[Show abstract][Hide abstract] ABSTRACT: As part of the consolidation of the cooperative group clinical trial program of the National Clinical Trials Network (NCTN) of the National Cancer Institute (NCI), an Imaging and Radiation Oncology Core services organization (IROC) has been formed from current leading quality assurance (QA) centers to provide QA, along with clinical and scientific expertise, for the entire NCTN (1). An integrated information technology (IT) infrastructure, the IROC cloud, has been implemented to foster collaborative and effective interactions among participating institutions, QA centers, NCTN cooperative groups and statistics data management centers, and the IT infrastructure of the NCI (Fig. 1).
International journal of radiation oncology, biology, physics 10/2014; 90(2):466-467. · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose/Objective(s)
To evaluate the feasibility of the ABAS for the automatic delineation of cardiac structures (pericardium, atria, ventricles) when compared with the manually contoured cardiac structures. Furthermore, we explored using the ABAS contouring as a quality assurance (QA) tool.
CT scans and treatment plans from 470 cases were used in this project. Five experienced thoracic radiation oncologists independently delineated the cardiac structures, blinded to submitted contours, following a consistent guideline. A total of 100 such recontoured cases, 20 from each oncologist, were chosen, and their CT images with the cardiac structure contours were used to build the heart atlas libraries for each cardiac structure using commercially available software (MIMvista Corp., Cleveland, OH). The atlas template voxel size was 3×3×3mm3. To quantify the precision of the automatically delineated cardiac structures using ABAS, they were compared with the manually delineated structures from experts. The discrepancies between the manual and automatic contouring were evaluated for 470 cases, and the Dice Similarity Coefficient (DSC), Jaccard Index (JI) and Housdorff Distance (HD) between the two types of contouring were calculated for geometrical comparisons. The fractional volume dose factors, (VD’s, D = 5, 15, 25, 35, 45, 55 Gy) were calculated for pericardium, for dosimetric comparison. To test the feasibility of using the ABAS for quality assurance, we used 373 patient cases with heart contours that result in discrepancy of more than 5% in mean heart dose. DSC between the test and ABAS contours were calculated. We tested the sensitivity of three different thresholds of DSC for picking out these discrepant contours.
The results were shown in Table 1. There is minimal difference between different VD’s for automatically and manually delineated pericardium contours. Using threshold value of 0.86, 0.87 and 0.88, the rate with which we can pick out discrepant contours is 0.85, 0.90 and 0.93, respectively.
ABAS demonstrates great potentials to accurately delineate the cardiac structures automatically, and it is feasible to be used for cost-effective QA for clinical trials. Extensive investigations are planned to comprehensively evaluate the operating characteristics (e.g., sensitivity and specificity) of ABAS as a QA tool.
International journal of radiation oncology, biology, physics 09/2014; 90(1):s735. · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose/Objective(s)
RTOG 1308 is a phase III randomized trial comparing overall survival after photon versus proton chemoradiation therapy for inoperable stage II-IIIB NSCLC, to determine if proton therapy can improve overall survival by reducing the risk of severe toxicity to organs at risk compared to photon-based IMRT. More stringent dose constraints are being used for RTOG 1308 than prior NSCLC RTOG studies. The purpose of this work is to establish the feasibility of the dosimetric criteria of this trial through testing against photon IMRT and passively scattered proton therapy (PSPT) plans and to assess the effect of different definitions of normal lungs (lungs minus GTV (DVHG), lungs minus CTV (DVHC) and lungs minus PTV (DVHP)) on lungs dose parameters.
Paired lung IMRT and PSPT (n = 26) plans were collected from two different institutions regularly treating NSCLC with PSPT. Plans were loaded into MIM, scaled to 70 Gy (RBE) (95% of PTV receives 70 Gy) and their DVHs were analyzed and tested against the dosimetric compliance criteria of RTOG 1308. Lungs dose parameters based on different definitions for the normal lung were also compared.
