Evaluation of coronary atheroma by 64-slice multidetector computed tomography: Comparison with intravascular ultrasound and angiography.

BACKGROUND: Recent improvements in multidetector computed tomography (MDCT) with 64-slice scanners have allowed acquisition of a coronary study in 5 s to 6 s, with good temporal and spatial resolution. Previous studies have reported an underestimation of plaque burden by MDCT. Whether shorter scan times can allow correct assessment of plaque volume requires comparison with intravascular ultrasound (IVUS). METHODS: Patients (n=30) scheduled for coronary angiography also underwent MDCT and IVUS examinations within 96 h. MDCT examination was performed with a 64-slice scanner. Nitroglycerin was administered before all imaging procedures. MDCT, quantitative coronary angiography (QCA) and IVUS analyses were performed by observers blinded to other results. Plaque volumes were determined by MDCT and IVUS in one vessel, and maximum percentage diameter stenosis was identified in each coronary segment by MDCT and QCA. RESULTS: The mean (+ or - SD) plaque volume was determined to be 179.1 + or - 78.9 mm(3) by MDCT and 176.1 + or - 87.9 mm(3) by IVUS. There was a strong positive correlation for plaque volume between MDCT and IVUS (r=0.84, P<0.0001). Percentage diameter stenosis assessed by MDCT and QCA also correlated well (r=0.88 per patient and r=0.87 per vessel, P<0.0001 for both). The maximum percentage diameter stenosis per vessel was 38.1 + or - 30.2% with MDCT and 34.1 + or - 27.6% with QCA. The sensitivity and specificity of MDCT in detecting stenoses above 50% per vessel were 100% and 91.0%, respectively. CONCLUSIONS: Plaque volumes measured by 64-slice MDCT and IVUS correlate well, without systematic underestimation. The sensitivity and specificity of MDCT to detect stenoses greater than 50% by QCA are excellent with the administration of nitroglycerin before imaging.

Unilateral renal artery stenosis: perfusion patterns with electron-beam dynamic CT--preliminary experience.

Renal dynamic computed tomographic (CT) data for 16 patients with unilateral renal artery stenosis were compared with those for 12 control subjects. Three patterns of perfusion were distinguished in stenotic kidneys: pattern A, symmetric time-attenuation curves; pattern B, asymmetric time-attenuation curve with similar perfusion; and pattern C, asymmetric time-attenuation curve with impaired perfusion. Additional functional data can be obtained from the initial timing scan in a CT study of unilateral renal artery stenosis.

In vitro quantification of flow using continuous infusion of Levovist and pairs of harmonic power Doppler images.

To evaluate the potential of harmonic power Doppler to quantify perfusion using a continuous infusion of contrast, two dialysis cartridges were perfused with different flow rates adjusted between 0 to 300 mL/min, corresponding to flow ratios comprised between 300:0 and 150:150. The contrast agent (Levovist, Schering) was injected at constant rates (0.6 to 5 g/h). Sequential pairs of images showing simultaneously the cross-sections of the two filters were acquired with a HDI 5000 (ATL) and the Doppler data were processed with HDI lab software (ATL). The absolute values of the signal in the different regions-of-interest (ROI) were not closely related to flow rate. At the opposite, the rapid signal decrease between the first and the second image of each pair was inversely proportional to the flow rate. An index of perfusion [PerI = image 1/(image 1 -- image 2)] was defined. It correlated closely with the absolute and relative flow rates. For the latter, the slopes of regression were found to be independent of the infusion rate of Levovist. Thus, the use of pairs of images combined with a continuous infusion of Levovist provide a quantification of perfusion.

Obstruction of left ventricular outflow tract by vegetation and periaortic abscess.

Echocardiography is the modality of choice for the noninvasive recognition of vegetations and abscesses that complicate endocarditis. Vegetation size is highly variable, and it has been suggested that large vegetations are related to a more complicated course. The case we present is unusual in that the echocardiographically detected vegetation was very large, highly mobile, and caused severe obstruction of the left ventricular outflow tract, which led to impaction and cardiac arrest.

Infectious pseudoaneurysms suspected at echocardiography: electron-beam CT findings.

