256‐ MDCT for evaluation of urolithiasis: Iterative reconstruction allows for a significant reduction of the applied radiation dose while maintaining high subjective and objective image quality

Purpose Multidetector CT ( MDCT ) is the established imaging modality in diagnostics of urolithiasis. The aim of iterative reconstruction ( IR ) is to allow for a radiation dose reduction while maintaining high image quality. This study evaluates its performance in MDCT for assessment of urolithiasis. Materials and Methods Fifty‐two patients underwent non‐contrast abdominal MDCT . Twenty‐six patients were referred to MDCT under suspicion of urolithiasis, and examined using a dose‐reduced scan protocol ( RDCT ). Twenty‐six patients, who had undergone standard‐dose MDCT , served as reference for radiation dose comparison. RDCT images were reconstructed using an IR system (i D ose4™, P hilips H ealthcare, C leveland, OH , USA ). Objective image noise ( OIN ) was recorded and five radiologists rated the subjective image quality independently. Radiation parameters were derived from the scan protocols. Results The CTDI vol could be reduced by 50% to 5.8 mGy ( P  < 0.0001). The same reduction was achieved for DLP and effective dose to 253 ± 27 mGy*cm ( P  < 0.0001) and 3.9 ± 0.4 mSv ( P  < 0.0001). IR led to a reduction of the OIN of up to 61% compared with classic filtered back projection ( FBP ) ( P  < 0.0001). The OIN declined with increasing IR levels. RDCT with FBP showed the lowest scores of subjective image quality (2.32 ± 0.04). Mean scores improved with increasing IR levels. i D ose6 was rated with the best mean score (3.66 ± 0.04). Conclusion The evaluated IR ‐tool and protocol may be applied to achieve a considerable radiation dose reduction in MDCT for diagnostics of urolithiasis while maintaining a confident image quality. Best image quality, suitable for evaluation of the entire abdomen concerning differential diagnoses, was achieved with i D ose6.