Multidetector computed tomography (MDCT) evaluation of myocardial viability: intraindividual comparison of monomeric vs. dimeric contrast media in a rabbit model

To evaluate the influence of different types of iodinated contrast media on the assessment of myocardial viability, acute myocardial infarction (MI) was surgically induced in six rabbits. Over a period of 45 min, contrast-enhanced cardiac MDCT (64 × 0.6 mm, 80 kV, 680mAs_eff.) was repeatedly performed using a contrast medium dose of 600 mg iodine/kg body weight. Animals received randomized iopromide 300 and iodixanol 320, respectively. Attenuation values of healthy and infarcted myocardium were measured. The size of MI was computed and compared with nitroblue tetrazolium (NBT)-stained specimen. The highest attenuation differences between infarcted and healthy myocardium occurred during the arterial phase with 140.0 ± 3.5 HU and 141.0 ± 2.2 HU for iopromide and iodixanol, respectively. For iodixanol the highest attenuation difference on delayed contrast-enhanced images was achieved 3 min post injection (73.5 HU). A slightly higher attenuation difference was observed for iopromide 6 min after contrast medium injection (82.2 HU), although not statistically significant (p = 0.6437). Mean infarct volume as measured by NBT staining was 33.5% ± 13.6%. There was an excellent agreement of infarct sizes among NBT-, iopromide- and iodixanol-enhanced MDCT with concordance-correlation coefficients ranging from ρ_{(c)  =} 0.9928–0.9982. Iopromide and iodixanol both allow a reliable assessment of MI with delayed contrast-enhanced MDCT.     

Intraindividual comparison of myocardial delayed enhancement MR imaging using gadobenate dimeglumine at 1.5 T and 3 T

For contrast-enhanced imaging techniques relying on strong T1 weighting, 3 T provides increased contrast compared with 1.5 T. The aim of our study was the intraindividual comparison of delayed enhancement MR imaging at 1.5 T and at 3 T. Twenty patients with myocardial infarction were examined at 1.5 T and 3 T. Fifteen minutes after injection of contrast agent (0.1 mmol gadobenate dimeglumine per kg body weight), inversion recovery gradient recalled echo (IR-GRE) sequences were acquired (1.5 T/3 T: TR 11.0/9.9 ms, TE 4.4/4.9 ms, flip 30°/30°, slice thickness 6/6 mm) to assess myocardial viability. Two observers rated image quality (Wilcoxon signed rank test). Quantification of hyperenhanced myocardium and standardized SNR/CNR measurements were performed (Student’s t test). There was no significant difference with respect to image quality (1.5 T/3 T: 3.5/3.3, p = 0.34, reader 1; 2.4/2.7, p = 0.12, reader 2) and infarction size (760 ± 566/828 ± 677 mm² at 1.5 T, 808 ± 639/826 ± 726 mm² at 3 T, reader 1/reader 2, p > 0.05). Mean SNR in hyperenhanced/normal myocardium was 19.2/6.2 at 1.5 T and 29.5/8.8 at 3 T (p < 0.05). Mean CNR was 14.3 at 1.5 T and 26.0 at 3 T (p < 0.05). Delayed enhancement MR imaging at 3 T is a robust procedure yielding superior tissue contrast at 3 T compared with 1.5 T which is, however, not reflected by increased image quality.     

Alterations in T1 of normal and reperfused infarcted myocardium after Gd-BOPTA versus GD-DTPA on inversion recovery EPI

This study tested whether Gd-BOPTA/Dimeg or Gd-DTPA exerts greater relaxation enhancement for blood and reperfused infarcted myocardium. Relaxivity of Gd-BOPTA is increased by weak binding to serum albumin. Thirty-six rats were subjected to reperfused infarction before contrast (doses = 0.05, 0.1, and 0.2 mmol/kg). ΔR1 was repeatedly measured over 30 min. Gd-BOPTA caused greater ΔR1 for blood and myocardium than did Gd-DTPA clearance of both agents from normal and infarcted myocardium was similar to blood clearance; plots of ΔR1myocardium/ΔR1blood showed equilibrium phase contrast distribution. Fractional contrast agent distribution volumes were approximately 0.24 for both agents in normal myocardium, 0.98 and 1.6 for Gd-DTPA and Gd-BOPTA, respectively, in reperfused infarction. The high value for Gd-BOPTA was ascribed to greater relaxivity in infarction versus blood. It was concluded that Gd-BOPTA/Dimeg causes a greater ΔR1 than Gd-DTPA in regions which contain serum albumin.     

