Spiral CT evaluation of coronary artery bypass graft patency

Multislice CT Evaluation of Coronary Artery Bypass Graft Patients

Continuous improvement in multislice computed tomography technology has further enabled advances in coronary artery bypass graft imaging. Multidetector platforms and retrospective electrocardiography gating have enabled sensitivities and specificities in the 95% to 99% range while avoiding the morbidity associated with invasive catheter angiography. Identification of bypass graft stenoses and bypass graft aneurysms/pseudoaneurysms is important in evaluation of these patients. Recognition of coronary artery bypass graft anatomy is particularly important to minimize the complications associated with reoperative cardiac surgery. The 3-dimensional demonstration of chest wall anatomy and its relationships to these coronary bypass grafts makes multislice computed tomography a superior technology in this patient population. Confident evaluation and assessment of the patient after coronary artery bypass graft surgery will become an increasingly important tool to the practicing radiologist.

Usefulness of 4-, 8-, and 16-slice computed tomography for detection of graft occlusion or patency after coronary artery bypass grafting

The sensitivity and specificity of computed tomographic angiography for the evaluation of coronary artery bypass grafts (CABGs) was reviewed. A search of published studies in all languages was performed, incorporating electronic and manual components. A total of 985 patients with 2,200 CABGs participated in investigations with single-detector computed tomography (CT), 441 patients (1,246 CABGs) with 4-slice CT, none with 8-slice CT, and 144 patients (416 grafts) with 16-slice CT. Pooled data showed a sensitivity for the detection of complete occlusion with single-slice CT of 81% (402 of 494 patients), with 4-slice CT of 93% (293 of 315 patients), and with 16-slice CT of 99% (75 of 76 patients). The specificity, based on pooled data, using single-slice CT was 89% (1,507 of 1,697 patients), with 4-slice CT was 96% (878 of 915 patients), and with 16-slice CT was 98% (301 of 306 patients). The detection of complete occlusion and the detection of patency in saphenous vein bypass grafts and arterial bypass grafts were similar with multislice CT. Limited data were available on the detection of significant stenosis, exclusive of complete occlusion. With 4-slice CT, the sensitivity was 74% (23 of 31 patients) and was 88% (21 of 24 patients) with 16-slice CT. In conclusion, single-detector CT was able to detect graft patency, but it was not sensitive for graft occlusion. The data suggest that 4- and 16-slice CT can be used for the detection of complete graft occlusion or graft patency of CABGs. Significant stenosis was better assessed with 16-slice CT than with 4-slice CT.

Advances in cardiovascular CT imaging: CT clinical imaging

Recent advances in cardiovascular CT imaging have dramatically changed the way we evaluate cardiac and great vessel disease. The superb spatial and faster temporal resolutions of the newer scanners, have allowed CT to gain acceptance not only in defining cardiac and great vessel anatomy but also has allowed its entry into the field of functional and perfusion imaging. This paper reviews the current status of CT in clinical imaging of the heart and great vessels.

Gadolinium-enhanced MDCT angiography of the abdomen: feasibility and limitations

OBJECTIVE

The purpose of this study was to evaluate a protocol for gadolinium-enhanced MDCT angiography of the abdomen and to identify technical parameters that optimize image quality.

CONCLUSION

The degree of enhancement and image quality achieved using this gadolinium-enhanced MDCT angiography appear adequate for angiographic evaluation of the abdominal aorta and its major branches.

CT for imaging coronary artery disease: defining the paradigm for its application

Current generation multidetector-row CT (MDCT) enables high-resolution, motion-free imaging of the heart within a single, short breath-hold. MDCT allows highly accurate and reproducible quantification of coronary artery calcium, a marker that has been used for the detection, exclusion and monitoring of coronary atherosclerosis. The exact role of coronary calcium measurements for cardiac risk stratification remains unclear to date. At contrast enhanced MDCT coronary angiography coronary arteries can be visualized with unprecedented detail. The accurate non-invasive assessment of the presence and degree of coronary artery stenosis appears within reach. With increasing accuracy MDCT enables non-invasive patency evaluation of coronary artery bypass grafts and coronary stents. The cross-sectional nature of contrast enhanced MDCT coronary angiography allows assessment of the vessel wall and may permit more accurate quantification of total atherosclerotic plaque burden than measuring calcified components alone. For a limited time, future technical improvement will be pursued mainly by accelerated gantry rotation speed and additional detector rows. However, novel concepts of CT image acquisition are already under investigation and may bring about yet another quantum leap for medical CT. This communication discusses potential approaches for the beneficial utilization of MDCT for the assessment of patients with known or suspected coronary heart disease.

