Exact measurement of vascular lumina in digital subtraction arteriography (DSA) during stent implantations and percutaneous transluminal angioplasty (PTA)

There are inherent difficulties in using high-resolution DSA in interventional radiology for measuring vascular luminal diameter since enlargement ratios are not constant. We present a system that permits accurate determination of vascular lumen diameters by means of a special angiographic catheter with pre-defined marking points. The accuracy of this measuring method was explored in tests using phantoms. In vivo practicability of the method was proved in PTA and stent implantations in 39 patients. This method with a maximum error of measurement of 5% appears to provide adequate safety in the choice of suitable dilating balloons and stents in interventional vascular procedures. In follow-up, it permits the accurate measurement of neo-intimal thickness.     

DSA测量技术误差与控制

目的探讨DSA测量技术误差的产生与控制。方法在GE公司生产的Advantx LCV Plus DSA机上测得数据。将显示屏分为中央区、中间区及边远区3个区带，对不同大小定标在不同检查床高度及不同点光源与增强器高度（SID）条件下，测量标的（人民币5角硬币）的放大、缩小情况。结果随着标的外移，由中央区到边远区标的逐渐放大，且纵向放大比横向放大显著。不同的定标对比，硬币（直径20．4mm）和钢球（直径7．7mm）测量相同标的结果相差较小，而导管（4F）定标有显著的低估实物倾向。同区带同轴向测量，测量误差控制在1．0％～-2．5％之间。结论将显示屏划分为中央区、中间区及边远区将有助于介入医师对测量误差的控制。以定标物的横向做定标来测量标的较为准确，同区带同轴向测量误差控制较好。     

Accurate geometric calibration in stepping-table digital subtraction angiography

Accurate measurements of vessel dimensions are desirable in many clinical applications. This work uses the known relative motion between X-ray source and the patient in stepping-table digital subtraction angiography (DSA) to provide an accurate geometric calibration for quantitative measurements. The method results in a calibration factor that converts the size of the object measured in pixels on the image to its size in millimetres. The main sources of error relate to: (i) the assessment of relative displacement of a structure in a series of images; (ii) patient motion throughout data acquisition; and (iii) image distortion. Error was evaluated both with a test object consisting of a large grid of ball bearings (2x2 cm spaced) and, in vivo, in five renal DSA examinations performed with identical catheters of known diameter. The calibration factor was calculated with 0.1% accuracy for the test object and at least 2% accuracy in vivo, even with breath holding and pulsatile motion. This demonstrates that the calculation of the calibration factor can be very accurate, and that the method we propose is capable of the submillimetre accuracy required for clinical studies if used in conjunction with an accurate measurement of the vessel size in pixels. In conclusion, accurate geometric measurements can be performed in stepping-table DSA, without the need for external reference objects.     

Size estimation and magnification error in radiographic imaging: implications for classification of arteriovenous malformations.

PURPOSETo assess magnification error in digital subtraction angiography as it pertains to arteriovenous malformation (AVM) size.METHODSA rectangular grid phantom with equally spaced markers mounted in a stereotactic frame was imaged with digital angiographic equipment. The location and orientation of the grid was altered relative to the central plane of the phantom. Both linear and area measurements were made according to the perceived location of phantom markers using a standard catheter calibration technique and compared with stereotactically derived estimates. Finally, a single case example of an angiographically imaged rolandic AVM was used to compare linear dimensions obtained with both described techniques.RESULTSThe determination of location and size with standard angiographic imaging is subject to error because of the divergent geometry of the incident x-ray beam. The resulting nonconstant geometric magnification causes errors in linear measurements of 10% to 13% at depths of 7 cm from the calibration plane. Errors in area measurements at the same position increase by 20% to 25%. Measurements of maximum diameter or cross-sectional area may have an additional error when nonspherical objects are inclined to the viewing direction (40% at 45 degrees inclination). These errors are reduced to less than 1 mm using the stereotactic technique. Some commercial angiographic systems have internal software to enable a spatial calibration based on known distances in the image or on the diameter of a catheter. The catheter technique was accurate in the calibration direction (perpendicular to the catheter axis) but had a 12% error in the direction parallel to the catheter because of a nonunity aspect ratio in the video system. Measurement of the dimensions of a rolandic AVM using the catheter calibration technique had an error that ranged from -3% to +26% (standard error, 20%) with respect to the stereotactic technique.CONCLUSIONSNumerous nonstereotactic referential systems for determining linear distances are inherently erroneous by varying degrees compared with the stereotactic technique. Area and volume determinations naturally increase this error further. To the extent that no standardized method for determining linear distances exists, significant variations in estimation of AVM size result. Classification schemes for AVMs have been hampered by this technical error.     

Comparison of intraarterial MR angiography at 3.0 T with X-ray digital subtraction angiography for detection of renal artery stenosis in swine

PURPOSE: To compare the accuracy of catheter-directed intraarterial (IA) magnetic resonance (MR) angiography at 3.0 T with that of x-ray digital subtraction angiography (DSA) for the measurement of renal artery stenosis (RAS) in swine. MATERIALS AND METHODS: Unilateral hemodynamically significant RAS (>50%) was induced surgically in six pigs with use of reverse cable ties. One to two weeks after surgery, each pig underwent x-ray DSA and MR angiography before and after percutaneous transluminal balloon angioplasty (PTA). X-ray DSA was performed before and after PTA of RAS by injection of iodinated contrast agent through a 5-F multiple-side hole angiographic catheter placed in the abdominal aorta under fluoroscopic guidance. MR angiography of RAS was performed before and after PTA of RAS on a 3.0-T clinical MR imager with use of gadolinium-based contrast agent. MR angiography and DSA images were analyzed with the full width at half maximum method. Percent stenosis measurements between x-ray DSA and MR angiography were compared with a paired t test and were correlated with linear regression and Bland Altman analysis (alpha = 0.05). RESULTS: Six cases of RAS were induced and imaged successfully with DSA and MR angiography techniques before and after PTA. On x-ray DSA, median stenoses was 64% (95% CI 57%-80%) before PTA and 20% (95% CI 5%-32%) after PTA. Corresponding MR angiography median stenosis measurement was 69% (95% CI 58%-80%) before PTA and 26% (95% CI 16%-36%) after PTA. A paired t test comparison did not show a difference between DSA and MR angiography (P = .16). RAS measurements on MR angiography correlated closely (P < .01) with DSA measurements (r(2) = 0.92). CONCLUSION: In swine, the accuracy of catheter-directed IA MR angiography with use of a clinical 3.0-T MR imaging unit for the measurement of RAS was similar to that of conventional x-ray DSA.     