Most of the RTOG 1308 protocol dosimetric criteria were achieved by both IMRT and PSPT plans, with a relatively high deviation unacceptable rate in the heart maximum dose (HMD). A deviation unacceptable rate of over 60% was scored for the HMD. However, the passing rate of the HMD was increased to 80% using the protocol allowable variations. Dose parameters for the target volume were very similar for IMRT and PSPT plans. PSPT plans led to lower lung V5Gy (%); maximum spinal cord dose; and heart V5Gy (%); V30Gy (%); V45Gy (%) and mean heart dose as compared with IMRT plans. The average percentage relative differences in lungs V5Gy (%) were 3.3 ± 0.4 (IMRT) and 5.6± 0.5 (PSPT) for DVHG Vs. DVHC and 7.1 ± 0.6 (IMRT) and 12.00 ± 1(PSPT) for DVHG Vs. DVHP; in lungs V20Gy (%) were 7.6 ± 0.7 (IMRT) and 7.8 ± 0.8 (PSPT) for DVHG Vs. DVHC and 16 ± 1 (IMRT) and 17 ± 1 (PSPT) for DVHG Vs. DVHP and in mean lung dose were 9.2 ± 0.8 (IMRT) and 10.8 ± 0.9 (PSPT) for DVHG Vs. DVHC and 19 ± 1 (IMRT) and 22 ± 2 (PSPT) for DVHG Vs. DVHP.
Most of the RTOG 1308 protocol dosimetric criteria were achieved with IMRT and PSPT. Both IMRT and PSPT lead to similar PTV dose parameters. However, PSPT plans led to lower dose parameters for most normal structures as compared with IMRT plans. Different definitions of normal lung (lungs minus GTV, lungs minus CTV and lungs minus PTV) led to different lungs doses and these differences can be as high as 15-22%.
International Journal of Radiation OncologyBiologyPhysics 09/2014; 90(1):s124. · 4.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose:
To review IGRT credentialing experience and unexpected technical issues encountered in connection with advanced radiotherapy technologies as implemented in RTOG clinical trials. To update IGRT credentialing procedures with the aim of improving the quality of the process, and to increase the proportion of IGRT credentialing compliance. To develop a living disease site-specific IGRT encyclopedia.
Numerous technical issues were encountered during the IGRT credentialing process. The criteria used for credentialing review were based on: image quality; anatomy included in fused data sets and shift results. Credentialing requirements have been updated according to the AAPM task group reports for IGRT to ensure that all required technical items are included in the quality review process. Implementation instructions have been updated and expanded for recent protocols.
Technical issues observed during the credentialing review process include, but are not limited to: poor quality images; inadequate image acquisition region; poor data quality; shifts larger than acceptable; no soft tissue surrogate. The updated IGRT credentialing process will address these issues and will also include the technical items required from AAPM: TG 104; TG 142 and TG 179 reports. An instruction manual has been developed describing a remote credentialing method for reviewers. Submission requirements are updated, including images/documents as well as facility questionnaire. The review report now includes summary of the review process and the parameters that reviewers check. We have reached consensus on the minimum IGRT technical requirement for a number of disease sites. RTOG 1311(NRG-BR002A Phase 1 Study of Stereotactic Body Radiotherapy (SBRT) for the Treatment of Multiple Metastases) is an example, here; the protocol specified the minimum requirement for each anatomical sites (with/without fiducials).
Technical issues are identified and reported. IGRT guidelines are updated, with the corresponding credentialing requirements. An IGRT encyclopedia describing site-specific implementation issues is currently in development.
Medical Physics 06/2014; 41(6):387. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose
To quantify variations in target and normal structure contouring and evaluate dosimetric impact of these variations in non-small cell lung cancer (NSCLC) cases. To study whether providing an atlas can reduce potential variation.
