Image quality and absorbed dose comparison of single‐ and dual‐source cone‐beam computed tomography

Abstract

PurposeDual‐source cone‐beam computed tomography (DCBCT) is currently available in the Vero4DRT image‐guided radiotherapy system. We evaluated the image quality and absorbed dose for DCBCT and compared the values with those for single‐source CBCT (SCBCT).MethodsImage uniformity, Hounsfield unit (HU) linearity, image contrast, and spatial resolution were evaluated using a Catphan phantom. The rotation angle for acquiring SCBCT and DCBCT images is 215° and 115°, respectively. The image uniformity was calculated using measurements obtained at the center and four peripheral positions. The HUs of seven materials inserted into the phantom were measured to evaluate HU linearity and image contrast. The Catphan phantom was scanned with a conventional CT scanner to measure the reference HU for each material. The spatial resolution was calculated using high‐resolution pattern modules. Image quality was analyzed using ImageJ software ver. 1.49. The absorbed dose was measured using a 0.6‐cm3 ionization chamber with a 16‐cm‐diameter cylindrical phantom, at the center and four peripheral positions of the phantom, and calculated using weighted cone‐beam CT dose index (CBCTDI w).ResultsCompared with that of SCBCT, the image uniformity of DCBCT was slightly reduced. A strong linear correlation existed between the measured HU for DCBCT and the reference HU, although the linear regression slope was different from that of the reference HU. DCBCT had poorer image contrast than did SCBCT, particularly with a high‐contrast material. There was no significant difference between the spatial resolutions of SCBCT and DCBCT. The absorbed dose for DCBCT was higher than that for SCBCT, because in DCBCT, the two x‐ray projections overlap between 45° and 70°.ConclusionsWe found that the image quality was poorer and the absorbed dose was higher for DCBCT than for SCBCT in the Vero4DRT.

Characterization of a prototype rapid kilovoltage x‐ray image guidance system designed for a ring shape radiation therapy unit

“…We acquired CBCT images with all eleven protocols by using these two phantoms, and performed image quality analysis. The analysis of Catphan‐based images was performed according to that recommended by previous publications, which include high‐resolution and low‐resolution sensitivity, image slice thickness, image uniformity, HU accuracy, and geometric accuracy. For the QUART phantom images, in addition to the directly measurable quantities, surrogate strategies are needed to measure slice thickness, high‐ and low‐contrast resolution, which will be discussed in the following section.…”