Independent Dose Verification Software Research Articles

Dose Calculation Accuracy of Beam Models in RadCalc for a 1.5 T MR-Linac

The purpose of this study is to evaluate RadCalc, an independent dose verification software, for patient-specific quality assurance (PSQA) in online adaptive planning with a magnetic resonance linear accelerator (MR-linac) of a 1.5 T. Version 7.1.4 of RadCalc to introduce the capability to establish a beam model that incorporates MR field characteristics. A total of six models were established, with one using manufacturer-provided data and the others differing in percentage depth dose (PDD) data sources. Overall, two models utilized PDD data from the treatment planning system (TPS), and three used commissioned PDD data from gantry angles of 0° and 270°. Simple tests on a virtual water phantom assessed dose-calculation accuracy, revealing percentage differences ranging from −0.5% to −20.6%. Excluding models with significant differences, clinical tests on 575 adaptive plans (prostate, liver, and breast) showed percentage differences of −0.51%, 1.12%, and 4.10%, respectively. The doses calculated using RadCalc demonstrated similar trends to those of the PSQA-based measurements. The newly released version of RadCalc enables beam modeling that considers the characteristics of the 1.5 T magnetic field. The accuracy of the software in calculating doses at 1.5 T magnetic fields has been verified, thereby making it a reliable and effective tool for PSQA in adaptive plans.

Is it necessary to perform measurement-based patient-specific quality assurance for online adaptive radiotherapy with Elekta Unity MR-Linac?

This study aimed to investigate the necessity of measurement-based patient-specific quality assurance (PSQA) for online adaptive radiotherapy by analyzing measurement-based PSQA results and calculation-based 3D independent dose verification results with Elekta Unity MR-Linac. There are two workflows for Elekta Unity enabled in the treatment planning system: adapt to position (ATP) and adapt to shape (ATS). ATP plans are those which have relatively slighter shifts from reference plans by adjusting beam shapes or weights, whereas ATS plans are the new plans optimized from the beginning with probable re-contouring targets and organs-at-risk. PSQA gamma passing rates were measured using an MR-compatible ArcCHECK diode array for 78 reference plans and corresponding 208 adaptive plans (129 ATP plans and 79 ATS plans) of Elekta Unity. Subsequently, the relationships between ATP, or ATS plans and reference plans were evaluated separately. The Pearson's r correlation coefficients between ATP or ATS adaptive plans and corresponding reference plans were also characterized using regression analysis. Moreover, the Bland-Altman plot method was used to describe the agreement of PSQA results between ATP or ATS adaptive plans and reference plans. Additionally, Monte Carlo-based independent dose verification software ArcherQA was used to perform secondary dose check for adaptive plans. For ArcCHECK measurements, the average gamma passing rates (ArcCHECK vs. TPS) of PSQA (3%/2mm criterion) were 99.51%±0.88% and 99.43%±0.54% for ATP and ATS plans, respectively, which were higher than the corresponding reference plans 99.34%±1.04% (p<0.05) and 99.20%±0.71% (p<0.05), respectively. The Pearson's r correlation coefficients were 0.720 between ATP and reference plans and 0.300 between ATS and reference plans with ArcCHECK, respectively. Furthermore,>95% of data points of differences between both ATP and ATS plans and reference plans were within±2σ (standard deviation) of the mean difference between adaptive and reference plans with ArcCHECK measurements. With ArcherQA calculation, the average gamma passing rates (ArcherQA vs. TPS) were 98.23%±1.64% and 98.15%±1.07% for ATP and ATS adaptive plans, separately. It might be unnecessary to perform measurement-based PSQA for both ATP and ATS adaptive plans for Unity if the gamma passing rates of both measurements of corresponding reference plans and independent dose verification of adaptive plans have high gamma passing rates. Periodic machine QA and verification of adaptive plans were recommended to ensure treatment safety.

