High-resolution multidetector CT in the preoperative evaluation of patients with renal cell carcinoma

OBJECTIVE

The purpose of our study was to evaluate the accuracy of multidetector CT (MDCT) using a high-resolution protocol in the preoperative assessment of patients with renal cell carcinoma who are possible candidates for nephron-sparing surgery.

MATERIALS AND METHODS

Forty patients with suspected renal cell carcinoma underwent MDCT. Contrast-enhanced acquisitions were obtained during arterial, nephrographic, and urographic phases using a thin-slice protocol. One-millimeter-thick source images were evaluated by two observers on a dedicated workstation for the identification and characterization of the tumor, presence of a pseudocapsule or invasion of perirenal fat, involvement of adrenal glands or surrounding tissues, presence of satellite lesions within Gerota's fascia, infiltration of renal vein and inferior vena cava, involvement of lymph nodes, and presence of distant metastases. Imaging findings were compared with surgical specimens using criteria from the Robson and TNM classification systems.

RESULTS

The presence and size of all lesions were correctly shown in all patients. In evaluating Robson stage I of renal cell carcinoma, we were able to diagnose fat infiltration on 1-mm scans with 96% sensitivity, 93% specificity, and 95% accuracy; the positive and negative predictive values were, respectively, 100% and 93%. One hundred percent accuracy was achieved in staging high-grade lesions.

CONCLUSION

High-resolution MDCT is accurate in the preoperative evaluation of patients with renal cell carcinoma.

The effect of intravenous metformin on glucose metabolism during hyperglycaemia in type 2 diabetes

A stepped intravenous metformin infusion was used in conjunction with the hyperglycaemic clamp technique to study the dose-response relationship of plasma metformin concentration with hepatic glucose production and peripheral glucose disposal in nine patients with Type 2 diabetes. The study was of double-blind crossover design, using NaCl infusion as control. Plasma metformin concentrations spanning the therapeutic range (1.64 +/- 0.13 mg l-1 and 6.57 +/- 0.61 mg l-1) were achieved. No differences in peripheral glucose disposal were demonstrated when compared with NaCl infusion (3.4 +/- 0.1 vs 3.6 +/- 0.2 (+/- SE) mg kg-1 min-1 and 3.4 +/- 0.2 vs 3.3 +/- 0.2 mg kg-1 min-1, respectively). There was also no difference in basal hepatic glucose production during metformin and NaCl infusion (2.7 +/- 0.3 vs 2.8 +/- 0.2 mg kg-1 min-1). No acute effect of metformin on hepatic glucose production or peripheral glucose disposal was observed, implying that a chronic persistent effect is more important in these respects than immediate effects consequent upon changes in plasma drug level.

Primary Cilia Signaling Promotes Axonal Tract Development and Is Disrupted in Joubert Syndrome-Related Disorders Models

Appropriate axonal growth and connectivity are essential for functional wiring of the brain. Joubert syndrome-related disorders (JSRD), a group of ciliopathies in which mutations disrupt primary cilia function, are characterized by axonal tract malformations. However, little is known about how cilia-driven signaling regulates axonal growth and connectivity. We demonstrate that the deletion of related JSRD genes, Arl13b and Inpp5e, in projection neurons leads to de-fasciculated and misoriented axonal tracts. Arl13b deletion disrupts the function of its downstream effector, Inpp5e, and deregulates ciliary-PI3K/AKT signaling. Chemogenetic activation of ciliary GPCR signaling and cilia-specific optogenetic modulation of downstream second messenger cascades (PI3K, AKT, and AC3) commonly regulated by ciliary signaling receptors induce rapid changes in axonal dynamics. Further, Arl13b deletion leads to changes in transcriptional landscape associated with dysregulated PI3K/AKT signaling. These data suggest that ciliary signaling acts to modulate axonal connectivity and that impaired primary cilia signaling underlies axonal tract defects in JSRD.

MR cholangiography of late biliary complications after liver transplantation

OBJECTIVE

The aim of our study was to assess the role of MR cholangiography in the diagnosis of late biliary complications after liver transplantation.

