Abstract
The purpose of this study was to develop and evaluate a noninvasive method to assess rotation time in modern commercial computed tomography (CT) systems. The rotation time was measured at a selected nominal rotation time (400 ms) utilizing two types of solid‐state detectors: the RTI's CT Dose Profiler (CTDP) and Unfors’ Xi (Xi) probes. Either CTDP or Xi was positioned on the inner cover of the gantry and a sheet of lead (1 mm thick) placed on top of the detector. Since a pair of two successive peaks is used to determine the gantry rotation time, by necessity the helical scan must be employed. Upon completion of the data acquisition, these peak times were determined with the dedicated software to obtain rotation time. The average rotation time obtained with CTDP and Xi operated under the dedicated software was found to be 400.6 and 400.5 ms, respectively. The detector for this measurement need not be specifically designed for CT dosimetry. The measurements of CT scanner rotation time can be accomplished with a radiation probe designed for the CT application or a conventional radiation probe designed for radiography and fluoroscopy applications. It is also noteworthy to point out that the measurement results are in good agreement between the two radiation detector systems. Finally, clinical medical physicists should be aware of the accuracy and precision of gantry rotation time, and take into consideration for QA where and when applicable.PACS number: 87.57.Q‐
Highlights
With the advent of slip ring technology, helical scan computed tomography (CT) was introduced in 1988.(1,2) The slip ring technology enabled continuous rotation of CT gantry and, initially, had a gantry rotation time of one second
CT scanner and two solid-state detector systems The multirow detector CT scanner (MDCT) scanner employed for this investigation was equipped with 64 rows of detector array with microdetector width of 0.625 mm
It has been shown that measurements of CT scanner rotation time can be accomplished with a radiation probe designed for the CT application or with a conventional radiation probe designed for radiography and fluoroscopy applications
Summary
With the advent of slip ring technology, helical scan computed tomography (CT) was introduced in 1988.(1,2) The slip ring technology enabled continuous rotation of CT gantry and, initially, had a gantry rotation time of one second. Ten years after the introduction of single-row detector CT (SDCT), multirow detector CT scanner (MDCT) was ushered in by several manufacturers.[3] In order to take full advantage of the slip ring technology, further development of existing X-ray components was inevitable Among such developments are increased heat capacity of the X-ray tube and increased speed of gantry rotation, which resulted in the capability to scan a longer anatomic coverage in the same or shorter time. The American Association of Physicists in Medicine (AAPM) published at least two reports on QA of CT scanners, Report 39(7) and Report 83,(8) that dealt with the specification and test procedures Both reports included evaluation of performance of electromechanical components (e.g., alignment of table to gantry, table motion, collimation, radiation dose profile, and the X-ray generator kVp accuracy). To the best of our knowledge, there have been no published studies measuring the gantry rotation time
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