Renal MR angiography at 1.0 T: three-dimensional (3D) phase-contrast techniques versus gadolinium-enhanced 3D fast low-angle shot breath-hold imaging

OBJECTIVE

The purpose of this study was to evaluate the diagnostic usefulness of three different MR angiographic techniques at 1.0 T.

SUBJECTS AND METHODS

In 22 patients with renal artery stenosis confirmed at intraarterial catheter angiography, we also performed unenhanced and gadolinium-enhanced three-dimensional phase-contrast MR angiography and gadolinium-enhanced single breath-hold three-dimensional fast low-angle shot MR angiography. We determined circulation time to optimize signal acquisition in gadolinium-enhanced breath-hold MR angiography after bolus injection of contrast material.

RESULTS

Sensitivity, defined as the detection of a hemodynamically significant stenosis (>50% luminal narrowing), was 85% for enhanced phase-contrast MR angiography, 91% for gadolinium-enhanced MR angiography, and 95% for unenhanced phase-contrast MR angiography. The combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography yielded 100% sensitivity for hilar artery stenoses. There were 13 false-positive findings with unenhanced phase-contrast MR angiography, 10 with enhanced phase-contrast MR angiography, and four with gadolinium-enhanced MR angiography (specificity: 38%, 52%, and 79%, respectively). Accessory renal arteries were not seen on unenhanced or enhanced phase-contrast MR angiography (0/8 patients) but were detected with gadolinium-enhanced MR angiography in five of the eight patients. Interobserver agreement (kappa = .62) was best with gadolinium-enhanced MR angiography. The quality of the images was unsatisfactory for adequate evaluation of segmental renal arteries with all three MR angiographic techniques.

CONCLUSION

A combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography at 1.0 T proved useful as a screening protocol for renal artery stenosis.

[A comparative study of HRCT and digital subtraction bronchography of bronchiectasis]

OBJECTIVE

To assess the value of HRCT in the diagnosis of bronchiectasis at segmental level.

METHODS

29 cases (522 segments) with bronchiectasis doubted by clinical evaluation were selected and HRCT scan and digital subtraction bronchography (DSB) were performed.

RESULTS

HRCT and DSB showed a good identity in the diagnosis of bronchiectasis. Of 92 segments diagnosed as bronchiectasis in HRCT, 84 were agreed with DSB; Of 430 segments diagnosed as no bronchiectasis by HRCT, 425 were agreed with DSB. Sensitivity of HRCT is 94%, specificity is 98%. The main HRCT findings were cylindric and cystic bronchiectasis.

CONCLUSIONS

HRCT is superior to bronchography for bronchiectasis. It is the first choice of the image diagnostic modalities for the patients in whom bronchiectasis is suspected.

[Digital 3D rotational angiography for the preoperative and preinterventional clarification of cerebral arterial aneurysms]

OBJECTIVE

Does the recently introduced 3D angiography provide additional information beyond standard angiography (DSA) for the diagnosis of cerebral aneurysms?

METHODS

During a 3-months period DSA and 3D-angiography were performed in 40 patients harbouring a total of 49 aneurysms. Vascular regions that presented an aneurysm diagnosed by DSA were reevaluated by 3D-angiography.

RESULTS

In two patients, vessel-loops previously described as aneurysms by DSA could be identified by 3D-angiography. In one patient, an aneurysm was diagnosed that could not be detected by DSA. In another case, the definitive diagnosis of an aneurysm was obtained only with 3D-angiography. In one patient, an aneurysm was diagnosed that could not be detected by DSA. In another case, the diagnosis of an aneurysm was obtained only with 3D-angiography. In two cases, aneurysms could be definitively excluded by 3D-angiography, whereas in another aneurysm a vessel originating from this lesion was identified. The size of the aneurysms measured by both methods was identical.

CONCLUSIONS

Multiple projections of 3D-angiography provide a better evaluation of the anatomic situation regarding the base of the aneurysm as well as the relationship of an aneurysm to neighbouring vessels. Further, an exact differentiation between a vessel loop and an aneurysm can be made. Therefore, 3D-angiography is a valuable tool when used in conjunction with DSA.

[MR angiography of the lower extremities with an automatic table translation (Mobitrak) compared to i.a. DSA]

PURPOSE

Comparison of the diagnostic information obtained by MRA using a moving bed ("MobiTrak") with i.a.DSA for angiography of the lower extremities.

MATERIALS AND METHODS

In 20 patients, i.a.DSA and MRA were performed within a few days. The image quality and diagnostic information were evaluated by two radiologists and two surgeons.