SUBJECTS AND METHODS

Twenty-three liver transplantation patients (18 men and five women; mean age, 46 years) underwent MR cholangiography using a nonbreath-hold, fat-suppressed three-dimensional turbo spin-echo sequence (TR/TE, 3000/700; echo train length, 128) optimized on a 0.5-T magnet. Inclusion criteria were liver function tests with abnormal results and hyperbilirubinemia with a clinical pattern not specific for biliary obstruction. All patients were referred by clinicians for contrast-enhanced cholangiography. Diagnostic confirmation was obtained with percutaneous transhepatic cholangiography (n = 4), endoscopic retrograde cholangiography (n = 8), T-tube cholangiography (n = 1), or clinical follow-up (n = 10).

RESULTS

In 11 patients, no abnormalities of the biliary tract were revealed by MR cholangiography. In 11 patients, twelve strictures were diagnosed (nine anastomotic, two nonanastomotic-intrahepatic, and one nonanastomotic-extrahepatic, with association between anastomotic and nonanastomotic strictures in two cases). In one other patient, kinking of the common bile duct at the level of the anastomosis was observed. In all cases, MR cholangiography correctly showed the site of the stricture and the dilatation of bile ducts above, with excellent correlation with contrast-enhanced cholangiographic findings. Strictures were correctly graded in eight of 10 patients and were overestimated in two. Other findings included a 1-cm stone detected proximal to the obstructed common bile duct in one patient and multiple intrahepatic stones in another patient.

CONCLUSION

MR cholangiography can show biliary obstruction and provide important information for planning therapeutic procedures.

MR cholangiography in the examination of patients with biliary-enteric anastomoses

OBJECTIVE

The aim of our study was to determine the role of MR cholangiography in the noninvasive examination of patients with biliary-enteric anastomoses.

SUBJECTS AND METHODS

Twenty-four patients (nine men and 15 women; mean age, 68.9 years old) with biliary-enteric anastomoses underwent MR cholangiography. We used a fat-suppressed three-dimensional turbo spin-echo sequence (3000/700 [TR/TE]; echo train length, 128) with no breath-hold, optimized with a 0.5-T magnet. Imaging studies were performed because of scheduled follow-up (five patients), persistent jaundice (six patients), cholangitis and abnormal liver function (eight patients), and a combination of transient jaundice, epigastric pain, and abnormal liver function (five patients).

RESULTS

Image quality was graded from optimal to good in 21 (88%) of 24 cases and poor in three (13%) of 24 cases. The degree of bile duct dilatation was correctly assessed, with complete agreement between the two observers in all cases. MR cholangiography correctly showed bile duct irregularities in six of the eight patients with cholangitis (kappa = .59), anastomotic strictures in all 19 patients with strictures (kappa = .86), and 3- to 15-mm stones in nine of 10 patients (kappa = .95). A slight overestimation of the strictures occurred in four of the 19 cases with strictures.

CONCLUSION

MR cholangiography is a reliable imaging technique for the examination of patients with biliary-enteric anastomoses.

Malignant tumours of the small intestine: a review of histopathology, multidetector CT and MRI aspects

Small bowel neoplasms, including adenocarcinoma, carcinoid tumour, lymphoma and gastrointestinal stromal tumours, represent a small percentage of gastrointestinal cancers, yet are among those with the poorest prognosis compared with other gastrointestinal malignancies. Unclear clinical scenarios and difficult radiological diagnosis often delay treatment with negative effects on patient survival. Recently, multidetector CT (MDCT) and MRI have been introduced as feasible and accurate diagnostic techniques for the identification and staging of small bowel neoplasms. These techniques are gradually replacing conventional barium radiography as the tool of choice. However, the inherent technical and physiological challenges of small bowel imaging require a familiarity with patient preparation and scan protocols. Adequate knowledge of the histopathology and natural evolution of small bowel neoplasms is also important for differential diagnosis. The aim of this article is to review MDCT and MRI protocols for the evaluation of small bowel tumours and to provide a concise yet comprehensive guide to the most relevant imaging features relative to histopathology.

MR-guided focused ultrasound (MRgFUS) ablation for the treatment of nonspinal osteoid osteoma: a prospective multicenter evaluation

BACKGROUND

Magnetic resonance-guided focused ultrasound (MRgFUS) is a novel imaging-guided surgical technique that allows the performance of noninvasive and radiation-free ablation. Presently, computed tomography (CT)-guided radiofrequency ablation, a minimally invasive percutaneous technique, is the standard for treating symptomatic osteoid osteomas. The purpose of this study was to evaluate the use of MRgFUS ablation for the treatment of nonspinal osteoid osteomas in terms of technical success, complications, and clinical success through one year of follow-up.