Low-dose gadobenate dimeglumine versus standard-dose gadopentate dimeglumine for delayed contrast-enhanced cardiac magnetic resonance imaging

RATIONALE AND OBJECTIVES: The purpose of our study was to compare gadopentate dimeglumine (Gd-DTPA) and gadobenate dimeglumine (Gd-BOPTA) for the evaluation of myocardial infarction (MI) and in the grading transmural extent on late-contrast enhanced cardiac magnetic resonance imaging. MATERIALS AND METHODS: Twenty-three patients with clinically proven MI were examined with the use of 0.2 mmol/kg Gd-DTPA and 0.1 mmol/kg Gd-BOPTA in 2 days interval. All patients were examined with the use of segmented two-dimensional inversion-recovery turbo fast-field echo pulse sequence with an inversion time 210-300 milliseconds. Fifteen minutes time delay was used on both examinations after the injection of contrast agent. Contrast-to-noise ratio between normal myocardium and infarcted myocardium and signal intensity ratio (SIR) of the enhanced myocardium to blood pool was derived and compared for each contrast agent. RESULTS: A total of 61 infarcted segments were analyzed. All of the infarcted segments were visualized on both Gd-BOPTA and Gd-DTPA enhanced images. There was statistically no significant difference between 0.2 mmol/kg Gd-DTPA and 0.1 mmol/kg Gd-BOPTA in the mean contrast-to-noise ratio (10.19 versus 10.22; P = .96), SNR (14.29 versus 14.25; P = .96), and SIR (4.34 versus 4.21; P = .38) of the infarcted segments. Intraobserver agreement (kappa) between Gd-DTPA and Gd-BOPTA were R1 = 91% and R2 = 86%. Interobserver agreements between the readers were Gd-DTPA = 85% and Gd-BOPTA = 88%. CONCLUSION: According to our data, the diagnostic efficacy of 0.1 mmol/kg dose Gd-BOPTA is equivalent to that of 0.2 mmol/kg Gd-DTPA for the assessment of MI on delayed enhanced magnetic resonance images.     

T1-relaxation kinetics of extracellular, intracellular and intravascular MR contrast agents in normal and acutely reperfused infarcted myocardium using echo-planar MR imaging

The objective of this study was to determine and compare if MR contrast agents distributed into various compartments can provide estimation of fractional distribution volume (FDV) in normal and infarcted myocardium using inversion recovery echo-planar MR imaging (IR EPI). Three different types of MR agents were investigated: (a) an extracellular agent, GdDTPA-BMA (0.1 mmol/kg); (b) an intravascular agent, GdDTPA-albumin (0.025 mmol/kg); and (c) an intracellular agent, manganese chloride (0.025 mmol/kg). The null point was determined from a series of IR EPI images in which TI was varied. Temporal changes in ΔR1 (ΔR1 = 1/T1_post-1/T1_pre) were measured during the initial 29–59 min after administration. Rats (n = 24) were subjected to 1-h coronary artery occlusion/reperfusion. Histochemical staining confirmed the presence and location of infarction. GdDTPA-BMA caused increase in ΔR1 of infarction < blood < < normal myocardium. ΔR1 ratios were 1.55 ± 0.08 for infarction and 0.33 ± 0.03 for normal myocardium, consistent with FDV of 0.82 ± 0.04 and 0.18 ± 0.01. The fractional distribution of this agent in normal myocardium approximated the extracellular space of myocardium. GdDTPA-albumin caused increase in ΔR1 of blood < < infarction < < normal myocardium. ΔR1 ratio in normal, but not infarcted, myocardium was constant at 0.10 ± 0.02 and approximated fractional blood volume. MnCl₂ caused equivalent increase in ΔR1 of normal and infarcted myocardium. ΔR1 of normal myocardium did not change overtime, whereas ΔR1 of blood rapidly decreased, leading to overestimation of FDV in normal and infarcted myocardium. In conclusion, extracellular, intravascular and intracellular MR contrast agents exhibited different T1-relaxation kinetics in both normal and infarcted myocardium. Constant ΔR1 ratio (myocardium/blood) after administration of MR contrast agent is a prerequisite for estimation of FDV of MR contrast agent in myocardium. Received: 22 December 1998; Revised: 7 April 1999; Accepted: 18 May 1999     

A comparative study between Gd-BOPTA, a biliary excretion contrast medium, and Gd-DTPA in the magnetic resonance imaging of the rat liver

