PO-1612 The relationship of MU density and gamma passing rate in patient-specific QA using EPID and Delta4

2021 ◽  
Vol 161 ◽  
pp. S1333-S1335
Author(s):  
D. Li ◽  
X. Li ◽  
X. Zhen ◽  
Z. Zhang ◽  
Y. Wang ◽  
...  
Keyword(s):  
Patient Specific ◽  
Passing Rate ◽  
Patient Specific Qa ◽  
Relationship Of ◽  
The Relationship ◽  
Gamma Passing Rate

scholarly journals Can clinically relevant dose errors in patient anatomy be detected by gamma passing rate or modulation complexity score in volumetric-modulated arc therapy for intracranial tumors?

2017 ◽  
Vol 58 (5) ◽  
pp. 685-692 ◽  
Author(s):  
Shingo Ohira ◽  
Yoshihiro Ueda ◽  
Masaru Isono ◽  
Akira Masaoka ◽  
Misaki Hashimoto ◽  
...  
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Patient Specific ◽  
Array Detector ◽  
Intracranial Tumors ◽  
Clinical Dose ◽  
Complexity Score ◽  
Passing Rate ◽  
Arc Therapy ◽  
Patient Specific Qa ◽  
Gamma Passing Rate

Abstract We investigated whether methods conventionally used to evaluate patient-specific QA in volumetric-modulated arc therapy (VMAT) for intracranial tumors detect clinically relevant dosimetric errors. VMAT plans with coplanar arcs were designed for 37 intracranial tumors. Dosimetric accuracy was validated by using a 3D array detector. Dose deviations between the measured and planned doses were evaluated by gamma analysis. In addition, modulation complexity score for VMAT (MCSv) for each plan was calculated. Three-dimensional dose distributions in patient anatomy were reconstructed using 3DVH software, and clinical deviations in dosimetric parameters between the 3DVH doses and planned doses were calculated. The gamma passing rate (GPR)/MCSv and the clinical dose deviation were evaluated using Pearson's correlation coefficient. Significant correlation (P < 0.05) between the clinical dose deviation and GPR was observed with both the 3%/3 mm and 2%/2 mm criteria in clinical target volume (D99), brain (D2), brainstem (D2) and chiasm (D2), albeit that the correlations were not ‘strong’ (0.38 < |r| < 0.54). The maximum dose deviations of brainstem were up to 4.9 Gy and 2.9 Gy for Dmax and D%, respectively in the case of high GPR (98.2% with 3%/3 mm criteria). Regarding MCSv, none of the evaluated organs showed a significant correlation with clinical dose deviation, and correlations were ‘weak’ or absent (0.01 < |r| < 0.21). The use of high GPR and MCSv values does not always detect dosimetric errors in a patient. Therefore, in-depth analysis with the DVH for patient-specific QA is considered to be preferable for guaranteeing safe dose delivery.

scholarly journals Evaluation of Delta4DVH Anatomy in 3D Patient-Specific IMRT Quality Assurance

2020 ◽  
Vol 19 ◽  
pp. 153303382094581
Author(s):  
Du Tang ◽  
Zhen Yang ◽  
Xunzhang Dai ◽  
Ying Cao
Keyword(s):  
Quality Assurance ◽  
Treatment Planning ◽  
Treatment Plan ◽  
Planning System ◽  
Treatment Planning System ◽  
Patient Specific ◽  
Pencil Beam ◽  
Ion Chamber ◽  
Passing Rate ◽  
Gamma Passing Rate