Methods and materials
Three NSCLC cases were distributed sequentially to multiple institutions for contouring and radiation therapy planning. No segmentation atlas was provided for the first 2 cases (Case 1 and Case 2). Contours were collected from submitted plans and consensus contour sets were generated. The volume variation among institution contours and the deviation of them from consensus contours were analyzed. The dose-volume histograms for individual institution plans were recalculated using consensus contours to quantify the dosimetric changes. An atlas containing targets and critical structures was constructed and was made available when the third case (Case 3) was distributed for planning. The contouring variability in the submitted plans of Case 3 was compared with that in first 2 cases.
Planning target volume (PTV) showed large variation among institutions. The PTV coverage in institutions’ plans decreased dramatically when reevaluated using the consensus PTV contour. The PTV contouring consistency did not show improvement with atlas use in Case 3. For normal structures, lung contours presented very good agreement, while the brachial plexus showed the largest variation. The consistency of esophagus and heart contouring improved significantly (t test; P < .05) in Case 3. Major factors contributing to the contouring variation were identified through a survey questionnaire.
The amount of contouring variations in NSCLC cases was presented. Its impact on dosimetric parameters can be significant. The segmentation atlas improved the contour agreement for esophagus and heart, but not for the PTV in this study. Quality assurance of contouring is essential for a successful multi-institutional clinical trial.
[Show abstract][Hide abstract] ABSTRACT: To provide quantitative and qualitative image quality metrics and imaging dose for modern Varian On-board Imager (OBI) (ver. 1.5) and Elekta X-ray Volume Imager (XVI) (ver. 4.5R) cone-beam computed tomography (CBCT) systems in a clinical adaptive radiation therapy environment by accounting for varying patient thickness.
Image quality measurements were acquired with Catphan 504 phantom (nominal diameter and with additional 10 cm thickness) for OBI and XVI systems and compared to planning CT (pCT) (GE LightSpeed). Various clinical protocols were analyzed for the OBI and XVI systems and analyzed using image quality metrics, including spatial resolution, low contrast detectability, uniformity, and HU sensitivity. Imaging dose measurements were acquired in Wellhofer Scanditronix i'mRT phantom at nominal phantom diameter and with additional 4 cm phantom diameter using GafChromic XRQA2 film. Calibration curves were generated using previously published in-air Air Kerma calibration method.
The OBI system full trajectory scans exhibited very little dependence on phantom thickness for accurate HU calculation, while half-trajectory scans with full-fan filter exhibited dependence of HU calculation on phantom thickness. The contrast-to-noise ratio (CNR) for the OBI scans decreased with additional phantom thickness. The uniformity of Head protocol scan was most significantly affected with additional phantom thickness. The spatial resolution and CNR compared favorably with pCT, while the uniformity of the OBI system was slightly inferior to pCT. The OBI scan protocol dose levels for nominal phantom thickness at the central portion of the phantom were 2.61, 0.72, and 1.88 cGy, and for additional phantom thickness were 1.95, 0.48, and 1.52 cGy, for the Pelvis, Thorax, and Spotlight protocols, respectively. The XVI system scans exhibited dependence on phantom thickness for accurate HU calculation regardless of trajectory. The CNR for the XVI scans decreased with additional phantom thickness. The uniformity of the XVI scans was significantly dependent on the selection of the proper FOV setting for all phantom geometries. The spatial resolution, CNR, and uniformity for XVI were lower than values measured for pCT. The XVI scan protocol dose levels at the central portion of the phantom for nominal phantom thickness were 2.14, 2.15, and 0.33 cGy, and for additional phantom thickness were 1.56, 1.68, and 0.21 cGy, for the Pelvis M20, Chest M20, and Prostate Seed S10 scan protocols, respectively.