A new lipophilic compound, Gd-BOPTA, presenting a high rate (38.6%) of biliary excretion was tested as an hepato-specific MR contrast agent. Its adequacy was compared to that of Gd-DTPA in laboratory animals. T1-weighted spin-echo sequences (TR 220 ms, TE 20 ms) both before and after the administration of the 2 contrast agents (doses: 0.25, 0.5, and 1.0 mmol/kg) showed better liver enhancement with Gd-BOPTA than with Gd-DTPA. Gd-BOPTA superiority was more evident at lower doses, while at 1.0 mmol/kg a comparable enhancement was achieved. Inversion recovery sequence at the T-null of liver parenchyma before contrast (TR 800 ms, TE 30 ms, TI 100 ms) was performed after the injection of 0.1 and 0.5 mmol/kg of Gd-DTPA and Gd-BOPTA. This sequence allowed the good and long-lasting liver enhancement achieved with Gd-BOPTA to be even better demonstrated, while Gd-DTPA provided only a slight and early enhancement with 0.1 mmol/kg and returned to baseline values 60' after the injection of the highest dose (0.5 mmol/kg). Gd-BOPTA proved to be a good contrast agent to obtain prolonged liver enhancement, thus providing the radiologist with the long time needed to acquire conventional T1-weighted pulse sequences.     

Energetic differences between viable and non-viable myocardium in patients with recent myocardial infarction are not an effect of differences in wall thinning— a multivoxel <Superscript>31</Superscript>P-MR-spectroscopy and MRI study

To evaluate multivoxel ³¹P-MR spectroscopy (MRS) for assessment of energy metabolism in patients with myocardial infarction (MI) in correlation to left ventricular (LV) wall thickness and the outcome of revascularization. Thirty patients with subacute anterior myocardial infarction and planned revascularization were enrolled. 3D–chemical shift imaging was applied to determine PCr/ATP ratios in two areas: infarcted/anterior and noninfarcted/septal myocardium. MRI was used to evaluate LV function and wall thickness, and was repeated 6 months after revascularization to assess myocardial viability. Fifteen volunteers were controls. Fifteen patients showed normalization of wall motion abnormalities after revascularization (Group 1; viable), 15 not (Group 2; non-viable). Regarding infarcted/anterior myocardium, Group 2 had lower PCr/ATP ratios (0.81 ± 0.60 vs 1.17 ± 0.25), and PCr/ATP ratios were reduced in both groups compared to controls (1.45 ± 0.29). Regarding noninfarcted/septal myocardium, again Group 2 had lower ratios (0.93 ± 0.53 vs 1.31 ± 0.38); however, compared to controls (1.51 ± 0.32) a reduction of PCr/ATP ratios was only found in Group 2. For both myocardial regions, no correlations between PCr/ATP ratios and LV wall thickness were detected. The more severe energetic alteration in irreversibly damaged myocardium is not an effect of differences of wall thinning. Additional alterations of noninfarcted, adjacent myocardium can be detected.     

Intraindividual comparison of T1 relaxation times after gadobutrol and Gd-DTPA administration for cardiac late enhancement imaging

Purpose

To evaluate T1-relaxation times of chronic myocardial infarction (CMI) using gadobutrol and gadopentetate dimeglumine (Gd-DTPA) over time and to determine the optimal imaging window for late enhancement imaging with both contrast agents.

Material and methods

Twelve patients with CMI were prospectively included and examined on a 1.5 T magnetic resonance (MR) system using relaxivity-adjusted doses of gadobutrol (0.15 mmol/kg) and Gd-DTPA (0.2 mmol/kg) in random order. T1-relaxation times of remote myocardium (RM), infarcted myocardium (IM), and left ventricular cavity (LVC) were assessed from short-axis TI scout imaging using the Look–Locker approach and compared intraindividually using a Wilcoxon paired signed-rank test (α < 0.05).

Results

Within 3 min of contrast agent administration (CA), IM showed significantly lower T1-relaxation times than RM with both contrast agents, indicating beginning cardiac late enhancement. Differences between gadobutrol and Gd-DTPA in T1-relaxation times of IM and RM were statistically not significant through all time points. However, gadobutrol led to significantly higher T1-relaxation times of LVC than Gd-DTPA from 6 to 9 min (220 ± 15 ms vs. 195 ± 30 ms p < 0.01) onwards, resulting in a significantly greater ΔT1 of IM to LVC at 9–12 min (−20 ± 35 ms vs. 0 ± 35 ms, p < 0.05) and 12–15 min (−25 ± 45 ms vs. −10 ± 60 ms, p < 0.05). Using Gd-DTPA, comparable ΔT1 values were reached only after 25–35 min.