CT of coronary artery disease

The socioeconomic importance of heart disease provides considerable motivation for development of radiologic tools for noninvasive imaging of the coronary arteries. Current computed tomographic (CT) techniques combine high speed and spatial resolution with sophisticated electrocardiographic synchronization and robustness of use. Application of these modalities for evaluation of coronary artery disease is a topic of active current research. Coronary artery calcium measurements with different CT techniques have been used for determining the risk of coronary events, but the exact role of this marker for cardiac risk stratification remains unclear pending results of population-based studies. Contrast material-enhanced CT coronary angiography has become an established clinical indication for some scenarios (eg, coronary artery anomalies, bypass patency, surgical planning). With current technology, the accuracy of CT coronary angiography for detection of coronary artery stenoses appears promising enough to warrant pursuit of this application, but sensitivity is still not high enough for routine diagnostic needs. The high negative predictive value of a normal CT coronary angiogram, however, may be useful for reliable exclusion of coronary artery stenosis. The cross-sectional nature of CT may allow noninvasive assessment of the coronary artery wall. Use of contrast-enhanced CT coronary angiography for detection, characterization, and quantification of atherosclerotic changes and total disease burden in coronary arteries as a potential tool for cardiac risk stratification is currently being investigated.

Evaluation of Patients after Coronary Artery Bypass Surgery: CT Angiographic Assessment of Grafts and Coronary Arteries

PURPOSE

To evaluate the accuracy of electrocardiography (ECG)-gated multi-detector row computed tomography (CT) in enabling the detection of obstruction of both bypass grafts and coronary arteries in symptomatic patients who have undergone coronary artery bypass grafting.

MATERIALS AND METHODS

ECG-gated contrast material-enhanced multi-detector row CT angiography was performed in 24 patients after bypass surgery. Two independent blinded observers evaluated all graft and coronary segments (> or =2.0-mm diameter) for occlusion and stenosis (50%-99% luminal reduction). Conventional angiography was regarded as the standard of reference. Descriptive parameters were calculated, and the results for arterial grafts, venous grafts, and coronary arteries, as well as for high and low heart rates, were compared by using a two-sided Fisher exact test.

RESULTS

The following results were obtained by observers 1 and 2, respectively: Of the 60 venous graft segments, 60 (100%) and 57 (95.0%) were assessable, with an overall detection of all 17 occlusions (both observers) and three (50.0%) and five (83.3%) of six stenoses. Of 26 arterial graft segments, 19 (73.1%) and 15 (57.7%) were assessable. In the assessable segments, four of four (100%) and two of three (66.7%) stenoses and occlusions were detected, while one and two obstructions were located in nonassessable segments. Of 211 coronary segments, 146 (69.2%) and 140 (66.4%) were assessable, and detection of 50%-100% obstruction yielded a sensitivity of 89.9% (71 of 79) and 79.4% (54 of 68) and a specificity of 74.6% (50 of 67) and 72.2% (52 of 72) for each observer. Unlike the assessment of venous and arterial grafts, assessment of the coronary arteries with multi-detector row CT was significantly better in patients with low heart rates (P <.01).

CONCLUSION

Multi-detector row CT allows noninvasive angiographic evaluation of both coronary arteries and bypass grafts in patients who have undergone bypass surgery. Multi-detector row CT is more effective in examining venous grafts compared with arterial grafts and diffusely diseased coronary arteries.

