Systematic radiation dose optimization of abdominal dual-energy CT on a second-generation dual-source CT scanner: assessment of the accuracy of iodine uptake measurement and image quality in an in vitro and in vivo investigations.

PURPOSE: To assess the accuracy of iodine quantification in a phantom study at different radiation dose levels with dual-energy dual-source CT and to evaluate image quality and radiation doses in patients undergoing a single-energy and two dual-energy abdominal CT protocols. METHODS: In a phantom study, the accuracy of iodine quantification (4.5-23.5 mgI/mL) was evaluated using the manufacturer-recommended and three dose-optimized dual-energy protocols. In a patient study, 75 abdomino-pelvic CT examinations were acquired as follows: 25 CT scans with the manufacturer-recommended dual-energy protocol (protocol A); 25 CT scans with a dose-optimized dual-energy protocol (protocol B); and 25 CT scans with a single-energy CT protocol (protocol C). CTDIvol and objective noise were measured. Five readers scored each scan according to six subjective image quality parameters (noise, contrast, artifacts, visibility of small structures, sharpness, overall diagnostic confidence). RESULTS: In the phantom study, differences between the real and measured iodine concentrations ranged from -8.8% to 17.0% for the manufacturer-recommended protocol and from -1.6% to 20.5% for three dose-optimized protocols. In the patient study, the CTDIvol of protocol A, B, and C were 12.5 ± 1.9, 7.5 ± 1.2, and 6.5 ± 1.7 mGycm, respectively (p < 0.001), and the average image noise values were 6.6 ± 1.2, 7.8 ± 1.4, and 9.6 ± 2.2 HU, respectively (p < 0.001). No significant differences in the six subjective image quality parameters were observed between the dose-optimized dual-energy and the single-energy protocol. CONCLUSION: A dose reduction of 41% is feasible for the manufacturer-recommended, abdominal dual-energy CT protocol, as it maintained the accuracy of iodine measurements and subjective image quality compared to a single-energy protocol.

Colorectal cancer: current imaging methods and future perspectives for the diagnosis, staging and therapeutic response evaluation.

In the last 10 years the mortality rate of colorectal cancer (CRC) has decreased by more than 20% due to the rising developments in diagnostic techniques and optimization of surgical, neoadjuvant and palliative therapies. Diagnostic methods currently used in the evaluation of CRC are heterogeneous and can vary within the countries and the institutions. This article aims to discuss in depth currently applied imaging modalities such as virtual computed tomography colonoscopy, endorectal ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) in the diagnosis of CRC. Special focus is put on the potential of recent diagnostic developments as diffusion weighted imaging MRI, MRI biomarkers (dynamic enhanced MRI), positron emission tomography with 2-(fluorine-18)-fluoro-2-deoxy-D-glucose (FDG-PET) combined with computed tomography (PET/CT) and new hepatobiliary MRI contrast agents. The precise role, advantage and disadvantages of these modalities are evaluated controversially in local staging, metastatic spread and treatment monitoring of CRC. Finally, the authors will touch upon the future perspectives in functional imaging evaluating the role of integrated FDG-PET/CT with perfusion CT, MRI spectroscopy of primary CRC and hepatic transit time analysis using contrast enhanced ultrasound and MRI in the detection of liver metastases. Validation of these newer imaging techniques may lead to significant improvements in the management of patients with colorectal cancer.

Kidney and urinary tract imaging: triple-bolus multidetector CT urography as a one-stop shop--protocol design, opacification, and image quality analysis.

PURPOSE: To retrospectively evaluate renal, vascular, and urinary tract visualization following a single postcontrast multidetector computed tomographic (CT) urographic sequence performed with three limited-volume bolus injections. MATERIALS AND METHODS: The institutional review board approved this retrospective study. Patient informed consent was waived. Triple-bolus multidetector CT urography was performed in 110 patients. Triple-bolus protocol consisted of 30 mL of contrast material at 2 mL/sec at 0 seconds, 50 mL at 1.5 mL/sec at 435 seconds, 65 mL at 3 mL/sec at 488 seconds, with total abdominal scanning time of 510 seconds. Two independent readers rated urinary tract opacification and qualitatively and quantitatively assessed renal parenchymal and vascular contrast enhancement. Upper urinary tract (UUT) distention was measured by one reader. Interobserver agreement was assessed by using kappa statistics. RESULTS: Complete opacification of the intrarenal collecting system and proximal ureter was achieved in 91% (184 of 202) (kappa = 0.62) and 82% (166 of 202) (kappa = 0.94) of segments, respectively. The distal ureter was not opacified in 21% of the cases (kappa = 0.92), and the bladder was not opacified in 20% of the cases. Mean distention was higher for proximal (3.9 mm) than for distal (3.7 mm) segments. Image quality of renal parenchymal enhancement was excellent in 76% of cases. Arteries showed better contrast enhancement than veins (excellent rating in 89% vs 59% of the cases). Radiation dose calculated for triple-bolus acquisition was 9.8 mSv. CONCLUSION: Triple-bolus multidetector CT urography is a dose-efficient protocol acquiring corticomedullary-nephrographic-excretory and vascular enhancement phases in a single acquisition and provides sufficient opacification and distention of the UUT. Simultaneously, adequate image quality of renal parenchyma and vascular anatomy is achieved.

Is ultrasound of the retroperitoneum a valuable staging method in selecting testicular cancer patients for primary retroperitoneal lymph node dissection?

OBJECTIVE: In nonseminomatous testicular cancer patients with normal serum tumor markers and no distant metastasis, postorchiectomy surgery is a valid treatment option if the disease extension into the retroperitoneum is not advanced. We assessed the ability of ultrasound (US) to exclude the presence of bulky retroperitoneal disease. MATERIALS AND METHODS: One hundred and forty testicular cancer patients underwent US and computed tomography (CT) of the retroperitoneum. US results were analyzed using three cutoffs: 5 cm (conventional staging), 3 cm (based on the minimal sonographical dimension of actual bulky disease) and 0 cm ('clean retroperitoneum' or any detectable nodes), and were compared with CT data using the 5-cm cutoff ('gold standard'). RESULTS: The sensitivity, specificity, overall accuracy, positive and negative predictive values of US in detecting of bulky retroperitoneum for the 5-cm cutoff were 83, 96, 93, 88 and 94%, for the 3-cm cutoff 100, 91, 94, 80 and 100%, and for the 0-cm cutoff 100, 66, 74, 49 and 100%, respectively. CONCLUSIONS: In stage I and IIA/B marker-negative nonseminomas if the treatment strategy is surgery, US may facilitate the selection process; the report of a clean retroperitoneum safely excludes the presence of bulky disease and may be an indication for lymphadenectomy, although in case of positive findings a CT should be performed.

Multidetector CT urography: techniques, clinical applications, and pitfalls.

For two decades, computed tomography (CT) has challenged intravenous urography (IVU) in the evaluation of urinary tract abnormalities. Compared with IVU, CT is more sensitive and specific in the detection and characterization of a variety of urinary tract disorders, including renal masses and urolithiasis. The last purported advantage of IVU has been its ability to depict subtle and mucosal abnormalities of the urothelium. Now, using multidetector CT (MDCT), this challenge has been overcome. In this article, we review the current role of MDCT urography in the evaluation of the urinary tract.