Conclusion

This study indicates good delineation of IM to RM with both contrast agents as early as 3 min after administration. However, we found significant differences in T1 relaxation times with greater ΔT1 IM–LVC using 0.15 mmol/kg gadobutrol compared to 0.20 mmol/kg Gd-DTPA after 9–15 min post-CA suggesting earlier differentiability of IM and LVC using gadobutrol.     

MR imaging of the wrist in rheumatoid arthritis using gadobenate dimeglumine

Objective. To determine the dosage of gadobenate dimeglumine (Gd-BOPTA) necessary for MRI of rheumatoid arthritis of the wrist. Design and patients. Seven wrists inflamed with rheumatoid arthritis were imaged using a dedicated 0.2-T MR unit. Four cumulative dosages of 0.0125, 0.025, 0.05 and 0.1 mmol/kg body weight (BW) Gd-BOPTA were tested. Three-dimensional T1-weighted gradient-recalled echo sequences (GRE; TR: 100 ms, TE: 18 ms, flip angle 90°, 4:55 min) were acquired prior to an intravenous injection and after each additional dosage of Gd-BOPTA. Relative enhancement, signal-difference-to-noise ratios (SDNRs) and the size of the inflamed tissue were quantified. Three radiologists independently evaluated the image quality, the size and the contrast of the enhancing tissue. Results. The readers agreed on a dose of 0.05 mmol/kg BW as satisfactory for the evaluation of the size of the inflammatory tissue and for determination of bone involvement (κ=0.9, P<0.001). Highly inflammatory pannus was depicted with adequate image contrast using 0.025 mmol/kg BW Gd-BOPTA. According to the SDNR and relative enhancement findings, a dose of 0.05 mmol/kg BW suffices for both off-center and centered regions of tissue inflammation (t-test, P<0.05). Conclusion. Gadolinium-BOPTA is an alternative contrast agent for MRI of rheumatoid disease. This study shows that a dose of 0.05 mmol/kg BW suffices at low field strength. Received: 7 June 2000 Revision requested: 22 August 2000 Revision received: 8 September 2000 Accepted: 21 September 2000     

Assessment of 18F-labeled mitochondrial complex I inhibitors as PET myocardial perfusion imaging agents in rats, rabbits, and primates

Purpose  Myocardial extractions of mitochondria complex I (MC-I) inhibitors were high and well correlated with flow. This study assessed the potential of MC-I inhibitors to be developed as myocardial perfusion imaging (MPI) agents. Methods  RP1003, RP1004, and RP1005 representing three classes of MC-I inhibitor were synthesized and radio-labeled with ¹⁸F. These agents were evaluated for IC₅₀ values, tissue biodistribution, and cardiac PET imaging. ¹⁸F-RP1004 was further examined for first-pass extraction and by imaging in non-human primates (NHP) and rats following coronary ligation. Results  RP1003, RP1004, and RP1005 exhibited high MC-I inhibitory activity with IC₅₀ of 3.7, 16.7, and 14.4 nM. Heart uptakes in rats (percent injected dose per gram tissue) at 15 and 60 min after injection were 3.52 ± 0.36 and 2.68 ± 0.20 for ¹⁸F-RP1003, 2.40 ± 0.21 and 2.67 ± 0.27 for ¹⁸F-RP1004, and 2.28 ± 0.12 and 1.81 ± 0.17 for ¹⁸F-RP1005. The heart to lung and liver uptake ratios were favorable for cardiac imaging with these agents. In isolated perfused rabbit hearts, the uptake of ¹⁸F-RP1004 increased from 0.74 ± 0.19 to 1.68 ± 0.39 mL/min/g at flow rates of 1.66 to 5.06 mL/min/g. These values were higher than or similar to that of ^99mTc-sestamibi. Cardiac imaging with these agents in rats and rabbits allowed visualization of the heart with minimal lung interference and rapid liver activity clearance. Imaging with ¹⁸F-RP1004 also showed clear myocardium and marked liver activity washout in the NHP and clear detection of the perfusion-deficit area associated with left coronary artery ligation in the rat. Conclusion  MC-I inhibitors have the potential to be a new class of MPI agent.     