RESULTS

The radiologists assessed the quality of MRA higher for 18%, for 79% image quality was equal, for 3% the quality was graded as lower in comparison to i.a.DSA. The surgeons found the quality of MRA higher for 16%, equal for 75% and lower for 9%. In all cases, MRA was sufficient for planning of further treatment.

CONCLUSIONS

For examinations of the arterial vessels of the lower extremities, MRA with a moving bed ("MobiTrak") can be used instead of i.a.DSA. The diagnostic information from MRA is sufficient for planning the further treatment. The advantages of MRA (no radiation, no i.a. puncture, no contrast medium with iodine) will lead to an increasing application of this method.

[The design and implement of PACS components in digital imaging apparatus]

The domestic application of PACS will surely be developed in the future, but it will still take a few years. This paper proposes a tradeoff scheme: Attaching to digital imaging apparatus the PACS components, which mainly contain the Auto-archiving unit, the Communication unit supporting WAN as well as LAN and the Converting Interface unit to the hospital PACS. In this way, a single digital imaging apparatus can archive and transmit data independently, also can merge with the hospital PACS conveniently in the future. In this paper, both the design and the implement are discussed in detail.

[Comparison of radiation exposure of patients caused by selected interventional and angiography procedures--initial results]

PURPOSE

To determine and judge patient doses caused by selected interventional and angiographic procedures using the "Multiskip" digital C-arm unit.

MATERIALS AND METHODS

The dose-area product and the fluoroscopic time were measured for 71 percutaneous transluminal angioplasties (PTA), 33 PTA with stent implantation, and 37 embolizations; in addition, they were also measured for 285 digital subtraction angiographies (DSA). In the case of 13 PTA, 10 embolizations, and 33 DSA the number of radiographs was determined, and the dose-area product was divided into two parts, fluoroscopy and radiography, applying a computer programme.

RESULTS

The median values of the dose-area product and the fluoroscopic time amounted to 36 Gy cm2 and 11.5 min for PTA, 131 Gy cm2 and 14.4 min for PTA with stent implantation, 197 Gy cm2 and 24.5 min for embolisation as well as 87 Gy cm2 and 3.7 min for DSA. For the relation between dose-area products caused by fluoroscopy and radiography and the number of radiographs, median values of 0.67 and 70 for PTA, 0.58 and 153 for embolisation as well as 1.35 and 135 for DSA were determined.

CONCLUSIONS

To reduce the relatively high patient doses the modification of the C-arm unit is aspired to realize pulsed fluoroscopy and automatic filter selection. Also experimental investigations will be done related to additional filtration and reduction of the image intensifier input dose rate and dose per frame, respectively. Then, the effect of dose reduction caused by these measures will be confirmed in a comparable patient study.

Minimally invasive direct coronary bypass versus cardiopulmonary technique: angiographic comparison

BACKGROUND

Studies comparing minimally invasive direct coronary artery bypass grafting (MIDCABG) with techniques using cardiopulmonary bypass (CPB) are needed.

METHODS

Sixteen patients underwent single-vessel left internal thoracic artery-left anterior descending (LITA-LAD) MIDCABG through a left anterior thoracotomy, and 10 underwent multivessel bypass grafting that included a LITA-LAD, using CPB. Intraoperative completion angiography was performed on all LITA-LAD bypasses, and graded. One point each was given for: anastomotic patency, pedicle patency, intercostal obliteration, proper placement into the correct native coronary artery, and Thrombosis In Myocardial Ischemia grade III flow.

RESULTS

There were no intraoperative deaths or morbidities. LITA takedown averaged 49 +/- 18.6 minutes for MIDCABG and 16 +/- 2.0 minutes for CPB CABG (p < 0.05). LITA length did not differ between groups (15.3 +/- 1.2 cm for MIDCABG, 14.3 +/- 1.08 cm for CPB CABG). Ischemic arrest time was significantly less for the CPB group (13.3 +/- 8.3 minutes versus 24.5 +/- 9.6 minutes; p < 0.05). Average grade for MIDCABG LITA-LAD was 4.06 +/- 0.98 points versus 4.77 +/- 0.98 points for CPB LITA-LAD bypass (p = not significant).

CONCLUSIONS

Intraoperative completion angiography is feasible and, when combined with a grading system, may facilitate the comparison of MIDCABG with standard techniques.

[Retinal hemodynamics in patients with normal pressure glaucoma. Quantification with digital laser scanning fluorescein angiography]

Chronic ischemia of the retina and the optic nerve head seems of importance especially in patients with normal-tension glaucoma (NTG). The purpose of this study was to examine the retinal hemodynamics in patients with NTG.