Effective clinical applications of Monte Carlo-based independent secondary dose verification software for helical tomotherapy

PurposeTo investigate the scope of the effective clinical application of Monte Carlo (MC)-based independent dose verification software for helical tomotherapy. MethodsDoseCHECK was selected as the MC-based dose calculation software. First, the dose calculation accuracy of DoseCHECK was evaluated with film and chamber measurements in a water-equivalent phantom. Second, the dose calculation accuracy was examined in several heterogeneous materials. Finally, dosimetric comparisons between DoseCHECK and the treatment planning system (TPS) were performed for clinical patient plans. Prostate IMRT, head and neck IMRT (HN), total body irradiation (TBI), and brain stereotactic radiotherapy (SRT) were evaluated. ResultThe DoseCHECK calculations agreed with the chamber and film measurements in the homogenous phantom. For heterogeneous phantom cases, the dose differences between DoseCHECK and TPS were within 3 %, except in air, in which large dose differences of 20 % were observed. In clinical patient plans, the median dose differences between the lung Dmean in TBI cases and the normal brain Dmean in brain SRT cases were significantly >3 %. For HN and brain SRT cases, the median target dose differences were >3 %. ConclusionOur results show that independent dose verification with the MC algorithm can detect systematic errors caused by the lack of heterogeneity correction in the TPS. In particular, MC-based independent dose verification is required for HN, TBI, and brain SRT cases in helical tomotherapy.

A study of an independent dose verification software for brachytherapy

Objective To report an implementation method and results of an independent brachytherapy dose verification software (DVS). Methods The DVS was developed based on Visual C+ + and the modular structure design was adopted. The DICOM RT files exported from the treatment planning system (TPS) were automatically loaded into the DVS. The TG-43 formalism was employed for dose calculation. Six cervical cancer patients who underwent brachytherapy were retrospectively selected to test the DVS. Different applicators were utilized for each patient. Dosimetric parameters and γ analysis (0.1cm, 5%) were used to evaluate the dose difference between the DVS and the TPS. Results Compared with the TPS dose, the γ pass rates of the doses calculated by the DVS were higher than 98%. For CTV, the dosimetric differences were less than 0.29% and 0.53% for D100% and D90%. For bladder, rectum and sigmoid, the agreement of D0.1cm3, D1cm3 and D2cm3 within a 0.5% level. Conclusion With minimal human-computer interactions, the DVS can verify the accuracy of dose calculated by TPS for brachytherapy. Key words: Brachytherapy; Dose verification; Treatment planning system; Quality assurance

A feasibility study of independent verification of dose calculation for Vero4DRT using a Clarkson-based algorithm

Dose verification for a gimbal-mounted image-guided radiotherapy system, Vero4DRT (Mitsubishi Heavy Industries Ltd., Tokyo, Japan) is usually carried out by pretreatment measurement. Independent verification calculations using Monte Carlo methods for Vero4DRT have been published. As the Clarkson method is faster and easier to use than measurement and Monte Carlo methods, we evaluated the accuracy of an independent calculation verification program and its feasibility as a secondary check for Vero4DRT. Computed tomography (CT)-based dose calculation was performed using a modified Clarkson-based algorithm. In this study, 120 patients' treatment plans were collected in our institute. The treatments were performed using conventional irradiation for lung and prostate, 3-dimensional (3D) conformal stereotactic body radiotherapy (SBRT) for the lung, and intensity-modulated radiation therapy (IMRT) for the prostate. Differences between the treatment planning system (TPS) and the Clarkson-based independent dose verification software were computed, and confidence limits (CLs, mean ± 2 standard deviation %) for Vero4DRT were compared with the CLs for the C-arms linear accelerators in the previous study. The results of the CLs, the conventional irradiation, SBRT, and IMRT showed 2.2 ± 3.5% (CL of the C-arms linear accelerators: 2.4 ± 5.3%), 1.1 ± 1.7% (−0.3 ± 2.0%), 4.8 ± 3.7% (5.4 ± 5.3%), and −0.5 ± 2.5% (−0.1 ± 3.6%) differences, respectively. The dose disagreement between the TPS and CT-based independent dose verification software was less than the 5% action level of American Association of Physicists in Medicine (AAPM) Task Group 114 (TG114). The CLs for the gimbal-mounted Vero4DRT were similar to the deviations for C-arms linear accelerators.

Impact of Different Independent Dose Verification Software Programs for Secondary Check.

