(2024) Huflage | Submillisievert PCCT for urinary calculi detection

Daniel Stromer

Retrospective single-center study of 507 patients undergoing unenhanced abdominal CT for suspected urinary calculi, comparing PCCT (n = 229) with optimized EID-CT (n = 278).

PCCT achieved a 44% lower effective radiation dose than EID-CT: 0.79 mSv vs 1.39 mSv, while maintaining excellent diagnostic confidence.

Despite the lower dose, PCCT provided higher SNR, with improvements of 30% at the kidney, 23% at the psoas, and 17% at the obturator level. Interreader agreement for calculus detection was near perfect (Krippendorff α ≥ 0.99).

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Figure 2. Axial contrast-unenhanced abdominal CT examinations in a 38-year-old female patient with a body mass index (calculated as weight in kilograms divided by height in meters squared) of 31.23 with known renal calculi for recurring events of flank pain. The patient underwent (A) dose-optimized energy-integrating detector CT (1.49 mSv) and (B) submillisievert photon-counting detector CT (0.94 mSv). Images from both examinations showed a 3-mm calculus in the left kidney (arrows).

Protocol

Detail	Value
Scanner	NAEOTOM Alpha
Scan area	Abdomen / urinary tract
Scan mode	Unenhanced ultra-low-dose CT
Acquisition mode	PCCT with tin prefiltration
Tin filter	0.4 mm
Tube voltage [kV]	Sn 100 / Sn 140, automatic selection
Tube current	Automatic
IQ level	20
Rotation time [s]	0.5
Detector slice collimation	144 × 0.4 mm
Reconstruction kernel	Br36
Reconstruction	Iterative reconstruction, strength 3
Slice thickness	1 mm
Contrast agent	None

Key results

Parameter	PCCT	EID-CT
Patients	229	278
CTDIvol	1.17 mGy	1.99 mGy
Effective dose	0.79 mSv	1.39 mSv
Dose reduction	44%	—
Image noise	15.88 HU	21.24 HU
Kidney SNR	2.15	1.66
Psoas SNR	3.01	2.44
Obturator SNR	3.25	2.79
Diagnostic confidence	5/5	5/5
Interreader agreement	α ≥ 0.99	α ≥ 0.99

PCCT therefore enabled submillisievert urinary stone imaging with simultaneous dose reduction and improved objective image quality, without loss of reader confidence.

Source: Huflage H, Kunz AS, Patzer TS, et al. Submillisievert Abdominal Photon-Counting CT versus Energy-integrating Detector CT for Urinary Calculi Detection: Impact on Diagnostic Confidence. Radiology. 2024;312(1). doi:10.1148/radiol.232453.