2% and slightly larger for single points and/or small regions. With patient plans the reported average discrepancies were less than from 3% to 5%. Almost without exceptions, the algorithm has proven to perform better than other existing commercial dose calculation algorithms. The number of such papers, in which the AXB algorithm is the only dose determination method, is already notable, which indicates that the accuracy of the algorithm is trusted for reference use and it also, with reported dosimetric results, implies that the AXB algorithm has reached its maturity
Nasopharyngeal Synovial Sarcoma - An Oncological Surprise
Get PDFSynovial sarcoma is a rare and aggressive high-grade neoplasm with poor prognosis. It is usually encountered in the lower extremities of young adults; only a few cases have been reported in the head and neck region. We report the fourth case of synovial sarcoma of the nasopharynx, treated with neoadjuvant chemotherapy, complete surgical excision and adjuvant radiation with extensive review of literature
Can an alternative backround-corrected [18F] fluorodeoxyglucose (FDG) standard uptake value (SUV) be used for monitoring tumor local control following lung cancer stereotactic body radiosurgery?
Get PDFPurpose: Although [18F] FDG-positron emission tomography (PET) provides vital information in diagnosing lung malignancies, the inherent uncertainties of standard uptake value (SUV) compromises its confidence. People have attempted to reduce this uncertainty by comparing the normal tissues, such as liver and spleen. However, those common reference structures may be inappropriate in some cases when pathological conditions exist. Hence, using alternative reference structures becomes valuable in such practice. The purpose of this study is to explore an alternative reference-correction method to reduce the inherent variation of SUV in the tumor or irradiated region. Methods: 106 analyzable FDG-PET scans from 49 cases who received lung SBRT for non-small cell lung cancer were retrospectively analyzed. The follow-up time ranges from 14.5 weeks to 113.2 weeks. The maximal SUV (SUVmax) was measured within the lung lesion or its corresponding region in post-SBRT. SUVmax was then corrected (or divided) by a reference SUV, or the mean SUV of the adjacent aorta, and results in the new SUVcmax. Results: SUVcmax of the positive group are significant higher than that of locally controlled cases (5.82 ± 3.10 vs. 1.45 ± 0.55, p = 0.026), while inconsequential differences were identified between the groups (p = 0.086). Respectively 85.2% and 96.3% of locally controlled cases post SBRT showed decreased values in the latter PET using SUVmax and SUVcmax. PET taken 24 weeks or sooner post-SBRT yielded higher uncertainties.Conclusion: Comparing with the conventional SUVmax, the alternative regional background-corrected SUV indicator, SUVcmax of PTV suggests a stronger correlation between low (<2.5 - 3.0) values and the local tumor control post lung SBRT for NSCLC. However, FDG-PET images taken earlier than 24 weeks post-SBRT presents larger variations in SUV of the irradiated region due to underlying radiation induced inflammatory changes, and is not recommended for assessing local tumor control after lung SBRT......................................................Cite this article as: Shang CY, Kasper ME, Kathriarachchi V, Benda RK, Kleinman JH, Cole J, Williams TR. Can an alternative backround-corrected [18F] fluorodeoxyglucose (FDG) standard uptake value (SUV) be used for monitoring tumor local control following lung cancer stereotactic body radiosurgery? Int J Cancer Ther Oncol 2014; 2(4):020317.DOI: 10.14319/ijcto.0203.1
On the evaluation of patient specific IMRT QA using EPID, dynalog files and patient anatomy