Myocardial delayed enhancement using a single dose (0.1 mmol/kg) of gadobenate dimeglumine: contrast resolution versus intraventricular blood and viable myocardium

Purpose

This study was done to estimate delayed enhancement (DE) contrast resolution of infarcted myocardium (IM) relative to intraventricular blood (IB) and viable myocardium (VM) using gadobenate dimeglumine (Gd-BOPTA).

Materials and methods

After approval from the Ethics Committee, we retrospectively evaluated 21 consecutive patients (61±10 years) with a healed myocardial infarction who underwent 1.5-T magnetic resonance (MR) imaging using an inversion-recovery-prepared turbo gradient-echo sequence 10 minutes after injection of 0.1 mmol/kg of Gd-BOPTA. Signal intensity (SI) was measured in arbitrary units (au) for IM, IB, VM, and outside the patient. Contrast-to-noise ratio (CNR) was calculated for IM to IB and IM to VM. Seven consecutive patients (59±6 years) with a healed myocardial infarction studied with similar technique but with 0.1 mmol/kg of gadoterate meglumine (Gd-DOTA) served as the control group. The Mann-Whitney U test was used to compare groups.

Results

Mean SI of IM was 44±16 au for Gd-BOPTA and 20±6 au for Gd-DOTA (p<0.001), that of IB 35±15 au and 14±5 au (p=0.016), and that of VM 7±3 au and 5±2 au (p=0.116), respectively. Mean IM to IB CNR was 10±7 for Gd-BOPTA and 8±5 for Gd-DOTA (p=0.836), that of IM to VM was 45±27 and 18±6, respectively (p=0.012).

Conclusions

Gd-BOPTA at 0.1 mmol/kg produced a higher myocardial DE and an IM to VM CNR than a single dose of Gd-DOTA. No significant difference was observed for IM to IB CNR.     

Aperistaltic effect of hyoscine N-butylbromide versus glucagon on the small bowel assessed by magnetic resonance imaging

The aim of this prospective study was to compare the intraindividual aperistaltic effect of 40 mg hyoscine N-butylbromide (HBB/Buscopan) with that of 1 mg glucagon on small bowel motility by using magnetic resonance imaging (MRI). Ten healthy volunteers underwent two separate 1.5-T MRI studies (HBB/glucagon) after a standardized oral preparation with an aqueous solution of Gd-DOTA and ispaghula (Metamucil). A 2D T1-w GRE sequence was acquired (TR 2.7 ms/TE 1.3 ms, temporal resolution 0.25 s) before and after intravenous (i.v.) drug administration and motility was followed over 1 h. On the resulting images the cross-sectional luminal diameters were assessed and plotted over time. Baseline motility frequency, onset of aperistalsis, duration of arrest, reappearance of motility and return to normal motility were analysed. Significant differences regarding reliability and duration of aperistalsis were observed. In the HBB group aperistalsis lasted a mean of 6.8 ± 5.3 min compared with 18.3 ± 7 min after glucagon (p < 0.0001). In 50% of cases HBB did not accomplish aperistalsis, whereas glucagon always succeeded (p = 0.05). There were no significant differences in terms of baseline and end frequencies for the onset of aperistalsis (22.2 ± 37.5 s HBB/13.4 ± 9.2 s glucagon, p = 0.1), nor for the return to normal motility. Arrest of small bowel motion is achieved more reliably and lasts significantly longer after i.v. administration of 1 mg glucagon compared with 40 mg HBB.     

Ultra low-dose of gadobenate dimeglumine for late gadolinium enhancement (LGE) imaging in acute myocardial infarction: A feasibility study

