Feasibility of wide detector CT perfusion imaging performed during routine staging and restaging of pancreatic ductal adenocarcinoma.

PURPOSE: To evaluate the feasibility of CT perfusion performed during routine multiphase contrast-enhanced CT on a 160 mm wide-coverage 256-slice scanner in patients with pancreatic ductal adenocarcinoma (PDAC). METHODS: Fifty-seven patients had a CT perfusion acquisition during their routine multiphase CT. Perfusion was performed 5 to 42.5 s (15 passes at 2.5 s intervals) after intravenous contrast administration (4.2-5 ml/s), followed by pancreatic parenchymal and portal venous phases for clinical interpretation. Perfusion maps were generated and blood flow (BF), blood volume (BV), and permeability surface area product (PS) for tumor and uninvolved pancreas were calculated using deconvolution algorithms and compared to existing similar publications. Radiation dose information was recorded and size-specific dose estimate (SSDE) was calculated using body dimensions. RESULTS: Diagnostic quality of standard images was unaffected by performing the perfusion acquisition. Average tumor center BF was 20.8 ± 12.1 ml/100 g/min, BV 2.5 ± 2.1 ml/100 g and PS 15.5 ± 39.4 ml/100 g/min. Average pancreas BF was 90.8 ± 50.2 ml/100 g/min, BV 11.9 ± 4.3 ml/100 g and PS 33.6 ± 27.7 ml/100 g/min. For the perfusion acquisition, mean SSDE was 57 ± 11 mGy, CTDIvol 43 ± 6 mGy and DLP 685 ± 100 mGy-cm. CONCLUSION: Adding a perfusion CT acquisition to standard pancreatic CT protocol is feasible using a wide-detector 256-slice CT scanner and adds quantitative information while maintaining diagnostic quality of the standard of care examination. This novel protocol adds no time or cost to the examination and yields perfusion parameters that are comparable to existing literature using a separate dedicated perfusion protocol.

Feasibility of wide detector three-pass arterial phase liver CT in patients with cirrhosis: timing of hyperenhancing lesion peak conspicuity.

PURPOSE: To evaluate feasibility of a wide detector liver CT protocol with three acquisitions in the hepatic arterial phase. METHODS: Forty-one patients with cirrhosis prospectively underwent a wide detector axial liver CT protocol. Three 16 cm axial liver acquisitions were obtained during a single breath hold at peak aortic enhancement plus 10, 20, and 25 s. Two readers working separately scored overall exam quality, identified hyperenhancing lesions, and subjectively scored and ranked relative lesion conspicuity. Objective lesion enhancement was measured and CNR calculated. Data were analyzed using a generalized linear models and Tukey's post hoc testing. RESULTS: Seventy-one hyperenhancing lesions were identified with average size of 1.8 cm (range 0.4-9.6 cm). The two readers separately identified 60 and 54 lesions on the 10 s arterial acquisition, 70 and 67 on the 20 s, and 52 and 51 on the 25 s. The readers determined all exams had diagnostic image quality. Subjective ranking of lesion conspicuity was greatest at 20 s in 62% of lesions but was greatest at 10 or 25 s in 38%. CNR was highest at 20 s in 58% of lesions but was highest at 10 or 25 s in 42%. Overall, there was no significant difference in mean CNR between the three arterial acquisitions. CONCLUSION: A wide detector axial liver CT protocol with three acquisitions in the hepatic arterial phase is technologically feasible and results in diagnostic image quality. With this protocol, peak subjective and objective hyperenhancing lesion conspicuity may be earlier or later than 20 s in up to 40% of lesions.

Endogenous MicroRNA Competition as a Mechanism of shRNA-Induced Cardiotoxicity.

Gene knockdown using short hairpin RNAs (shRNAs) is a promising strategy for targeting dominant mutations; however, delivering too much shRNA can disrupt the processing of endogenous microRNAs (miRNAs) and lead to toxicity. Here, we sought to understand the effect that excessive shRNAs have on muscle miRNAs by treating mice with recombinant adeno-associated viral vectors (rAAVs) that produce shRNAs with 19-nt or 21-nt stem sequences. Small RNA sequencing of their muscle and liver tissues revealed that shRNA expression was highest in the heart, where mice experienced substantial cardiomyopathy when shRNAs accumulated to 51.2% ± 13.7% of total small RNAs. With the same treatment, shRNAs in other muscle tissues reached only 12.1% ± 5.0% of total small RNAs. Regardless of treatment, the predominant heart miRNAs remained relatively stable across samples. Instead, the lower-expressed miR-451, one of the few miRNAs processed independently of Dicer, changed in relation to shRNA level and toxicity. Our data suggest that a protective mechanism exists in cardiac tissue for maintaining the levels of most miRNAs in response to shRNA delivery, in contrast with what has been shown in the liver. Quantifying miRNA profiles after excessive shRNA delivery illuminates the host response to rAAV-shRNA, allowing for safer and more robust therapeutic gene knockdown.

Dual-Energy CT Urography With 50% Reduced Iodine Dose Versus Single-Energy CT Urography With Standard Iodine Dose.

OBJECTIVE: The purpose of this study was to compare dual-energy CT (DECT) urography with a 50% reduced iodine dose to single-energy CT (SECT) urography with a standard iodine dose with respect to attenuation of renal vascular and urinary tract structures and with respect to image quality. SUBJECTS AND METHODS: The study included 62 patients undergoing evaluation of urinary tract lithiasis, tumor, or hematuria. Thirty-one patients underwent DECT urography with a 50% reduced iodine dose and reconstruction at 50 and 77 keV. These subjects were sex, age, and size matched to a group of 31 patients who underwent 120-kVp SECT urography with a standard iodine dose. The mean iodine dose was 22 g for DECT and 44 g for SECT. Attenuation was measured at seven locations in the renal arteries, renal veins, and urinary tract. Two reviewers subjectively scored the image quality parameters image noise, sharpness of urinary tract contours, enhancement of urinary structures, and streak artifacts. RESULTS: Mean DECT attenuation at 50 keV was the same as or greater than SECT attenuation at each of the seven locations. Measured image noise was highest at 50-keV DECT but was the same for 77-keV DECT and 120-kVp SECT. Mean subjective scores for DECT image quality parameters were the same as or higher than those of SECT, except for streak artifact and sharpness of urinary tract contours. CONCLUSION: DECT urography with a 50% reduced iodine dose may result in measured renal vascular and urinary tract attenuation the same as or higher than and image quality measurements and scores similar to those obtained with 120-kVp SECT urography with a standard iodine dose.