Get PDFPurpose: This research, investigates the viability of using the Electronic portal imaging device (EPID) coupled with the treatment planning system (TPS), to calculate the doses delivered and verify agreement with the treatment plan. The results of QA analysis using the EPID, Delta4 and fluence calculations using the multi-leaf collimator (MLC) dynalog files on 10 IMRT patients are presented in this study.Methods: EPID Fluence Images in integrated mode and Dynalog files for each field were acquired for 10 IMRT (6MV) patients and processed through an in house MatLab program to create an opening density matrix (ODM) which was used as the input fluence for dose calculation with the TPS (Pinnacle3, Philips). The EPID used in this study was the aSi1000 Varian on a Novalis TX linac equipped with high definition MLC. The resulting dose distributions were then exported to VeriSoft (PTW) where a 3D gamma was calculated using 3 mm-3% criteria. The Scandidos Delta4 phantom was also used to measure a 2D dose distribution for all 10 patients and a 2D gamma was calculated for each patient using the Delta4 software.Results: The average 3D gamma for all 10 patients using the EPID images was 98.2% ± 2.6%. The average 3D gamma using the dynalog files was 94.6% ± 4.9%. The average 2D gamma from the Delta4 was 98.1% ± 2.5%. The minimum 3D gamma for the EPID and dynalog reconstructed dose distributions was found on the same patient which had a very large PTV, requiring the jaws to open to the maximum field size. Conclusion: Use of the EPID, combined with a TPS is a viable method for QA of IMRT plans. A larger ODM size can be implemented to accommodate larger field sizes. An adaptation of this process to Volumetric Arc Therapy (VMAT) is currently under way.-----------------------------Cite this article as: Defoor D, Mavroidis P, Quino L, Gutierrez A, Papanikolaou N, Stathakis S. On the evaluation of patient specific IMRT QA using EPID, dynalog files and patient anatomy. Int J Cancer Ther Oncol 2014; 2(2):020219. DOI: 10.14319/ijcto.0202.1
Development and implementation of an anthropomorphic pediatric spine phantom for the assessment of craniospinal irradiation procedures in proton therapy
Get PDFPurpose: To design an anthropomorphic pediatric spine phantom for use in the evaluation of proton therapy facilities for clinical trial participation by the Imaging and Radiation Oncology Core (IROC) Houston QA Center (formerly RPC).Methods: This phantom was designed to perform an end-to-end audit of the proton spine treatment process, including simulation, dose calculation by the treatment planning system (TPS), and proton treatment delivery. The design incorporated materials simulating the thoracic spinal column of a pediatric patient, along with two thermoluminescent dosimeter (TLD)-100 capsules and radiochromic film embedded in the phantom for dose evaluation. Fourteen potential materials were tested to determine relative proton stopping power (RSP) and Hounsfield unit (HU) values. Each material was CT scanned at 120 kVp, and the RSP was obtained from depth ionization scans using the Zebra multi-layer ion chamber (MLIC) at two energies: 160 MeV and 250 MeV. To determine tissue equivalency, the measured RSP for each material was compared to the RSP calculated by the Eclipse TPS for a given HU.Results: The materials selected as bone, tissue, and cartilage substitutes were Techron HPV Bearing Grade (Boedeker Plastics, Inc.), solid water, and blue water, respectively. The RSP values did not differ by more than 1.8% between the two energies. The measured RSP for each selected material agreed with the RSP calculated by the Eclipse TPS within 1.2%.Conclusion: An anthropomorphic pediatric proton spine phantom was designed to evaluate proton therapy delivery. The inclusion of multiple tissue substitutes increases heterogeneity and the level of difficulty for institutions to successfully treat the phantom. The following attributes will be evaluated: absolute dose agreement, distal range, field width, junction match and right/left dose profile alignment. The phantom will be tested at several institutions using a 5% dose agreement criterion, and a 5%/3mm gamma analysis criterion for the film planes.--------------------------------------Cite this article as: Lewis DJ, Summers PA, Followill DS, Sahoo N, Mahajan A, Stingo FC, Kry SF. Development and implementation of an anthropomorphic pediatric spine phantom for the assessment of craniospinal irradiation procedures in proton therapy. Int J Cancer Ther Oncol 2014; 2(2):020227. DOI: 10.14319/ijcto.0202.2