Imaging of aortic aneurysms and dissection: CT and MRI

There are numerous approaches to the diagnosis of aortic aneurysms and aortic dissection. Echocardiography, computed tomography (CT), and magnetic resonance imaging (MRI) have enthusiastic proponents promoting each technique, which to some extent obscures the real value of each technique. This review examines the role of these techniques in the diagnosis of aortic disease, with special reference to the most recent published literature and an emphasis on the use of CT and MRI. For most patients with chronic aortic disease, MRI is the most appropriate investigation. In acute situations, CT scanning is usually the most useful technique, with echocardiography added for those with ascending aortic disease or cardiac complications.

MRI changes in myocarditis--evaluation with spin echo, cine MR angiography and contrast enhanced spin echo imaging

AIM

Myocarditis is probably under-diagnosed with clinical criteria generally used for diagnosis. Magnetic resonance imaging (MRI) has shown promise in detecting heart muscle disorders and we set out to assess the role of cine magnetic resonance angiography (MRA) and contrast enhancement in myocarditis, as there is a need for a non-invasive tool that can aid prognosis and follow-up.

MATERIALS AND METHODS

Twenty patients were evaluated with T1 SE pre- and post-gadolinium enhancement and cine MRA. Four patients were histologically proven to have myocarditis, eight others were diagnosed as having myocarditis by clinical criteria and eight did not have myocarditis. Images were evaluated in a blinded fashion for regional wall motion abnormality and contrast enhancement pattern. Analysis of contrast enhancement by signal intensity measurement was also performed.

RESULTS

Focal myocardial enhancement with associated regional wall motion abnormality correlated with myocarditis in 10 out of 12 patients, two patients with abnormal focal enhancement alone also clinically had myocarditis. None of the non-myocarditis patients showed abnormal focal enhancement. Enhancement analysis suggests that focal corrected myocardial enhancement of > 40% is abnormal.

CONCLUSION

In the correct clinical context, focal myocardial enhancement on spin echo MRI strongly supports a diagnosis of myocarditis, especially when associated with regional wall motion abnormality.Roditi, G. H. (2000). Clinical Radiology55, 752-758.

Imaging in blood stasis. The role of imaging techniques in defining the causes, presence, and effects of blood stasis

There have been considerable developments in the ability to image blood vessels and blood flow using ultrasound, CT, and MR imaging. The effects of vascular pathology in causing changes in the blood leading to thrombus formation now can be seen clearly because of these developments. In particular, new ultrasound MR imaging techniques allow more precise assessment of vessel walls and flow than has ever been possible before using conventional techniques, such as angiography. MR imaging has a unique potential for noninvasively demonstrating the natural history of developing vascular disease and the effects of this on blood flow and progression to thrombosis.

Optimized diagnostic angiography in high-risk patients with severe peripheral vascular disease

Conventional arteriography remains the usual method for preoperative assessment of severe peripheral vascular disease (PVD). Unfortunately, many peripheral arteriograms are still performed with a suboptimal technique, which can cause significant diagnostic errors in patients with severe PVD. A suboptimal technique may be due to poor collimation (causing incorrect exposure and incorrect gray scale), excessive patient-film distance (magnification unsharpness), inadequate volume or density of contrast material, poor contrast resolution (screen-film arteriography), nonselective injection, patient movement, and pressure from restraints or incorrect patient position (failure to profile lesions, pseudo-occlusion from external pressure or plantar flexion). The technique of selective digital subtraction arteriography (DSA) allows one to avoid these errors. The superior contrast resolution of DSA allows use of lower concentrations of contrast material. Selective injection into the external iliac artery allows proper positioning and improves image quality. Demonstration of distal vessels is best achieved by using biplane arteriography. For patients with severe resting ischemia, especially those with diabetes, high-quality selective DSA is essential to ensure that all distal vessels suitable for distal bypass grafting are identified. When properly performed, selective DSA remains the investigation of choice for reliably demonstrating arterial anatomy in high-risk patients with severe PVD.