METHODS

In this prospective multicenter study, thirty consecutive patients with a nonspinal osteoid osteoma were enrolled between May 2010 and April 2012 at three different university centers; twenty-nine of the patients were treated with use of MRgFUS. Lesions had been previously diagnosed on the basis of imaging, including dynamic contrast-enhanced MR. The mean number of sonications and energy deposition were determined. Technical success was evaluated through an assessment of complications immediately after treatment. Clinical success was determined on the basis of pain reduction as measured with a visual analog scale (VAS), recurrence, and long-term complications through twelve months.

RESULTS

Technical success of MRgFUS was observed for all twenty-nine patients. The mean number of sonications (and standard deviation) was 7 ± 3, and the mean delivered acoustic energy was 1180 ± 736 J. At the twelve-month follow-up, complete clinical success was observed in twenty-six (90%) of the twenty-nine patients (95% confidence interval [CI] = 84 to 95; mean VAS, 0 ± 0 points). Partial success was observed in three (10%) of the twenty-nine patients (95% CI = 5 to 16; mean VAS score, 5 ± 0 points); two of these patients subsequently underwent CT-guided radiofrequency ablation, and one underwent open surgery. Pain score values showed a significant reduction (p < 0.001) between baseline (mean VAS score, 8 ± 1 points) and post treatment (mean VAS score, 1 ± 2 points). No complications were observed.

CONCLUSIONS

MRgFUS may be an effective and safe alternative approach in the treatment of nonspinal osteoid osteoma. A complete clinical success rate of 90% was demonstrated without adverse events. MRgFUS is totally noninvasive and eliminates radiation exposure.

Light regulation of assimilatory sulphate reduction in Arabidopsis thaliana

Adenosine 5'-phosphosulphate reductase (APR) is considered to be a key enzyme of sulphate assimilation in higher plants. We analysed the diurnal fluctuations of total APR activity and protein accumulation together with the mRNA levels of three APR isoforms of Arabidopsis thaliana. The APR activity reached maximum values 4 h after light onset in both shoots and roots; the minimum activity was detected at the beginning of the night. During prolonged light, the activity remained stable and low in shoots, but followed the normal rhythm in roots. On the other hand, the activity decreased rapidly to undetectable levels within 24 h of prolonged darkness both in shoots and roots. Subsequent re-illumination restored the activity to 50% in shoots and to 20% in roots within 8 h. The mRNA levels of all three APR isoforms showed a diurnal rhythm, with a maximum at 2 h after light onset. The variation of APR2 mRNA was more prominent compared to APR1 and APR3. 35SO42- feeding experiments showed that the incorporation of 35S into reduced sulphur compounds in vivo was significantly higher in light than in the dark. A strong increase of mRNA and protein accumulation as well as enzyme activity during the last 4 h of the dark period was observed, implying that light was not the only factor involved in APR regulation. Indeed, addition of 0.5% sucrose to the nutrient solution after 38 h of darkness led to a sevenfold increase of root APR activity over 6 h. We therefore conclude that changes in sugar concentrations are also involved in APR regulation.

Utility of T2-weighted short-tau inversion recovery (STIR) sequences in cardiac MRI: an overview of clinical applications in ischaemic and non-ischaemic heart disease

T2-weighted short-tau inversion recovery (T2w-STIR) imaging is the best approach for oedema-weighted cardiac magnetic resonance imaging (MRI), as it suppresses the signal from flowing blood and from fat and enhances sensitivity to tissue fluid. The purpose of this pictorial review is to illustrate the clinical use and application of this technique in various ischaemic and non-ischaemic conditions. In ischaemic heart disease, T2w-STIR represents the technique of choice for detecting oedema in patients with acute myocardial infarction (MI), allowing discrimination of acute and chronic injuries. Myocardial haemorrhage may also be depicted as a region of signal abnormality characterised by a central hypointense core with a peripheral hyperintense rim, presumably reflecting the presence of intracellular methaemoglobin within the necrotic area. In the acute setting, elevated T2 relaxation times in association with regional contractile dysfunction but no signs of delayed enhancement may also signify a reversible ischaemic injury without necrosis. In acute myocarditis, the distribution pattern of T2w hyperintensity may be focal in approximately 30% of patients or diffuse in the remaining 70%, and myocardial oedema may be the only marker of disease. Tissue oedema may also be observed in various other conditions, such as primary cardiomyopathies (CMP), storage disease, pulmonary hypertension and cardiac transplant rejection. T2w-STIR represents an appealing and versatile technique that can be applied in a wide variety of ischaemic and non-ischaemic conditions, allowing detection of segmental or global increase of myocardial free water content, reflecting an acute myocardial injury.

