Finding the optimal tube current and iterative reconstruction strength in liver imaging; two needles in one haystack.

OBJECTIVES: The aim of the study was to find the lowest possible tube current and the optimal iterative reconstruction (IR) strength in abdominal imaging. MATERIAL AND METHODS: Reconstruction software was used to insert noise, simulating the use of a lower tube current. A semi-anthropomorphic abdominal phantom (Quality Assurance in Radiology and Medicine, QSA-543, Moehrendorf, Germany) was used to validate the performance of the ReconCT software (S1 Appendix). Thirty abdominal CT scans performed with a standard protocol (120 kVref, 150 mAsref) scanned at 90 kV, with dedicated contrast media (CM) injection software were selected. There were no other in- or exclusion criteria. The software was used to insert noise as if the scans were performed with 90, 80, 70 and 60% of the full dose. Consequently, the different scans were reconstructed with filtered back projection (FBP) and IR strength 2, 3 and 4. Both objective (e.g. Hounsfield units [HU], signal to noise ratio [SNR] and contrast to noise ratio [CNR]) and subjective image quality were evaluated. In addition, lesion detection was graded by two radiologists in consensus in another 30 scans (identical scan protocol) with various liver lesions, reconstructed with IR 3, 4 and 5. RESULTS: A tube current of 60% still led to diagnostic objective image quality (e.g. SNR and CNR) when IR strength 3 or 4 were used. IR strength 4 was preferred for lesion detection. The subjective image quality was rated highest for the scans performed at 90% with IR 4. CONCLUSION: A tube current reduction of 10-40% is possible in case IR 4 is used, leading to the highest image quality (10%) or still diagnostic image quality (40%), shown by a pairwise comparison in the same patients.

Development of an ultrasound-capable phantom with patient-specific 3D-printed vascular anatomy to simulate peripheral endovascular interventions.

PURPOSE: Today, ultrasound-guided peripheral endovascular interventions have the potential to be an alternative to conventional interventions that are still X-ray and contrast agent based. For the further development of this approach, a research environment is needed that represents the individual patient-specific endovascular properties as realistically as possible. Aim of the project was the construction of a phantom that combines ultrasound capabilities and the possibility to simulate peripheral endovascular interventions. MATERIAL AND METHODS: We designed a modular ultrasound-capable phantom with exchangeable patient specific vascular anatomy. For the manufacturing of the vascular pathologies, we used 3D printing technology. Subsequently, we evaluated the constructed simulator with regards to its application for endovascular development projects. RESULTS: We developed an ultrasound-capable phantom with an exchangeable 3D-printed segment of the femoral artery. This modality allows the study of several patient-specific 3D-printed pathologies. Compared to the flow properties of a human artery (male; age 28) the phantom shows realistic flow properties in the duplex ultrasound image. We proved the feasibility of the simulator by performing an ultrasound-guided endovascular procedure. Overall, the simulator showed realistic intervention conditions. CONCLUSIONS: With the help of the constructed simulator, new endovascular procedures and navigation systems, such as ultrasound-guided peripheral vascular interventions, can be further developed. Additionally, in our opinion, the use of such simulators can also reduce the need for animal experiments.

Application of polychromatic µCT for mineral density determination.

Accurate assessment of mineral density (MD) provides information critical to the understanding of mineralization processes of calcified tissues, including bones and teeth. High-resolution three-dimensional assessment of the MD of teeth has been demonstrated by relatively inaccessible synchrotron radiation microcomputed tomography (SRµCT). While conventional desktop µCT (CµCT) technology is widely available, polychromatic source and cone-shaped beam geometry confound MD assessment. Recently, considerable attention has been given to optimizing quantitative data from CµCT systems with polychromatic x-ray sources. In this review, we focus on the approaches that minimize inaccuracies arising from beam hardening, in particular, beam filtration during the scan, beam-hardening correction during reconstruction, and mineral density calibration. Filtration along with lowest possible source voltage results in a narrow and near-single-peak spectrum, favoring high contrast and minimal beam-hardening artifacts. More effective beam monochromatization approaches are described. We also examine the significance of beam-hardening correction in determining the accuracy of mineral density estimation. In addition, standards for the calibration of reconstructed grey-scale attenuation values against MD, including K(2)PHO(4) liquid phantom, and polymer-hydroxyapatite (HA) and solid hydroxyapatite (HA) phantoms, are discussed.