PurposeTo assess the feasibility of using an ultra-low dose (0.05 mmol/kg of body weight [BW]) of high relaxivity contrast agent for late gadolinium enhancement (LGE) imaging in patients with acute myocardial infarction (AMI).Materials and methods17 consecutive patients (mean age, 60.1 ± 10.3 years) with ST-segment elevation AMI underwent two randomized cardiac magnetic resonance studies (exam intervals between 24 and 48 h) on a 1.5 T unit during the first week after the event using gadobenate dimeglumine (Gd-BOPTA) at the dose of 0.1 mmol/kg BW (standard dose or SD group) and 0.05 mmol/kg BW (half dose or HD group). Image quality was qualitatively assessed. Quantitative analysis of LGE were performed by measuring signal intensity (SI), signal-to-noise ratio (SNR) in the infarcted myocardium (IM), non-infarcted myocardium (N-IM) and left ventricular cavity (LVC) in images acquired at 1, 3, 5, 10, 15 and 20 min after administration of Gd-BOPTA using both contrast media protocol. Contrast-to-noise ratio (CNR) between IM and N-IM (CNR IM/N-IM) and between IM and LVC (CNR IM/LVC) were also quantified for each time point. Moreover the extent of infarcted myocardium was measured.Results102 LGE images were evaluated for each dose group. Quality score was significantly higher for SD at 1, 15 and 20 min (0.002 < p < 0.046) and for HD at 5 min (p = 0.013). SNR has been higher in the SD group compared to the HD group even though not statistically significant at any time-point for both IM (SD vs. HD: 87.7 ± 73 vs. 65 ± 66; 0.15 < p < 0.38) and N-IM (SD vs. HD: 22 ± 61 vs. 9.9 ± 6.5; 0.09 < p < 0.43). LVC SNR was significantly higher with SD at 10 min (p = 0.03), 15 min (p = 0.001) and 20 min (p = 0.004). CNR between the IM and N-IM was significantly higher using SD compared to HD (1382.24 ± 1049 vs. 695.4 ± 500; 0.000 < p < 0.028) at 10, 15 and 20 min. No significant differences in CNR IM/LVC were noted for HD acquired 5 min after CM administration compared to SD acquired at 10 (p = 0.34), 15 (p = 0.96) and 20 (p = 0.41) min, and between HD at 10 min compared to SD acquired at 15 min (p = 0.78) and 20 min (p = 0.32). Good correlation between SD and HD (0.56 < r² < 0.85, p < 0.024) was found at all time-points in the measuring of IA.ConclusionThe use of a 0.05 mmol/kg dose of gadobenate dimeglumine is feasible for LGE imaging of acute MI and the best image quality is obtained at 5 min after contrast administration. It could be beneficial in patient with renal failure and a solution to improve the identification of subendocardial infarction reducing examination time, costs and total gadolinium load. However, the standard dose of 0.1 mmol/kg provides overall better image quality, with the best performance obtained at the delay of 10 min or more after Gd-BOPTA administration, and it should be routinely preferred.     

Dynamic multi-section CT imaging in acute myocardial infarction: preliminary animal experience

To evaluate the feasibility of myocardial first-pass perfusion imaging with multidetector CT (MDCT). In five pigs, myocardial infaction was induced by permanent balloon occlusion of the left anterior descending coronary artery. Dynamic contrast-enhanced MDCT (12×1.5 mm, 120 kV, 30 mAs, 64 acquisitions, 40 ml iopromide 370@4ml/s) and contrast-enhanced first-pass perfusion magnetic resonance (MR) imaging (TR 7.7 ms/TE 2.6 ms, 64 acquisitions, 0.05 mmol/kg Gd-DTPA) were performed. Finally, the animals were sacrificed, and the heart was excised and stained with triphenyltetrazolin-chloride (TTC). Maximum signal intensity (SI_max), contrast material arrival time (CAT), wash-in time (T_max) and slope were calculated from time-density/signal-intensity curves. The area of myocardial hypoperfusion was measured as the percentage of the left-ventricular area (%LV). Parameters were compared using Bland-Altman plots and Student's t-tests. The hypoperfused area on MDCT was 19.3±4.5%LV (MR imaging 17.2±4.0%LV). The mean size of infarction was 18.7±5.7%LV with TTC. Semiquantitative analysis of MR imaging and MDCT for SI_max, T_max and slope showed significant differences between normal and infarcted myocardium (P<0.05). No significant differences were found for CAT. MDCT and MR imaging both allowed for the differentiation of hypoperfused and normal myocardium. Results given in absolute values differed significantly between both imaging modalities (P<0.05). MDCT has the potential for visual and semiquantitative assessment of first-pass myocardial perfusion.     