Metabolic effects of suppression of nonesterified fatty acid levels with acipimox in obese NIDDM subjects

NEFAs characteristically are elevated in obese NIDDM patients in both the basal state and after insulin. This elevation might aggravate glycemic control both by decreasing peripheral glucose disposal (glucose-fatty acid cycle), and by increasing HGO. Thus, lowering plasma NEFA levels might improve carbohydrate metabolism. We therefore measured HGO and fuel use (by indirect calorimetry) both in the basal state and during the last 30 min of a hyperinsulinemic clamp (0.025U.kg-1.h-1) in 8 obese NIDDM patients (BMI 34.8 +/- 1.0 kg/m2) after complete overnight suppression of plasma NEFA levels with acipimox, a new nicotinic acid analogue. After acipimox, mean basal plasma NEFA and glycerol levels were lower than control values (0.11 +/- 0.02 vs. 0.65 +/- 0.04 mM, P < 0.001; and 16 +/- 3 vs. 68 +/- 7 microM, P = 0.004, respectively) and were accompanied by a fall in lipid oxidation (acipimox vs. placebo: 16.1 +/- 1.2 vs. 38.8 +/- 2.4 mg.m-2 x min-1; P < 0.001) and a rise in glucose oxidation (91.1 +/- 6.2 vs. 54.1 +/- 9.0 mg.m-2 x min-1; P = 0.002). Basal HGO and fasting plasma glucose levels were lower (94.1 +/- 9.2 vs. 118.5 +/- 9.5 mg.m-2 x min-1, P = 0.01; and 8.3 +/- 1.2 vs. 9.8 +/- 1.2 mM; P < 0.001), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreatic adenocarcinoma: combination of MR imaging, MR angiography and MR cholangiopancreatography for the diagnosis and assessment of resectability

The purpose of this study was to determine the possibility of integrating MR cholangiopancreatography (MRCP) and MR angiography (MRA) to conventional MR images in the diagnosis and assessment of resectability of pancreatic adenocarcinoma. Twenty-three patients with pancreatic adenocarcinoma were prospectively examined with MR. Conventional MR images were acquired in all patients. Three-dimensional MRCP and MRA images were acquired in all patients with suspected biliary and vascular involvement. Acquisition time was less than 45 min in all cases. Images were independently evaluated by two radiologists, with final reading decided by consensus among readers. Diagnosis was confirmed with surgery in 16 patients and with percutaneous biopsy in 7. Concordance among readers was high with a kappa value of 0.83. Pancreatic adenocarcinoma was observed in all patients. Correct assessment of unresectability due to vascular involvement was found in 22 of 23 patients. Biliary obstruction was evident in 13 patients, involving the biliary and pancreatic ducts in 9 and the biliary ducts only in 4. Technical advances permit extensive use of MRI in the evaluation of abdominal pathologies. The combination of MR imaging, MRCP, and MRA can provide sufficient information for the diagnosis and assessment of resectability of pancreatic adenocarcinoma, which otherwise would require three different exams.

Computed tomographic colonography (virtual colonoscopy): blinded prospective comparison with conventional colonoscopy for the detection of colorectal neoplasia

BACKGROUND AND STUDY AIMS

Computed tomographic colonography (CTC), also known as virtual colonoscopy, is a recently introduced imaging modality for the detection of colorectal neoplasia. The aim of our study was to evaluate the performance of CTC in a blinded comparison with conventional colonoscopy.

PATIENTS AND METHODS

A total of 66 consecutive, symptomatic patients underwent spiral computed tomography (CT) examination after standard bowel preparation. CT images were analyzed and subsequently compared with conventional colonoscopy findings.

