Gamma Evaluation with Portal Dosimetry for Volumetric Modulated Arc Therapy and Intensity-Modulated Radiation Therapy

Kim, Jung-In; Choi, Cheol Young; Park, So‐Yeon; An, Hyun-Joon; Wu, Hong‐Gyun; Park, Jong Min

doi:10.14316/pmp.2017.28.2.61

Cited by 7 publications

(12 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The gamma passing rates of the patient-specific verification demonstrated that the plans normalized by the transmission factor can be applied for clinical purposes when a clinically acceptable criterion (i.e., 2%/2 mm) is used [ 10 ]. For the SABR plan, the gamma passing rates of the original and normalized plans were poor with the 1%/1 mm criterion because SABR had small fields and high-gradient dose profiles.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Validation of new transmission detector transmission factors for online dosimetry: an experimental study

Park

Kim

et al. 2018

Radiat Oncol

Self Cite

View full text Add to dashboard Cite

BackgroundThe demand for dose verification during treatment has risen with the increasing use of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) in modern radiation therapy. This study aims to validate the transmission factors of a new transmission detector, the Dolphin online monitoring system (IBA Dosimetry, Schwarzenbruck, Germany), for clinical use.MethodsThe transmission factors of the Dolphin detector were evaluated using 6 MV, 6 flattening filter free (FFF), 10 MV, and 10 FFF clinical beams from a TrueBeam STx linear accelerator system. Two-dimensional (2D) dose distributions were measured through portal dosimetry with and without Dolphin to derive the transmission factors. The measurements were performed using 10 IMRT and 10 VMAT treatment plans. The transmission factors were calculated using a non-negative least squares problem solver for the 2D dose matrix. Normalized plans were generated using the derived transmission factors. Patient-specific quality assurance with normalized plans was performed using portal dosimetry and an ArcCheck detector to verify the transmission factors. The gamma passing rates were calculated for the 2%/2 mm and 1%/1 mm criteria.ResultsThe transmission factors for the 6 MV, 6 FFF, 10 MV, and 10 FFF beams, were 0.878, 0.824, 0.913, and 0.883, respectively. The average dose difference between the original plan without Dolphin and the normalized plan with Dolphin was less than 1.8% for all measurements. The mean passing rates of the gamma evaluation were 98.1 ± 2.1 and 82.9 ± 12.6 for the 2%/2 mm and 1%/1 mm criteria, respectively, for portal dosimetry of the original plan. In the case of the portal dosimetry of the normalized plan, the mean passing rates of the gamma evaluation were 97.2 ± 2.8 and 79.1 ± 14.8 for the 2%/2 mm and 1%/1 mm criteria, respectively.ConclusionsThe Dolphin detector can be used for online dosimetry when valid transmission factors are applied to the clinical plan.

show abstract

Section: Discussionmentioning

confidence: 99%

“…In recent decades, IMRT verification techniques have been developed to increase the efficiency and accuracy of associated QA procedures [ 10 ]. Plan verification is generally performed using detector array systems, ion chamber, or film before first treatment.…”

Section: Introductionmentioning

confidence: 99%

Validation of new transmission detector transmission factors for online dosimetry: an experimental study

Park

Kim

et al. 2018

Radiat Oncol

Self Cite

View full text Add to dashboard Cite

show abstract

“…[10][11][12] PD has been established utilizing EPID for pretreatment verification. 13,14) 138 www.ksmp.or.kr Modern radiotherapy has increased the need for online dose verification owing to the complexity and accuracy of the new delivery techniques. (e.g., VMAT or Stereotactic ablative radiotherapy (SABR)).…”

Section: ) Portal Dosimetry (Pd)mentioning

confidence: 99%

Verification of Extended Source-To-Imager Distance (SID) Correction for Portal Dosimetry

et al. 2018

Self Cite

View full text Add to dashboard Cite

This study aimed to evaluate and verify a process for correcting the extended source-to-imager distance (SID) in portal dosimetry (PD). In this study, eight treatment plans (four volumetric modulated arc therapy and four intensity-modulated radiation therapy plans) at different treatment sites and beam energies were selected for measurement. A Varian PD system with portal dose image prediction (PDIP) was used for the measurement and verification. To verify the integrity of the plan, independent measurements were performed with the MapCHECK device. The predicted and measured fluence were evaluated using the gamma passing rate. The output ratio was defined as the ratio of the absolute dose of the reference SID (100 cm) to that of each SID (120 cm or 140 cm). The measured fluence for each SID was absolutely and relatively compared. The average SID output ratios were 0.687 and 0.518 for 120 SID and 140 SID, respectively; the ratio showed less than 1% agreement with the calculation obtained by using the inverse square law. The resolution of the acquired EPIDs were 0.336, 0.280, and 0.240 for 100, 120, and 140 SID, respectively. The gamma passing rates with PD and MapCHECK exceeded 98% for all treatment plans and SIDs. When autoalignment was performed in PD, the X-offset showed no change, and the Y-offset decreased with increasing SID. The PD-generated PDIP can be used for extended SID without additional correction.

show abstract

“…IMRT modulates the photon-beam intensity by changing the position of the multileaf collimator (MLC) [10], thereby delivering a nonuniform fluence from any given position of the patient's treatment beam and optimizing the dose distribution [11]. How-ever, the calculation of the small or irregular fields frequently used in IMRT has been reported as inaccurate; even with state-of-theart dose calculation algorithms, the calculated dose distribution and the dose distribution delivered to the patient may differ [10]. Therefore, for all patients undergoing IMRT treatment, patient-specific quality assurance (QA) must be performed prior to radiotherapy [12].…”

mentioning

confidence: 99%

“…In particular, the gamma index analysis method, which compares and analyzes the calculated and measured doses, is the most used for patient-specific QA in IMRT treatment. In IMRT treatment, although the values of acceptable dose difference (DD) and distance-to-agreement (DTA) are not clearly defined, the clinically well-accepted values are 3% and 3 mm, respectively [10][11][12][13][14][15][16][17]. Our institution used these same values; as the passing criterion, such as DD or DTA increases, the passing gamma value will increase.…”

mentioning

confidence: 99%

Clinical performance of FractionLab in patient-specific quality assurance for intensity-modulated radiotherapy: a retrospective study

Kim

Park

et al. 2022

J Yeungnam Med Sci

View full text Add to dashboard Cite

Intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT), which deliver the desired radiation dose to the targeted tumors with minimal radiation to the surrounding normal tissue, are extensively used in radiotherapy. IMRT technology increases the daily radiation dose (dose per fraction) based on these technical advantages and contributes significantly to patient convenience by enhancing the radiation treatment

show abstract

Gamma Evaluation with Portal Dosimetry for Volumetric Modulated Arc Therapy and Intensity-Modulated Radiation Therapy

Cited by 7 publications

References 18 publications

Validation of new transmission detector transmission factors for online dosimetry: an experimental study

Validation of new transmission detector transmission factors for online dosimetry: an experimental study

Verification of Extended Source-To-Imager Distance (SID) Correction for Portal Dosimetry

Clinical performance of FractionLab in patient-specific quality assurance for intensity-modulated radiotherapy: a retrospective study

Contact Info

Product

Resources

About