Quality assurance for computed-tomography simulators and the computed-tomography-simulation process: Report of the AAPM Radiation Therapy Committee Task Group No. 66

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116

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States.The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner.Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized.The following terms are used in the AAPM practice guidelines: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline.Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances. Approved by AAPM Professional Council 3‐31‐2017 and Executive Committee 4‐4‐2017.

Section: Acceptance Testing and Commissioningmentioning

confidence: 99%

AAPM‐RSS Medical Physics Practice Guideline 9.a. for SRS‐SBRT

Halvorsen

Cirino

Das

et al. 2017

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116

“…Assuming 50 cm to be the typical width of a tabletop, image rotation of 1° would result in 9 mm of difference between the vertical position of the left and right edges of the tabletop in the image. This would be unacceptable, since, according to AAPM recommendations, in radiotherapy applications the tabletop should be level with respect to the image within

\pm 2 mm

over its width (8) . If the tabletop were aligned horizontally with a precise level, any rotation between the tabletop and image would be caused by image rotation.…”

Section: Discussionmentioning

confidence: 99%

“…The geometric accuracy of CT images needs to be checked more thoroughly when they are used for planning radiation therapy with external beams. The tests may include checking the accuracy of distances in the image, couch movement, gantry tilt, and the level of the tabletop 3 , 8 . If the right and left edges of the tabletop are at different heights in a CT image, two possible causes (or a combination of both) should be considered: either the tabletop itself is not level, or the images are rotated.…”

Section: Introductionmentioning

confidence: 99%

Measurement of image rotation angle in CT for radiotherapy treatment planning

Skrzyński

Ślusarczyk-Kacprzyk

2016

The geometric accuracy of CT images is essential when they are used for planning radiation therapy. In this study, a method of quantitative testing of image rotation in CT is presented, based on the automated analysis of an image of a phantom half‐filled with water. A plug‐in was written for ImageJ software for automated detection of a water surface in an image and measurement of its angle relative to a horizontal line. A water phantom can be used for the evaluation of image rotation for axial mode. In helical mode the movement of the table would cause movement of the water. The difference between image rotation for axial and helical scans can be evaluated by measuring and comparing the angles of the tabletop surface for both modes. Preliminary results of measurements for three CT scanners show that image rotation does not exceed 0.5°, and is less than 0.1° for the dedicated CT simulator. It was observed that, for one CT scanner image, the rotation angle depended on tube rotation time.PACS number(s): 87.57.Q‐, 87.55.Qr, 06.30.Bp

“…The KPI positioning needs a dedicated positioning part in a manufacturer's phantom, while the others are determined from images of the water part. The available QC procedures of various parameters in a QA program, 5 , 6 , 7 , 8 , 9 and the KPIs main dependencies on QC parameters are illustrated in Table 1 …”

Section: Methodsmentioning

confidence: 99%

Quality control of CT systems by automated monitoring of key performance indicators: a two‐year study

Nowik

Bujila

Poludniowski

et al. 2015

The purpose of this study was to develop a method of performing routine periodical quality controls (QC) of CT systems by automatically analyzing key performance indicators (KPIs), obtainable from images of manufacturers' quality assurance (QA) phantoms. A KPI pertains to a measurable or determinable QC parameter that is influenced by other underlying fundamental QC parameters. The established KPIs are based on relationships between existing QC parameters used in the annual testing program of CT scanners at the Karolinska University Hospital in Stockholm, Sweden. The KPIs include positioning, image noise, uniformity, homogeneity, the CT number of water, and the CT number of air. An application (MonitorCT) was developed to automatically evaluate phantom images in terms of the established KPIs. The developed methodology has been used for two years in clinical routine, where CT technologists perform daily scans of the manufacturer's QA phantom and automatically send the images to MonitorCT for KPI evaluation. In the cases where results were out of tolerance, actions could be initiated in less than 10 min. 900 QC scans from two CT scanners have been collected and analyzed over the two‐year period that MonitorCT has been active. Two types of errors have been registered in this period: a ring artifact was discovered with the image noise test, and a calibration error was detected multiple times with the CT number test. In both cases, results were outside the tolerances defined for MonitorCT, as well as by the vendor. Automated monitoring of KPIs is a powerful tool that can be used to supplement established QC methodologies. Medical physicists and other professionals concerned with the performance of a CT system will, using such methods, have access to comprehensive data on the current and historical (trend) status of the system such that swift actions can be taken in order to ensure the quality of the CT examinations, patient safety, and minimal disruption of servicePACS numbers: 87.57.C‐, 87.57.N‐, 87.57.Q‐