Pal Suranyi

Iso-Osmolality versus Low-Osmolality Iodinated Contrast Medium at Intravenous Contrast-enhanced CT: Effect on Kidney Function

PURPOSE To determine the effects of iso-osmolality contrast medium compared with a low-osmolality agent on renal function (serum creatinine [SCr] and glomerular filtration rate [GFR]) in high-risk patients undergoing intravenous contrast material-enhanced CT. MATERIALS AND METHODS This HIPAA-compliant study was IRB-approved; formal consent was obtained. One hundred seventeen patients (83 men, 34 women; mean age, 64.3 years; range, 18-86 years) with decreased renal function underwent contrast-enhanced CT with either iso-osmolality iodixanol (n = 61) or low-osmolality iopromide (n = 56). Outcome measures were of SCr increase or GFR decrease for 3 days after CT, a SCr increase (of >or=0.5 mg/dL [44.2 micromol/L, 25%] or >or=1.0 mg/dL [88.4 micromol/L, 50%]), a GFR reduction (of >or=5 mL/min), and patient outcome at 30- and 90-day follow-up. RESULTS Iodixanol decreased SCr (mean +/- standard deviation) from 1.77 mg/dL +/- 0.24 (156.47 micromol/L +/- 21.22) at baseline to 1.65 mg/dL +/- 0.35 (145.86 micromol/L +/- 30.94, P = .046) at day 1, 1.73 mg/dL +/- 0.53 (152.93 micromol/L +/- 46.85, not significant) at day 2, and 1.73 mg/dL +/- 0.55 (152.93 micromol/L +/- 48.62, not significant) at day 3 (not significant). Iopromide increased SCr from 1.75 mg/dL +/- 0.32 (154.7 micromol/L +/- 28.29) at baseline to 1.8 mg/dL +/- 0.42 (159.12 micromol/L +/- 15.59) at day 1, 1.77 mg/dL +/- 0.49 (156.47 micromol/L +/- 43.32) at day 2, and 1.77 mg/dL +/- 0.62 (156.47 micromol/L +/- 54.81) at day 3 (not significant). Iodixanol increased and iopromide decreased GFR on all 3 days after CT (not significant). Fewer patients in the iodixanol group (8.5%) than in the iopromide group (27.8%) had SCr increase 0.5 mg/dL or higher (>or=25%, P = .012). Two patients in each group had SCr increase of 1.0 mg/dL or more (not significant). More patients in the iopromide group (42.3%) than in the iodoxanol group (24.1%) had a GFR reduction of 5 mL/min or higher (P = .0426). No patient had a contrast material-related adverse event at 30- or 90-day follow-up. CONCLUSION Intravenous contrast material application in high-risk patients is unlikely to be associated with permanent adverse outcomes. SCr levels after contrast material administration are lower in iodixanol than iopromide groups.

Right Heart: Split-Bolus Injection of Diluted Contrast Medium for Visualization at Coronary CT Angiography

PURPOSE To retrospectively compare a split-bolus contrast medium injection protocol with a biphasic and a monophasic protocol in terms of visualization of the right and left heart, contrast medium-related streak artifacts, and level of attenuation in the cardiac chambers and coronary arteries at coronary computed tomographic (CT) angiography. MATERIALS AND METHODS The human research committee approved this HIPAA-compliant study and waived informed consent. Seventy-five patients had undergone 64-section coronary CT angiography: 25 were injected by using a monophasic, contrast-medium-only protocol with a single-syringe injector; 25 were injected by using a biphasic protocol with a dual-syringe injector; and 25 were injected by using a split-bolus protocol with a dual-syringe injector and an initial bolus of contrast medium followed by 50 mL of a 70%:30% saline-to-contrast medium mixture and a 30-mL saline chaser. Two radiologists rated the visualization of right and left heart structures and the degree of streak artifacts. One observer performed attenuation measurements of the cardiac chambers and of the coronary arteries. Data were analyzed with one-way analysis of variance and Duncan post-hoc multiple comparison procedures. RESULTS Data for 27 women and 48 men (mean age, 62 years) were included. Mean contrast medium attenuation in the right heart was significantly (P < .001) higher in the split-bolus group than in the biphasic injection group but was significantly (P < .001) lower than in the monophasic injection group. For the left heart and the coronary arteries, there were no significant differences among the three groups. Artifacts occurred less frequently (P < .001) in the biphasic and split-bolus groups than in the monophasic group. Visualization of right heart structures was rated significantly (P < .05) better in the split-bolus group than in the two other groups, while there was no difference for visualization of left heart structures. CONCLUSION Split-bolus injection provides sufficient attenuation for visualization of the right heart, while streak artifacts from high-attenuation contrast material can generally be avoided and arterial attenuation is maintained.

