Browsing by Author "Payomthip S."

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    Computed Tomography Dose Index Measurements in Wide-beam Computed Tomography System
    (2026-01-01) Asavaphatiboon S.; Payomthip S.; Sodkokkruad P.; Prasertsilpakul W.; Iamsuk T.; Ardmontree S.; Tangboonduangjit P.; Asavaphatiboon S.; Mahidol University
    Computed tomography (CT) produces cross-sectional images for medical diagnosis; however, in wide cone-beam CT, conventional CT dose index (CTDI) measurements using a 100-mm ionization chamber (IC) underestimate dose for larger beam widths. This study evaluated and compared CTDI measurements in wide beam using different methods for wide-beam CT, following International Atomic Energy Agency Human Health Report No. 5. Measurements were performed on an Aquilion™ ONE CT scanner (160 mm beam width) using 100-and 300-mm ICs (Radcal 10 × 6–3CT and PTW TM30017). CTDIfree-in-air and weighted CTDI (CTDIw) were obtained under brain and abdomen protocols, both in free air and phantom conditions, at the Advanced Diagnostic Imaging Center, Faculty of Medicine Ramathibodi Hospital, Thailand. For free-in-air measurements at 80 mm beam width, CTDI100air(no-step) was slightly smaller than CTDI300air with percentage differences of −1.27% and −1.94%, while CTDI100air(two-step) showed +6.79% and +6.48% differences for brain and abdomen protocols, respectively. At 160 mm beam width, CTDI100air(no-step) was significantly lower due to incomplete dose coverage, whereas two-and three-step methods yielded slightly higher values. For CTDIw at 80 mm, percentage differences were −17.06% and −15.05% (no-step), −3.29% and +1.88% (two-step), and −8.94% and −3.45% (calculated two-step) for brain and abdomen, respectively. At 160 mm, CTDI100w(no-step) was 41.27% and 36.38% lower than CTDI300W, while CTDI100w(three-step) exceeded CTDI300w due to scattering or overlap. Overall, CTDI measurements using a 100 mm IC underestimate dose for beam widths >NT +40 mm. The two-step technique is sufficient for wide-beam CT dosimetry measurements.