Coronary plaque burden in patients with stable and unstable coronary artery disease using multislice CT coronary angiography

PURPOSE

We evaluated the multislice computed tomography (MSCT) coronary plaque burden in patients with stable and unstable angina pectoris.

MATERIALS AND METHODS

Twenty-one patients with stable and 20 with unstable angina pectoris scheduled for conventional coronary angiography (CCA) underwent MSCT-CA using a 64-slice scanner offering a fast rotation time (330 ms) and higher X-ray tube output (900 mAs). To determine the MSCT coronary plaque burden, we assessed the extent (number of diseased segments), size (small or large), type (calcific, noncalcific, mixed) of plaque, its anatomic distribution and angiographic appearance in all available ≥2-mm segments. In a subset of 15 (seven stable, eight unstable) patients, the detection and classification of coronary plaques by MSCT was verified by intracoronary ultrasound (ICUS).

RESULTS

Sensitivity and specificity of MSCT compared with ICUS to detect significant plaques (defined as ≥1-mm plaque thickness on ICUS) was 83% and 87%. Overall, 473 segments were examined, resulting in 11.6±1.5 segments per patient. Plaques were present in 62% of segments and classified as large in 47% of diseased segments. Thirty-two percent were noncalcific, 25% calcific and 43% mixed. Plaques were most frequently located in the proximal and mid segments. Plaque was found in 33% of segments classified as normal on CCA. Unstable patients had significantly more noncalcific plaques when compared with stable patients (45% vs. 21%, p<0.05).

CONCLUSIONS

MSCT-CA provides important information regarding the coronary plaque burden in patients with stable and unstable angina.

Impact of tube current in the quantitative assessment of acute reperfused myocardial infarction with 64-slice delayed-enhancement CT: a porcine model

PURPOSE

This study evaluated the impact of tube current (mAs) in delayed-enhancement computed tomography (CT) imaging for assessing acute reperfused myocardial infarction in a porcine model.

MATERIALS AND METHODS

In five domestic pigs (mean weight 24 kg), the circumflex coronary artery was balloon-occluded for 2 h and then reperfused. After 5 days, CT imaging was performed following administration of iodinated contrast material. A 64-slice CT system was used to perform first-pass coronary angiography with a tube current of 15 mAs/kg [Arterial Phase (ART)] followed by two delayed-enhancement (DE) scans 15 min after contrast material administration, with a tube current of 15 mAs/kg and 37.5 mAs/kg, respectively (DE(1) and DE(2)). The mean heart rate decreased to 51±9 beats/min after administration of zatebradine (10 mg/kg IV). The data set was reconstructed during the end-diastolic phase of the cardiac cycle. Areas with DE, no reflow and remote myocardium [remote left ventricular (LV)] were calculated. CT values expressed in Hounsfield units (HU) were measured using five regions of interest (ROI): DE, no reflow, remote LV, LV cavity (LV lumen) and in air, respectively. Differences, correlations, image quality [signal-to-noise ratio (SNR)] and contrast resolution [contrast-to-noise ratio (CNR)] were calculated.

RESULTS

Significant differences were found between attenuation of areas of DE, no reflow and remote LV (p<0.001) within the different scans. There was a fair correlation between DE and no-reflow attenuation (r=0.6; p<0.001). In DE(1) vs. DE(2), areas of DE and no reflow were not significantly different (p>0.05). The SNR and CNR were not significantly different in DE(1) vs. DE(2) (p>0.05).

CONCLUSIONS

Tube current does not significantly affect infarction area, image quality or contrast resolution of DE imaging with CT.

Impact of contrast material volume on quantitative assessment of reperfused acute myocardial infarction using delayed-enhancement 64-slice CT: experience in a porcine model

PURPOSE

Our purpose in this study was to compare the impact of contrast material volume in delayed-enhancement computer tomography (CT) imaging for assessing acute reperfused myocardial infarction.