Hepatic chemoembolization: effect of intraarterial lidocaine on pain and postprocedure recovery

PURPOSE

To determine if intraarterial lidocaine reduces pain during and after chemoembolization, and whether it influences postprocedure recovery.

METHODS

Two patient cohorts undergoing selective hepatic chemoembolization were compared. Chemoembolization was performed without lidocaine (control group) in 27 patients and intraarterial lidocaine was used (lidocaine group) in 29 similar patients. Objective changes in patient management were assessed. Pain reduction in 31 more procedures with lidocaine (total 60) was assessed and related to tumor type.

RESULTS

During chemoembolization, intraarterial lidocaine reduced the need for additional intravenous analgesics from 69% to 19%. After chemoembolization the mean Dilaudid dose in the first 24 hr was reduced from 9.5 mg to 4.15 mg; accordingly, the mean length of hospital stay was reduced from 67.5 to 53.5 hr. During the day of chemoembolization, the mean oral fluid intake increased from 420 ml (control group) to 487 ml (lidocaine group); the percentage of patients taking solid food on the day of chemoembolization increased from 3% to 43%.

CONCLUSION

Intraarterial lidocaine during chemoembolization reduces the severity and duration of pain after chemoembolization resulting in faster recovery thus reducing the length of hospitalization.

Diabetic versus nondiabetic limb-threatening ischemia: outcome of percutaneous iliac intervention

OBJECTIVE

The purpose of this study was to compare the effectiveness of iliac angioplasty and outcomes in diabetic patients and nondiabetic patients with limb-threatening ischemia.

MATERIALS AND METHODS

Records of 91 consecutive patients with limb-threatening ischemia (rest pain, nonhealing ulceration, or gangrene) who, during a 6-year period, underwent iliac angioplasty of hemodynamically significant lesions were reviewed. Stents were placed in patients with suboptimal findings at angioplasty. Sixty-eight (75%) of the 91 patients were diabetic. Life table analysis and log-rank significance tests were used to compare rates of primary iliac artery patency, primary and secondary graft patency, limb salvage, and survival in diabetic patients versus nondiabetic patients.

RESULTS

One hundred seven iliac lesions were treated with percutaneous angioplasty. Ten iliac stents were placed because of suboptimal results at angioplasty. The mean time of follow-up was 20 months (range, 2-62 months). Sixty-eight patients (75%) underwent peripheral reconstruction. Outcomes were comparable in both patient groups for primary iliac patencies at 4 years (diabetic patients, 85%; nondiabetic patients, 76%; p = .5), primary and secondary graft patencies at 4 years (diabetic patients, 65% and 73%, respectively; nondiabetic patients, 74% and 100%, respectively; p = .7 and .19, respectively), 4-year limb-salvage rates (diabetic patients, 93%; nondiabetic patients, 79%; p = .07). Major complications of angioplasty occurred in four patients (4.4%).

CONCLUSION

Outcomes of iliac angioplasty and limb-salvage rates were comparable for diabetic patients and nondiabetic patients who underwent current methods of iliac angioplasty and infrainguinal reconstruction.

Breathhold cardiac MRI and MRA

Recent developments in MRI software and hardware have increased the speed and versatility of cardiac MRI by allowing image acquisition in a single breathhold. Many studies have shown that conventional cardiac MRI is as accurate as echocardiography or cardiac catheterization for diagnosing numerous cardiac conditions. In many cases cardiac MRI is the most accurate diagnostic technique but has not been widely adopted for routine cardiac imaging. One reason why the use of cardiac MRI has been limited is the long examination times required for conventional cardiac MRI. The development of better hardware, such as faster gradient amplifiers and dedicated surface coils, has allowed the implementation of much faster EKG-gated imaging sequences. These can be used in a single breathhold period, with a significant improvement in image quality compared with conventional sequences. Breathhold sequences can provide all the information provided by conventional cardiac MRI in a shorter time and with equal or better accuracy. Breathhold imaging will allow much wider application of MRI to routine cardiac diagnosis.