Cardiac computed tomography imaging: a history and some future possibilities

Cardiac computed tomography (CT) is a special subset of CT, a subject about which much has been written in terms of the underlying concepts and mathematics and the sociologic impact. Cardiac CT has passed through three, chronologically overlapping, developmental stages and is now in its fourth stage of development. The first stage was fluoroscopy-based CT (1972-1995) stimulated by physiologic research needs, and the next was clinical CT-based exploration (1975-1980) of the potential of clinical CT in cardiology. This was followed by the electron beam CT-based stage (1980-present), which was the first CT approach applicable to clinical cardiology. Finally, volume-scanning CT imaging methods achieved with multislice scanning approaches of helical CT and by flat panel-based CT (1990-present), show great promise for clinically applicable CT of the cardiovascular system.

Coronary artery bypass graft flow: qualitative evaluation with cine single-detector row CT and comparison with findings at angiography

A four-point ordinal-scale qualitative flow index was used for assessment of patency of 75 coronary artery bypass grafts in 26 patients examined with spiral computed tomography (CT). CT findings were compared with selective graft angiographic findings. Of 54 open grafts, 52 were patent at initial selective graft angiography and 50 were patent at spiral CT; accuracy rates were 97% (73 of 75) and 95% (71 of 75), respectively. Spiral CT flow index agreed with angiographically determined flow in 85% (95% CI: 0.77, 0.93) of grafts. The kappa statistic demonstrated very good to excellent intermodality (0.75) and interobserver (0.89) agreement. Spiral CT may be a feasible means of assessing quality of flow in bypass grafts.

Noninvasive coronary angiography by retrospectively ECG-gated multislice spiral CT

BACKGROUND

We investigated the applicability and image quality of contrast-enhanced coronary artery visualization by multislice spiral CT using retrospective ECG gating.

METHODS AND RESULTS

Twenty-five patients in sinus rhythm (significant coronary artery stenoses ruled out by invasive angiography) were studied with a multislice spiral CT (Siemens SOMATOM Volume Zoom). In inspiration (mean breath-hold, 37 seconds), a volume data set of the heart was acquired (intravenous contrast agent; 4 x 1-mm slice thickness; 500-ms rotation; table feed, 1.5 mm/360 degrees ). Simultaneous recording of the ECG permitted retrospective reconstruction of contiguous cross sections in intervals of 1 mm at any desired interval of the cardiac cycle. The mean duration of the image reconstruction window was 185 ms. Next to 3-dimensional reconstructions of the heart and coronary arteries, multiplanar reconstructions were rendered to determine the visualized length of the coronary arteries, the contrast-to-noise ratio, and the correlation of coronary artery diameters to quantitative coronary angiography.

CONCLUSIONS

The coronary arteries could be visualized over long segments (left main, 9+/-4 mm; left anterior descending, 112+/-34 mm; left circumflex, 80+/-29 mm; right coronary artery, 116+/-33 mm). On average, 78+/-16% of these distances were visualized free of motion artifacts. The mean contrast-to-noise ratio was 9.3+/-3.3. Coronary artery diameters in multislice spiral CT showed close correlation to quantitative coronary angiography (CT, 3.3+/-1.0 mm; angiography, 3. 2+/-0.9 mm; mean difference, 0.38 mm; r=0.86). Contrast-enhanced multislice spiral CT permits visualization of the coronary artery lumen. Further studies are necessary to determine whether image quality is sufficient to reliably detect coronary artery stenoses.

Non-invasive coronary bypass graft imaging after multivessel revascularisation

Non-invasive imaging techniques for the detection of graft patency after multivessel coronary revascularisation may be useful for follow-up after surgery. Forty consecutive asymptomatic patients (38 men, age 59.9+/-1.3 years) who had undergone coronary bypass surgery with at least three grafts were examined by spiral computed tomography or magnetic resonance angiography 24.9+/-0.3 months after surgery, using conventional angiography as reference. In total, 133 grafts (37 internal mammary artery, 96 venous grafts) were analysed. Spiral computed tomography studies were performed with a subsecond scanner; for magnetic resonance angiography, a three-dimensional contrast-enhanced gradient echo technique with ultrashort echo time during breath holding was used. For spiral computed tomography, sensitivities were 76% (internal mammary artery) and 100% (venous graft). This was compared with 100% (internal mammary artery) and 92% (venous graft) assessed by magnetic resonance angiography (P=ns). The positive predictive values were 100% for internal mammary artery and venous graft (spiral computed tomography) and 100% (internal mammary artery), 92% for venous grafts studied by magnetic resonance angiography (P=ns). Both subsecond spiral computed tomography and contrast-enhanced magnetic resonance angiography are highly accurate and relatively non-invasive approaches of assessing coronary graft patency after multivessel revascularisation and have potential for follow-up assessment in the long term.