A multi-institutional study was performed to identify the impact of different independent dose verification programs on independent dose verification software program. Data for 1,543 treatment fields were collected in three institutions. RADCALC and Simple MU Analysis (Simple MU) using the Clarkson-based algorithm were used. RADCALC needs the input of radiological path length (RPL) from radiotherapy treatment planning systems (RTPSs) (Eclipse or Pinnacle3). The Simple MU computes the RPL using CT images independently from the RTPSs. Ion-chamber measurements were performed for commissioning the two programs and the RTPSs. Next, the results of the two programs were compared to the RTPSs obtained in the clinically-approved plans in all three institutions. The commissioning results showed ±1.5% variation in the ion-chamber measurements and there was slight difference between the institutions. The RADCALC (0.9±2.2%) and the Simple MU (1.7±2.1%) results showed a slight systematic difference. Pinnacle3 computed longer RPLs because it used CT-physical density tables. Thus, there was an impact on the accuracy in the treatment plans involving bone and other high-density materials. Dose calculation algorithms in different dose verification programs provided similar results. However, care must be taken because different RPL calculation methods in the RTPSs may affect dose difference between different independent dose verification programs by 1%.

SU‐F‐T‐288: Impact of Trajectory Log Files for Clarkson‐Based Independent Dose Verification of IMRT and VMAT

Purpose:To investigate the effect of the trajectory files from linear accelerator for Clarkson‐based independent dose verification in IMRT and VMAT plans.Methods:A CT‐based independent dose verification software (Simple MU Analysis: SMU, Triangle Products, Japan) with a Clarksonbased algorithm was modified to calculate dose using the trajectory log files. Eclipse with the three techniques of step and shoot (SS), sliding window (SW) and Rapid Arc (RA) was used as treatment planning system (TPS). In this study, clinically approved IMRT and VMAT plans for prostate and head and neck (HN) at two institutions were retrospectively analyzed to assess the dose deviation between DICOM‐RT plan (PL) and trajectory log file (TJ). An additional analysis was performed to evaluate MLC error detection capability of SMU when the trajectory log files was modified by adding systematic errors (0.2, 0.5, 1.0 mm) and random errors (5, 10, 30 mm) to actual MLC position.Results:The dose deviations for prostate and HN in the two sites were 0.0% and 0.0% in SS, 0.1±0.0%, 0.1±0.1% in SW and 0.6±0.5%, 0.7±0.9% in RA, respectively. The MLC error detection capability shows the plans for HN IMRT were the most sensitive and 0.2 mm of systematic error affected 0.7% dose deviation on average. Effect of the MLC random error did not affect dose error.Conclusion:The use of trajectory log files including actual information of MLC location, gantry angle, etc should be more effective for an independent verification. The tolerance level for the secondary check using the trajectory file may be similar to that of the verification using DICOM‐RT plan file. From the view of the resolution of MLC positional error detection, the secondary check could detect the MLC position error corresponding to the treatment sites and techniques.This research is partially supported by Japan Agency for Medical Research and Development (AMED)

SU‐F‐T‐268: A Feasibility Study of Independent Dose Verification for Vero4DRT

Purpose:Vero4DRT (Mitsubishi Heavy Industries Ltd.) has been released for a few years. The treatment planning system (TPS) of Vero4DRT is dedicated, so the measurement is the only method of dose verification. There have been no reports of independent dose verification using Clarksonbased algorithm for Vero4DRT. An independent dose verification software program of the general‐purpose linac using a modified Clarkson‐based algorithm was modified for Vero4DRT. In this study, we evaluated the accuracy of independent dose verification program and the feasibility of the secondary check for Vero4DRT.Methods:iPlan (Brainlab AG) was used as the TPS. PencilBeam Convolution was used for dose calculation algorithm of IMRT and X‐ray Voxel Monte Carlo was used for the others. Simple MU Analysis (SMU, Triangle Products, Japan) was used as the independent dose verification software program in which CT‐based dose calculation was performed using a modified Clarkson‐based algorithm. In this study, 120 patients’ treatment plans were collected in our institute. The treatments were performed using the conventional irradiation for lung and prostate, SBRT for lung and Step and shoot IMRT for prostate. Comparison in dose between the TPS and the SMU was done and confidence limits (CLs, Mean ± 2SD %) were compared to those from the general‐purpose linac.Results:As the results of the CLs, the conventional irradiation (lung, prostate), SBRT (lung) and IMRT (prostate) show 2.2 ± 3.5% (CL of the general‐purpose linac: 2.4 ± 5.3%), 1.1 ± 1.7% (−0.3 ± 2.0%), 4.8 ± 3.7% (5.4 ± 5.3%) and −0.5 ± 2.5% (−0.1 ± 3.6%), respectively. The CLs for Vero4DRT show similar results to that for the general‐purpose linac.Conclusion:The independent dose verification for the new linac is clinically available as a secondary check and we performed the check with the similar tolerance level of the general‐purpose linac.This research is partially supported by Japan Agency for Medical Research and Development (AMED)