RESULTS

Conventional colonoscopy detected 15 colorectal carcinomas and 52 polyps. CTC correctly identified all carcinomas, 13 of 14 polyps greater than 10.0 mm (sensitivity 92.8 %; 95 % confidence interval (95 % CI); 77 - 100), 11 of 13 polyps between 6.0 and 9.0 mm (sensitivity 84.6 %; 95 % CI; 62 - 100), and six of 25 polyps smaller than 5.0 mm (sensitivity 24 %; 95 % CI; 6 - 42). The per-patient sensitivity and specificity were 93.7 % and 94.1 %, respectively.

CONCLUSIONS

Computed tomographic colonography is an accurate imaging modality for the detection of colorectal neoplasia, especially for lesions larger than 6.0 mm in diameter.

Multislice spiral computed tomography angiography of mesenteric arteries

The introduction of multislice technology has improved and expanded the clinical applications of computed tomography angiography (CTA), and it is now possible to detect subtle vascular abnormalities. We optimised a high resolution CTA protocol to study the anatomy of mesenteric arteries with a multislice spiral CT scanner. We showed that multislice CTA produces images of high quality, with excellent anatomical visualisation of the main mesenteric trunks, and small collateral vessels. CTA may facilitate the diagnosis of vascular diseases, such as chronic mesenteric ischaemia, as well as acute disorders such as gastrointestinal bleeding.

Multidetector–row CT angiography of renal artery stenosis in 50 consecutive patients: prospective interobserver comparison with DSA

PURPOSE

The purpose of this study was to establish the diagnostic value of multidetector-row computed tomography (MDCT) angiography compared with digital subtraction angiography (DSA) for detection and quantification of both main and accessory renal artery stenosis in patients with secondary hypertension.

MATERIALS AND METHODS

Fifty consecutive patients scheduled for DSA were considered candidates for MDCT angiography. In all patients, MDCT angiography of the abdominal aorta was performed before DSA. For the purpose of interpretation, the arteries were separately interpreted either with DSA or MDCT angiography in order to provide qualitative and quantitative information. For qualitative evaluation, one experienced reader graded the opacification of renal arteries as excellent, good or poor; for quantitative evaluation, MDCT and DSA were independently evaluated for the number of renal arteries and the presence, location and degree of stenosis in random order by three readers. On the basis of consensus readings, calculations of sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) for detection of degree of stenosis were made by using DSA findings as the standard of reference. Interobserver variability was also assessed.

RESULTS

With regard to qualitative analysis, arterial enhancement was considered excellent in 39 patients and good in 11. For quantitative analysis, 73 arteries were classified as normal with DSA. Although 72 of these were also classified as normal with CT angiography, one was overestimated by one grade; at DSA, 16 arteries were classified as moderately stenotic; in two arteries, there was an overestimation of one grade. Perfect correlation was achieved for the diagnosis of occlusion. In two patients, all three readers detected multiple severe stenoses on both modalities, with a "string-of-beads" appearance typical of fibromuscular dysplasia. Accessory arteries were correctly identified as such by all three readers on either DSA or MDCT. Levels of sensitivity, specificity and accuracy regarding degree of stenosis were 100%, 98.6% and 96.9%, respectively, with PPV and NPV of 97.6% and 100%, respectively. When we considered significant arterial stenosis (50%-100% luminal narrowing), sensitivity, specificity and accuracy were 100%, 97.3% and 97.8%, respectively, with a PPV and NPV of 98.2% and 97.8%, respectively. For all observers, interobserver agreement was almost perfect (k=0.81-1) for both MDCT and DSA, with a k value between 0.82 and 0.95.

CONCLUSIONS

MDCT angiography is very accurate and robust, even for the assessment of renal artery stenosis, and has the potential to become a viable substitute, in most cases, for diagnostic catheter-based DSA.

Detection of hepatic metastases from colorectal cancer: prospective evaluation of gray scale US versus SonoVue® low mechanical index real time-enhanced US as compared with multidetector-CT or Gd-BOPTA-MRI

PURPOSE

To compare ultrasound (US), low-mechanical index contrast enhanced US (CEUS) and multidetector-CT (MDCT) for the detection of hepatic metastases from colorectal cancer.

METHODS AND MATERIALS

From January to June 2006, 110 patients (65 males, 45 females; mean age 62 years; range 39-78) with suspected hepatic lesions from colorectal cancer were prospectively evaluated with US, CEUS and MDCT by two independent readers. Intraoperative ultrasonography (IOUS, n = 45) or a follow-up up for at least 6 months by using MDCT or Gd-BOPTA-enhanced MRI was considered the gold standard. McNemar test was employed.