Purpose: To evaluate the performance of Delta4DVH Anatomy in patient-specific intensity-modulated radiotherapy quality assurance. Materials and Methods: Dose comparisons were performed between Anatomy doses calculated with treatment plan dose measured modification and pencil beam algorithms, treatment planning system doses, film doses, and ion chamber measured doses in homogeneous and inhomogeneous geometries. The sensitivity of Anatomy doses to machine errors and output calibration errors was also investigated. Results: For a Volumetric Modulated Arc Therapy (VMAT) plan evaluated on the Delta4 geometry, the conventional gamma passing rate was 99.6%. For a water-equivalent slab geometry, good agreements were found between dose profiles in film, treatment planning system, and Anatomy treatment plan dose measured modification and pencil beam calculations. Gamma passing rate for Anatomy treatment plan dose measured modification and pencil beam doses versus treatment planning system doses was 100%. However, gamma passing rate dropped to 97.2% and 96% for treatment plan dose measured modification and pencil beam calculations in inhomogeneous head & neck phantom, respectively. For the 10 patients’ quality assurance plans, good agreements were found between ion chamber measured doses and the planned ones (deviation: 0.09% ± 1.17%). The averaged gamma passing rate for conventional and Anatomy treatment plan dose measured modification and pencil beam gamma analyses in Delta4 geometry was 99.6% ± 0.89%, 98.54% ± 1.60%, and 98.95% ± 1.27%, respectively, higher than averaged gamma passing rate of 97.75% ± 1.23% and 93.04% ± 2.69% for treatment plan dose measured modification and pencil beam in patients’ geometries, respectively. Anatomy treatment plan dose measured modification dose profiles agreed well with those in treatment planning system for both Delta4 and patients’ geometries, while pencil beam doses demonstrated substantial disagreement in patients’ geometries when compared to treatment planning system doses. Both treatment planning system doses are sensitive to multileaf collimator and monitor unit (MU) errors for high and medium dose metrics but not sensitive to the gantry and collimator rotation error smaller than 3°. Conclusions: The new Delta4DVH Anatomy with treatment plan dose measured modification algorithm is a useful tool for the anatomy-based patient-specific quality assurance. Cautions should be taken when using pencil beam algorithm due to its limitations in handling heterogeneity and in high-dose gradient regions.

The relationship of vancomycin 24-hour AUC and trough concentration

2021 ◽  
Author(s):  
David E Nix ◽  
Lisa E Davis ◽  
Kathryn R Matthias
Keyword(s):  
Trough Concentration ◽  
Elimination Rate ◽  
Compartment Model ◽  
Patient Specific ◽  
Pharmacokinetic Parameters ◽  
Time Curve ◽  
Dosing Interval ◽  
Trough Concentrations ◽  
Relationship Of ◽  
The Relationship

Abstract Disclaimer In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time. Purpose Prior to the 2020 release of a joint consensus guideline on monitoring of vancomycin therapy for serious methicillin-resistant Staphylococcus aureus (MRSA) infections, clinicians had escalated vancomycin doses for 2 decades while targeting trough concentrations of 15 to 20 µg/mL, leading to an increased frequency of nephrotoxicity. For MRSA infections, the 2020 guideline recommends adjusting doses to achieve a 24-hour area under the concentration-time curve (AUC) of 400 to 600 µg · h/mL; however, monitoring of trough concentrations has been entrenched for 3 decades. Calculating dose regimens based on AUC will require obtaining an increased number of vancomycin serum concentrations and, possibly, advanced software. The aim of this investigation was to determine the relationship between AUC and trough concentration and the influence of dosing regimen on goal achievement. Methods The relationship between trough concentration and AUC was explored through derivation of an equation based on a 1-compartment model and simulations. Results 24-hour AUC is related to dosing interval divided by half-life in a nonlinear fashion. The target trough concentration can be individualized to achieve a desired AUC range, and limiting use of large doses (>15-20 mg/kg) can protect against excessive 24-hour AUC with trough-only monitoring. Conclusion After initially determining pharmacokinetic parameters, subsequent monitoring of AUC can be accomplished using trough concentrations only. Trough concentration may be used as a surrogate for AUC, although the acceptable target trough concentration will vary depending on dosing interval and elimination rate constant. This work included development of an AUC-trough equation to establish a patient-specific target for steady-state trough concentration.