PATIENTS

Twenty-five patients with NTG were examined (3 weeks washout period) in this study (age 58 +/- 16 years). The arteriovenous passage (AVP) time and arterial and venous diameters from scanning laser fluorescein angiograms were evaluated by means of digital image analysis.

RESULTS

The AVP time in patients with NTG (2.78 +/- 1.1 s) was significantly prolonged (P < 0.0001) compared with healthy subjects (1.58 +/- 0.4 s). No significant correlation was found between arterial and venous diameters, intraocular pressure, blood pressure or calculated perfusion pressure and retinal arteriovenous passage time.

CONCLUSION

Patients with NTG showed prolonged retinal passage, which could cause chronic hypoxia. This prolongation of circulation is not correlated with any of the clinical parameters. Thus, a circulatory defect might be a primary factor in the pathogenesis of NTG.

Scatter-glare estimation for digital radiographic systems: comparison of digital filtration and sampling techniques

The scatter and veiling glare distribution in images acquired with a digital subtraction angiography imaging system was estimated using a digital filtration and a beam-stop technique. The digital filtration technique utilizes exposure parameters and image gray levels to estimate scatter-glare intensity based on previous phantom measurements. The beam-stop technique uses an array of lead discs in order to sample scatter-glare intensity for each patient. To test the ability of digital filtration and beam-stop techniques to estimate the scatter-glare intensity, they were applied to images of postmortem swine animal models at different projections and beam energies. The systematic and root-mean-square (rms) percentage errors of these estimates were obtained by comparison to directly measured scatter-glare images using a scanning lead strip technique. The average rms percentage error for the digital filtration and beam-stop techniques were 8.07% and 6.67%, respectively. The changes in scatter-glare intensity due to contrast injection during coronary arteriography and ventriculography were also measured using the beam-stop technique. The maximum changes in scatter-glare intensities during coronary arteriography and ventriculography were 19 and 88%, respectively. The results indicate that the digital filtration technique is more suited for applications such as coronary arteriography and ventriculography where the iodinated contrast material significantly changes the scatter-glare intensity.

Carotid artery stenosis, occlusion, and pseudo-occlusion: first-pass, gadolinium-enhanced, three-dimensional MR angiography--preliminary study

PURPOSE

To determine the accuracy of gadolinium-enhanced three-dimensional magnetic resonance (MR) angiography in the evaluation of carotid artery stenosis.

MATERIALS AND METHODS

A prospective blinded comparison of first-pass MR angiography with conventional digital subtraction angiography (DSA) was performed in 21 patients suspected of having carotid artery stenosis. MR angiography was performed on a 1.5-T magnet with gradient overdrive equipment, with a coronal radio-frequency-spoiled, three-dimensional, fast low-angle shot sequence after intravenous injection of contrast material. The guidelines of the North America Symptomatic Carotid Endarterectomy Trial for measuring stenosis of the internal carotid artery were applied on maximum intensity projection images and conventional angiograms.

RESULTS

Grading of stenoses at MR angiography agreed with that at DSA in 92% of the 44 carotid arteries. In the 18 carotid arteries with severe stenosis (70%-99%), agreement was 94%. All internal carotid occlusions (n = 7) or pseudo-occlusions (n = 3) were accurately detected with MR angiography.

CONCLUSION

The accuracy of gadolinium-enhanced MR angiography in characterizing the degree of carotid stenosis was high. Findings with MR angiography were accurate for differentiating between occlusion and pseudo-occlusion.

Extrahepatic arterial supply to the liver: observation with a unified CT and angiography system during temporary balloon occlusion of the proper hepatic artery

PURPOSE

To evaluate routes of potential extrahepatic arterial supply to the liver.

MATERIALS AND METHODS

Twenty-three patients with liver tumors underwent computed tomographic (CT) arteriography of extrahepatic arteries before and after temporary balloon occlusion of the proper hepatic artery. The right inferior phrenic artery (RIPA), left inferior phrenic artery (LIPA), superior mesenteric artery (SMA), celiac axis, and left gastric artery (LGA) were evaluated.

RESULTS

During temporary balloon occlusion of the proper hepatic artery, extrahepatic arterial supply was immediately evident in 22 of 23 patients (96%). The liver was supplied by the RIPA in 17 of 20 patients (85%), by the LIPA in five of six (83%), by the SMA in eight of 16 (50%), by the celiac axis in two of 10 (20%), and by the LGA in one of six (17%). There was no apparent relationship between the enhanced zones supplied by extrahepatic arteries and the presence or absence of nearby tumors.