The OBI system offered comparable spatial resolution and CNR results to the results for pCT. Full trajectory scans with the OBI system need little-to-no correction for HU calculation based on HU stability with changing phantom thickness. The XVI system offered lower spatial resolution and CNR results than pCT. In addition, the HU calculation for all scan protocols was dependent on the phantom thickness. The uniformity for each CBCT system was inferior to that of pCT for each phantom geometry. The dose for each system and scan protocol in the interior of the phantom tended to decrease by approximately 25% with 4 cm additional phantom thickness.
Medical Physics 03/2014; 41(3):031908. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To give a preliminary report of clinical and treatment factors associated with toxicity in men receiving high-dose radiation therapy (RT) on a phase 3 dose-escalation trial.
The trial was initiated with 3-dimensional conformal RT (3D-CRT) and amended after 1 year to allow intensity modulated RT (IMRT). Patients treated with 3D-CRT received 55.8 Gy to a planning target volume that included the prostate and seminal vesicles, then 23.4 Gy to prostate only. The IMRT patients were treated to the prostate and proximal seminal vesicles to 79.2 Gy. Common Toxicity Criteria, version 2.0, and Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer late morbidity scores were used for acute and late effects.
Of 763 patients randomized to the 79.2-Gy arm of Radiation Therapy Oncology Group 0126 protocol, 748 were eligible and evaluable: 491 and 257 were treated with 3D-CRT and IMRT, respectively. For both bladder and rectum, the volumes receiving 65, 70, and 75 Gy were significantly lower with IMRT (all P<.0001). For grade (G) 2+ acute gastrointestinal/genitourinary (GI/GU) toxicity, both univariate and multivariate analyses showed a statistically significant decrease in G2+ acute collective GI/GU toxicity for IMRT. There were no significant differences with 3D-CRT or IMRT for acute or late G2+ or 3+ GU toxicities. Univariate analysis showed a statistically significant decrease in late G2+ GI toxicity for IMRT (P=.039). On multivariate analysis, IMRT showed a 26% reduction in G2+ late GI toxicity (P=.099). Acute G2+ toxicity was associated with late G3+ toxicity (P=.005). With dose-volume histogram data in the multivariate analysis, RT modality was not significant, whereas white race (P=.001) and rectal V70 ≥15% were associated with G2+ rectal toxicity (P=.034).
Intensity modulated RT is associated with a significant reduction in acute G2+ GI/GU toxicity. There is a trend for a clinically meaningful reduction in late G2+ GI toxicity with IMRT. The occurrence of acute GI toxicity and large (>15%) volumes of rectum >70 Gy are associated with late rectal toxicity.
International journal of radiation oncology, biology, physics 10/2013; · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose/Objective(s)
Rapid reviews of the first cases entered on experimental arms of RTOG clinical trials are meant to ensure that the quality of treatment planning will support the conclusions for the primary endpoint. Institutions must pass the rapid review prior to treating the patient. We analyzed cases that failed the rapid review in the RTOG 1005 phase III trial for early stage breast cancer comparing accelerated hypofractionated whole breast irradiation (WBI) with concurrent boost (ARM II) versus standard WBI plus sequential boost (ARM I).
Target volume and dose volume (DV) analysis forms, designed specifically for the rapid review process, with data for all the cases that failed to pass the contouring and/or dose volume (DV) criteria of RTOG 1005 were analyzed. The overall failure rate, and the reason and frequency for specific failure were studied.
A total of 145 cases were submitted for the rapid review of RTOG 1005 at the time of abstract submission with 51 cases (35%) failing to meet the compliance criteria. Among these cases, 40 (78%) became compliant on second submission, 8 cases required a third submission and 3 cases chose not to resubmit. Among the 51 failed cases at first submission, 45 cases (88%) did not meet either the contouring criteria alone or both contouring and DV criteria, and 6 cases (12%) did not meet the DV criteria alone. The number of structures that did not meet the contouring criteria was: one in 20 cases; two in 9 cases; three in 6 cases; four in 4 cases; five in 3 cases; six in one case, and seven in 2 cases. The most frequent structures that failed the contouring criteria were PTV_WB_EVAL (17 times); CTV_WB (11 times); PTV_WB (11 times), PTV_BOOST_EVAL (9 times); thyroid (8 times); PTV_SURG_BED_EVAL (8 times), and CTV_SURG_BED (6 times). Among the 6 cases that failed to meet the DV criteria alone, 5 cases were due to higher than permitted dose to the contralateral breast. For all the cases submitted, 26% (13/49) of IMRT cases and 15% (14/96) of 3DCRT cases failed the DV criteria.