Chemoembolization of hepatic neoplasms: safety, complications, and when to worry

Chemoembolization of the liver for unresectable malignancy, although controversial, is being used with increasing frequency. Chemoembolization can be difficult, and there is great potential for causing complications. There are also findings after chemoembolization, particularly on computed tomographic scans, that may appear to indicate complications but are common and of no concern. Chemoembolization requires an understanding of the congenital and acquired variations of arterial anatomy that may be seen supplying the liver. Assessment of the patency of the portal vein is also required. An abnormal portal vein demands significant changes in technique to allow safe chemoembolization. Partial or complete occlusion of the portal vein is associated with significantly decreased survival but does not prevent a worthwhile response to chemoembolization and is not an absolute contraindication. The presence of chemoembolization material in the gallbladder is not uncommon; with the technique used by the authors, the chemoembolization material infrequently causes cholecystitis or gallbladder infarction. Extrahepatic chemoembolization material is commonly seen in other organs but usually does not cause problems, presumably because the dose deposited outside the liver is small compared with the dose delivered to the liver. Other complications include pseudocirrhosis, liver infarction and abscess formation, carcinoid crisis, hepatorenal syndrome, and liver rupture.

Complete MR angiography and Doppler ultrasound as the sole imaging modalities prior to carotid endarterectomy

OBJECTIVE

To assess the combination of duplex Doppler ultrasound (DUS) and complete carotid magnetic resonance angiography (MRA) for the non-invasive imaging of carotid disease and their effect on outcomes. Determine inter-reader agreement of carotid MRA.

MATERIALS AND METHODS

One-hundred and ten carotid bifurcations were evaluated using DUS, 2D and 3D time-of-flight MRA from the aortic arch to the Circle of Willis in 55 patients. Percentage stenoses were determined by two blinded readers using standardized criteria. Clinical follow-up was by chart review.

RESULTS

Correlation of Doppler and MRA was excellent (r=0.903, P<0.001). Inter-reader agreement (K) for MRA was good: internal carotid artery (ICA) (0.750), external carotid artery (ECA) (0.674) and common carotid artery (CCA) (0.410). Differences in CCA readings were due to minor differences in categorizing lesions as CCA versus ICA or ECA. MRA and Doppler detected nine occluded ICAs. Two DUS occlusions had ICA flow by MRA; one due to a reconstituted precavernous ICA, one a near occluded vessel. Five patients (9%) had surgical management modified by MRA with four not having surgery: three distal ICA/Siphon occlusions and one less severe stenosis by MRA. One tandem lesion not visualized by DUS was surgically significant. Nine aortic arch abnormalities had no surgical impact, possibly due to small sample size. Of 41 endarterectomies, there were no complications from errors of diagnosis.

CONCLUSION

Carotid MRA correlates well with DUS with good inter-reader agreement. MRA confirms Doppler findings, expands anatomical information and identifies tandem lesions from the aortic arch to the Circle of Willis which can affect surgical management. This approach to carotid artery imaging appears to have no negative effect on surgical outcome.

New developments in cardiac magnetic resonance imaging

Technical developments have increased the speed and versatility of cardiac magnetic resonance imaging (MRI). Numerous studies show that cardiac MRI is as accurate as more conventional alternatives for diagnosis of many cardiac conditions. This review looks at the current state of cardiac MRI, indicates those areas where MRI has become established as a reliable diagnostic technique and discusses future developments.

MRI and echocardiography: how do they compare in adults?

TTE with color flow imaging remains the most appropriate initial method for imaging CHD in adults. In many patients with minor abnormalities, this will be the only imaging required. For complicated intracardiac anomalies not well shown by TTE, TEE or MRI are usually adequate with the choice of technique being dependent on the availability of appropriate equipment and expertise. For great vessel abnormalities, further evaluation with MRI and MRA is most appropriate. In patients suspected of having significant systemic or pulmonary venous abnormalities or abnormalities of the aortic arch, MRI and MRA should be regarded as the definitive imaging technique. MRI and MRA are robust methods for evaluating intracardiac disease and can provide accurate information on cardiac chamber anatomy relationships, valvar lesions, and shunts. However, in most patients, this information is provided more rapidly and cost effectively by color Doppler echocardiography.