CT and arteriography in the evaluation of indirect myocardial revascularization with a free-muscle transplant: initial experience

PURPOSE

To examine patients with advanced cardiovascular disease with radiology after indirect myocardial revascularization with a free-skeletal-muscle transplant and to determine whether the attached vessel remains patent over the middle and long terms.

MATERIALS AND METHODS

In 10 patients with advanced, inoperable cardiovascular disease treated with indirect myocardial revascularization with a free-muscle transplant, radiologic follow-up was performed postoperatively and every 6 months. All 10 patients underwent selective arteriography of the anastomosed vessel and contrast material-enhanced helical computed tomography (CT) (transverse sections and reconstructions).

RESULTS

All patients showed adequate vascular conditions postoperatively, as did nine of 10 patients after 1 year. In one patient, the anastomosed artery was occluded. CT showed time-dependent muscle degeneration in all patients. Postoperative, contrast-enhanced, superselective CT showed an area of high-attenuating uptake in the muscle transplant in all patients. After 1 year, CT depicted perfusion defects of the skeletal muscle in two patients. In eight patients, however, small vascular bridges from the skeletal muscle to the myocardium were detected. Radiologic results correlated well with clinical outcome and stress electrocardiograms.

CONCLUSION

Helical intraarterial CT and arteriography were sensitive in depicting enhancement and remaining vital function in nine of 10 patients after indirect myocardial revascularization with a free-muscle transplant. This combination seems promising for postoperative examination in such patients.

Value of navigator echo magnetic resonance angiography in detecting occlusion/patency of arterial and venous, single and sequential coronary bypass grafts

Aim of our work was to validate magnetic resonance angiography (MRA) in detecting occlusion/patency of coronary artery bypass grafts. Twenty patients with previous history of bypass surgery and recurrent episodes of chest pain were enrolled. Two patients could not be studied (claustrophobia, erratic breathing). Thus, 18 patients with 51 bypasses were examined using a navigator echo sequence: 21 arterial grafts (six sequential) and 30 saphenous vein grafts (five sequential). All patients had undergone contrast conventional angiography 3-15 days before MRA. The magnetic resonance (MR) data set was analyzed by two independent readers blinded to the results of conventional angiography (occlusion of 12 of 51 grafts). At magnetic resonance, two bypasses of the posterior descending artery, patent at conventional angiography, could not be visualized because of imaging slab malpositioning. Interobserver concordance was 96% (47/49). Magnetic resonance and conventional angiography provided identical answers in 47 out of 49 (96%) of the examined grafts. Eleven out of 12 occluded grafts and 36 out of 37 patent grafts were correctly identified with MR. As far as occlusion is concerned, the sensitivity of MR was 91%, the specificity 97%. To summarize, a 30 min outpatient MR examination is highly reliable in determining occlusion/patency of arterial and venous, single and sequential bypasses.

Diagnosis of saphenous coronary graft aneurysm by spiral computed tomography

We report two cases of coronary saphenous vein graft aneurysms diagnosed by spiral computed tomography.