SU-F-T-609: Impact of Dosimetric Variation for Prescription Dose Using Analytical Anisotropic Algorithm (AAA) in Lung SBRT

Purpose: Actual irradiated prescription dose to patients cannot be verified. Thus, independent dose verification and second treatment planning system are used as the secondary check. AAA dose calculation engine has contributed to lung SBRT. We conducted a multi-institutional study to assess variation of prescription dose for lung SBRT when using AAA in reference to using Acuros XB and Clarkson algorithm. Methods: Six institutes in Japan participated in this study. All SBRT treatments were planed using AAA in Eclipse and Adaptive Convolve (AC) in Pinnacle3. All of the institutes used a same independent dose verification software program (Simple MU Analysis: SMU, Triangle Product, Ishikawa, Japan), which implemented a Clarkson-based dose calculation algorithm using CT image dataset. A retrospective analysis for lung SBRT plans (73 patients) was performed to compute the confidence limit (CL, Average±2SD) in dose between the AAA and the SMU. In one of the institutes, a additional analysis was conducted to evaluate the variations between the AAA and the Acuros XB (AXB). Results: The CL for SMU shows larger systematic and random errors of 8.7±9.9 % for AAA than the errors of 5.7±4.2 % for AC. The variations of AAA correlated with the mean CT values in the voxels of PTV (a correlation coefficient : −0.7) . The comparison of AXB vs. AAA shows smaller systematic and random errors of −0.7±1.7%. The correlation between dose variations for AXB and the mean CT values in PTV was weak (0.4). However, there were several plans with more than 2% deviation of AAPM TG114 (Maximum: −3.3 %). Conclusion: In comparison for AC, prescription dose calculated by AAA may be more variable in lung SBRT patient. Even AXB comparison shows unexpected variation. Care should be taken for the use of AAA in lung SBRT. This research is partially supported by Japan Agency for Medical Research and Development (AMED)

SU‐F‐T‐494: A Multi‐Institutional Study of Independent Dose Verification Using Golden Beam Data

Purpose:In general, beam data of individual linac is measured for independent dose verification software program and the verification is performed as a secondary check. In this study, independent dose verification using golden beam data was compared to that using individual linac's beam data.Methods:Six institutions were participated and three different beam data were prepared. The one was individual measured data (Original Beam Data, OBD) .The others were generated by all measurements from same linac model (Model‐GBD) and all linac models (All‐GBD). The three different beam data were registered to the independent verification software program for each institute. Subsequently, patient's plans in eight sites (brain, head and neck, lung, esophagus, breast, abdomen, pelvis and bone) were analyzed using the verification program to compare doses calculated using the three different beam data.Results:1116 plans were collected from six institutes. Compared to using the OBD, the results shows the variation using the Model‐GBD based calculation and the All‐GBD was 0.0 ± 0.3% and 0.0 ± 0.6%, respectively. The maximum variations were 1.2% and 2.3%, respectively. The plans with the variation over 1% shows the reference points were located away from the central axis with/without physical wedge.Conclusion:The confidence limit (2SD) using the Model‐GBD and the All‐GBD was within 0.6% and 1.2%, respectively. Thus, the use of golden beam data may be feasible for independent verification. In addition to it, the verification using golden beam data provide quality assurance of planning from the view of audit.This research is partially supported by Japan Agency for Medical Research and Development(AMED)