Comparison between different Dosimetric Tools based on Intensity-modulated Radiotherapy (IMRT): A Phantom Study

2021 ◽  
Vol 19 (11) ◽  
pp. 141-150
Author(s):  
Ahmed H. Waheeb ◽  
Zeinab Eltaher ◽  
Mohamed N. Yassin ◽  
Magdy M. Khalil
Keyword(s):  
Dose Distribution ◽  
Low Dose ◽  
Planning System ◽  
Treatment Planning System ◽  
Patient Specific ◽  
Dose Threshold ◽  
Passing Rate ◽  
Gamma Analysis ◽  
Calculated Dose ◽  
Gamma Passing Rate

This study examined the gamma passing rate (GPR) consistency during applying different kinds of gamma analyses and dosimeters to IMRT. Methods: Import treatment protocols for QA phantom irradiation have been recalculated. A gamma analysis was used for comparing the measured and calculated dose distribution of IMRT for different gamma criteria (2%/2mm, 3%/3mm, 4%/4mm, 3%/5mm, 3%/5mm). These criteria are evaluated when 5%, 10%, or 15% of the dose distribution is suppressed. Measured and calculated dose distribution was evaluated with gamma analysis to dose difference (DD) with DTA criteria (distance to agreement). IMRT QA plans to 25 patients from various sites were formed with the Varian Eclipse treatment planning system. Results: Results indicate different diverse hardware and software combinations show varied levels of agreement with expected analysis for the same pass-rate criterion. For a dosimetry audit of the IMRT technique, an EPID detector is superior to conventional methods comparable to Gafchromic EPT3 film and 2D array due to cost, time-consuming, and set up error to get result analysis. The gamma passing rate (GPR) average is increased by increasing the low-dose threshold for different dosimetric tools. For EPID, regardless of the gamma criterion employed, the %GP does not appear to be dependent on the low-dose threshold values (5%-15%) because it indicates that fulfilment the low-dose threshold to global normalization has little effect on patient-specific QA outcomes. Conclusions: It is concluded that GPRs differ depending on gamma, dosimetric tools, and the suppressing dose ratio. To get the best results of quality assurance, each institution should thus carefully develop its procedure for gamma analysis by defining the gamma index analysis and gamma criterion using its dosimetric tools.

3D PRINTER’S PARAMETER OPTIMIZATION FOR POTENTIAL PATIENT SPECIFIC IMPLANT FABRICATION

2015 ◽  
Vol 76 (7) ◽  
Author(s):  
Abdul Manaf Abdullah ◽  
Dasmawati Mohamad ◽  
Tuan Noraihan Azila Tuan Rahim ◽  
Hazizan Md Akil ◽  
Zainul Ahmad Rajion
Keyword(s):  
Surface Roughness ◽  
Testing Machine ◽  
Patient Specific ◽  
3D Printer ◽  
Topological Properties ◽  
Layer Height ◽  
Universal Testing ◽  
Potential Patient ◽  
Relationship Of ◽  
The Relationship

This study attempted to investigate the effect of printing orientation and layer height on mechanical and topological properties of printed ABS specimens. 2 printing orientations (xy and yz) with 3 different layer heights (0.1, 0.2 and 0.3mm) were chosen and specimens were printed utilizing a 3D printer. Tensile, morphological and topological properties were evaluated utilizing Universal Testing Machine (Shimadzu AGX-2plus), FESEM and surface profilometer respectively. Statistical analysis of two-way Anova was carried out to investigate the relationship of layer height and printing orientation on the tensile strength and surface roughness of the specimens

scholarly journals A comparison of the quality assurance of four dosimetric tools for intensity modulated radiation therapy

