Quick question: in a routine adult 4-bitewing set, which change lowers patient dose more — switching from round to rectangular collimation with a beam-aiming ring, or dropping kVp from 70 to 60 while keeping image density constant by adjusting mAs? I routinely measure roughly a 60–70% entrance skin dose reduction with rectangular collimation and fewer retakes from improved alignment, which to me is the safer ALARA choice — do your numbers line up?
Rectangular collimation wins; your “60–70%” tracks — use a 16-inch PID with the ring. Dropping kVp with mAs compensation seldom helps.
@OP I’ve found the rectangular collimator with a “beam-aiming ring” is the bigger saver on 4 bitewings, and switching to sensor-specific rectangular holders so the ring matches the sensor’s active area nearly eliminated cone cuts. Have you tried the XCP-DS Fit? On older tubes with lighter filtration, dropping from 70 to 60 kVp and upping mAs can raise skin dose, so I’d keep 70 and dial in alignment.
In our clinic, the bigger drop came after we locked 70 kVp and drilled 3‑point contact with a rectangular ring and a 30 cm cone to stop cone‑cuts and retakes. > to 60 kVp and upping mAs can raise skin dose, so I’d keep 70 and dial in — same here. @OP do you have room for a 30 cm PID?