SU‐E‐T‐48: A Multi‐Institutional Study of Independent Dose Verification for Conventional, SRS and SBRT

Purpose:To show the results of a multi‐institutional study of the independent dose verification for conventional, Stereotactic radiosurgery and body radiotherapy (SRS and SBRT) plans based on the action level of AAPM TG‐114.Methods:This study was performed at 12 institutions in Japan. To eliminate the bias of independent dose verification program (Indp), all of the institutions used the same CT‐based independent dose verification software (Simple MU Analysis, Triangle Products, JP) with the Clarkson‐based algorithm. Eclipse (AAA, PBC), Pinnacle3 (Adaptive Convolve) and Xio (Superposition) were used as treatment planning system (TPS). The confidence limits (CL, Mean±2SD) for 18 sites (head, breast, lung, pelvis, etc.) were evaluated in comparison in dose between the TPS and the Indp.Results:A retrospective analysis of 6352 treatment fields was conducted. The CLs for conventional, SRS and SBRT were 1.0±3.7 %, 2.0±2.5 % and 6.2±4.4 %, respectively. In conventional plans, most of the sites showed within 5 % of TG‐114 action level. However, there were the systematic difference (4.0±4.0 % and 2.5±5.8 % for breast and lung, respectively). In SRS plans, our results showed good agreement compared to the action level. In SBRT plans, the discrepancy between the Indp was variable depending on dose calculation algorithms of TPS.Conclusion:The impact of dose calculation algorithms for the TPS and the Indp affects the action level. It is effective to set the site‐specific tolerances, especially for the site where inhomogeneous correction can affect dose distribution strongly.

SU‐E‐T‐455: Impact of Different Independent Dose Verification Software Programs for Secondary Check

Purpose:There have been many reports for different dose calculation algorithms for treatment planning system (TPS). Independent dose verification program (IndpPro) is essential to verify clinical plans from the TPS. However, the accuracy of different independent dose verification programs was not evident. We conducted a multi‐institutional study to reveal the impact of different IndpPros using different TPSs.Methods:Three institutes participated in this study. They used two different IndpPros (RADCALC and Simple MU Analysis (SMU), which implemented the Clarkson algorithm. RADCALC needed the input of radiological path length (RPL) computed by the TPSs (Eclipse or Pinnacle3). SMU used CT images to compute the RPL independently from TPS). An ion‐chamber measurement in water‐equivalent phantom was performed to evaluate the accuracy of two IndpPros and the TPS in each institute. Next, the accuracy of dose calculation using the two IndpPros compared to TPS was assessed in clinical plan.Results:The accuracy of IndpPros and the TPSs in the homogenous phantom was +/−1% variation to the measurement. 1543 treatment fields were collected from the patients treated in the institutes. The RADCALC showed better accuracy (0.9 ± 2.2 %) than the SMU (1.7 ± 2.1 %). However, the accuracy was dependent on the TPS (Eclipse: 0.5%, Pinnacle3: 1.0%). The accuracy of RADCALC with Eclipse was similar to that of SMU in one of the institute.Conclusion:Depending on independent dose verification program, the accuracy shows systematic dose accuracy variation even though the measurement comparison showed a similar variation. The variation was affected by radiological path length calculation. IndpPro with Pinnacle3 has different variation because Pinnacle3 computed the RPL using physical density. Eclipse and SMU uses electron density, though.