MATERIALS AND METHODS

In five domestic pigs (20-30 kg), the circumflex coronary artery (CX) was balloon-occluded for 2 h followed by reperfusion. After 5 days, CT imaging was performed after intravenous administration of iodinated contrast material (Iomeprol 400 mgI/ml; Bracco, Italy). A 64-slice multidetector CT (MDCT) (Sensation 64, Siemens) scanner was used for imaging, with standard angiography characteristics. Three scans were performed: first, coronary angiography at first pass with 1.25 gI/kg of contrast material (ART); and remaining delayed-enhancement (DE(1)-DE(2)) 15 min after administration of 1.25 (DE(1)) and 15 min after additional administration of 2.50 gI/kg (=total 3.75 gI/kg - DE(2)). Mean heart rate decreased to 51+/-9 bpm after intravenous administration of Zatebradine (10 mg/kg). Data sets were reconstructed during the end-diastolic phase of the cardiac cycle. Areas of infarction-enhanced (DE), no-reflow (no-reflow) and remote myocardial [remote left ventricle (LV)] were manually contoured. CT attenuation values (Hounsfield units) were measured using five regions of interest: DE, no-reflow, remote LV, left ventricular cavity (lumen LV) and in air. Differences, correlations, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated.

RESULTS

We found significant differences between the attenuation of DE, no-reflow and remote LV (p<0.001). DE and no-reflow size were assessed accurately with DEMDCT. In particular, SNR and CNR showed higher values in DE(2) (approximately 6.0 and 3.5, respectively; r(2)=0.90) vs. DE(1) (approximately 4.0 and 2.2, respectively; r(2)=0.85).

CONCLUSIONS

The increase of contrast material volume determines a significant improvement in myocardial infarction image quality with DE-MDCT.

Dose reduction in spiral CT coronary angiography with dual-source equipment. Part I. A phantom study applying different prospective tube current modulation algorithms

PURPOSE

The authors sought to compare different algorithms for dose reduction in retrospectively echocardiographically (ECG)-gated dual-source computed tomography (CT) coronary angiography (DSCT-CA) in a phantom model.

MATERIALS AND METHODS

Weighted CT dose index (CTDI) was measured by using an anthropomorphic phantom in spiral cardiac mode (retrospective ECG gating) at five pitch values adapted with two heart-rate-adaptive ECG pulsing windows using four algorithms: narrow pulsing window, with tube current reduction to 20% (A) and 4% (B) of peak current outside the pulsing window; wide pulsing window, with tube current reduction to 20% (C) and 4% (D). Each algorithm was applied at different heart rates (45, 60, 75, 90, 120 bpm).

RESULTS

Mean CTDI volume (CTDIvol) was 36.9+/-9.7 mGy, 23.9+/-5.6 mGy, 49.7+/-16.2 mGy and 38.5+/-12.3 mGy for A, B, C and D, respectively. Consistent dose reduction was observed with protocols applying the 4% tube current reduction (B and D). Using the conversion coefficient for the chest, the mean effective dose was the highest for C (9.6 mSv) and the lowest for B (4.6 mSv). Heart-ratedependent pitch values (pitch=0.2, 0.26, 0.34, 0.43, 0.5) and the use of heart-rate-adaptive ECG pulsing windows provided a significant decrease in the CTDIvol with progressively higher heart rates (45, 60, 75, 90, 120 bpm), despite using wider pulsing windows.

CONCLUSIONS

Radiation exposure with DSCT-CA using a narrow pulsing window significantly decreases when compared with a wider pulsing window. When using a protocol with reduced tube current to 4%, the radiation dose is significantly lower.

[Colonoscopic endosonography in the diagnosis and follow-up care of colorectal tumors]

We studied the usefulness and accuracy of a flexible endoscopic ultrasound system (EUS) in preoperative staging of tumor invasion and involvement of lymph nodes of rectal tumors. Comparison of preoperative EUS findings with histopathologic TNM classification (UICC 1987) was possible in 12 patients. The depth of tumor invasion was correctly staged in 9/12 patients (75%), and lymph node staging was correctly predicted in 9/12 patients (75%). Our results indicate that flexible coloscopic ultrasonography is as accurate as rigid systems for staging of colorectal cancer. It will become a sensitive method for early diagnosis of local recurrence. The flexible endoscopes are well tolerated by patients and more proximal lesions which cannot be reached with the rigid instruments can also be examined.

[Endosonography: progress in the diagnosis of endocrine pancreatic tumors]

Diagnostic procedures for secreting endocrine pancreatic tumors comprise biochemical tests, CT scans, conventional abdominal sonography, angiography and occasionally MR imaging and isotope scans. Due to their small size, insulinomas and gastrinomas, the most common of these tumors, elude these diagnostic procedures. Preoperative sonography and CT scans were negative in over 60%, angiograms in 35% of the patients. The example of a patient with insulinoma demonstrates that in the future endosonography will offer itself as an accurate method with little risk.

