Vertical Mis-Centering During CT Produces Largest Peripheral Dose Variations

Background: Since the adoption of flat-panel x-ray detectors in the late 1990s, CT imaging has rapidly evolved, improving 3-dimensional visualization while raising concerns about patient radiation exposure. To address dose optimization, modern CT systems incorporate strategies such as tube current modulation and size-specific dose estimates, both of which rely on accurate assessment of patient size and volumetric CT dose index (CTDI). Hardware components like the bowtie filter play a critical role in shaping the x-ray beam to reduce unnecessary exposure, but their effectiveness depends on precise patient centering. Prior studies have shown that even modest mis-centering can cause meaningful dose variations and increased image noise, particularly at the body surface. Building on this work, the present study uses CTDI phantoms and ionization chamber measurements to quantify how vertical and lateral mis-centering alters central and peripheral dose distribution and image quality, with th more...