Luigi Lepanto

Contrast-induced nephropathy in patients with chronic kidney disease undergoing computed tomography: a double-blind comparison of iodixanol and iopamidol.

Background:Based on a single clinical trial, it has been suggested that the contrast agent iodixanol, which is isotonic to human plasma, may be less nephrotoxic than other nonionic contrast agents in renally impaired patients after intra-arterial injection. We compared the effects on renal function of iopamidol-370 injection (796 mOsm/kg) and iodixanol-320 (290 mOsm/kg) in patients with chronic kidney disease undergoing contrast-enhanced multidetector computed tomography (CE-MDCT) examinations using a multicenter, double-blind, randomized, parallel-group design. Methods:A total of 166 patients with stable moderate-to-severe chronic kidney disease (screening and baseline serum creatinine, SCr, ≥1.5 mg/dL and/or creatinine clearance, CrCl, ≤60 mL/min) who were undergoing CE-MDCT of the liver or peripheral arteries were randomized to receive equi-iodine IV doses (40 gI) of either iopamidol-370 (370 mgI/mL) or iodixanol-320 (320 mgI/mL) at 4 mL/s. SCr and CrCl were obtained at screening, baseline, and at 48–72 ± 6 hours after dose (mean, 57.4 hours). Contrast-induced nephropathy (CIN) was defined as an absolute increase ≥0.5 mg/dL (44.2 &mgr;mol/L) and/or a relative increase in SCr ≥25% from baseline. Results:A total of 153 patients were included in the final analysis (13 patients excluded because of lack of follow-up, hemodialysis to remove contrast, average daily CrCl variation >1% at screening). The 2 study groups were comparable with regard to age, gender distribution, the presence of diabetes, concomitant medications, hydration, and contrast dose. Mean predose SCr was 1.6 ± 0.4 mg/dL in both groups (P = 0.9). An absolute increase ≥0.5 mg/dL (44.2 &mgr;mol/L) in SCr was observed in none of the patients receiving iopamidol-370 and in 2.6% (2/76) of patients receiving iodixanol-320 (95% confidence interval −6.2, 1.0, P = 0.2). A relative increase ≥25% in SCr occurred in 4% (3/77) of patients receiving iopamidol-370 and in 4% (3/76) of the patients receiving iodixanol-320 (95% confidence interval −6.2, 6.1, P = 1.0). Conclusion:The rate of CIN was similarly low in risk patients after intravenous administration of iopamidol-370 or iodixanol-320 for CE-MDCT.

Differentiating lumbar disc protrusions, disc bulges, and discs with normal contour but abnormal signal intensity. Magnetic resonance imaging with discographic correlations.

STUDY DESIGN Independent evaluation by two observers of 132 lumbar discs in 45 patients with chronic low back pain investigated by both magnetic resonance imaging and discography. OBJECTIVES To assess some of the fundamental differences between lumbar disc protrusions, disc bulges, and discs with normal contour but abnormal signal intensity on T2-weighted magnetic resonance images. SUMMARY OF BACKGROUND DATA Moderate interobserver agreement has been reported when the morphologic terms normal, bulge, protrusion, and extrusion are used. The validity of this nomenclature remains unknown. METHODS Discs were evaluated on magnetic resonance images for central and peripheral signal characteristics, height, contour, and nerve root compression. Discograms were classified according to degrees of disc degeneration, disruption, and pain reproduction. RESULTS Loss of intervertebral height or abnormal signal intensity on magnetic resonance imagery was significantly associated with disc disruptions extending into or beyond the outer anulus on discograms. All 23 protrusions (100%) and 12 of 15 disc bulges (80%) were associated with Stage 2 or 3 anular disruptions and, in most instances, similar or exact reproduction of pain during disc injection. There was no significant difference between disc protrusions, disc bulges, and discs with normal contour but abnormal signal, with respect to degree of disc degeneration, extent of disruptions, or presence of discogenic pain. CONCLUSIONS In patients with chronic low back pain, loss of disc height or abnormal signal intensity is highly predictive of symptomatic tears extending into or beyond the outer anulus. Disc bulges and disc protrusions do not represent discs with significantly different internal architecture, based on the findings of discography, and are no more suggestive of symptomatic tears than discs showing normal contour but decreased height or abnormal signal intensity.