One third of rapid review cases on the RTOG 1005 trial (to date) failed to meet the protocol contouring and dosimetry compliance criteria on first submission. The PTV_WB_EVAL is the structure that failed most to meet criteria, while the DV constraint that was not met the most was the dose to the contralateral breast. In response, the protocol was amended by clarifying contouring guidelines and making the DV constraints for the contralateral breast more flexible. The high failure rate in the rapid review process on this large phase III trial demonstrates the need for rigorous QA. More standardization and pre-enrollment training on both contouring and dosimetry planning techniques may be helpful.
International journal of radiation oncology, biology, physics 10/2013; 87(2):s228. · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: American College of Radiology and American Society for Radiation Oncology Practice Guideline for the Performance of Stereotactic Radiosurgery (SRS). SRS is a safe and efficacious treatment option of a variety of benign and malignant disorders involving intracranial structures and selected extracranial lesions. SRS involves a high dose of ionizing radiation with a high degree of precision and spatial accuracy. A quality SRS program requires a multidisciplinary team involved in the patient management. Organization, appropriate staffing, and careful adherence to detail and to established SRS standards is important to ensure operational efficiency and to improve the likelihood of procedural success. A collaborative effort of the American College of Radiology and American Society for Therapeutic Radiation Oncology has produced a practice guideline for SRS. The guideline defines the qualifications and responsibilities of all the involved personnel, including the radiation oncologist, neurosurgeon, and qualified medical physicist. Quality assurance is essential for safe and accurate delivery of treatment with SRS. Quality assurance issues for the treatment unit, stereotactic accessories, medical imaging, and treatment-planning system are presented and discussed. Adherence to these practice guidelines can be part of ensuring quality and patient safety in a successful SRS program.
American journal of clinical oncology 06/2013; 36(3):310-315. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: To investigate the effect of energy (kVp) and filters (no filter, half Bowtie, and full Bowtie) on the dose response curves of the Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters (OSLDs) in CBCT dose fields. To measure surface and internal doses received during x-ray volume imager (XVI) (Version R4.5) and on board imager (OBI) (Version 1.5) CBCT imaging protocols using these two types of dosimeters.Methods: Gafchromic XRQA2 film and nanoDot OSLD dose response curves were generated at different kV imaging settings used by XVI (software version R4.5) and OBI (software version 1.5) CBCT systems. The settings for the XVI system were: 100 kVp∕F0 (no filter), 120 kVp∕F0, and 120 kVp∕F1 (Bowtie filter), and for the OBI system were: 100 kVp∕full fan, 125 kVp∕full fan, and 125 kVp∕half fan. XRQA2 film was calibrated in air to air kerma levels between 0 and 11 cGy and scanned using reflection scanning mode with the Epson Expression 10000 XL flat-bed document scanner. NanoDot OSLDs were calibrated on phantom to surface dose levels between 0 and 14 cGy and read using the inLight(TM) MicroStar reader. Both dosimeters were used to measure in field surface and internal doses in a male Alderson Rando Phantom.Results: Dose response curves of XRQA2 film and nanoDot OSLDs at different XVI and OBI CBCT settings were reported. For XVI system, the surface dose ranged between 0.02 cGy in head region during fast head and neck scan and 4.99 cGy in the chest region during symmetry scan. On the other hand, the internal dose ranged between 0.02 cGy in the head region during fast head and neck scan and 3.17 cGy in the chest region during chest M20 scan. The average (internal and external) dose ranged between 0.05 cGy in the head region during fast head and neck scan and 2.41 cGy in the chest region during chest M20 scan. For OBI system, the surface dose ranged between 0.19 cGy in head region during head scan and 4.55 cGy in the pelvis region during spot light scan. However, the internal dose ranged between 0.47 cGy in the head region during head scan and 5.55 cGy in the