Retrospective IMRT Dose Reconstruction Based on Cone-Beam CT and MLC Log-File

Lee, Louis; Le, Quynh‐Thu; Li, Xing

doi:10.1016/j.ijrobp.2007.09.054

Cited by 88 publications

(79 citation statements)

References 28 publications

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“…CT numbers are most accurate if using a FOV greater than the patient diameter. All previous publications reported investigations using a D = L = 20 cm cylindrical phantom (phantom 1) with inserts of known electron densities (Yoo and Yin 2006, Ding et al 2007a, Lee et al 2008. Full-and half-fan scans were reported to produce CT numbers within 5% of accepted values.…”

Section: Discussionmentioning

confidence: 99%

The effects of field-of-view and patient size on CT numbers from cone-beam computed tomography

et al. 2009

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The effects of field-of-view and patient size on CT numbers from cone-beam computed tomography." (2009) Abstract Cone-beam computed tomography (CBCT) is used for patient alignment before treatment and is ideal for use in adaptive radiotherapy to account for tumor shrinkage, organ deformation and weight loss. However, CBCT images are prone to artifacts such as streaking and cupping effects, reducing image quality and CT number accuracy. Our goal was to determine the optimum combination of cone-beam imaging options to increase the accuracy of image CT numbers. Several phantoms with and without inserts of known relative electron densities were imaged using the Varian on-board imaging system. It was found that CT numbers are most influenced by the selection of field-of-view and are dependent on object size and filter type. Image acquisition in half-fan mode consistently produced more accurate CT numbers, regardless of phantom size. Values measured using full-fan mode can differ by up to 7% from planning CT values. No differences were found between CT numbers of all phantom images with low and standard dose modes.

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Section: Discussionmentioning

confidence: 99%

The effects of field-of-view and patient size on CT numbers from cone-beam computed tomography

et al. 2009

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“…Both CT and CBCT images were acquired according to our H&N protocols. We compared different materials from air to Teflon (CF 2 3 ), and low density polyethylene (C 2 H 4 , 0.92 g/cm 3 ). These ranged approximately from 21000 to 11000 in HU.…”

Section: Validation Of Dose Calculation On Cbctmentioning

confidence: 99%

Volumetric and Dosimetric Assessment by Cone-Beam Computed Tomography Scans in Head and Neck Radiation Therapy: A Monitoring in Four Phases of Treatment

Cozzolino

Fiorentino

Oliviero

et al. 2014

Technol Cancer Res Treat

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Due to the anatomical changes frequently occurring during the course of head and neck (H&N) cancer radiotherapy, the dose distribution, which was actually delivered to the patient, might significantly differ from that planned. The aim of this paper is to investigate these volumetric changes and the resulting dosimetric implications on organs at risk (OARs) and clini- and 25 th CBCT (13.3%) but it complied with dose constraint. The differences observed for the spinal cord and mandible maximum doses were not clinically relevant. In conclusion, the dosimetric analysis on CBCT can help clinicians to monitor treatment progress and to evaluate whether and when a new plan is necessary. The main benefit of replanning could be to preserve the parotids and our data support the hypothesis that the 3 rd week of radiotherapy should be a check point for parotids.

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“…One approach to MLC QA is to analyze the machine's logfile to perform MLC QA,2, 3 and this approach can be used with data from a dynamic delivery (MLC position, Gantry Angle, and Monitor Unit) with higher sampling rate (10–50 ms). In addition, logfile QA can be performed using three‐dimensional dose reconstruction based on patient geometry, and several recent reports have described this technique 4, 5, 6…”

Section: Introductionmentioning

confidence: 99%

Comparison of MLC error sensitivity of various commercial devices for VMAT pre‐treatment quality assurance

Saito

Sano

Shibata

et al. 2018

J Applied Clin Med Phys

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The purpose of this study was to compare the MLC error sensitivity of various measurement devices for VMAT pre‐treatment quality assurance (QA). This study used four QA devices (Scandidos Delta4, PTW 2D‐array, iRT systems IQM, and PTW Farmer chamber). Nine retrospective VMAT plans were used and nine MLC error plans were generated for all nine original VMAT plans. The IQM and Farmer chamber were evaluated using the cumulative signal difference between the baseline and error‐induced measurements. In addition, to investigate the sensitivity of the Delta4 device and the 2D‐array, global gamma analysis (1%/1, 2%/2, and 3%/3 mm), dose difference (1%, 2%, and 3%) were used between the baseline and error‐induced measurements. Some deviations of the MLC error sensitivity for the evaluation metrics and MLC error ranges were observed. For the two ionization devices, the sensitivity of the IQM was significantly better than that of the Farmer chamber (P < 0.01) while both devices had good linearly correlation between the cumulative signal difference and the magnitude of MLC errors. The pass rates decreased as the magnitude of the MLC error increased for both Delta4 and 2D‐array. However, the small MLC error for small aperture sizes, such as for lung SBRT, could not be detected using the loosest gamma criteria (3%/3 mm). Our results indicate that DD could be more useful than gamma analysis for daily MLC QA, and that a large‐area ionization chamber has a greater advantage for detecting systematic MLC error because of the large sensitive volume, while the other devices could not detect this error for some cases with a small range of MLC error.

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Retrospective IMRT Dose Reconstruction Based on Cone-Beam CT and MLC Log-File

Cited by 88 publications

References 28 publications

The effects of field-of-view and patient size on CT numbers from cone-beam computed tomography

The effects of field-of-view and patient size on CT numbers from cone-beam computed tomography

Volumetric and Dosimetric Assessment by Cone-Beam Computed Tomography Scans in Head and Neck Radiation Therapy: A Monitoring in Four Phases of Treatment

Comparison of MLC error sensitivity of various commercial devices for VMAT pre‐treatment quality assurance

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