Conformational Pulsatile Changes of the Aortic Annulus: Impact on Prosthesis Sizing by Computed Tomography for Transcatheter Aortic Valve Replacement

OBJECTIVES This study sought to investigate pulsatile changes of the aortic annulus and their impact on prosthesis selection by computed tomography (CT). BACKGROUND Precise noninvasive prosthesis sizing is a prerequisite for transcatheter aortic valve replacement. METHODS A total of 110 patients with severe aortic stenosis (mean age: 82.9 ± 8 years, mean aortic valve area: 0.69 ± 0.18 cm(2)) underwent electrocardiogram-gated CT. Aortic annulus dimensions were planimetrically quantified as area-derived diameter (D(A) = 2 ×✓(CSA/π), where CSA is the cross-sectional area) and perimeter-derived diameter (D(P) = P/π, where P is the length of the perimeter) in 5% increments of the RR interval. Hypothetical prosthesis sizing was based on D(A) and D(P) (23-mm prosthesis for <22 mm; 26 mm: 22 to 25 mm; 29 mm: >25 mm) and compared between maximum and traditional cardiac CT reconstruction phases at 35% and 75% of RR. Agreement for prosthesis selection was calculated by κ statistics. RESULTS D(A) and D(P) were increased and eccentricity was reduced during systole, with D(A-MAX) and D(P-MAX) most often observed at 20% of RR. D(P) was consistently larger than D(A). Average net differences were 2.0 ± 0.6 mm and 1.7 ± 0.5 mm by D(A-MIN) versus D(A-MAX) and D(P-MIN) versus D(P-MAX). Agreement for prosthesis sizing was found in 93 of 110 patients (κ = 0.75) by D(A-75%) and in 80 of 110 patients (κ = 0.53) by D(A-MAX) compared with D(A-35%); and in 94 of 110 patients (κ = 0.73) by D(P-75%) and in 93 of 110 patients (κ = 0.73) by D(P-MAX) compared with D(P-35%). With sizing by D(A-75%) or D(P-75%), nominal prosthesis diameter was smaller than D(A-MAX) or D(P-MAX) in 15 and 6 patients respectively. CONCLUSIONS Aortic annulus morphology exhibits conformational pulsatile changes throughout the cardiac cycle due to deformation and stretch. These changes affect prosthesis selection. Prosthesis selection by diastolic perimeter- or area-derived dimensions harbors the risk of undersizing.

Percent infarct mapping: An R1‐map‐based CE‐MRI method for determining myocardial viability distribution

Viability detection is crucial for the management of myocardial infarction (MI). Signal intensity (SI)‐based MRI methods may overestimate infarct size in vivo. In contrast to SI, the longitudinal relaxation‐rate enhancement (ΔR1) is an intrinsic parameter that is linearly proportional to the concentration of contrast agent (CA). Determining ΔR1 in the presence of an infarct‐avid persistent CA (PCA) allows determination of the per‐voxel percentage of infarcted tissue. Introduced here is a ΔR1‐based CE‐MRI method, termed percent infarct mapping (PIM), for quantifying myocardial viability following delayed PCA accumulation. In a canine MI model (N = 6), PIMs were generated using a persistent CA (PCA) and validated using triphenyltetrazolium‐chloride (TTC) histochemistry. Voxel‐by‐voxel R1 maps of the entire left ventricle (LV) were generated 24 and 48 hr after PCA administration using inversion recovery (IR) with multiple inversion times (TIs). PI values were calculated voxel by voxel. Significant correlations (P < 0.01, R = 0.97) were obtained for PI per slice (PIS) determined using PIM vs. corresponding TTC‐based values. Median deviations of PIS with PIM from that with TTC were only 1.01% and –0.53%, at 24 hr and 48 hr. Median deviations from the true infarction fraction (IF) were 1.23% and 0.49% of LV at 24 hr and 48 hr, respectively. No significant difference was found between PIM24 hr and PIM48 hr. ΔR1‐based PIM is an accurate and reproducible method for quantifying myocardial viability distribution, and thus enhances the clinical utility of CE‐MRI. Magn Reson Med, 2006.

