Image-guided point-shear-wave elastography: a valid and reliable technique for liver fibrotic staging.

PURPOSE: Despite progressive implementation of image-guided point-shear wave elastography (pSWE) in guidelines as an alternative to transient elastography for the staging of fibrotic liver disease, pSWE is not widely adopted in clinical workflow. More information on reliability and validity of pSWE systems is needed. Therefore, we performed a phantom study to evaluate the validity and reliability of pSWE with ultrasound systems. METHODS: Validity and reliability of pSWE measurements from three ultrasound systems were evaluated. Measurements were performed on an elasticity phantom with reference elasticities of 7 ± 1 (low) (median ± interquartile range (IQR)), 14 ± 2 (medium) and 26 ± 3 (high) kPa. Measurements were repeated in tenfold for each reference at 2, 3 and 4 cm depth. Results were considered valid when median elasticity ± IQR was between the uncertainty limits (IQR) for each reference elasticity value and reliable when IQR/median < 0.30. RESULTS: pSWE with the systems provided valid results for all reference elasticities and focal depths, except for overestimation of high reference elasticity at 2 and 4 cm depth for one system (41.5 ± 4.3 and 39.0 ± 1.2 kPa, respectively). Measurements were reliable with a maximum IQR/median of 0.13, well below the guideline of IQR/median < 0.30. DISCUSSION: The results support the use of pSWE as an alternative to invasive or non-image guided noninvasive techniques for liver fibrotic staging. CONCLUSIONS: pSWE with ultrasound systems from different vendors is valid and reliable and can therefore be implemented to optimize clinical workflow by performing imaging and elastography simultaneously.

Impact of new X-ray technology on patient dose in pacemaker and implantable cardioverter defibrillator (ICD) implantations.

PURPOSE: New X-ray technology providing new image processing techniques may reduce radiation exposure. The aim of this study was to quantify this radiation exposure reduction for patients during pacemaker and implantable cardioverter defibrillator (ICD) implantation. METHODS: In this retrospective study, 1185 consecutive patients who had undergone de novo pacemaker or ICD implantation during a 2-year period were included. All implantations in the first year were performed using the reference technology (Allura Xper), whereas in the second year, the new X-ray technology (AlluraClarity) was used. Radiation exposure, expressed as the dose area product (DAP), was compared between the two time periods to determine the radiation exposure reduction for pacemaker and ICD implantations without cardiac resynchronization therapy (CRT) and with CRT. Procedure duration and contrast volume were used as measures to compare complexity and image quality. RESULTS: The study population consisted of 591 patients who had undergone an implantation using the reference technology, and 594 patients with the new X-ray technology. The two groups did not differ in age, gender, or body mass index. The DAP decreased with 69 % from 16.4 ± 18.5 to 5.2 ± 6.6 Gy cm2 for the non-CRT implantations (p < 0.001). The DAP decreased with 75 % from 72.1 ± 60.0 to 17.8 ± 17.4 Gy cm2 for the CRT implantations (p < 0.001). Nevertheless, procedure duration and contrast volume did not differ when using the new technology (p = 0.09 and p = 0.20, respectively). CONCLUSIONS: Introduction of new X-ray technology resulted in a radiation exposure reduction of more than 69 % for patients during pacemaker and ICD implantation while image quality was unaffected.

Improving the detection of small lesions using a state-of-the-art time-of-flight PET/CT system and small-voxel reconstructions.

UNLABELLED: A major disadvantage of (18)F-FDG PET involves poor detection of small lesions and lesions with low metabolism, caused by limited spatial resolution and relatively large image voxel size. As spatial resolution and sensitivity are better in new PET systems, it is expected that small-lesion detection could be improved using smaller voxels. The aim of this study was to test this hypothesis using a state-of-the-art time-of-flight PET/CT device. METHODS: (18)F-FDG PET scans of 2 image-quality phantoms (sphere sizes, 4-37 mm) and 39 consecutive patients with lung cancer were analyzed on a time-of-flight PET/CT system. Images were iteratively reconstructed with standard 4 × 4 × 4 mm voxels and smaller 2 × 2 × 2 mm voxels. For the phantom study, we determined contrast-recovery coefficients and signal-to-noise ratios (SNRs). For the patient study, (18)F-FDG PET-positive lesions in the chest and upper abdomen with a volume less than 3.0 mL (diameter, <18 mm) were included. Lesion mean and maximum standardized uptake values (SUVmean and SUVmax, respectively) were determined in both image sets. SNRs were determined by comparing SUVmax and SUVmean with background noise levels. A subanalysis was performed for lesions less than 0.75 mL (diameter, <11 mm). For qualitative analysis of patient data, 3 experienced nuclear medicine physicians gave their preference after visual side-by-side analysis. RESULTS: For phantom spheres 13 mm or less, we found higher contrast-recovery coefficients and SNRs using small-voxel reconstructions. For 66 included (18)F-FDG PET-positive lesions, the average increase in SUVmean and SUVmax using the small-voxel images was 17% and 32%, respectively (P < 0.01). For lesions less than 0.75 mL (21 in total), the average increase was 21% and 44%, respectively. Moreover, averaged over all lesions, the mean and maximum SNR increased by 20% and 27%, respectively (P < 0.01). For lesions less than 0.75 mL, these values increased up to 23% and 46%, respectively. The physicians preferred the small-voxel reconstructions in 76% of cases. CONCLUSION: Supported by a phantom study, there was a visual preference toward (18)F-FDG PET images reconstructed with 2 × 2 × 2 mm voxels and a profound increase in standardized uptake value and SNR for small lesions. Hence, it is expected that small-lesion detection improves using small-voxel reconstructions.