Morphologic and functional evaluation of coronary artery bypass conduits

There is clear evidence in the literature that conventional spin-echo and gradient-echo magnetic resonance imaging (MRI) is capable of assessing patency of coronary artery vein grafts. With more recently introduced breath-hold two-dimensional (2D) and contrast-enhanced 3D techniques, the predictive accuracy has further improved, with sensitivities and specificities in the 90% range. Limitations arise with regard to assessing obstructive disease and evaluating distal segments of sequential grafts, due to insufficient spatial resolution, low signal-to-noise ratio, and cardiac motion. Imaging of arterial grafts is complicated by the metallic clip artifacts. Adding information on graft flow patterns and flow reserve using velocity-encoded cine MRI may help to reduce some of the problems. Clinically, these functional measurements may become of use in non-invasive monitoring of gradually increasing graft narrowing. However, apart from a few exceptions, most patients undergo evaluation of their grafts because they are considered for a re-intervention by angioplasty or coronary artery bypass graft surgery. In these cases information on the status of the native coronary arteries is required. A broader clinical use of MRI in the evaluation of patients with coronary artery bypass grafts may therefore only be expected with further improvement in MR techniques for coronary angiography. J. Magn. Reson. Imaging 1999;10:734-740.

Electron-beam CT angiography with three-dimensional reconstruction in the evaluation of coronary artery bypass grafts

RATIONALE AND OBJECTIVES

The authors evaluated the use of electron-beam computed tomographic (CT) angiography and three-dimensional (3D) reconstruction for evaluation of coronary artery bypass grafts (CABGs).

MATERIALS AND METHODS

Sixty patients (53 men and seven women; mean age, 56 years +/- 8) with 152 CABGs (29 internal mammary artery and 123 saphenous vein grafts) underwent electron-beam CT with 3D reconstruction. The time from bypass surgery to CT scanning was 7 days to 120 months (mean, 17 months +/- 28). Enhanced single-section and flow mode studies were performed in all cases. The results were correlated with CABG operation records, and patency was determined with time-attenuation curves.

RESULTS

All patients were successfully examined. On the basis of time-attenuation curve criteria, 124 (81.6%) of 152 grafts were patent. The patency rate for the internal mammary artery subgroup was 93% (27 of 29 grafts); for the saphenous vein graft subgroup, 78.9% (97 of 123 grafts).

CONCLUSION

Used in contrast-enhanced, single-section mode and flow studies with time-attenuation curves, electron-beam CT angiography with 3D reconstruction can provide quantitative data for evaluation of CABG patency.

Spiral CT angiography of the renal arteries: should a scan delay based on a test bolus injection or a fixed scan delay be used to obtain maximum enhancement of the vessels?

PURPOSE

The purpose of this work was to assess the optimal scan delay for spiral CT angiography (SCTA) of the renal arteries in achieving optimal vascular contrast enhancement and to compare the utility of a delay based on these bolus injection versus that of a fixed scan delay.

METHOD

Seventy patients underwent renal artery SCTA with a 140 ml bolus of contrast agent injected a 3 ml/s. In 35 patients (Group A), a fixed scan delay of 27 s was used; in the other 35 (Group B), the scan delay was based on the transit time (TTest) of a test bolus injection. The scan delays in this group were set at TTest + 5 s (n = 5), TTest + 10 s (n = 8), TTest + 15 s (n = 4), or TTest + 20 s (n = 18). For all 70 patients, the time intervals between TRA (time to scanning the renal arteries) and TMax (time to maximum aortic enhancement after 140 ml bolus injection) were calculated, after which it was determined in which group of patients TRA occurred closest to TMax. Linear regression and mean squared error (MSE) were used for statistical analysis.

RESULTS

For Group A, mean TRA and TMax were 38 and 50 s, respectively. Mean (TRA - TMax) was -12 s with MSE of 185.76. For Group B, mean TRA and Tmax were 45 and 52 s. Mean (TRA - TMax) values were -15, -12, -11, and -1 s for scan delays of TTEST + 5 s, TTEST + 10 s, TTest + 15 s, and TTEST + 20 s, respectively, with MSEs of 253.80, 158.00, 137.50, and 30.00.

CONCLUSION

SCTA of the renal arteries was best performed with a scan delay of TTEST + 20 s. However, analysis of our data showed that similar results could be expected with a delay of 44 s.

Left main coronary artery patch angioplasty: midterm experience and follow-up with spiral computed tomography

BACKGROUND

Patch angioplasty is an alternative surgical technique in cases of left main coronary artery stenosis. We report our experience with this technique, with particular mention of the use of spiral computed tomography for the follow-up of our patients.