Coronary artery plaque formation at coronary CT angiography: morphological analysis and relationship to hemodynamics

We aimed to demonstrate that coronary CT angiography (cCTA) can be used to non-invasively study the effect of hemodynamic factors in the pathophysiology of plaque formation. cCTA data of 73 patients were analyzed. All detected plaques were classified according to location (bifurcation, non-branching segment), configuration (eccentric, concentric), orientation (myocardial, lateral, epicardial side of the vessel wall), and composition (calcified, mixed, non-calcified). Bifurcation lesions were further characterized using the Medina classification. Of 382 plaques, 8.1% were in the LM, 46.3% in the LAD, 18.3% in the LCx, and 25.9% in the RCA. Also, 25.1% were completely calcified, 72.3% were mixed, and 2.6% were purely non-calcified. Of the plaques, 51.3% were bifurcation lesions. The most frequent (40%) Medina pattern was 1.1.0 (lesion starts before, extends beyond bifurcation, sparing the side branch). Eighty percent of plaques were eccentric. A significant (p < 0.01) majority (55%) were on the myocardial side, while 17.3% were lateral, and 27.7% epicardial. Of all non-calcified and mixed plaques, 45.1% (p < 0.01) were myocardial, whereas only 14.3% were lateral, 20.6% epicardial, and 19.9% concentric. We conclude that cCTA can non-invasively study the effect of vascular hemodynamics, such as turbulent flow (bifurcations) and low shear stress (myocardial vessel wall), on the distribution and composition of atherosclerotic plaque deposition.

Application of an Advanced Image-Based Virtual Monoenergetic Reconstruction of Dual Source Dual-Energy CT Data at Low keV Increases Image Quality for Routine Pancreas Imaging.

Purpose To compare image quality on contrast-enhanced dual-energy computed tomography (DECT) during the pancreatic parenchymal phase of pancreatic masses between linearly-blended simulated 120 kVp images (routine) and advanced image-based virtual monoenergetic reconstructions at 55 keV. Methods This was a retrospective evaluation of 24 nonconsecutive adults found to have a focal pancreatic mass on a multiphasic abdominal dual-source DECT (12 adenocarcinoma, 5 neuroendocrine, 7 cystic tumors). For pancreatic-parenchymal phase images, subjects had routine and 55 keV images reconstructed at the time of clinical evaluation. Quantitative evaluation by contrast-to-noise ratio and qualitative evaluations of image quality by (1) direct comparison of image pairs (preference) and (2) blinded assessment of image quality measures based on Likert scores were performed. Results Mean patient weight was 205.8 ± 26.6 lbs. Mean pancreatic lesion contrast-to-noise ratio was significantly higher at 55 keV (6.8 ± 4.1) compared to the routine image series (5.8 ± 3.8; P = 0.0002). All 3 readers preferred the 55-keV images over routine blended images in 70.1% to 95.8% of cases. No significant differences were observed for subjective sharpness of the mass, visualization of internal mass structures, or image noise. Conclusions Use of a single advanced image-based virtual monoenergetic reconstruction at 55 keV in pancreatic DECT showed improved objective image quality and reader preference compared to routine images. As this image reconstruction can be incorporated into the scan protocol, this technique should be considered for routine clinical use.

Differentiation of acute and four-week old myocardial infarct with Gd(ABE-DTTA)-enhanced CMR.

