Beam Quality Measurements in Diagnostic Roentgenology

Ed, Trout; Jp, Kelley; To¨re, G.

doi:10.2214/ajr.112.3.622

Cited by 1 publication

(1 citation statement)

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“…KV beam quality–determination of HVL: A self-made collimator with field size (5.5x5.5)cm 2 in the isocenter was used to achieve narrow-beam geometry to minimize scatter effects [ 21 ]. The x-ray source was positioned at 0° and the detector was moved out of the field-of-view (FOV).…”

Section: Methodsmentioning

confidence: 99%

Phantom-based evaluation of dose exposure of ultrafast combined kV-MV-CBCT towards clinical implementation for IGRT of lung cancer

et al. 2017

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PurposeCombined ultrafast 90°+90° kV-MV-CBCT within single breath-hold of 15s has high clinical potential for accelerating imaging for lung cancer patients treated with deep inspiration breath-hold (DIBH). For clinical feasibility of kV-MV-CBCT, dose exposure has to be small compared to prescribed dose. In this study, kV-MV dose output is evaluated and compared to clinically-established kV-CBCT.MethodsAccurate dose calibration was performed for kV and MV energy; beam quality was determined. For direct comparison of MV and kV dose output, relative biological effectiveness (RBE) was considered. CT dose index (CTDI) was determined and measurements in various representative locations of an inhomogeneous thorax phantom were performed to simulate the patient situation.ResultsA measured dose of 20.5mGE (Gray-equivalent) in the target region was comparable to kV-CBCT (31.2mGy for widely-used, and 9.1mGy for latest available preset), whereas kV-MV spared healthy tissue and reduced dose to 6.6mGE (30%) due to asymmetric dose distribution. The measured weighted CTDI of 12mGE for kV-MV lay in between both clinical presets.ConclusionsDosimetric properties were in agreement with established imaging techniques, whereas exposure to healthy tissue was reduced. By reducing the imaging time to a single breath-hold of 15s, ultrafast combined kV-MV CBCT shortens patient time at the treatment couch and thus improves patient comfort. It is therefore usable for imaging of hypofractionated lung DIBH patients.

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Section: Methodsmentioning

confidence: 99%