PURPOSE: To review the electron-beam computed tomographic (CT) findings in patients with clinical endocarditis and suspected of having perivalvular pseudoaneurysms at echocardiography and to compare these findings with echocardiographic data. MATERIALS AND METHODS: Data on 17 patients who underwent electron-beam CT for suspicion of perivalvular infectious pseudoaneurysm at echocardiography were retrospectively reviewed. Thirteen patients had a history of valvular surgery. Electron-beam CT findings-lesion size, number, extent, and relationships with surrounding structures, and associated lesions-were compared with echocardiographic and surgical and/or autopsy data. RESULTS: In all patients, electron-beam CT depicted one or more abnormal cavities that filled with contrast material after bolus injection. The mean size (3.5 cm) and number (n = 21) of pseudoaneurysms recorded with electron-beam CT were greater than those recorded with echocardiography (2.9 cm and n = 13, respectively). Associated electron-beam CT findings included valvular vegetations in three patients; mediastinitis in two; and coronary arterial involvement in six. In eight (47%) patients, electron-beam CT depicted a pseudoaneurysm or an additional pseudoaneurysm that was only suspected-not depicted-at echocardiography. Transthoracic and transesophageal echocardiography resulted in underestimation of lesion number, size, and extent and associated lesions, particularly in patients with valvular prostheses or voluminous lesions. CONCLUSION: Thoracic infectious pseudoaneurysms are well depicted with electron-beam CT, which may be a useful addition to echocardiography for detection of this disease and thus help in preoperative planning.

In vitro flow quantification with contrast power Doppler imaging.

To evaluate the effectiveness of contrast harmonic (power Doppler imaging) as an ultrasonic modality to quantify flow, an in vitro model of perfusion was studied using Optison, a second-generation ultrasound (US) contrast agent. The in vitro model was made of two dialysis cartridges placed parallel and allowed absolute and relative flow quantification on both tube (entry lines) and tissue (cartridges) simulations. Video intensity curves were generated using intermittent harmonic power Doppler imaging after bolus injection of contrast. Correlation between flow and different parameters extracted from time-intensity curves and previously defined as indicators of flow was established for both tissue and entry lines, for flow rates ranging from 0 to 400 mL/min. Single-compartment equations were also tested on the model. A good correlation for the tissue model was observed between absolute flow and onset time (O), time to maximal enhancement (TME), peak intensity (P), area under the curve (AUC), and maximal ascending slope (S) parameters, with a r = 0.94, 0.94, 0.91, 0.92 and 0.92, respectively. The correlation for O, TME, P and AUC parameters was r = 0.86, 0.90, 0.78 and 0.82, respectively for entry lines. The correlation for tissue model and entry line was slightly improved when comparing flow ratios with peak ratios (P1/P2) and slope ratios (S1/S2) (r = 0.95 and 0.94). Flow calculation using the gradient-relationship method also showed a good correlation (r = 0.88) with the experimental flow. The results obtained indicated that absolute and relative quantification of flow using PDI is feasible in tube and tissue models. Several clinical applications, namely in myocardial, hepatic and renal artery studies, could be derived from these results.

Idiopathic dilatation of the pulmonary artery: report of four cases.

Idiopathic dilatation of the pulmonary artery (IDPA) is a rare congenital disease which is usually detected fortuitously on chest x-ray, thus radiologists must be aware of this clinical entity. This report describes four cases to which Magnetic Resonance Imaging (MRI) played a major role in diagnosing IDPA and in detecting the concomitant findings observed in this disease. MRI is a non-invasive procedure with many advantages for the accurate and reproducible measurement of artery structures, which makes it the preferred option for combined use with echocardiography in the diagnosis and follow-up of patients with IDPA.

Transesophageal echocardiographic evaluation of perioperative coronary sinus trauma.

Retrograde cardioplegia is relatively safe, with a rate of coronary sinus rupture of 0.6%. With the advent of perioperative transesophageal echocardiography, it is now possible to detect and evaluate the extent of damage consequent to the use of retrograde cardioplegia and better formulate an intraoperative course of action. The evolution of these lesions can also be monitored by transesophageal echocardiography during the postoperative period.

Level of suspicion of a mammographic lesion: use of features defined by BI-RADS lexicon and correlation with large-core breast biopsy.

OBJECTIVE: To determine whether the categories defined in the Breast Imaging Reporting and Data System (BI-RADS) are useful predictors of malignancy and to assess their positive predictive value. PATIENTS AND METHODS: A retrospective study was undertaken from July 1, 1994, to June 30, 1995. Of 568 abnormal mammograms for which largecore biopsy was recommended, 495 were available for review. The mammographic features of the lesions, as defined by the BI-RADS lexicon, were used to assess the level of suspicion. The lesions were classified as "probably benign," "suspicious" or "highly suggestive of malignancy." These diagnostic impressions were then correlated with the histologic diagnosis made after core biopsy. RESULTS: The diagnostic impressions before core biopsy were as followed: 16 (3%) benign lesions, 397 (80%) suspicious lesions and 82 (17%) lesions highly suggestive of malignancy. All benign lesions remained in the same category after core biopsy, whereas, of the suspicious lesions, 91% were diagnosed as benign, only 4% as malignant, and the other 5% as atypical hyperplasia. Among the lesions highly suggestive of malignancy according to the BI-RADS lexicon, 54% were found to be malignant at core biopsy. CONCLUSION: The BI-RADS lexicon is helpful in discriminating between lesions that are probably benign and probably malignant from the mammographic features. However, the rate of malignancy in the "suspicious" category is low.