Modern imaging techniques in urinary stone disease

Purpose of review Radiological imaging techniques are a fast developing field in medicine. Therefore, the purpose of this review was to identify and discuss the latest changes of modern imaging techniques in the management of urinary stone disease. Recent findings The introduction of iterative image reconstruction enables low-dose and ultra-low-dose (ULD) protocols. Although current guidelines recommend their utilization in nonobese patients recent studies indicate that low-dose imaging may be feasible in obese (< 30 kg/m(2)) but not in bariatric patients. Use of dual energy computed tomography (CT) technologies should balance between additional information and radiation dose aspects. If available on a dose neutral basis, dual energy imaging and analysis should be performed. Current guidelines recommend measuring the largest diameter for clinical decision making; however, recent studies suggest a benefit from measuring the volume based on multiplanar reformation. Quantitative imaging is still an experimental approach. Summary The use of low-dose and even ULD CT protocols should be diagnostic standard, even in obese patients. If dual energy imaging is available, it should be limited to specific clinical questions. The stone volume should be reported in addition to the largest diameter for treatment decision and a more valid comparability of upcoming studies

Dual-Energy CT of the Abdomen: Radiology In Training

A 61-year-old man with an esophageal cancer diagnosis underwent staging dual-energy CT of the chest and abdomen in the portal venous phase after contrast media administration. Aside from the primary tumor and suspicious local lymph nodes, CT revealed hypoattenuating ambiguous liver lesions, an incidental right adrenal nodule, and a right renal lesion with soft-tissue attenuation. In addition, advanced atherosclerosis of the abdominal aorta and its major branches was noted. This article provides a case-based review of dual-energy CT technologies and their applications in the abdomen. The clinical utility of virtual monoenergetic images, virtual unenhanced images, and iodine maps is discussed. (C) RSNA, 202

Solitary PSMA-Positive Pulmonary Metastasis in Biochemical Relapse of Prostate Cancer

A 63-year-old man with a history of prostate cancer, treated with resection, radiation, and androgen-depriving therapy over 4 years, was referred to our department with suspicion of recurrence based on increased blood PSA levels (1.60 ng/mL). Ga-68 PSMA PET/CT identified a solitary, PSMA-positive pulmonary nodule in the right lung. After resection, histologic analysis confirmed prostatic origin, and the blood PSA level decreased to 0.13 ng/mL. Solitary pulmonary metastasis from prostate cancer is rare. The benefits of local treatment of a single metastasis even in advanced disease are disputed among oncologists. Here, biochemical response to resection was excellent

Virtual versus true non-contrast images of the brain from spectral detector CT: comparison of attenuation values and image quality

Background Prior studies focused on utilization of dual-energy computed tomography (DECT) to better detect intracranial pathology and to reduce artifacts. It is still unclear whether virtual non-contrast (VNC) images of DECT can replace true non-contrast (TNC) images. Purpose To compare attenuation values and image quality of VNC images to TNC images of the brain, obtained using spectral detector CT (SDCT). Material and Methods We retrospectively evaluated patients that underwent head CT with and without contrast material, on a SDCT scanner at our institution (n = 33). The attenuation values of different brain structures were obtained from TNC images, the conventional images of the post-contrast exams (n = 16) or the CT angiography (CTA) (n = 17), and the derived VNC images. In total, 591 regions of interest were obtained, including white and gray matter. Two neuroradiologists independently evaluated the image quality of the VNC and TNC images, using a 5-point Likert scale. Results The mean difference between the attenuation values on the VNC versus the TNC images was <4 HU for almost all the structures. The difference reached statistical significance (P < 0.05) for the deep gray structures but not for the white matter. The image quality score of the TNC images was 5 in all the patients (excellent gray-white matter differentiation). The scores of the VNC images differed between post-contrast and CTA examinations, with means of 4.9 +/- 0.3 (excellent) and 3.2 +/- 0.4 (fair), respectively (P < 0.001). Conclusion Our results show minor differences between attenuation values of different brain structures on VNC versus TNC images of SDCT

Renal cystic lesions characterization using spectral detector CT (SDCT): Added value of spectral results

Objectives: To evaluate the added value of spectral results derived from Spectral Detector CT (SDCT) to the characterization of renal cystic lesions (RCL). Methods: This retrospective study was approved by the local Institutional review board. 70 consecutive patients who underwent abdominopelvic SDCT and had at least one RCL were included. 84 RCL were categorized as simple, complex or neoplastic based on attenuation values on single-phase post-contrast images. Attenuation values were measured in each lesion on standard conventional CT images (stCl) and virtual monoenergetic images of 40keV and 100keV. A spectral curve slope was calculated and intra lesional iodine concentration (IC) was measured using iodine-density maps. Reference standard was established using histopathologic correlation, prior and follow-up imaging. Analysis of variance (ANOVA) was used to compare between the groups. Results: Mean attenuation values for benign simple and complex RCL differed significantly (42 +/- 16 vs 8 +/- 3 HU; p < 0.001). IC was almost identical in benign simple and complex RCL (0.23 +/- 0.04 mg ml(-1) vs 0.24 +/- 0.04 mg ml(-1)), while IC in neoplastic RCL was significantly higher (2.10 +/- 0.08 mg ml(-1) p < 0.001). The mean spectral curve slope did not differ significantly between simple and complex RCL (0.30 +/- 0.03 vs 0.33 +/- 0.05) but was significantly higher in neoplastic RCL (2.60 +/- 0.10; p < 0.001). Conclusions: Spectral results of SDCT are highly promising in distinguishing benign complex RCL from enhancing neoplastic RCL based on single-phase post-contrast imaging only. Advances in knowledge: SDCT can assist in differentiating between benign complex and neoplastic renal cystic lesions

Inter-scan and inter-scanner variation of quantitative dual-energy CT: evaluation with three different scanner types

Objectives: To investigate inter-scan and inter-scanner variation of iodine concentration (IC) and attenuation in virtual monoenergetic images at 65 keV (HU65keV) in patients with repeated abdominal examinations on dual-source (dsDECT), rapid kV switching (rsDECT), and dual-layer detector DECT (dlDECT). Methods: We retrospectively included 131 patients who underwent two abdominal DECT examinations on the same scanner (dsDECT: n = 46, rsDECT: n = 45, dlDECT: n = 40). IC and HU65keV were measured by placing regions of interest in the liver, spleen, kidneys, aorta, portal vein, and inferior vena cava. Overall IC and HU65keV for each scanner, their inter-scan differences and proportional variation were calculated and compared between scanner types. Results: The three scanner-specific cohorts showed similar weight, body diameter, age, sex, and contrast media injection parameters as well as inter-scan differences hereof (p range: 0.23-0.99). Absolute inter-scan differences of HU65keV and IC were comparable between scanners (p range: 0.08-1.0). Overall inter-scan variation was significantly higher in IC than HU65keV (p < 0.05). For the liver, rsDECT showed significantly lower inter-scan variation of IC compared to dsDECT/dlDECT (p = 0.005/0.01), while for the spleen, this difference was only significant compared to dsDECT (p = 0.015). Normalizing IC of the liver to the portal vein and of the spleen to the aorta did not significantly reduce inter-scan variation (p = 0.97 and 0.50). Conclusions: Iodine measurements across different DECT scanners show inter-scan variation which is higher compared to variation of attenuation values. Inter-scanner differences in longitudinal variation and overall iodine concentration depend on the scanner pairs and organs assessed and should be acknowledged in clinical and scientific DECT applications