CONCLUSION

Extrahepatic arterial supply to the liver was readily evident in a large proportion of patients during temporary balloon occlusion of the proper hepatic artery. This finding suggests a need for consideration of extrahepatic arterial supply when angiographic intervention for liver tumors is contemplated.

Prospective analysis of complications of catheter cerebral angiography in the digital subtraction angiography and magnetic resonance era

Permanent and temporary neurological complications of catheter cerebral angiography were prospectively evaluated in 500 consecutive diagnostic cerebral angiographic procedures, 268 performed on 213 males and 232 on 175 females. Complications were divided into permanent (> 1 week), reversible (< or = 1 week, > 24 hours), and temporary (< or = 24 hours). There were four permanent (0.8%), one reversible (0.2%), and nine temporary neurological complications (1.8%). There was no death. With the correct selection of patients, catheter cerebral angiography is considered to be safe with acceptable rates of complications.

Detection of paraumbilical or splenorenal shunts by intra-arterial-DSA in bleeding varices: another risk factor?

In six of 46 consecutive patients with liver cirrhosis and bleeding varices, selective intra-arterial digital subtraction angiography detected large spontaneous portosystemic shunts including three patent paraumbilical veins and three splenorenal shunts. Twenty-one patients died during a median 73-month follow up period after devascularization with (44 cases) or without (2 cases) esophageal transection. Univariate analysis of preoperative variables concerning hepatic reserve failed to show significant predictability on postoperative survival rate. Instead, the postoperative survival rate of patients with the decompressive shunts was significantly lower than that of patients without the shunt. In a subgroup of patients with well-compensated liver cirrhosis and bleeding varices, the coexistence of paraumbilical or splenorenal portosystemic shunt may be another potent variable predicting poor prognosis.

Contrast-enhanced 3D MR DSA of the carotid artery bifurcation: preliminary study of comparison with unenhanced 2D and 3D time-of-flight MR angiography

PURPOSE

To compare the delineation of stenosis at the carotid artery bifurcation on three-dimensional (3D) magnetic resonance (MR) digital subtraction angiographic (DSA) images with that on two-dimensional (2D) and 3D time-of-flight (TOF) MR angiographic images.

MATERIALS AND METHODS

Twenty-six patients with 29 carotid artery bifurcations and symptoms of cerebral ischemia underwent 3D MR DSA. A time-resolved series was generated with 3D MR DSA after the bolus injection of gadodiamide. The resolution for a carotid artery examination was 0.4 x 0.4 x 1.0 mm, with volumes reconstructed at 4.5-second intervals. The 3D MR DSA images were compared with contemporaneously acquired unenhanced 2D and 3D TOF images. Two observers ranked the 2D and 3D TOF MR angiographic and 3D MR DSA images according to the following: (a) stenosis delineation, (b) internal carotid artery delineation, (c) intravascular signal intensity, and (d) diagnostic confidence.

RESULTS

The mean ranking for diagnostic confidence was 1.10 (1 = best technique, 3 = worst technique) for 3D MR DSA. Compared with the pooled 2D TOF and 3D TOF ranks, the 3D MR DSA rank was significantly better (P < .01). Similar levels of statistical significance were found for the other criteria.

CONCLUSION

Three-dimensional MR DSA improves the delineation of carotid arterial stenosis by virtually eliminating saturation effects and reducing intravoxel dephasing. Surface morphology and nearly occluded vessels ("string sign") were easily identified. Confidence in identifying carotid arterial occlusions was also very high with this technique.

Transbrachial selective pulmonary angiography using a new 4 Fr curved pigtail catheter and hydrophilic-coated guidewire

We have employed a new 4 Fr curved pigtail catheter with a hydrophilic-coated guidewire for transbrachial, selective pulmonary angiography using digital subtraction imaging. Eighteen patients and 27 pulmonary arteries were catheterized and selective pulmonary digital subtraction angiography was performed. Clinical diagnosis included lung cancer in 14 patients, thymoma in 1, bronchogenic cyst in 1, and pulmonary embolism in 2. Selective pulmonary arteriograms were obtained in all patients. No catheter-related complication occurred, although occasional premature ventricular contractions were noted. The high-flow injection rate of the contrast material resulted in clear visualization of the pulmonary arteries in all cases. This newly developed pigtail catheter combined with a hydrophilic-coated guidewire allowed easier and exact transbrachial selective pulmonary angiography to be performed. This technique does not require bedrest after the procedure and thus can be used in outpatients. It can also be used in patients who have thrombi along the transfemoral route.