Renal tolerance of gadolinium-DTPA/dimeglumine in patients with chronic renal failure

Safety data for renal tolerance of gadolinium-DTPA(Gd-DTPA)/dimeglumine were evaluated in 21 patients (age: mean +/- standard deviation [SD], 58 +/- 12 years) with impaired renal function. The mean +/- SD serum creatinine level at baseline was 213 +/- 101 mumol/L (range, 89.2-551 mumol/L). Creatinine clearance at baseline averaged 34.5 +/- 19.2 mL/minute (range, 7.2-70 mL/minute). Gd-DTPA was injected at a dose of 0.1 mmol/kg body weight. Serum parameters (creatinine, sodium, and potassium) were determined before and 6, 24, 48, and 120 hours after administration of Gd-DTPA. Urinary parameters (N-acetyl-beta-D-glucosaminidase [beta-NAG], protein, and albumin) were determined before (spot urine sample) and after treatment for collection periods 0 to 3, 3 to 6, 6 to 12, 12 to 24, and 24 to 48 hours. A final spot urine sample was taken at 120 hours. There was no significant statistical change of serum creatinine level within the observation period, and there was no single patient matching the criteria of acute renal failure (increase of serum creatinine level of 88.4 mumol/L [1 mg/dL] or more within 48 hours after injection). Serum values of sodium and potassium levels remained unchanged. Beta-NAG was slightly increased 0 to 3 hours after injection, but returned to baseline values during the collection periods up to 120 hours. There was no increase of protein or albumin excretion. These preliminary results suggest Gd-DTPA has good renal tolerance in patients with pre-existing chronic renal failure.

Pharmacokinetics of Gd-DTPA in patients with chronic renal failure

We investigated the pharmacokinetics of dimeglumine gadopentetate (Gd-DTPA), a contrast agent for magnetic resonance imaging (MRI), in 24 patients with chronic renal failure whose creatinine clearance ranged from 7.2 to 70.0 mL/minute (median 25.4 mL/minute). After single intravenous administration of 0.1 mmol/kg, the serum levels of Gd-DTPA were monitored up to five days and urine and feces were collected quantitatively up to two days. The pharmacokinetic parameters were calculated from the concentration-time profile in the serum and urine using an open two-compartment model. No changes in the volume of distribution (Vc and Varea) or in the half-life of distribution were found for patients with chronic renal failure as compared to patients with normal renal function. However, in correlation with the reduced glomerular filtration rate in patients with chronic renal failure, the half-life of elimination was prolonged and serum and renal clearance were decreased. The recovery of Gd-DTPA in urine was 92.1% +/- 12.1% of the dose administered, and extrarenal elimination was less than 0.4%, indicating that glomerular filtration remains the predominant route of elimination. Only for patients with highly impaired renal function (creatinine clearance less than 20 mL/minute) was the recovery in the urine less than complete.

Semiautomated ROI analysis in dynamic MR studies. Part II: Application to renal function examination

Fast MR techniques and the application of water-soluble contrast agents allow the simultaneous examination of renal morphology and the functional aspects of glomerular filtration using bolus injections of Gd-DTPA. Spatial resolution is sufficient to resolve individual renal pyramids, but the quantitative examination of regions of interest (ROIs) is severely impeded by organ movements due to variations of the end-inspiratory position. A new image-processing scheme has been used and tested in 23 normal volunteers and patients. This scheme replaces a tedious frame-by-frame ROI analysis by positional correction of renal regions of all frames of the sequence such that the definition of the regions has to be performed only once. The signal intensities (SIs) of the local regions in each frame are used to compute statistics and to generate curves representing local temporal SI changes due to contrast agent excretion. The success rate of the procedure depends largely on the image quality and on the adherence to a proved acquisition protocol. The present article shows that the combination of MR and robust and reliable image-processing methods can be important for the highly automated analysis of a large number of images acquired as dynamic studies.

[MR of the shoulder joint with surface coils at 1.5 tesla. Its anatomy and possible clinical use]

High spatial resolution magnetic resonance images of the shoulder were obtained in axial, sagittal and coronal orientations using a 1.5 T imaging system and anatomically shaped, wrap-around surface coils. Variations in scapular position induced by patient positioning change the relationship of the planes to the shoulder anatomy and make reproducibility of sagittal and coronal planes difficult. We, therefore, use--after axial orientation--image-oblique planes perpendicular and parallel to the glenoid fossa. In this manner MRI can visualise the anatomic structures of the shoulder including rotator cuff, long biceps tendon, articular capsule, articular cartilage, muscles and bones due to the high soft tissue contrast of MRI.