Thrombolysis of infrapopliteal bypass grafts: efficacy and underlying angiographic pathology

OBJECTIVE

The purpose of this study was to determine retrospectively the effectiveness of thrombolysis of occluded infrapopliteal bypass grafts and to identify factors affecting success.

MATERIALS AND METHODS

The records of 52 consecutive patients (52 grafts) who underwent selective urokinase thrombolysis of grafts to the pedal or tibial arteries were reviewed. The need for subsequent surgery and the influence of diabetes on outcome were analyzed.

RESULTS

There were 43 vein and nine Goretex (W-L Gore, Flagstaff, AZ) and vein composite grafts inserting into tibial and peroneal arteries (n = 28) or pedal arteries (n = 24). Mean time of follow-up was 19 months. All grafts were entered, and technical success was achieved in 73% of patients. Twenty-six patients required some form of graft revision. Overall patency at 30 days was 76%. Thirty-day limb-salvage and mortality rates were 82% and 4%, respectively. No significant difference was found in 1-yr outcomes between diabetic and nondiabetic patients or between pedal and tibial grafts. Major complications occurred in eight patients (15%).

CONCLUSION

Thrombolysis of occluded grafts that insert into the pedal or tibial vessels was as effective as thrombolysis of more proximal grafts and native arterial thrombolysis, which have reported 30-day limb-salvage rates that range between 80% and 90%. Diabetes and grafting to foot vessels did not adversely affect response to thrombolysis. Surgery was often required to correct an underlying lesion revealed by thrombolysis. Despite the small size of the arteries to which the grafts were anastomosed, selective thrombolysis of occluded infrapopliteal bypass grafts proved to be an effective procedure.

Safety of MR imaging in patients who have retained metallic materials after cardiac surgery

OBJECTIVE

Epicardial pacing wires retained in patients who undergo cardiac surgery are thought to be a relative contraindication to MR imaging. However, to our knowledge no published evidence supports this belief. Because other metallic materials retained after cardiac surgery might represent a hazard to patients who undergo MR imaging, we sought to determine the safety of such imaging.

SUBJECTS AND METHODS

We examined 200 patients who underwent MR imaging at 1 or 1.5 T after cardiac surgery. Eighty-one were examined with ECG monitoring. The presence of temporary epicardial pacing wires, prosthetic valves, and other metal materials was confirmed by chest radiography.

RESULTS

Of the 200 patients reviewed, all had postoperative metallic material visible on chest radiographs. Temporary epicardial pacing wire, cut short at the skin, was seen in 51 patients. Of the 81 patients examined with ECG monitoring, we found that MR imaging produced no changes from baseline ECG rhythms. None of the 200 patients reported symptoms suggesting arrhythmia or other cardiac dysfunction during MR imaging.

CONCLUSION

MR imaging can be performed safely in patients who have undergone cardiac surgery and have retained metallic material, including valve replacements and temporary epicardial pacing wires cut short at the skin. MR imaging of patients with pacemakers was not evaluated, and we recommend that pacemakers remain a contraindication to MR imaging.

Magnetic resonance angiography demonstration of congenital heart disease in adults

OBJECTIVE

There are limitations when using spin-echo MR imaging to evaluate congenital heart disease (CHD). These include limited ability to detect small shunts, long acquisition times, in-plane or slow flow signal and limited ability to represent complicated three-dimensional (3D) anatomy. However, MR angiography can image flow direction and disturbances, assess function and easily represents 3D anatomy. This may be valuable when evaluating adults with CHD.

PATIENTS AND METHODS

Fifty consecutive adult patients were referred for MR evaluation of possible or known CHD using time-of-flight MR angiography. Cine, breathhold and presaturation cine MR angiography were acquired as appropriate, with 3D (MIP) reconstruction of all extracardiac anomalies.