2015 ◽  
Vol 49 (3) ◽  
pp. 307-313 ◽  
Author(s):  
Jaeman Son ◽  
Taesung Baek ◽  
Boram Lee ◽  
Dongho Shin ◽  
Sung Yong Park ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Radiation Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Planning System ◽  
Treatment Planning System ◽  
Patient Specific ◽  
Intensity Modulated ◽  
Passing Rates ◽  
Passing Rate ◽  
Patient Specific Qa

Abstract Background. This study was designed to compare the quality assurance (QA) results of four dosimetric tools used for intensity modulated radiation therapy (IMRT) and to suggest universal criteria for the passing rate in QA, irrespective of the dosimetric tool used. Materials and methods. Thirty fields of IMRT plans from five patients were selected, followed by irradiation onto radiochromic film, a diode array (Mapcheck), an ion chamber array (MatriXX) and an electronic portal imaging device (EPID) for patient-specific QA. The measured doses from the four dosimetric tools were compared with the dose calculated by the treatment planning system. The passing rates of the four dosimetric tools were calculated using the gamma index method, using as criteria a dose difference of 3% and a distance-to-agreement of 3 mm. Results. The QA results based on Mapcheck, MatriXX and EPID showed good agreement, with average passing rates of 99.61%, 99.04% and 99.29%, respectively. However, the average passing rate based on film measurement was significantly lower, 95.88%. The average uncertainty (1 standard deviation) of passing rates for 6 intensity modulated fields was around 0.31 for film measurement, larger than those of the other three dosimetric tools. Conclusions. QA results and consistencies depend on the choice of dosimetric tool. Universal passing rates should depend on the normalization or inter-comparisons of dosimetric tools if more than one dosimetric tool is used for patient specific QA.

scholarly journals A systematic study of independently-tuned room-specific PBS beam model in a beam-matched multiroom proton therapy system

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yu-Hua Huang ◽  
Chunfeng Fang ◽  
Tao Yang ◽  
Lin Cao ◽  
Gaolong Zhang ◽  
...  
Keyword(s):  
Proton Therapy ◽  
Patient Specific ◽  
Model Parameters ◽  
Beam Model ◽  
Model Based ◽  
Modeling Process ◽  
Passing Rate ◽  
Patient Specific Qa ◽  
Model Sharing ◽  
High Level

Abstract Background In the existing application of beam-matched multiroom proton therapy system, the model based on the commissioning data from the leading treatment room was used as the shared model. The purpose of this study is to investigate the ability of independently-tuned room-specific beam models of beam-matched gantries to reproduce the agreement between gantries’ performance when considering the errors introduced by the modeling process. Methods Raw measurements of two gantries’ dosimetric characteristics were quantitatively compared to ensure their agreement after initially beam-matched. Two gantries’ beam model parameters, as well as the model-based computed dosimetric characteristics, were analyzed to study the introduced errors and gantries’ post-modeling consistency. We forced two gantries to share the same beam model. The model-sharing patient-specific quality assurance (QA) tasks were retrospectively performed with 36 cancer patients to study the clinical impact of beam model discrepancies. Results Intra-gantry comparisons demonstrate that the modeling process introduced the errors to a certain extent indeed, which made the model-based reproduced results deviate from the raw measurements. Among them, the deviation introduced to the IDD curves was generally larger than that to the beam spots during modeling. Cross-gantry comparisons show that, from the beam model perspective, the introduced deviations deteriorated the high agreement of the dosimetric characteristics originally shown between two beam-matched gantries, but the cross-gantry discrepancy was still within the clinically acceptable tolerance. In model-sharing patient-specific QA, for the particular gantry, the beam model usage for intensity-modulated proton therapy (IMPT) QA plan generation had no significant effect on the actual delivering performance. All reached a high level of 95.0% passing rate with a 3 mm/3% criterion. Conclusions It was preliminary recognized that among beam-matched gantries, the independently-tuned room-specific beam model from any gantry is reasonable to be chosen as the shared beam model without affecting the treatment efficacy.

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