Abstract
Mobile fluoroscopy (c‐arm) units offering 3D image reconstruction are becoming more common in surgical settings. Although these images are “CT‐like” and sometimes replace the postoperative CT, the acquisition is technically very different from a traditional CT acquisition. Dose assessment is complicated by a large beam width, automatic exposure rate control, and a rotation of less than 360°. The purpose of this work was to explore the impact of these factors on the volumetric dose calculation and to provide practical recommendations for clinical physicists assessing dose from these units using commonly available equipment. CTDIW was calculated using the IAEA method for dosimetry of wide beams and compared to scans of the 32‐cm CTDI phantom using the full beam width and a 20‐mm collimated beam width. The impact of the partial rotation on the CTDIW calculation was assessed by acquiring measurements at four and twelve positions on the phantom periphery. For the system tested, the CTDIW was calculated to be 16.1 mGy using the IAEA method with default clinical protocol. Results showed that measuring CTDIW with the full beam width or a collimated beam width alone resulted in CTDI values of 19.0 mGy and 19.5 mGy, respectively. Using four peripheral measurements instead of 12 resulted in a difference of 4% for a collimated beam and 6% for an open beam. Variations in positioning on the order of a few centimeters resulted in a variation of only 4% with an open beam. The excellent reproducibility of the measurements using the full beam width suggests that this simple method is adequate for year‐to‐year comparisons. In contrast, the IAEA method is difficult to employ, particularly with 180° acquisitions. Use of peripheral measurements in excess of the usual four is time‐consuming and not necessary for most applications obtained with the geometry specific to this system.
Highlights
Mobile fluoroscopy (c-arm) units are commonly used during surgical procedures
Caution must be taken when comparing this value to the CTDIvol reported for a conventional CT unit. (For the case of the c-arm, CTDIW and CTDIvol are equivalent, since there is no table movement.) For both types of units, the CTDIvol provides an estimate of the energy imparted to a standardized phantom, averaged over the scan volume
The purpose of this study was to assess the practical aspects of measuring a volumetric dose from a mobile c-arm with 3D image acquisition
Summary
Mobile fluoroscopy (c-arm) units are commonly used during surgical procedures. Some units possess the ability to perform rotating acquisitions with 3D image reconstruction to produce images similar to traditional CT images (Fig. 1), and are increasingly being used to replace the postoperative CT. The unit investigated in this study, the Ziehm Imaging (Orlando, FL, USA) Vision RFD 3D mobile c-arm, does not provide any volumetric dose metrics. The only “dose” quantities provided are the beam-on time and dose to a reference point used for fluoroscopic imaging. The typical volumetric dose from the 3D acquisition is unknown. Dose assessment using the CTDIW is complicated due to the way in which the images are acquired. The beam width is approximately 150 mm at isocenter[1] and cannot be collimated during the acquisition.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