RESULTS

Forty-nine patients had a diagnostic examination (one was unsatisfactory because of arrhythmia). Correlation with alternative imaging (TTE = 36, TOE = 13, cardiac catheter = 16) or surgery was available in 39 patients (MR angiography correct in 36 patients). MRA demonstrated or excluded all confirmed congenital valve (12/12), aortic (9/9), and venous (7/7) anomalies. Thirty-five patients were evaluated for shunts. MR angiography detected 31/33 confirmed shunts (shunts present in 26 patients, sensitivity 94%, specificity 95%). Although not used in all cases, spin-echo was unreliable in demonstrating shunts as signal loss in the region of the secundum septum frequently mimicked atrial septal defects (reducing accuracy for excluding intracardiac shunts, specificity 58%).

CONCLUSION

MR angiography accurately defines intra- and extra-cardiac anatomy and is superior to spin-echo in detecting or excluding shunts. MR angiography safely and accurately demonstrates many aspects of CHD in adults.

First-pass evaluation of myocardial output during dipyridamole stress using turbo-FLASH magnetic resonance imaging

RATIONALE AND OBJECTIVES

This study evaluated the value of dynamically enhanced fast low-angle shot (FLASH) magnetic resonance (MR) imaging in measuring cardiac output with and without dipyridamole pharmacological stress.

METHODS

Ten subjects underwent rest and stress MR imaging. Rest images were acquired using electrocardiogram gated MR (turbo-FLASH: repetition time = 6 mseconds; echo time = 12 mseconds; flip angle = 12 degrees, inversion time = 100) 10 to 45 seconds after intravenous bolus of 0.04 mmol/kg gadolinium (Gd)-DTPA using a Siemens 1.0-tesla Magnetom SP. Stress was induced within the MR imaging scanner with 0.56 mg/kg dipyridamole over 4 minutes with stress MR images obtained after a second bolus of Gd-DTPA in exactly the same position and time intervals. Cardiac output was calculated with a least squares error analysis before and after dipyridamole stress for the left and right ventricles in all 10 patients, and comparison was made with cardiac output by Fick dilution technique during cardiac catheterization in seven patients.

RESULTS

This MR analysis methodology shows reasonable correlation (r = 0.953) between left ventricular and right ventricular cardiac output with no effect on cardiac output during immediate dipyridamole stress. Fick dilution studies demonstrated a correlation of 0.96.

CONCLUSIONS

Turbo-FLASH MR can demonstrate time-activity curves and cardiac output calculations consistent with theoretical predictions.

Transfemoral repositioning of malpositioned central venous catheters

PURPOSE

To determine the efficacy of the transfemoral vein approach to repositioning malpositioned central venous catheters.

METHODS

During a 4(1/2)-year period, malpositioned central venous catheters were repositioned 91 times in 83 patients via the transfemoral vein approach. All repositioning was initially attempted with a Grollman catheter or other pigtail catheter and a tip-deflecting wire. If these techniques failed or the venous anatomy was unfavorable, gooseneck or long loop snares were used.

RESULTS

During 48 repositionings, rotating a pigtail-type catheter alone was used successfully in 39 (81%). In 6 of 9 failures, the addition of a tip-deflecting wire also failed. A Grollman catheter and tip-deflecting wire were used initially in 39 repositionings (6 failures; 85% success). Successful repositioning required a snare in 8 (4 as the primary repositioning technique) and a long-loop technique in 5. All repositionings were ultimately successful and there were no complications.

CONCLUSION

Central venous catheters can be repositioned consistently by the transfemoral route. Pigtail catheters or tip-deflecting wires alone are successful in over 80% of cases.

Primary biliary tract malignant melanoma

Primary melanoma is rarely diagnosed in the biliary tract; only three cases of primary melanoma of the bile ducts have been reported previously. The skin and squamous mucous membranes are the most common primary sites. We report two patients who represent the fourth and fifth reported cases of primary bile duct melanoma.