Assessment of renal artery stenosis with CT angiography: usefulness of multiplanar reformation, quantitative stenosis measurements, and densitometric analysis of renal parenchymal enhancement as adjuncts to MIP film reading

PURPOSE

Our goal was to evaluate CT angiography (CTA) in diagnosing renal artery stenosis (RAS).

METHOD

Thirty-seven patients underwent digital subtraction angiography (DSA) and CTA. Visual interpretation and stenosis measurements were made from maximum intensity projection (MIP) and multiplanar reformation (MPR) laser film prints of 78 renal arteries.

RESULTS

Visual reading of MIP films showed good diagnostic performance by receiver operating characteristic curve analysis, with 100% sensitivity in the assessment of > or = 50% RAS but only 42-54% specificity (overall accuracy 60-75%). The false-positive rate decreased when MIP and MPR films were read together, but the excess of false negatives among the calcified lesions disabled this diagnostic algorithm. Combining visual interpretation of MIP films with quantitative measurements yielded the best diagnostic performance: 92% sensitivity, 80% specificity, and 84% overall accuracy. Renal cortical enhancement measurements (26 patients) had 81% overall accuracy.

CONCLUSION

The overall accuracy of CTA with MIP film reading can be enhanced by quantitative measurement of stenosis or reviewing MPRs.

Lower extremity: nonstepping digital angiography with photostimulable imaging plates versus conventional angiography

PURPOSE

To compare nonstepping digital subtraction angiography (DSA) (ie, storage phosphor radiography adapted to a stationary imaging plate changer) with conventional screen-film angiography in the evaluation of the lower extremities.

MATERIALS AND METHODS

Fifty-one patients with peripheral vascular disease underwent both nonstepping DSA and screen-film angiography. The angiographic and radiologic techniques of both systems were kept identical for each patient. Three radiologists independently rated the overall quality of each angiogram. In their evaluations for each of 12 arterial segments on all 102 angiograms, they also rated the degree of opacification, the diameter reduction of the most severe stenosis, and their level of confidence.

RESULTS

Mean overall quality scores and levels of confidence were better for nonstepping DSA than for screen-film angiography (P < .001). Full opacification was reported in 95.6% and 89.2% of all 1,836 segments with nonstepping DSA and screen-film angiography, respectively (P < .0001). The difference between the mean stenosis grades obtained with screen-film angiography and nonstepping DSA was not statistically significant. Intertechnique agreements were good (kappa = 0.77, 0.81, and 0.81), whereas interobserver agreements were influenced by the observer's experience with the imaging techniques.

CONCLUSION

Nonstepping DSA images of the lower extremity were of better diagnostic quality than were screen-film angiograms. The development of dedicated nonstepping DSA equipment is warranted.

Carbon dioxide (CO2) digital subtraction angiography: 26-year experience at the University of Florida

Although the vascular system is presently being imaged by multiple high technology modalities, contrast angiography continues to be the gold standard; however, severe complications rarely occur. During the last 25 years (in over 1400 patients), CO2 has proven to be extremely safe (no allergy or renal failure). However, it is imperative to understand CO2's physical properties and potential dangers. Recently, CO2 is being routinely utilized not only because of safety, but for detection of minute amounts of bleeding, better collateral filling, and for most interventional procedures since unlimited volumes of CO2 can be injected between the catheter and guidewire. Presently, safe, reliable and "user-friendly" delivery systems are now commercially available. CO2 DSA images are now nearly comparable to iodinated contrast, and improvement in DSA images are evolving, including "stacking" software.

An algorithm for correction of distortion in stereotaxic digital subtraction angiography

An algorithm for correction of the geometrical distortion in digital subtraction angiography (DSA) images was developed. Originally invented for 3D X-ray angiography, the algorithm was implemented in a computer program designed to fulfil the specific needs of stereotaxic DSA. The algorithm is based on transformation of an image of a grid from a distorted image back into its original pattern. The same transformation is then applied pixel-by-pixel to the angiographic images, which are acquired in direct conjunction with the grid image, without moving the gantry. The algorithm was tested in phantom studies and in the clinical situation with seven patients in ten examinations. Comparisons were made between co-ordinate determinations made on conventional full-size cut film and those performed on uncorrected and corrected DSA images, using 30- and 23-cm fields of view. With our method of measurement we could not shown any remaining geometric distortion in the corrected DSA images. This distortion correction can, if properly applied, be used for high-precision stereotaxic DSA.