METHODS

In this retrospective study we analyzed the results obtained in all 7 patients (3 women and 4 men) who were operated on with this technique in our institution between July 1992 and August 1994. Five consenting patients also underwent graft patency assessment with spiral computed tomographic imaging.

RESULTS

The operation was uneventful in all patients and there were no hospital deaths. Two patients required reoperation (1 of them dying at reoperation), 1 because of restenosis of the graft and 1 because of the presence of a new stenosis in the proximal anterior descending coronary artery. The remaining 5 patients were asymptomatic after 51 +/- 2 months. Spiral computed tomographic images were artifacted and of poor quality.

CONCLUSIONS

Patch angioplasty of the left main coronary artery can be a valuable therapeutic method in selected cases. Conventional spiral computed tomography is not an optimal noninvasive method for the assessment of graft patency.

Accuracy of spiral computed tomography for identifying arterial and venous coronary graft patency

Late outcome after coronary artery bypass grafting (CABG) mainly depends on the status of graft patency. The recent generation of spiral computed tomography (SCT) scanners may have potential in the long-term follow-up of CABG. In this study, graft patency in patients with internal mammary (IMA) and venous CABG was investigated using SCT and angiography. Forty-nine consecutive patients (age 61 +/- 8 years, 45 men) who had undergone CABG were examined by SCT and angiography 22 +/- 6 months after CABG. In total, 134 bypass grafts (42 IMA and 92 venous grafts) were analyzed. The angiographically determined patency rate of grafts was 86% for IMA (n = 36 of 42) and 74% for venous grafts (n = 68 of 92). By SCT, 32 IMA and 64 venous grafts were diagnosed correctly as patent. Sensitivity was 89% (IMA) and 94% (venous); overall sensitivity was 92%. None of the truly occluded venous grafts was diagnosed falsely patent by SCT (specificity 100%), whereas the specificity of IMA graft visualization was somewhat lower (88%, p = NS [overall 97%]). The accuracy for a patent graft was 88% (IMA) and 96% (venous CABG, p = NS). Compared with previous studies, these data suggest that SCT using one of the recent generation scanners (single scan time 0.75 second) is a highly accurate and relatively noninvasive approach for assessing not only saphenous vein graft patency, but also IMA graft patency. To date, this technique has only limited use in visualizing graft stenosis or distal anastomosis site patency.

A practical approach to MRI of coronary artery bypass graft patency and flow

Direct visualization of coronary artery bypass grafts can be obtained non-invasively by magnetic resonance imaging. Several studies demonstrated a high sensitivity and somewhat lower specificity for detection of vein-graft patency, using the conventional spin-echo and gradient-echo techniques. In addition, the true functional status can be assessed by determining the flowrate within the graft using phase velocity mapping. Important limitations of the previously applied techniques include the inability to accurately evaluate the different segments of jump grafts and the presence of graft stenoses. Further improvement is to be expected from the recent introduction of breath-hold imaging sequences and the forthcoming introduction of bloodpool-avid contrast agents.

Noninvasive, three-dimensional visualization of coronary artery bypass grafts by electron beam tomography

Electron beam tomography (EBT, ultrafast computed tomography [CT], cine CT) combines unique temporal and high spatial resolution and is especially well suited for cardiac imaging. We established and evaluated a protocol for the noninvasive visualization and assessment of aortocoronary artery bypass grafts. Twenty-five patients with 56 bypass grafts were studied by EBT. Forty contiguous cross-sectional images were acquired triggered to the electrocardiogram during breathhold and intravenous injection of contrast agent. Three-dimensional reconstructions of the heart and bypass grafts were performed and compared with selective angiography of the bypass grafts. In 1 patient with 2 bypass grafts, a technically inadequate EBT examination was obtained. In the remaining patients (54 grafts), all 13 bypass occlusions were diagnosed with a sensitivity and specificity of 100%. Evaluation for hemodynamically relevant stenosis was possible in 84% of cases (36 of 43 patent grafts) and yielded a sensitivity of 100% (5 of 5 high-grade stenoses correctly detected) and specificity of 97% (1 false-positive diagnosis of high-grade graft stenosis). The main reasons for impaired ability to evaluate the scans were breathing artifacts and misplacement of the imaging volume, causing parts of the bypass grafts to be cut off. EBT permits noninvasive determination of bypass graft occlusion and relevant stenosis with high accuracy.