MR perfusion imaging of the kidney pre- and post-dipyridamole stress

Animal studies have demonstrated that renal MR contrast enhancement depends on the timing of image acquisition. Limited human studies have demonstrated effects of dipyridamole (DP) on total renal perfusion. This study assessed the effect of DP on total and regional renal perfusion using gated perfusion MRI for patients undergoing DP stress. Five subjects with no evidence of renal ischemia were examined at rest and after DP stress. Rest MRI images in the left kidney were acquired using electrocardiogram (ECG)-gated MR: turbo fast low-angle shot (FLASH); echo time (TE) = 12, repetition time (TR) = 6, flip angle = 12, inversion time (TI) = 100) 10 to 45 seconds after injection of gadopentetate dimeglumine. Stress was induced in the MRI scanner (DP, .56 mg/kg over 4 minutes) followed by stress MRI after a second bolus of gadopentetate dimeglumine in the same position and identical time intervals. MR signal in the whole left kidney and renal medulla and cortex pre- and post-DP demonstrated a 70% depression of total renal perfusion with relative preservation of cortical perfusion at the expense of medullary perfusion. Post-DP MR images demonstrated a decrease in cortical perfusion with an additional 29% depression of medullary perfusion (P < .001) with respect to cortical perfusion. Turbo FLASH MRI can provide adequate time and spatial resolution to demonstrate changes in renal perfusion. Depression of renal medullary perfusion after DP appears to be caused by the intrarenal effect of DP and may have clinical impact.

Magnetic resonance imaging of pericardial constriction: comparison of cine MR angiography and spin-echo techniques

AIM

Spin-echo (SE) MRI detects pericardial thickening in pericardial constriction but the validity of extrapolating SE criteria to cine MRA imaging has not been tested. Pericardial thickness measured by SE and cine MRA was compared in patients with and without pericardial thickening to determine if the range of pericardial thickness measured by the two techniques is the same.

PATIENT AND METHODS

Fourteen patients, investigated for possible pericardial constriction (PC), were compared with 24 subjects without evidence of pericardial disease (controls). Images were acquired using SE and cine MRA. Pericardial thickness was compared with final diagnosis.

RESULTS

Pericardial thickening ( > 3.5 mm) by SE detected pericardial constriction: sensitivity = 100% specificity = 96%, kappa = 0.91. Cine MRA had a sensitivity = 86%, specificity = 63%, kappa = 0.33. Maximum differences between SE and cine MRA pericardial thickness ranged from +2.5 mm to -2/7 mm.

CONCLUSIONS

Spin-echo identifies pericardial thickening with little overlap between measurements in patients with and without pericardial constriction. Pericardial thickness on cine MRA usually exceeds SE thickness, but with considerable overlap of thickness measurements in patients with and without pericardial constriction. Cine MRA cannot be used alone to diagnose pericardial thickening.

Time-of-flight MR angiography of the portal venous system: value compared with other imaging procedures

OBJECTIVE

The purpose of this study was to retrospectively compare two-dimensional time-of-flight MR angiography with other imaging procedures in the evaluation of the portal venous system in 152 consecutive patients.

MATERIALS AND METHODS

The findings on MR angiography performed on 152 patients to depict breath-hold, two-dimensional time of flight MR angiography. Selective arterial presaturation, bolus tracking, and three-dimensional reconstruction were used routinely. Findings were correlated with findings on sonography (104 patients), CT (8 patients), and conventional digital subtraction angiography (19 patients) as well as surgery (23 patients).

RESULTS

Agreement between results of MR angiography and alternative types of imaging was excellent (99%). Agreement with sonography (100 of 104), CT (8 of 8), conventional angiography (18 of 19), and surgery (23 of 23) was good. Visualization of varices and spontaneous shunts by MR angiography was superior to that by other imaging techniques.

CONCLUSION

Our experience shows that time-of-flight MR angiography is reliable and accurate for depicting portal venous anatomy. MR angiography shows vessels that are not visible with sonography. Complicated pathology is clearly visualized in a way that is not possible with other techniques.

Demonstration of inferior vena cava patency by retrograde azygous venography

Gaining access for vena cavography may be difficult in patients with multiple venous occlusions. We report the use of selective azygous venography to demonstrate potency of the proximal inferior vena cava (IVC) when no alternative route was available and noninvasive techniques were not applicable. The proximal superior vena cava and the distal IVC were occluded.