Lower fractional anisotropy at the anterior body of the normal-appearing corpus callosum in multiple sclerosis versus symptomatic carotid occlusion

Introduction  Not uncommonly, differentiating multiple sclerosis (MS) from ischemic cerebral vascular disease is difficult based on conventional magnetic resonance imaging (MRI). We aim to determine whether preferential occult injury in the normal-appearing corpus callosum (NACC) is more severe in patients with MS than symptomatic carotid occlusion by comparing fractional anisotropy (FA) from diffusion tensor imaging (DTI). Methods  Eighteen patients (eight men, ten women; mean age, 38.6 years) with MS and 32 patients (24 men, eight women; mean age, 64.0 years) with symptomatic unilateral internal carotid occlusion were included. DTI (1.5 T) were performed at corpus callosum which were normal-appearing on fluid-attenuated inversion recovery MRI. Mean FA was obtained from the genu, anterior body, posterior body, and splenium of NACC. Independent-sample t test statistical analysis was performed. Results  The FA values in various regions of NACC were lower in the MS patients than symptomatic carotid occlusion patients, which was statistically different at the anterior body (0.67 ± 0.12 vs 0.74 ± 0.06, P = 0.009), but not at genu, posterior body, and splenium (0.63 ± 0.09 vs 0.67 ± 0.07, P = 0.13; 0.68 ± 0.09 vs 0.73 ± 0.05, P = 0.07; 0.72 ± 0.09 vs 0.76 ± 0.05, P = 0.13). Conclusion  MS patients have lower FA in the anterior body of NACC compared to patients with symptomatic carotid occlusion. It suggests that DTI has potential ability to differentiate these two conditions due to the more severe preferential occult injury at the anterior body of NACC in MS.     

Absolute choline concentration measured by quantitative proton MR spectroscopy correlates with cell density in meningioma

Introduction  This study was aimed to investigate the relationship between quantitative proton magnetic resonance spectroscopy (1H-MRS) and pathological changes in meningioma. Materials and methods  Twenty-two meningioma cases underwent single voxel 1H-MRS (point-resolved spectroscopy sequence, repetition time/echo time = 2,000 ms/68, 136, 272 ms). Absolute choline (Cho) concentration was calculated using tissue water as the internal reference and corrected according to intra-voxel cystic/necrotic parts. Pathological specimens were stained with MIB-1 antibody to measure cell density and proliferation index. Correlation analysis was performed between absolute Cho concentration and cell density and MIB-1 labeled proliferation index. Results  Average Cho concentration of all meningiomas before correction was 2.95 ± 0.86 mmol/kg wet weight. It was increased to 3.23 ± 1.15 mmol/kg wet weight after correction. Average cell density of all meningiomas was 333 ± 119 cells/HPF, and average proliferation index was 2.93 ± 5.72%. A linear, positive correlation between cell density and Cho concentration was observed (r = 0.650, P = 0.001). After correction of Cho concentration, the correlation became more significant (r = 0.737, P < 0.001). However, no significant correlation between Cho concentration and proliferation index was found. There seemed to be a positive correlation trend after correction of Cho concentration but did not reach significant level. Conclusion  Absolute Cho concentration, especially Cho concentration corrected according to intra-voxel cystic/necrotic parts, reflects cell density of meningioma. Grant: This study was supported by the Japan-China Sasakawa Medical Fellowship (Nippon Foundation, Japan)     

Fast T2 mapping of the patellar articular cartilage with gradient and spin-echo magnetic resonance imaging at 1.5 T: validation and initial clinical experience in patients with osteoarthritis

Objective To evaluate the T2 mapping of patellar articular cartilage in patients with osteoarthritis using gradient and spin-echo (GRASE) magnetic resonance (MR) imaging. Materials and methods After the imaging of a phantom consisting of two sealed 50-ml test objects with different concentrations (30% and 90% weight/volume) of copper sulphate, the T2 mapping of patellar articular cartilage was performed in 35 patients (21 male and 14 female; mean age ± SD 42 ± 17 years) with moderate degree of patellar osteoarthritis. Turbo-spin-echo (TSE) (TR milliseconds/minimum–maximum TE milliseconds 3,000/15–120; total acquisition time 5 min 52 s) and GRASE (TR milliseconds/minimum–maximum TE milliseconds 3,000/15–120; total acquisition time 1 min 51 s) were employed. In each patient patellar cartilage was segmented at nine locations (three superior, three central, and three inferior) by manually defined regions of interest. T2 relaxation times were calculated using a linear fit applied to the logarithm of signal intensity decay. Results In the phantom the T2 values measured by GRASE were similar to those measured by MR spectroscopy (test object 1: 48.1 ms vs 51 ms; test object 2: 66.8 ms vs 71 ms; P > 0.05, Wilcoxon test). In patients GRASE and TSE-derived T2 values demonstrated good agreement (mean difference ± SD, 1.81 ± 3.63 ms). The within-patient coefficient of variation was 22% for TSE and 23% for GRASE. Conclusion Fast T2 mapping of the patellar articular cartilage can be performed with GRASE within a third of the time of that of standard sequences. This study was performed thanks to the support of a private grant, “Arduino Ratti”, provided through the Italian Society of Medical Radiology.     

