The impact of x-ray tube stabilization on localized radiation dose in axial CT scans: Initial results in CTDI phantoms

Kelsey Boitnott Mathieu, Michael F. McNitt-Gray, Dianna Cody

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Rise, fall, and stabilization of the x-ray tube output occur immediately before and after data acquisition on some computed tomography (CT) scanners and are believed to contribute additional dose to anatomy facing the x-ray tube when it powers on or off. In this study, we characterized the dose penalty caused by additional radiation exposure during the rise, stabilization, and/or fall time (referred to as overscanning). A 32 cm CT dose-index (CTDI) phantom was scanned on three CT scanners: GE Healthcare LightSpeed VCT, GE Healthcare Discovery CT750 HD, and Siemens Somatom Definition Flash. Radiation exposure was detected for various x-ray tube start acquisition angles using a 10 cm pencil ionization chamber placed in the peripheral chamber hole at the phantom's 12 o'clock position. Scan rotation time, ionization chamber location, phantom diameter, and phantom centering were varied to quantify their effects on the dose penalty caused by overscanning. For 1 s single, axial rotations, CTDI at the 12 o'clock chamber position (CTDI 100, 12:00 ) was 6.1%, 4.0%, and 4.4% higher when the start angle of the x-ray tube was aligned at the top of the gantry (12 o'clock) versus when the start angle was aligned at 9 o'clock for the Siemens Flash, GE CT750 HD, and GE VCT scanner, respectively. For the scanners' fastest rotation times (0.285 s for the Siemens and 0.4 s for both GE scanners), the dose penalties increased to 22.3%, 10.7%, and 10.5%, respectively, suggesting a trade-off between rotation speed and the dose penalty from overscanning. In general, overscanning was shown to have a greater radiation dose impact for larger diameter phantoms, shorter rotation times, and to peripheral phantom locations. Future research is necessary to determine an appropriate method for incorporating the localized dose penalty from overscanning into standard dose metrics, as well as to assess the impact on organ dose.

Original languageEnglish (US)
Pages (from-to)7363-7376
Number of pages14
JournalPhysics in medicine and biology
Volume61
Issue number20
DOIs
StatePublished - Oct 3 2016

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Tomography
X-Rays
Radiation
X-Ray Computed Tomography Scanners
Delivery of Health Care
Anatomy
Radiation Exposure

Keywords

  • CT
  • axial CT
  • organ dose
  • overscanning
  • patient positioning
  • radiation dosimetry

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging

Cite this

The impact of x-ray tube stabilization on localized radiation dose in axial CT scans : Initial results in CTDI phantoms. / Mathieu, Kelsey Boitnott; McNitt-Gray, Michael F.; Cody, Dianna.

In: Physics in medicine and biology, Vol. 61, No. 20, 03.10.2016, p. 7363-7376.

Research output: Contribution to journalArticle

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