Body magnetic resonance angiography and its effect on the use of alternative imaging--experience in 1026 patients

Time-of-flight magnetic resonance (MR) angiography has been described for numerous applications but the number of patients described in published reports is usually relatively small. There is little information concerning the general utility of MR angiography in the body, outside the cranial circulation, or its effect on use of other imaging studies. Utilization of two-dimensional (2D) time-of-flight MR angiography over a 3 year period was reviewed to determine its accuracy and impact on other imaging modalities. Cranial and cardiac studies were excluded. Correlation was made with alternative imaging and surgical findings. Between January 1990 and December 1992 2D time-of-flight MR angiography was used to examine 1026 patients. MR angiography was used most frequently to examine the venous system. There was a slight reduction in the use of alternative imaging with two exceptions. When chest MR venography was performed, alternative imaging was completely abolished. Also, contrast portal venography was virtually eliminated. Five errors (0.2% of total MR angiography examinations) were recorded. Time-of-flight MR angiography, especially MR venography, is accurate and can replace contrast venography for abdominal and thoracic applications. Cost and limited availability means that other imaging, usually ultrasound, often precedes MR angiography.

MR angiography of congenital heart disease in adults

Magnetic resonance (MR) angiographic techniques are useful in evaluation of adult patients with congenital heart disease (CHD). The available techniques include cine, breath-hold ungated, and segmented k-space time-of-flight MR angiography. Three-dimensional (3D) image reconstruction with maximum-intensity projection can be used with all of these techniques to demonstrate great vessel anomalies associated with CHD. Selective presaturation MR angiography can be used to detect intracardiac shunts. MR angiography allows clarification of difficult diagnostic points that are not fully demonstrated with other imaging techniques, such as cardiac catheterization and angiocardiography, echocardiography, nuclear medicine studies, and conventional spin-echo MR imaging. In many patients with CHD in adulthood, the use of appropriate MR angiographic techniques may allow definitive diagnosis and preclude the need for cardiac catheterization. The wide field of view, sensitivity to shunts, and rapid 3D imaging capability of MR angiography make it a valuable method of evaluating CHD in adults.

Interventional radiology and cross sectional imaging in venous access

The role of radiology and the interventional radiologist in the care of patients requiring long term venous access is expanding. This role includes multimodality imaging for anatomic evaluation, guided catheter placement or repositioning, and diagnosis and treatment of catheter occlusion or related venous thrombosis. Interventional procedures have been developed for relief of venous obstruction, repositioning of catheters, and placement of unconventional access devices.

Magnetic resonance angiography of the central chest veins. A new gold standard?

PURPOSE

The systemic chest veins may be difficult to show comprehensively by contrast venography, especially if there is limited venous access or contraindications to intravenous contrast. As an alternative, can magnetic resonance angiography (MRA) reliably detect occluded chest veins and predict suitable sites for central venous access?

PATIENTS AND METHODS

Eighty-four patients were examined using breath-hold time-of-flight MRA and three-dimensional image reconstruction. Thirty-three were evaluated to identify possible central venous access. Fifty-seven patients were examined to diagnose and stage central venous occlusion.

RESULTS

The associated diagnoses were malignancy 46, parenteral nutrition 21, hemodialysis 6, chemotherapy 4, and other long-term venous access 7. Of the 28 patients in whom MRA predicted a patent site for central venous access, satisfactory access was achieved. In two patients, cannulation of veins shown to be occluded on MRA was attempted unsuccessfully. Correlation with contrast venography was available in 17. There was agreement with MRA concerning the level of occluded veins in all cases. Contrast venography did not show all patent veins, including some accessed during surgical line placement.

CONCLUSION

Compared with surgical line placement or contrast venography, MRA of the systemic chest veins is accurate. Patent and occluded chest veins are reliably defined, including potential sites for central line placement, in a way that is not possible with other techniques. MRA may be the new "gold standard" for defining systemic venous anatomy in the chest.