pelvis region during spot light scan. The average (internal and external) dose ranged between 0.45 cGy in the head region during head scan and 3.59 cGy in the pelvis region during spot light scan. Both Gafchromic XRQA2 film and nanoDot OSLDs gave close estimation of dose (within uncertainties) in many cases. Though, discrepancies of up to 20%-30% were observed in some cases.Conclusions: Dose response curves of Gafchromic XRQA2 film and nanoDot OSLDs indicated that the dose responses of these two dosimeters were different even at the same photon energy when different filters were used. Uncertainty levels of both dosimetry systems were below 6% at doses above 1 cGy. Both dosimetry systems gave almost similar estimation of doses (within uncertainties) in many cases, with exceptions of some cases when the discrepancy was around 20%-30%. New versions of the CBCT systems (investigated in this study) resulted in lower imaging doses compared with doses reported on earlier versions in previous studies.
Medical Physics 06/2013; 40(6):062102. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The National Cancer Institute clinical cooperative groups have been instrumental over the past 50 years in developing clinical trials and evidence-based process improvements for clinical oncology patient care. The cooperative groups are undergoing a transformation process as we further integrate molecular biology into personalized patient care and move to incorporate international partners in clinical trials. To support this vision, data acquisition and data management informatics tools must become both nimble and robust to support transformational research at an enterprise level. Information, including imaging, pathology, molecular biology, radiation oncology, surgery, systemic therapy, and patient outcome data needs to be integrated into the clinical trial charter using adaptive clinical trial mechanisms for design of the trial. This information needs to be made available to investigators using digital processes for real-time data analysis. Future clinical trials will need to be designed and completed in a timely manner facilitated by nimble informatics processes for data management. This paper discusses both past experience and future vision for clinical trials as we move to develop data management and quality assurance processes to meet the needs of the modern trial.
Frontiers in Oncology 03/2013; 3:31.
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[Show abstract][Hide abstract] ABSTRACT: Total body irradiation (TBI) is a specialized radiotherapy technique. It is frequently used as a component of treatment plans involving hematopoietic stem cell transplant for a variety of disorders, most commonly hematologic malignancies. A variety of treatment delivery techniques, doses, and fractionation schemes can be utilized. A collaborative effort of the American College of Radiology and American Society for Radiation Oncology has produced a practice guideline for delivery of TBI. The guideline defines the qualifications and responsibilities of the involved personnel, including the radiation oncologist, physicist, dosimetrist, and radiation therapist. Review of the typical indications for TBI is presented, and the importance of integrating TBI into the multimodality treatment plan is discussed. Procedures and special considerations related to the simulation, treatment planning, treatment delivery, and quality assurance for patients treated with TBI are reviewed. This practice guideline can be part of ensuring quality and safety in a successful TBI program.
American journal of clinical oncology 02/2013; 36(1):97-101. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Surface doses received during seven different imaging protocols (using the kV XVI imager) were measured on a Rando phantom surface using nanoDot optical stimulated luminescence dosimeters (OSLD) for three different body regions (head and neck, chest and pelvis). For each protocol, the surface dose was measured at four different locations on the surface of the phantom (ANT., POST., LLAT. and RLAT.). The surface dose at any location in the irradiated area can range between 0.008 cGy (fast head and neck protocol) and 4.38 cGy (symmetry 4D). The average surface dose in the irradiated area ranged between 0.038 cGy and 2.34 cGy. The measured doses were compared with nominal scan dose, provided by the vendor and calculated doses.
