Exhibit Hall | Forum 8
Purpose: Recent ACR report showed kidney stone CT optimized mainly with Dose Length Product as a dose target , which is neither size nor population specific. Our health system currently performs adult kidney stone CT scans using a routine non-contrast-enhanced abdomen CT protocol. Aims: (i) Implement size-specific dose estimate (SSDE) as dose targe for CT dose optimization; (ii) develop kidney-stone specific CT metrics to evaluate the image quality of dose-reduced protocols.
Methods: CTDIvol in the routine protocol was evaluated to identify baseline SSDE. To mimic patients with different body sizes, Mercury 4.0 phantom (Sun Nuclear, Middleton, WI) was scanned with Philips Ingenuity CT with different SSDE targets (5, 7, and 10 mGy) and reconstruction methods (iDose 3, 4, 5). Kidney-specific imaging tasks were modeled as spheres with contrast and size reported. CT images were analyzed using kidney-stone specific task transfer functions using ImQuest , including detectability (stone-specific), modulation transfer function, and noise power spectrum(NPS).
Results: Baseline routine abdomen CT dose across facilities was determined (Q3 CTDIvol =20 mGy; median CTDIvol = 14.2 mGy; SSDE 10 mGy, Figure 1) at 120 kV using iDose 3. D-prime showed non-inferior detectability of small low-densitystones in protocols with SSDE 7 mGyat 120 kV using iDose 5 and SSDE 5 mGy at 100 kV using iDose 5(Table 1). Both candidates had non-inferior f50 for small stone size (3 mm, Table 2). Normalized NPS are similar in shape to the baseline protocol, suggesting minimal changes in noise texture (Figure 2).
Conclusion: Dose reduction with non-inferior image quality for specific tasks can be achieved prospectively with advanced reconstruction methods. Reduced dose protocols using the suggested dose target and reconstruction combination can be further implemented for kidney stone follow-up scans. Further task definitions and validations are needed to evaluate dose-reduced CT protocols for screening purposes.
Low-dose CT, Low Contrast Detectability, Dosimetry Protocols