Organ Dose Modulation: a useful tool for dose reduction in clinical practice?

Abstract

Purpose: To quantify the reduction in effective dose achieved through organ dose modulation (ODM) on a General Electric Revolution Apex CT scanner, while preserving image quality.

Methods: First, the noise index (NI) corresponding to comparable image quality-defined by signal-to-noise ratio (SNR)-was determined using a PMMA cylindrical phantom (CTDI phantom), both with and without ODM. Scan protocols for the thorax, abdomen, and head were evaluated. Next, radiation dose was measured at every 10° scan angle using a 10 cm ionization chamber for each protocol, with and without ODM. Finally, effective dose was estimated using the angle-dependent dose measurements in Monte Carlo simulation software (PCXMC), for tube voltages of 80, 100, and 120 kVp.

Results: Effective dose was reduced by 12-14 ± 1% for thorax, 12-13 ± 1% for abdomen. when using ODM. No significant change in effective dose was found for CT head. Notably, radiosensitive organs such as the breasts and eye lenses received 19-21 ± 1% and 25 ± 7% (upper-bound estimate) less dose, respectively.

Conclusions: This study demonstrates that ODM could significantly reduce both effective and organ-specific radiation doses without compromising image quality, especially when applied to the whole scan field.

Advances in knowledge: This study demonstrates with dose measurements with 10° angular accuracy that for this specific implementation of ODM, it should be applied to the whole scan field for both dose reduction and consistent image quality. This finding is contradictory to the vendor's recommendation to apply ODM only to an area with a specific radiosensitive organ, such as the breasts.