Noninvasive quantitation of human liver steatosis using magnetic resonance and bioassay methods

The purpose was to evaluate the ability of three magnetic resonance (MR) techniques to detect liver steatosis and to determine which noninvasive technique (MR, bioassays) or combination of techniques is optimal for the quantification of hepatic fat using histopathology as a reference. Twenty patients with histopathologically proven steatosis and 24 control subjects underwent single-voxel proton MR spectroscopy (MRS; 3 voxels), dual-echo in phase/out of phase MR imaging (DEI) and diffusion-weighted MR imaging (DWI) examinations of the liver. Blood or urine bioassays were also performed for steatosis patients. Both MRS and DEI data allowed to detect steatosis with a high sensitivity (0.95 for MRS; 1 for DEI) and specificity (1 for MRS; 0.875 for DEI) but not DWI. Strong correlations were found between fat fraction (FF) measured by MRS, DEI and histopathology segmentation as well as with low density lipoprotein (LDL) and cholesterol concentrations. A Bland-Altman analysis showed a good agreement between the FF measured by MRS and DEI. Partial correlation analyses failed to improve the correlation with segmentation FF when MRS or DEI data were combined with bioassay results. Therefore, FF from MRS or DEI appear to be the best parameters to both detect steatosis and accurately quantify fat liver noninvasively.

Pan-Canadian Evaluation of Irreversible Compression Ratios (“Lossy” Compression) for Development of National Guidelines

New technological advancements including multislice CT scanners and functional MRI, have dramatically increased the size and number of digital images generated by medical imaging departments. Despite the fact that the cost of storage is dropping, the savings are largely surpassed by the increasing volume of data being generated. While local area network bandwidth within a hospital is adequate for timely access to imaging data, efficiently moving the data between institutions requires wide area network bandwidth, which has a limited availability at a national level. A solution to address those issues is the use of lossy compression as long as there is no loss of relevant information. The goal of this study was to determine levels at which lossy compression can be confidently used in diagnostic imaging applications. In order to provide a fair assessment of existing compression tools, we tested and compared the two most commonly adopted DISCOM compression algorithms: JPEG and JPEG-2000. We conducted an extensive pan-Canadian evaluation of lossy compression applied to seven anatomical areas and five modalities using two recognized techniques: objective methods or diagnostic accuracy and subjective assessment based on Just Noticeable Difference. By incorporating both diagnostic accuracy and subjective evaluation techniques, enabled us to define a range of compression for each modality and body part tested. The results of our study suggest that at low levels of compression, there was no significant difference between the performance of lossy JPEG and lossy JPEG 2000, and that they are both appropriate to use for reporting on medical images. At higher levels, lossy JPEG proved to be more effective than JPEG 2000 in some cases, mainly neuro CT. More evaluation is required to assess the effect of compression on thin slice CT. We provide a table of recommended compression ratios for each modality and anatomical area investigated, to be integrated in the Canadian Association of Radiologists standard for the use of lossy compression in medical imaging.

Impact of PACS on Dictation Turnaround Time and Productivity

This study was conducted to measure the impact of PACS on dictation turnaround time and productivity. The radiology information system (RIS) database was interrogated to calculate the time interval between image production and dictation for every exam performed during three 90-day periods (the 3 months preceding PACS implementation, the 3 months immediately following PACS deployment, and a 3-month period 1 year after PACS implementation). Data were obtained for three exam types: chest radiographs, abdominal CT, and spine MRI. The mean dictation turnaround times obtained during the different pre- and post-PACS periods were compared using analysis of variance (ANOVA). Productivity was also determined for each period and for each exam type, and was expressed as the number of studies interpreted per full-time equivalent (FTE) radiologist. In the immediate post-PACS period, dictation turnaround time decreased 20% (p < 0.001) for radiography, but increased 13% (ns) for CT and 28% (p < 0.001) for MRI. One year after PACS was implemented, dictation turnaround time decreased 45% (p < 0.001) for radiography and 36% (p < 0.001) for MRI. For CT, 1 year post-PACS, turnaround times returned to pre-PACS levels. Productivity in the immediate post-PACS period increased 3% and 38% for radiography and CT, respectively, whereas a 6% decrease was observed for MRI. One year after implementation, productivity increased 27%, 98%, and 19% in radiography, CT, and MRI, respectively. PACS benefits, namely, shortened dictation turnaround time and increased productivity, are evident 1 year after PACS implementation. In the immediate post-PACS period, results vary with the different imaging modalities.

