Computed tomography with a full FOV photon-counting detector in a clinical setting, the first experience.

OBJECTIVES: to assess the feasibility of CT with an integrated photon-counting-detector system (PC-CT) in the body imaging of clinical patients. METHODS: 120 examinations using photon counting detector CT were evaluated in six groups: 1/ a standard-dose lung, 2/ low-dose lung, 3/ ultra-high resolution (UHR) lung, 4/ standard-dose abdominal, 5/ lower-dose abdominal, 6/ UHR abdominal CTA. All CT examinations were performed on a single-source prototype device equipped with a photon counting detector covering a 50 cm scan field of view. Standard dose examinations were performed with the use of detector element size of 0.4 mm, ultra-high-resolution examinations with the detector element size of 0.2 mm, respectively. The stability of the system during imaging was tested. The diagnostic quality of the acquired images was assessed based on the imaging of key structures and the noise level in five-point scale, the effective dose equivalent, dose length product and noise level, and also relation to body mass index and body surface area were compared with three similar groups of CT images made with energy integrating high end scanner. The parameters were evaluated using Wilcoxon test for independent samples, the independence was tested using Kruskal-Wallis test. RESULTS: When PC-CT images radiation dose is compared with the similar imaging using energy integrating CT, the PC-CT shows lower dose in ultra-high resolution mode, the dose is significantly lower (p < 0.0001), the standard dose examinations were performed with the comparable radiation doses. PC-CT exhibited the significantly higher ratio between parenchyma signal and background noise both in lung and in abdominal imaging (p < 0.0001). CONCLUSIONS: PC-CT showed imaging stability and excellent diagnostic quality at dose values that are comparable or better to the quality of energy integrating CT, the better signal and improved resolution is most important advantage of photon counting detector CT over energy integrating detector CT.

Low contrast volume run-off CT angiography with optimized scan time based on double-level test bolus technique--feasibility study.

PURPOSE: To verify the technical feasibility of low contrast volume (40 mL) run-off CT angiography (run-off CTA) with the individual scan time optimization based on double-level test bolus technique. MATERIALS AND METHODS: A prospective study of 92 consecutive patients who underwent run-off CTA performed with 40 mL of contrast medium (injection rate of 6 mL/s) and optimized scan times on a second generation of dual-source CT. Individual optimized scan times were calculated from aortopopliteal transit times obtained on the basis of double-level test bolus technique--the single injection of 10 mL test bolus and dynamic acquisitions in two levels (abdominal aorta and popliteal arteries). Intraluminal attenuation (HU) was measured in 6 levels (aorta, iliac, femoral and popliteal arteries, middle and distal lower-legs) and subjective quality (3-point score) was assessed. Relations of image quality, test bolus parameters and arterial circulation involvement were analyzed. RESULTS: High mean attenuation (HU) values (468; 437; 442; 440; 342; 274) and quality score in all monitored levels was achieved. In 91 patients (0.99) the sufficient diagnostic quality (score 1-2) in aorta, iliac and femoral arteries was determined. A total of 6 patients (0.07) were not evaluable in distal lower-legs. Only the weak indirect correlation of image quality and test-bolus parameters was proved in iliac, femoral and popliteal levels (r values: -0.263, -0.298 and -0.254). The statistically significant difference of the test-bolus parameters and image quality was proved in patients with occlusive and aneurysmal disease. CONCLUSION: We proved the technical feasibility and sufficient quality of run-off CTA with low volume of contrast medium and optimized scan time according to aortopopliteal transit time calculated from double-level test bolus.