RESULTS

Reference standards revealed 430 metastases in 110 patients. On a patient-by-patients analysis, CEUS improved US sensitivity from 67.4-71.6% to 93.4-95.8% (p < 0.05). On a lesion-by-lesion analysis, CEUS improved the sensitivity of US from 60.9-64.9% to 85.3-92.8% (p < 0.001). The specificity increased from 50-60% to 76.7-83.3%. No significant differences in sensitivity or specificity between CEUS and MDCT were found. Contrast-enhanced US was significantly more sensitive than baseline US in the detection of metastases smaller than 1 cm (p < 0.001) with an increase in sensitivity from 29.1-35% to 63.3-76.6% no significant statistical difference was identified when compared with MDCT (sensitivity of 73.3-75.8%).

CONCLUSIONS

CEUS is significantly more accurate than US and highly comparable with MDCT in the detection of liver metastases from colorectal cancer. Therefore, in the evaluation of patients with suspected hepatic metastases from colorectal tumour, US examination must be performed after contrast administration.

Focal nodular hyperplasia: typical and atypical MRI findings with emphasis on the use of contrast media

Focal nodular hyperplasia is a benign hypervascular hepatic tumour, frequently detected in asymptomatic patients undergoing imaging studies for unrelated reasons. Magnetic resonance imaging (MRI) generally allows a confident differential diagnosis with other hypervascular liver lesions, either benign or malignant. In addition, due to the recent development of hepatospecific MRI contrast agents, MRI concomitantly enables functional and morphological information to be obtained, thus providing important clues for the detection and characterization of focal nodular hyperplasia lesions.

Metabolic and cardiovascular assessment in moderate obesity: effect of weight loss

Metabolic and hemodynamic abnormalities have been separately described in obesity, and weight reduction is known to lead to some improvement in each. Our aim was to simultaneously assess metabolic and cardiovascular function in normotensive, normotolerant patients with moderate obesity (body mass index = 32.6 +/- 1.1 kg/m2) before and after weight loss. The obese were insulin resistant [37.4 +/- 4.8 mumol/min.kg FFM; P < 0.02 vs. 12 lean controls (50.6 +/- 2.6), on a euglycemic insulin clamp], secreted more insulin both in the fasting state and after oral glucose (70 +/- 10 vs. 48 +/- 6 nmol/mmol.L plasma glucose; P < 0.05), and had higher resting energy expenditure (4.62 +/- 0.18 vs. 4.00 +/- 0.23 kJ/min), systolic and mean blood pressure, stroke volume (87 +/- 8 vs. 67 +/- 4 mL/min; P = 0.05), and cardiac output. There was, however, no relationship between the metabolic and hemodynamic abnormalities. After a weight loss of 11 +/- 1 kg (approximately 15%), insulin sensitivity improved in proportion to the weight reduction, whereas insulin hypersecretion and high energy expenditure persisted. In contrast, all hemodynamic changes reverted to normal. We conclude that in moderate obesity, the metabolic and cardiovascular abnormalities are largely independent of one another; accordingly, weight loss affects them differentially. Partial weight normalization may provide sufficient cardiovascular protection.

Influence of long-term diabetes on renal glycogen metabolism in the rat

BACKGROUND/AIMS

The effects of acute insulin deficiency on the kidney have been investigated in animal models of experimental diabetes; however, the impact of long-term diabetes has not been determined.

METHODS

We measured renal glycogen contents in streptozotocin (STZ)-diabetic rats 3 weeks (n = 12) or 9 months (n = 12) after the induction of diabetes, and in 2 groups of control rats of similar age (n = 16 and n = 12, respectively), in the fed state and after a 24-hour fast.