Internal mammary arteriography without selective cannulation using a new balloon occlusion catheter

Internal mammary artery (IMA) angiography can be difficult and time-consuming. We evaluated a custom designed balloon-tipped catheter, a Berman catheter (Arrow International, Reading, PA) modified by creating an end-hole to allow passage of a wire through the central lumen, for imaging the IMA without selective cannulation. We compared ease of use, procedure time, and image quality of the new catheter with the standard selective catheter technique. Thirty-six patients with IMA grafts were randomly assigned to imaging with either the study catheter or a standard catheter. Image quality, graded from poor to excellent, time to catheter placement in the subclavian artery (TIME 1), time to initial IMA angiography (TIME 2), and the difference between these two (TIME 3) were recorded. TIME 3 defined the time required to find and seat the catheter at the IMA site. The image quality was good or excellent in all but one patient. This one patient, randomized to the standard catheter technique, had poor image quality with the selective catheter. However, exchange for the study catheter resulted in excellent image quality. There was no difference in TIME 1 (P = 0.57) or TIME 2 (P = 0.55) between the two techniques. There was a significant difference in TIME 3 (P = 0.05) favoring the study catheter. There were no complication using either technique and the total contrast volume used was not significantly different between the two techniques (P = 0.32). We conclude that a new catheter technique for imaging the IMA without selective cannulation is safe, fast, easy to use, and may offer particular advantage in patients whose internal mammary artery is difficult to access.

Spiral CT angiography for preoperative planning in patients with epigastric tumors: comparison with arteriography

PURPOSE

Spiral CT angiography (CTA) was performed on 22 patients for the preoperative assessment of epigastric tumors in comparison with intraarterial angiography.

METHODS

One hundred fifty milliliters of contrast material was administered with a flow of 4 ml/s. After a delay of 30 s, a spiral CT examination of the epigastrium was performed (slice thickness 3 mm, table feed 6 mm/s). Axial images were reconstructed at 2 mm increments. Postprocessing was performed with a maximum intensity projection and shaded surface display imaging program. Plain film arteriography was performed via a catheter inserted transfemorally and placed into the epigastric arteries. The following parameters were evaluated: visualization of the arteries and the portal vein and involvement of these vessels by disease.

RESULTS

The vessels (22/22 = 100%) and variations (1/22 = 4.5%) were clearly identified with both techniques. Involvement was diagnosed by angiography 15 times compared with 22 findings by CTA.

CONCLUSION

Concerning vessel anatomy, the correlation between both techniques was excellent and vessel involvement showed good correlation, especially when using the axial slices additionally. CTA has the potential to become a minimally invasive diagnostic tool for preoperative planning in epigastric tumors.

Helical CT imaging of bronchial arteries with curved reformation technique in comparison with selective bronchial arteriography: preliminary report

PURPOSE

Our goal was to evaluate the ability of helical CT to identify and demonstrate the origins and courses of bronchial arteries, using the curved reformation technique, in patients undergoing bronchial arterial interventional procedures.

METHODS

Thin section helical CT was performed on seven patients before bronchial arterial interventional procedures. The curved reformation technique was used to demonstrate the origins and continuous vessel tracing of bronchial arteries and compared with bronchial arteriographic findings.

RESULTS

In all, 16 bronchial arteries were evaluated, 8 on the right and 8 on the left. The origins of 12 bronchial arteries were identified. In the demonstration of tracing vessels, seven right bronchial arteries and three left were classified as excellent or fair.

CONCLUSION

Helical CT imaging with the curved reformation technique is helpful in identifying bronchial arteries, especially on the right, in patients with indications for bronchial arterial interventional procedures.