Relationship between pre-TIPS liver perfusion by the portal vein and the incidence of post-TIPS chronic hepatic encephalopathy

OBJECTIVE:In the present study we evaluated the predictive value of pretransjugular intrahepatic portosystemic shunt (TIPS) portal perfusion as assessed by Doppler ultrasonography for the onset of chronic encephalopathy after TIPS.METHODS:A total of 231 cirrhotic patients were followed-up prospectively after TIPS placement. The pattern of intrahepatic portal flow was assessed before TIPS. Patients were divided into two groups according to Doppler findings. Group 1 comprised patients with prograde portal flow (n = 200), whereas group 2 comprised those with loss of portal perfusion (hepatofugal or back-and-forth flow or portal vein thrombosis; n = 31). The presence of chronic encephalopathy during a median follow-up of 32 months was prospectively recorded. The prognostic value of the following parameters for the onset of chronic recurrent encephalopathy after TIPS was evaluated: age, presence of encephalopathy before TIPS, alcoholism, Pugh score, and loss of portal perfusion before TIPS. The independent prognostic value of each variable was tested with a multiple logistic regression analysis.RESULTS:The two groups were comparable in terms of age, incidence of prior episodes of hepatic encephalopathy, and portacaval gradient before and after the procedure; however, liver failure was more severe in patients in group 2 (Pugh score: 9.2 ± 1.9 vs 10.3 ± 1.7). The 3-yr survival was identical for both groups; 25% of the 200 patients in group 1 developed chronic encephalopathy as compared to 6% of the 31 patients in group 2 (p = 0.03). Multiple logistic regression analysis demonstrated that loss of portal perfusion and age >65 yr were the only independent predictors of the onset of post-TIPS chronic encephalopathy (odds ratios 0.24 and 1.98, respectively).CONCLUSIONS:Cirrhotic patients with loss of portal perfusion before TIPS were protected against post-TIPS chronic hepatic encephalopathy despite a more severe liver dysfunction at baseline. The only other independent predictive factor for the onset of this complication was age.

Effect of the Learning Process on Procedure Times and Radiation Exposure for CT Fluoroscopy-guided Percutaneous Biopsy Procedures

PURPOSE To assess if the learning process associated with computed tomography fluoroscopy (CTF) technology influences procedure and fluoroscopy times for percutaneous biopsy procedures. MATERIALS AND METHODS Prospective analysis of the initial 250 consecutive patients who underwent percutaneous biopsy with use of a CT scanner equipped with rapid image reconstruction and fluoroscopic capabilities in a 24-month period. All procedures were performed with both continuous and spot fluoroscopic technique, with typical radiation parameters of 50 mA, 120 kV, and a 10-mm-slice thickness. The procedures were all performed by a single experienced interventional radiologist to limit the variables of physician expertise, interventional materials used, and biopsy approach. The subject group was divided into five equal consecutive groups of 50 patients. In each subgroup, the authors recorded mean lesion size, success, and complication rates, as well as mean procedure and fluoroscopy times. RESULTS The five subgroups were similar patient populations as documented by the absence of statistically significant differences when comparing mean lesion size, procedure success, and complication rates (P > .05; ANOVA test). A statistically significant decrease in mean fluoroscopy (groups 1-5: 50.26 vs 45.24 vs 33.86 vs 32.68 vs 25.8 sec/patient) and mean procedure times (groups 1-5: 30.08 vs 27.9 vs 26.34 vs 25.6 vs 21.6 min/patient) was recorded between the patient subgroups (P < .0001; ANOVA test). CONCLUSION The learning process associated with CTF technology impacts procedure parameters by decreasing both mean procedure and fluoroscopy times, thereby increasing patient turnover and decreasing radiation exposure to the patient and the operator.