SU‐E‐T‐762: Toward Volume‐Based Independent Dose Verification as Secondary Check

Purpose:Lung SBRT plan has been shifted to volume prescription technique. However, point dose agreement is still verified using independent dose verification at the secondary check. The volume dose verification is more affected by inhomogeneous correction rather than point dose verification currently used as the check. A feasibility study for volume dose verification was conducted in lung SBRT plan.Methods:Six SBRT plans were collected in our institute. Two dose distributions with / without inhomogeneous correction were generated using Adaptive Convolve (AC) in Pinnacle3. Simple MU Analysis (SMU, Triangle Product, Ishikawa, JP) was used as the independent dose verification software program, in which a modified Clarkson‐based algorithm was implemented and radiological path length was computed using CT images independently to the treatment planning system. The agreement in point dose and mean dose between the AC with / without the correction and the SMU were assessed.Results:In the point dose evaluation for the center of the GTV, the difference shows the systematic shift (4.5% ± 1.9 %) in comparison of the AC with the inhomogeneous correction, on the other hands, there was good agreement of 0.2 ± 0.9% between the SMU and the AC without the correction. In the volume evaluation, there were significant differences in mean dose for not only PTV (14.2 ± 5.1 %) but also GTV (8.0 ± 5.1 %) compared to the AC with the correction. Without the correction, the SMU showed good agreement for GTV (1.5 ± 0.9%) as well as PTV (0.9% ± 1.0%).Conclusion:The volume evaluation for secondary check may be possible in homogenous region. However, the volume including the inhomogeneous media would make larger discrepancy. Dose calculation algorithm for independent verification needs to be modified to take into account the inhomogeneous correction.

SU‐E‐T‐49: A Multi‐Institutional Study of Independent Dose Verification for IMRT

Purpose:AAPM TG114 does not cover the independent verification for IMRT. We conducted a study of independent dose verification for IMRT in seven institutes to show the feasibility.Methods:384 IMRT plans in the sites of prostate and head and neck (HN) were collected from the institutes, where the planning was performed using Eclipse and Pinnacle3 with the two techniques of step and shoot (S&amp;S) and sliding window (SW). All of the institutes used a same independent dose verification software program (Simple MU Analysis: SMU, Triangle Product, Ishikawa, JP), which is Clarkson‐based and CT images were used to compute radiological path length. An ion‐chamber measurement in a water‐equivalent slab phantom was performed to compare the doses computed using the TPS and an independent dose verification program. Additionally, the agreement in dose computed in patient CT images between using the TPS and using the SMU was assessed. The dose of the composite beams in the plan was evaluated.Results:The agreement between the measurement and the SMU were −2.3±1.9 % and −5.6±3.6 % for prostate and HN sites, respectively. The agreement between the TPSs and the SMU were −2.1±1.9 % and −3.0±3.7 for prostate and HN sites, respectively. There was a negative systematic difference with similar standard deviation and the difference was larger in the HN site. The S&amp;S technique showed a statistically significant difference between the SW. Because the Clarkson‐based method in the independent program underestimated (cannot consider) the dose under the MLC.Conclusion:The accuracy would be improved when the Clarkson‐based algorithm should be modified for IMRT and the tolerance level would be within 5%.

SU‐E‐T‐50: A Multi‐Institutional Study of Independent Dose Verification Software Program for Lung SBRT

Purpose:The accuracy of dose distribution depends on treatment planning system especially in heterogeneity‐region. The tolerance level (TL) of the secondary check using the independent dose verification may be variable in lung SBRT plans. We conducted a multi‐institutional study to evaluate the tolerance level of lung SBRT plans shown in the AAPM TG114.Methods:Five institutes in Japan participated in this study. All of the institutes used a same independent dose verification software program (Simple MU Analysis: SMU, Triangle Product, Ishikawa, JP), which is Clarkson‐based and CT images were used to compute radiological path length. Analytical Anisotropic Algorithm (AAA), Pencil Beam Convolution with modified Batho‐method (PBC‐B) and Adaptive Convolve (AC) were used for lung SBRT planning. A measurement using an ion‐chamber was performed in a heterogeneous phantom to compare doses from the three different algorithms and the SMU to the measured dose. In addition to it, a retrospective analysis using clinical lung SBRT plans (547 beams from 77 patients) was conducted to evaluate the confidence limit (CL, Average±2SD) in dose between the three algorithms and the SMU.Results:Compared to the measurement, the AAA showed the larger systematic dose error of 2.9±3.2% than PBC‐B and AC. The Clarkson‐based SMU showed larger error of 5.8±3.8%. The CLs for clinical plans were 7.7±6.0 % (AAA), 5.3±3.3 % (AC), 5.7±3.4 % (PBC ‐B), respectively.Conclusion:The TLs from the CLs were evaluated. A Clarkson‐based system shows a large systematic variation because of inhomogeneous correction. The AAA showed a significant variation. Thus, we must consider the difference of inhomogeneous correction as well as the dependence of dose calculation engine.