Radiation dose and image quality of X-ray volume imaging systems: cone-beam computed tomography, digital subtraction angiography and digital fluoroscopy.

OBJECTIVE: Radiation dose and image quality estimation of three X-ray volume imaging (XVI) systems. METHODS: A total of 126 patients were examined using three XVI systems (groups 1-3) and their data were retrospectively analysed from 2007 to 2012. Each group consisted of 42 patients and each patient was examined using cone-beam computed tomography (CBCT), digital subtraction angiography (DSA) and digital fluoroscopy (DF). Dose parameters such as dose-area product (DAP), skin entry dose (SED) and image quality parameters such as Hounsfield unit (HU), noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were estimated and compared using appropriate statistical tests. RESULTS: Mean DAP and SED were lower in recent XVI than its previous counterparts in CBCT, DSA and DF. HU of all measured locations was non-significant between the groups except the hepatic artery. Noise showed significant difference among groups (P < 0.05). Regarding CNR and SNR, the recent XVI showed a higher and significant difference compared to its previous versions. Qualitatively, CBCT showed significance between versions unlike the DSA and DF which showed non-significance. CONCLUSION: A reduction of radiation dose was obtained for the recent-generation XVI system in CBCT, DSA and DF. Image noise was significantly lower; SNR and CNR were higher than in previous versions. The technological advancements and the reduction in the number of frames led to a significant dose reduction and improved image quality with the recent-generation XVI system. KEY POINTS: • X-ray volume imaging (XVI) systems are increasingly used for interventional radiological procedures. • More modern XVI systems use lower radiation doses compared with earlier counterparts. • Furthermore more modern XVI systems provide higher image quality. • Technological advances reduce radiation dose and improve image quality.

Ultrafast cone-beam computed tomography: a comparative study of imaging protocols during image-guided therapy procedure.

OBJECTIVE: To evaluate two ultrafast cone-beam CT (UF-CBCT) imaging protocols with different acquisition and injection parameters regarding image quality and required contrast media during image-guided hepatic transarterial chemoembolization (TACE). METHODS: In 80 patients (male: 46, female: 34; mean age: 56.8 years; range: 33-83) UF-CBCT was performed during TACE for intraprocedural guidance. Imaging was performed using two ultrafast CBCT acquisition protocols with different acquisition and injection parameters (imaging protocol 1: acquisition time 2.54 s, and contrast 6 mL with 3 s delay; imaging protocol 2: acquisition time 2.72 s, and contrast 7 mL with 6 s delay). Image evaluation was performed with both qualitative and quantitative methods. Contrast injection volume and dose parameters were compared using values from the literature. RESULTS: Imaging protocol 2 provided significantly better (P < 0.05) image quality than protocol 1 at the cost of slightly higher contrast load and patient dose. Imaging protocol 1 provided good contrast perfusion but it mostly failed to delineate the tumors (P < 0.05). On the contrary, imaging protocol 2 showed excellent enhancement of hepatic parenchyma, tumor, and feeding vessels. CONCLUSION: Tumor delineation, visualization of hepatic parenchyma, and feeding vessels are clearly possible using imaging protocol 2 with ultrafast CBCT imaging. A reduction of required contrast volume and patient dose were achieved due to the ultrafast CBCT imaging.

Dual-energy CT spectral and energy weighted data sets: carotid stenosis and plaque detection.

RATIONALE AND OBJECTIVES: To evaluate dual-energy computed tomography spectral and energy weighted (W) image data sets concerning carotid stenosis and calcified plaque detection. MATERIALS AND METHODS: Ninety patients were evaluated using contrast media injection. Energy used for dual-energy computed tomography was tin filter with 140/80 kiloVoltage and effective milli Ampere second was 147.4/270.6. Image reconstruction was performed using D30f kernel and 0.0, 0.3, 0.6, 0.8, 1.0 weightings. Data sets were analyzed using both qualitative and quantitative methods. RESULTS: The signal-to-noise ratio, contrast-to-noise ratio, and figure-of-merit were significantly higher in 0.6-W compared to 140-kV or 80-kV data (all P < .05). Plaque thickness, span, and longitudinal diameters were different for 140-kV, 0.6-W, and 80-kV data (all P < .05). Stenotic intra-luminal diameter was significantly different among 140 kV, 0.6 W, and 80 kV data (all P < .05). A comparison between 0.6 W and digital subtraction angiography was nonsignificant (P > .05) in normal lumen measurement. CONCLUSIONS: The dimension of calcified plaque and carotid artery with contrast media decreased with increased energy. The percentage of carotid artery stenosis does not vary with different energy. Care must be taken for procedural planning like sizing of stents. Measured diameters of the 0.6 W were close to digital subtraction angiography; we suggest that planning should be based on the images acquired using 0.6 weighting.