Evaluating PACS Success: A Multidimensional Model

A picture archiving and communications system (PACS) is an integrated workflow system for managing images and related data which is designed to streamline operations throughout the whole patient care delivery process. PACS has become a mature technology over the past few years and has been widely implemented in several developed countries. Evaluation of PACS success is a major challenge to healthcare organizations. A review of previous PACS research suggests a fragmented and focused evaluation approach, thus offering limited discussion of comprehensive views of PACS success or systematic and practical guidance to its evaluations. Based on two prevalent information systems success models, this paper proposes and describes an integrated framework for evaluating PACS success in hospital settings. It details the validation process of the proposed model and its related measurement instrument at a large tertiary-care teaching hospital in Canada. Future research directions that extend the proposed research model are highlighted.

Fatty liver deposition and sparing: a pictorial review

ObjectiveFatty liver deposition is a very common finding, but it has many atypical patterns of distribution that can represent diagnostic pitfalls. The purpose of this pictorial essay is to review different patterns of fatty liver deposition and sparing.MethodsWe searched our archive retrospectively, reviewed the literature, and identified six patterns of liver steatosis.ResultsSteatosis may be diffuse, geographic, focal, subcapsular, multifocal or perivascular.ConclusionsPrevious knowledge of atypical patterns of steatosis distribution may prevent misdiagnosis of infiltrative disease or focal liver lesions. When an unusual form of fatty liver deposition is suspected on ultrasound or computed tomography, magnetic resonance imaging may be used to confirm the diagnosis.

A comparison of the efficacy and safety of iopamidol-370 and iodixanol-320 in patients undergoing multidetector-row computed tomography.

Objectives:To prospectively compare the effects on heart rate (HR) and contrast enhancement efficacy of iopamidol-370 and iodixanol-320 in contrast-enhanced, multidetector-row computed tomography (CE-MDCT). Methods:IMPACT is a multicenter, double-blind study involving 166 patients undergoing CE-MDCT of the liver (n = 121) or peripheral arteries (n = 45) randomized to receive equi-iodine doses (40 gI) of iopamidol-370 or iodixanol-320 intravenous at 4 mL/s. CE-MDCT was performed using 16-MDCT scanners according to predefined imaging protocols. HR was measured with the patient in the supine position before and continuously for 5 minutes after contrast medium administration. Mean and peak increases in HR and the proportion of subjects with predefined HR increases (>5 to <10, 10 to <15, 15 to <20, >20 bpm) were compared in the 2 populations. Liver images were assessed by 2 independent, blinded readers for contrast enhancement [Hounsfield unit (HU)], using predefined regions-of-interest during the arterial and portal-venous phase of enhancement. Results:Effects on HR: Eighty-four subjects received iopamidol-370 whereas 82 received iodixanol-320. Mean age, gender distribution, weight, total iodine dose, dose/body weight, concomitant medications and use of β-blockers were comparable in the 2 groups. Mean baseline HR was similar in the 2 groups (iopamidol-370: 72.3 ± 12.5 bpm; iodixanol-320: 74.5 ± 11.9 bpm). Mean changes from baseline to peak postdose were similar in the 2 groups (8.0 ± 9.3 bpm after iopamidol-370 and 8.4 ± 14.7 after iodixanol-320, P = 0.72). The proportion of subjects in each group having increases of <5, >5 to <10, 10 to <15, 15 to <20, or >20 bpm was comparable (P = 0.87). Two subjects experienced postcontrast tachycardia (HR increase >70 bpm, peak HR of 146 and 164 bpm), both in the iodixanol-320 group (2.4%). Contrast Enhancement: Of the 121 patients undergoing liver CT, 60 received iopamidol-370 whereas 61 received iodixanol-320. Mean age, gender distribution, weight, total iodine dose, and dose/body weight were comparable in the 2 groups. Iopamidol-370 provided significantly higher HU values in abdominal aorta during the arterial phase of enhancement for both readers [R1: 301.3 ± 80.2 vs. 273.6 ± 65.9 HU, 95% confidence interval (6.1–56.8), P = 0.02; R2: 302.0 ± 73.6 vs. 275.1 ± 62.9 HU, 95% confidence interval (2.3–51.3), P = 0.03]. No significant difference was observed between the 2 contrast medium during the portal venous phase of enhancement. Conclusions:When the same injection rate and iodine dose is used, the effects on HR of bolus intravenous injections of iopamidol-370 and iodixanol-320 were similar. Iopamidol-370 provides significantly greater enhancement during the arterial phase and similar enhancement during the portal venous phase compared with iodixanol-320.