RESULTS

Diabetic rats had high glucose levels, low insulin but normal glucagon concentrations in portal blood. In the fasting state, kidney glycogen content was very low in both young control and young diabetic rats (54 +/- 15 and 189 +/- 26 microg/g, respectively, mean +/- SD); in contrast, glycogen levels were markedly elevated in rats with long-standing diabetes as compared to old nondiabetic animals (2,628 +/- 1,023 +/- and 1,968 +/- 989 microg/g of diabetic rat, fasting and fed, respectively, p < 0.001 vs. 0 +/- 0 and 4 +/- 6 microg/g of control rats). On electron microscopy, large glycogen clusters were localized to the renal tubules. Kidney phosphorylase activity was higher, and synthase activity lower in diabetic than control rats (p < 0.05 for both), whereas kidney glycogen was strongly related to plasma glucose levels, suggesting that the enzyme changes were secondary to glycogen accumulation itself. Renal hexosephosphates and fructose-2,6-bisphosphate contents were both increased in long-term diabetic rats (p < 0.05), implying enhanced fluxes through both glycolysis and gluconeogenesis.

CONCLUSION

In chronic, untreated diabetes glycogen accumulates in the renal tubules; prolonged hyperglycemia is the sole driving force for this phenomenon.

Noninvasive imaging of the coronary arteries using a 64-row multidetector CT scanner: initial clinical experience and radiation dose concerns

PURPOSE

We present our initial clinical experience with a recently introduced 64-detector computed tomography (64-MDCT) scanner that makes use of a periodic motion of the focal spot in the longitudinal direction (z-flying focal spot), which enables it to reach a final spatial resolution of 0.4 x 0.4 x 0.4 mm(3) and a temporal resolution of 83 ms.

MATERIALS AND METHODS

A total of 114 patients (108 men, six women; age range 36-77 years, mean 63.1 years) underwent retrospective electrocardiogram (ECG)-gated examination of the coronary arteries using a 64-MDCT scanner (Somatom Sensation 64, Siemens Medical Solutions, Germany). Acquisition parameters were the following: collimation 64 x 0.6 mm, 800 quality reference milliampere second (mAs), 120 kVp, 0.33-s gantry rotation time and pitch 0.2. Images were acquired in all cases after i.v. administration of 80 ml of contrast agent (Iomeron 400 mgI/dl, Bracco, Italy) + 30 ml of saline at 4 /s and delay time determined using a bolus triggering technique. Oral betablockers were administered to patients with heart rate (HR) >75 bpm. To reduce radiation exposure, an automatic exposure control system was applied in all cases to adapt tube current to patient size and anatomic shape (CARE Dose 4D, Siemens Medical Solutions, Germany). The optimal temporal window for raw data reconstruction was chosen from an initial preview of images reconstructed with different phase settings (range 0%-95% RR interval with 5% gap) at a selected anatomical level in the mid part of the right coronary artery. CT dose index volume and effective dose were quantified in all patients using dedicated software.

RESULTS

Mean HR recorded during image acquisition was 65.6+/-19.2 bmp (range: 44-96 bmp), and beta-blockers were administered to 16/114 patients (14.0%). Technical adequacy was achieved in all patients but two (2/114; 1.7%). In patients with HR <60 bmp, the best reconstruction intervals were identified in the end-systolic (30%-35% of the RR interval) and end-diastolic (60%-65% of the RR interval) phases; with faster HR (>80 bmp), high image quality was observed in end-systole (30%-35% of the RR interval). Mean CT dose index (CTDI) volume was 36.53+/-8.30 mGy per patient. In comparison with a conventional examination with fixed mAs, the use of the CARE Dose 4D system provided a 33.3% CTDI volume reduction (p<0.001). Mean effective dose was 9.5+/-3.4 millisievert (mSv) per patient (range 7.1-17.7).

CONCLUSIONS

The 64-MDCT scanner diagnostic performance for coronary CT angiography is further improved with better spatial and temporal resolution and faster scan times; besides, initial clinical results are promising. The use of dose-reducing acquisition techniques is mandatory to limit radiation exposure to the patient.

Pancreatic beta-cell tumors: MRI

Ten consecutive patients with surgically proven beta-islet cell tumors, strongly suspected clinically because of positive laboratory findings, were studied by MRI at 0.5 T. Results were correlated with CT and angiography. MRI detected all 10 insulinomas, with the location confirmed at surgery. Lesion size was < 1 cm in three cases, between 1 and 2 cm in five cases, and between 2 and 3 cm in two cases. A false-negative diagnosis was obtained with CT in 6 of 10 and with angiography in 3 of 10 cases. Our results suggest that if motion artifact can be controlled or reduced, MRI can be employed to localize insulinomas in patients with positive clinical and laboratory findings.