Biliary tree necrosis in transplanted liver detected by spiral CT with three-dimensional reconstruction

We present a case where spiral computed tomography (CT) with three dimensional reconstruction was able to generate cholangiographic images demonstrating biliary tree necrosis in a transplanted liver. Volumetric CT as a one step diagnostic solution to establish a diagnosis in patients after liver transplantation can expedite appropriate therapy and reduce the number of invasive studies. By the integration of volumetric CT techniques and rapid three-dimensional display of biliary structures, volumetric cholangiography may become practical. Though spatial resolution may prove to be a limiting factor in replacing cholangiography for subtle mural disease, volumetric CT can yield clinically useful information.

Efficacy of unanesthetized spiral computed tomography scanning in initial evaluation of childhood leukocoria

PURPOSE

To evaluate the use of spiral/helical computed tomography (CT) in the preoperative evaluation of pediatric leukocoria.

METHODS

A total of 34 patient charts and imaging studies were reviewed from a consecutive series of children referred with the diagnosis of presumed retinoblastoma. Of these patients, 31 had a confirmed diagnosis of retinoblastoma. Three patients had simulating lesions, including one patient with persistent hyperplastic primary vitreous and two with Coats disease.

RESULTS

In all patients, a diagnosis of intraocular retinoblastoma could be established or excluded at the same clinical level by spiral CT as by conventional CT. Spiral CT of the eye, orbit, and midline structures was performed without a requirement for patient anesthesia. This technique resulted in a reduced volume of contrast material required for evaluation of the central nervous system and a small decrease in total radiation exposure. There was an attendant reduction in the amount of monitoring equipment required and the necessity for attending anesthesia staff.

CONCLUSIONS

The primary advantage of spiral CT is reduced anesthesia risk in small children. In addition, this technique provides necessary clinical information with a reduction in image acquisition time, monitoring equipment, and monitoring staff.

Three-dimensional computed tomographic angiography in the preoperative evaluation of cerebrovascular lesions

Although three-dimensional computed tomographic angiography was developed as a screening tool for use in patients with suspected cerebrovascular disease, this imaging modality has also proven to be of value in surgical planning for patients with large or unusual vascular lesions of the brain. The three-dimensional images generated by this technique yield valuable information regarding the size and configuration of intracranial aneurysms and vascular malformations, the presence and extent of intra-aneurysmal thrombus, the relationship of the vascular lesion to other cerebrovascular or skeletal structures, aneurysm wall thickness, and the presence and orientation of an aneurysm neck. The use of three-dimensional computed tomographic angiography in representative cases of patients with large or unusual cerebrovascular lesions is presented. It has been our experience that this imaging modality displays anatomical information that is not readily available from standard, intra-arterial angiography, provides better detail for surgical planning than magnetic resonance angiography, and is less expensive than either of these other imaging modalities.

Gastroepiploic artery as an in situ coronary artery bypass graft: evaluation of MRI and colour Doppler ultrasound in follow-up

The right gastroepiploic artery, increasingly used as an in situ coronary artery bypass graft, has good long-term patency. This study aimed to assess the accuracy and limitations of magnetic resonance imaging (MRI) and colour Doppler ultrasound (US) in postoperative follow-up of such cases. In eight consecutive patients (6 men, 2 women, mean age 57 years), conventional angiography, MRI and US were performed to evaluate graft patency. Colour Doppler US, performed within a week of the operation, correctly detected flow in three patent grafts. MRI (1.5 tesla) was performed c. 17 months after surgery, using a spine coil and a coronal two-dimensional Flash-type imaging sequence. At angiography six of the eight gastroepiploic artery grafts were patent, and two were occluded. The sensitivity and specificity of MRI were 100%. This accuracy makes MRI a promising method for noninvasive post-operative evaluation of right gastroepiploic artery graft patency.

Spiral CT of the thorax

Spiral CT represents a major advance in CT technology. While the patient is advanced through the scanner gantry, continuous data acquisition occurs during suspended respiration eliminating many of the limitations associated with conventional thoracic CT. By eliminating respiratory misregistration and by offering the ability to reconstruct overlapping images at small intervals, spiral CT is advantageous for pulmonary nodule detection. Airway pathology and lesions adjacent to the diaphragm are better visualized with spiral CT and can be displayed in multiplanar or three-dimensional formats. Vascular imaging, including pulmonary embolus detection, is improved by spiral CT because scanning occurs rapidly at the peak of vascular enhancement.