Contrast-enhanced magnetic resonance angiography (MRA): evaluation of three different contrast agents at two different doses (0.05 and 0.1?mmol/kg) in pigs at 1.5?Tesla

Objective  

To compare the image quality of contrast-enhanced magnetic resonance angiography (CE-MRA) of the supra-aortic vessels at 0.05 mmol/kg bw and 0.1 mmol/kg bw, between gadobutrol, Gd-DTPA and Gd-BOPTA quantitatively and qualitatively a total of eight pigs were evaluated intraindividually at 1.5 T.     

Low-dose gadobenate dimeglumine versus standard dose gadopentetate dimeglumine for contrast-enhanced magnetic resonance imaging of the liver: an intra-individual crossover comparison

RATIONALE AND OBJECTIVES: Gadobenate dimeglumine (Gd-BOPTA) has a two-fold higher T1 relaxivity compared with gadopentetate dimeglumine (Gd-DTPA) and can be used for both dynamic and delayed liver MRI. This intraindividual, crossover study was conducted to compare 0.05 mmol/kg Gd-BOPTA with 0.1 mmol/kg Gd-DTPA for liver MRI. MATERIALS AND METHODS: Forty-one patients underwent two identical MR examinations separated by >or= 72 hours. Precontrast T1-FLASH-2D and T2-TSE sequences and postcontrast T1-FLASH-2D sequences were acquired during the dynamic and delayed (1-2 hours) phases after each contrast injection. Images were evaluated on-site by two independent, blinded off-site readers in terms of confidence for lesion detection, lesion number, character and diagnosis, enhancement pattern, lesion-to-liver contrast, and benefit of dynamic and delayed scans. Additional on-site evaluation was performed of the overall diagnostic value of each agent. RESULTS: Superior diagnostic confidence was noted by on-site investigators and off-site assessors 1 and 2 for 6, 4 and 2 patients with Gd-BOPTA, and for 3, 1 and 2 patients with Gd-DTPA, respectively. No consistent differences were noted for other parameters on dynamic phase images whereas greater lesion-to-liver contrast was noted for more patients on delayed images after Gd-BOPTA. More correct diagnoses of histologically confirmed lesions (n = 26) were made with the complete Gd-BOPTA image set than with the complete Gd-DTPA set (reader 1: 68% vs. 59%; reader 2: 78% vs. 68%). The overall diagnostic value was considered superior after Gd-BOPTA in seven patients and after Gd-DTPA in one patient. CONCLUSION: The additional diagnostic information on delayed imaging, combined with the possibility to use a lower overall dose to obtain similar diagnostic information on dynamic imaging, offers a distinct clinical advantage for Gd-BOPTA for liver MRI.     

Effects of percutaneous transluminal angioplasty on muscle BOLD-MRI in patients with peripheral arterial occlusive disease: preliminary results

The purpose was to evaluate the effect of percutaneous transluminal angioplasty (PTA) of the superficial femoral artery (SFA) on the blood oxygenation level-dependent (BOLD) signal change in the calf musculature of patients with intermittent claudication. Ten patients (mean age, 63.4 ± 11.6 years) with symptomatic peripheral arterial occlusive disease (PAOD) caused by SFA stenoses were investigated before and after PTA. Patients underwent BOLD-MRI 1 day before and 6 weeks after PTA. A T2*-weighted single-shot multi-echo echo-planar MR-imaging technique was applied. The BOLD measurements were acquired at mid-calf level during reactive hyperaemia at 1.5 T. This transient hyperperfusion of the muscle tissue was provoked by suprasystolic cuff compression. Key parameters describing the BOLD signal curve included maximum T2* (T2*_max), time-to-peak to reach T2*_max (TTP) and T2* end value (EV) after 600 s of hyperemia. Paired t-tests were applied for statistic comparison. Between baseline and post-PTA, T2*_max increased from 11.1 ± 3.6% to 12.3 ± 3.8% (p = 0.51), TTP decreased from 48.5 ± 20.8 s to 35.3 ± 11.6 s (p = 0.11) and EV decreased from 6.1 ± 6.4% to 5.0 ± 4.2% (p = 0.69). In conclusion, BOLD-MRI reveals changes of the key parameters T2*_max, TTP, and EV after successful PTA of the calf muscles during reactive hyperaemia.