BackgroundStandard extracellular cardiovascular magnetic resonance (CMR) contrast agents (CA) do not provide differentiation between acute and older myocardial infarcts (MI). The purpose of this study was to develop a method for differentiation between acute and older myocardial infarct using myocardial late-enhancement (LE) CMR by a new, low molecular weight contrast agent.Dogs (n = 6) were studied in a closed-chest, reperfused, double myocardial infarct model. Myocardial infarcts were generated by occluding the Left Anterior Descending (LAD) coronary artery with an angioplasty balloon for 180 min, and four weeks later occluding the Left Circumflex (LCx) coronary artery for 180 min. LE images were obtained on day 3 and day 4 after second myocardial infarct, using Gd(DTPA) (standard extracellular contrast agent) and Gd(ABE-DTTA) (new, low molecular weight contrast agent), respectively. Triphenyltetrazolium chloride (TTC) histomorphometry validated existence and location of infarcts. Hematoxylin-eosin and Massons trichrome staining provided histologic evaluation of infarcts.ResultsGd(ABE-DTTA) or Gd(DTPA) highlighted the acute infarct, whereas the four-week old infarct was visualized by Gd(DTPA), but not by Gd(ABE-DTTA). With Gd(ABE-DTTA), the mean ± SD signal intensity enhancement (SIE) was 366 ± 166% and 24 ± 59% in the acute infarct and the four-week old infarct, respectively (P < 0.05). The latter did not differ significantly from signal intensity in healthy myocardium (P = NS). Gd(DTPA) produced signal intensity enhancements which were similar in acute (431 ± 124%) and four-week old infarcts (400 ± 124%, P = NS), and not statistically different from the Gd(ABE-DTTA)-induced SIE in acute infarct. The existence and localization of both infarcts were confirmed by triphenyltetrazolium chloride (TTC). Histologic evaluation demonstrated coagulation necrosis, inflammation, and multiple foci of calcification in the four day old infarct, while the late subacute infarct showed granulation tissue and early collagen deposition.ConclusionsLate enhancement CMR with separate administrations of standard extracellular contrast agent, Gd(DTPA), and the new low molecular weight contrast agent, Gd(ABE-DTTA), differentiates between acute and late subacute infarct in a reperfused, double infarct, canine model.

Percent infarct mapping for delayed contrast enhancement magnetic resonance imaging to quantify myocardial viability by Gd(DTPA).

To demonstrate the advantages of signal intensity percent‐infarct‐mapping (SI‐PIM) using the standard delayed enhancement (DE) acquisition in assessing viability following myocardial infarction (MI). SI‐PIM quantifies MI density with a voxel‐by‐voxel resolution in clinically used DE images.

Gd(ABE-DTTA), a novel contrast agent, at the MRI-effective dose shows absence of deleterious physiological effects in dogs

The physiological effects of a novel MRI contrast agent, Gd(ABE-DTTA), were investigated in dogs, monitoring parameters in blood samples. Each animal (n = 8 in the short-term, n = 4 in the long-term group) underwent isoflurane anesthesia followed by the generation of myocardial infarction and received a contrast agent at the MRI effective dose. Blood samples were collected 24 and 48 h, and 7, 14, 28, 35, 49 and 56 days after contrast agent administration. No significant changes exceeding the normal range were detected in any of the investigated parameters except in alanine aminotransferase (ALT). ALT enzyme activity increased in the short-term group 24 and 48 h after agent administration as expected from the effect of isoflurane anesthesia. Between days 7 and 56 no elevation in ALT was observed. In dogs no substantial short- or long-term effect was observed on the investigated, physiological parameters after Gd(ABE-DTTA) administration at the MRI effective dose.

Automated multidetector computed tomography evaluation of subacutely infarcted myocardium

BACKGROUND Delayed enhanced (DE) multidetector computed tomography (MDCT) can identify acute and chronic myocardial infarct. To our knowledge, automated techniques for infarct quantification on DE-MDCT have not been used. OBJECTIVE We evaluated an automated signal intensity (SI) threshold method for quantification of subacute myocardial infarct and identified and quantified microvascular obstruction (MO) in subacute infarct. METHODS DE-MDCT imaging was performed on 5 pigs 6-7 days after mid left anterior descending artery occlusion-reperfusion. DE-MDCT images were compared with triphenyl tetrazolium chloride (TTC) staining for infarct quantification and with hematoxylin and eosin (H&E) staining for MO quantification. Pixels with SI more than the mean SI of a remote normal myocardial region (SI(remote)) plus 2 times the standard deviation (SI(remote) + 2 SD) value were considered infarct pixels. The ratio of infarct to total area of a given slice, the percentage of infarct area per slice (PIS), was calculated. MO as a percentage of total infarct area was also calculated. RESULTS The average density values on DE-MDCT (5 minutes after contrast injection) were remote normal myocardium of 93 +/- 19 Hounsfield units (HU), infarct myocardium of 159 +/- 40 HU, blood of 140 +/- 26 HU, and MO of 85 +/- 30 HU. PIS(MDCT) showed substantial agreement with PIS(TTC) (y = 1.003x + 4.12; R = 0.90, P < 0.05). A relation was also shown between MO determined by MDCT compared with H&E staining (y = 0.74x + 3.4). CONCLUSIONS We show the feasibility of using a semiautomated SI threshold technique for quantification of subacute myocardial infarct. We also show the persistent MO in subacute myocardial infarct on DE-MDCT images.