[Show abstract][Hide abstract] ABSTRACT: Purpose: To evaluate the effect of different beam filters on the dose response curves of nanoDot OSL dosimeters at kV CBCT energy. Methods: The InLight™ OSL dosimetry system (Landauer,Inc., Glenwood, IL, USA) consisting of nanoDot dosimeters and MicroStar reader was calibrated using the X‐ray Volume Imager (XVI) mounted on the Elekta Synergy (Elekta, Crawley, UK) linac and the On Board Imager(OBI) mounted on the Varian True Beam (Varian Medical systems, Palo Alto, CA) linac. Doses ranged between 0 and 12 cGy were delivered to nanoDot OSLDs on 5 cm thick PMMA slab using 120kVp F0(no filter) and F1(Bowtie filter)XVI CBCT beams, 125 kVp half fan (HF) and full fan (FF) OBI beams. Dose points were correlated to absolute air kerma levels measured in air using the 0.6 cc Farmer ionization chamber and converted to dose in water at the phantom surface according to AAPM TG61. Results: Dose response curves for all imaging settings were linear. The dose response curves for the 120 kVp F0 and F1 VXI CBCT beams differed by 8 to 9 %. The dose response curves for the 125 kVp FF and HF OBI CBCT beams also differed by 7 to 8 %. These results suggest that nanoDot dosimeters are sensitive not only to differences in kVp of the beam but also to differences in spectra resulted from the use of different filters. Conclusion: Dose response curves of nanoDot OSLDs for photon beams of same kVp but filtered with different filters are different. Hence,the use of correction factors (based solely on differences in the response of the OSLDs at different kVps) to allow the reading of the MicroStar reader to be converted from one set of reference condition to another is not sufficient to ensure accurate estimation of measured doses.It is important to create dose response curve at every irradiation setting. This project is funded, in part, under a grant with the Pennsylvania Department of Health. The Department specifically declaims responsibility for any analyses, interpretations or conclusions
Medical Physics 01/2013; 40(6):126. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: To measure CBCT dose profiles inside phantom using Gafchromic XRQA2 film. Methods: Gafchromic XRQA2 film (International Specialty Products, Wayne, NJ) whole sheets were placed between slabs of the IMRT head and torso free point phantom, model 002H9K (Computerized Imaging Reference Systems, Inc, Norfolk, Virginia). Doses were acquired during chest and head imaging protocols of the Volume Imager (XVI) mounted on the Elekta linar accelerator (Elekta, Crawley, UK). Scanned films were analyzed using ImageJ (National Institute of Health, Bethesda, MD). Results: For the Chest protocol (full trajectory), dose ranged between 1.25 and 2.11 cGy, with average dose of 1.78 cGy. Here, the dose increased over the first 3 cm from the right surface of the phantom, it then leveled off, with average fluctuation of around 5% (within uncertainty level, with the exception of few points where a fluctuation of 24% was observed). Dose eventually started to drop in the left side of the phantom till it reached its lowest value. For the head and neck protocol (trajectory is 200°), dose ranged between 0.02 and 0.13 cGy, with average value of 0.09 cGy. The dose was more or less uniform from the right surface of the phantom till its center (it fluctuated within uncertainty level of 20 to 40% and even higher at some low dose points) and then started to increase from almost the center of the phantom until it reached its highest value near the left surface. Conclusion: Full trajectory protocol led to uniform dose distribution in the middle part of the phantom and doses were less near surfaces. However, for a protocol with a trajectory of 200° degree, the dose was uniform in one part of the phantom and showed increase in the other part, consistent with the start/stop angle of the gantry. Measured dose fluctuated mostly within uncertainty levels. This project is funded, in part, under a grant with the Pennsylvania Department of Health. The Department specifically declaims responsibility for any analyses, interpretations or conclusions
Medical Physics 01/2013; 40(6):126. · 3.01 Impact Factor