Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: comparison of beam pitch and detector coverage with 128-detector row CT

Shirasaka, Takashi; Funama, Yoshinori; Hayashi, Mutsukazu; Awamoto, Shinichi; Kondo, Masatoshi; Nakamura, Yasuhiko; Hatakenaka, Masamitsu; Honda, Hiroshi

doi:10.1007/s12194-011-0135-0

Cited by 9 publications

(3 citation statements)

References 22 publications

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“…In order to reduce the overranging dose, manufacturers introduced dynamic or adaptive collimators to block the dose which is irrelevant for image reconstruction [ 11 – 13 ]. Dynamic collimators are mechanical blades which move in and out of the radiation area to block the irrelevant radiation.…”

Section: Introductionmentioning

confidence: 99%

Efficacy of a dynamic collimator for overranging dose reduction in a second- and third-generation dual source CT scanner

2017

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ObjectivesThe purpose of this study was to assess the efficacy of the renewed dynamic collimator in a third-generation dual source CT (DSCT) scanner and to determine the improvements over the second-generation scanner.MethodsCollimator efficacy is defined as the percentage overranging dose in terms of dose–length product (DLP) that is blocked by the dynamic collimator relative to the total overranging dose in case of a static collimator. Efficacy was assessed at various pitch values and different scan lengths. The number of additional rotations due to overranging and effective scan length were calculated on the basis of reported scanning parameters. On the basis of these values, the efficacy of the collimator was calculated.ResultsThe second-generation scanner showed decreased performance of the dynamic collimator at increasing pitch. Efficacy dropped to 10% at the highest pitch. For the third-generation scanner the efficacy remained above 50% at higher pitch. Noise was for some pitch values slightly higher at the edge of the imaged volume, indicating a reduced scan range to reduce the overranging dose.ConclusionsThe improved dynamic collimator in the third-generation scanner blocks the overranging dose for more than 50% and is more capable of shielding radiation dose, especially in high pitch scan modes.Key points• Overranging dose is to a large extent blocked by the dynamic collimator • Efficacy is strongly improved within the third-generation DSCT scanner • Reducing the number of additional rotations can reduce overranging with increased noise

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Section: Introductionmentioning

confidence: 99%

Efficacy of a dynamic collimator for overranging dose reduction in a second- and third-generation dual source CT scanner

2017

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“…It is an indispensable mechanism for overranging reduction during volume helical scanning. Shirasaka et al measured overranging in a 128‐detector row CT scanner. Brilliance iCT can also perform helical acquisitions of up to 80 mm coverage.…”

Section: Discussionmentioning

confidence: 99%

“…To reduce the increased overranging in MDCT, a dynamic z ‐collimator was installed in advanced CT scanners . Shirasaka et al measured overranging in a 128‐detector row CT scanner (Brilliance iCT; Philips Healthcare, Cleveland, OH, USA) and concluded that the spiral dynamic z ‐collimator is important for unnecessary overrange dose reduction.…”

Section: Introductionmentioning

confidence: 99%

Overranging and overbeaming measurement in area detector computed tomography: A method for simultaneous measurement in volume helical acquisition

Urikura

Hara

Yoshida

et al. 2019

J Applied Clin Med Phys

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Purpose We propose a novel method to assess overbeaming and overranging, as well as the effect of reducing longitudinal exposure range, by using a dynamic z‐collimator in area detector computed tomography. Methods and materials A 500‐mm diameter cylindrical imaging plate was exposed by helical scanning in a dark room. The beam collimation of the helical acquisitions was set at 32 and 80 mm. Overbeaming and overranging with the dynamic z‐collimator were measured. Results The actual beam widths were approximately 39 and 88 mm at 32 and 80 mm collimation, respectively, and were relatively reduced owing to increased beam collimation. Overranging was 27.0 and 48.2 mm with a pitch of 0.83 and 1.49 at 32 mm collimation and 72.5 and 83.1 mm with a pitch of 0.87 and 0.99 at 80 mm collimation. The dynamic z‐collimator relatively reduced the overranging by 17.3% and 17.1% for the 32 and 80 mm collimation, respectively. Conclusion We devised a method to simultaneously measure overbeaming and overranging with only one helical acquisition. Although the dynamic z‐collimator reduced the overranging by approximately 17%, wider collimation widths and higher pitch settings would increase the exposure dose outside the scan range.

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Evaluation of an adaptive detector collimation for prospectively ECG-triggered coronary CT angiography with third-generation dual-source CT

et al. 2017

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Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: comparison of beam pitch and detector coverage with 128-detector row CT

Cited by 9 publications

References 22 publications

Efficacy of a dynamic collimator for overranging dose reduction in a second- and third-generation dual source CT scanner

Efficacy of a dynamic collimator for overranging dose reduction in a second- and third-generation dual source CT scanner

Overranging and overbeaming measurement in area detector computed tomography: A method for simultaneous measurement in volume helical acquisition

Evaluation of an adaptive detector collimation for prospectively ECG-triggered coronary CT angiography with third-generation dual-source CT

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