Intraarterial digital subtraction angiography: A comparative view

Intraarterial digital subtraction angiography (IA DSA) was performed in 122 patients undergoing a variety of diagnostic and interventional angiographic procedures. Owing to the increased contrast resolution of DSA, diluted contrast material in concentrations of from 12-19% could be employed, thereby significantly reducing contrast material doses compared to doses used with conventional film-screen angiography or intravenous DSA. Patient discomfort was convincingly reduced due to the injection of dilute contrast material. Subtracted digital images could be viewed immediately on a cathode ray tube (CRT) resulting in faster procedures with less catheter time. Savings in film costs relative to conventional angiography were also achieved.     

How should we estimate carotid stenosis using magnetic resonance angiography?

Our purpose was to assess the reproducibility of and differences between the most commonly used methods for assessing carotid artery stenosis using magnetic resonance angiography (MRA). We studied 55 patients who underwent axial three-dimensional time-of-flight MRA (1.5 T). Quantitative caliper measurements were performed from maximum intensity projection (MIP) and multiple planar reconstruction (MPR) images, according to the criteria of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST). The measurements were compared to each other and to visual interpretation, using conventional angiography as the reference. The measured percentage stenoses were higher on MRA than on digital subtraction angiography (DSA) using both NASCET (mean difference 1.9–3.0%) and ECST (6.3–6.7%) criteria. The kappa coefficients for the agreement between DSA and MRA were higher using the NAS-CET (0.61–0.76) than the ECST criteria (0.52–0.65). No statistically significant differences were found between measurements from MIP and MPR images. The ECST measurement criteria gave significantly higher percentage stenoses than the NASCET criteria (P<0.001), this difference being more prominent on MRA (mean difference in diameter stenosis percentage 14.3–16.4%) than on DSA (7.6–11.2%) and most important with mild stenoses. The difference between visual interpretation and quantitative measurements on MRA was significant (P=0.01–0.001). There were no statistically significant interobserver differences in the MRA film readings, either in visually estimated degrees of stenosis or stenosis measurements. Thus, the different criteria of the two multicentre trials led to significantly different results, especially in the assessment of mild stenosis, and these differences are more important with MRA than with aging modalities or the reconstruction programs seem less important.     

Automated calibration in vascular X-ray images using the accurate localization of catheter marker bands

RATIONALE AND OBJECTIVES: To develop a new automated calibration method for vessel measurements in vascular x-ray images. METHODS: Radiopaque marker bands mounted equidistantly on a small catheter were acquired in vitro at five image intensifier (II) sizes in x-ray projection images. The positions of the marker centers were detected by using a Hough transform and were computed at subpixel precision by using either a novel, iterative center-of-gravity approach (CGA) or a symmetry filter. Curve-fitting procedures were used to reject false-positive marker detections and to calculate intermarker distances. The calibration factor was calculated from the true marker distance and the average of the measured distances in pixels. Results were compared statistically with a grid calibration method, which was taken as the gold standard. A simulation study was performed to assess the influence of image noise on the CGA method. RESULTS: The iterative CGA method was convergent and faster than the symmetry-based technique. For four II sizes (17, 20, 25, and 31 cm), the results from the CGA method were not significantly different from the results obtained with grid calibration. For the II size of 38 cm, a significant difference (0.3% of the grid calibration factor) was found; however, this was caused by the quantification error in the image data and was not clinically relevant. In general, the performance of the CGA method improved with increasing signal-to-noise ratio. CONCLUSIONS: A practical new calibration method for small catheter sizes was developed and validated for quantitative vascular arteriography.     

Computed tomography hepatic arteriography has a hepatic falciform artery detection rate that is much higher than that of digital subtraction angiography and 99mTc-MAA SPECT/CT: Implications for planning 90Y radioembolization?

Purpose

To compare the hepatic falciform artery (HFA) detection rates of digital subtraction angiography (DSA), computed tomography hepatic arteriography (CTHA) and 99mTc-macroaggregated albumin (99mTc-MAA) single photon emission computed tomography with integrated CT (SPECT/CT) and to correlate HFA patency with complication rates of yttrium-90 (90Y) radioembolization.

Material and methods

From August 2008 to November 2010, 79 patients (range 23–83 years, mean 62.3 years; 67 male) underwent pre-treatment DSA, CTHA and 99mTc-MAA scintigraphy (planar/SPECT/CT) to assess suitability for radioembolization with 90Y resin microspheres. Thirty-seven patients were excluded from the study, because CTHA was performed with a catheter position that did not result in opacification of the liver parenchyma adjacent to the falciform ligament. DSA, CTHA and 99mTc-MAA SPECT/CT images and medical records were retrospectively reviewed.

Results

A patent HFA was detected in 22 of 42 patients (52.3%). The HFA detection rates of DSA, CTHA and 99mTc-MAA SPECT/CT were 11.9%, 52.3% and 13.3%, respectively (p < 0.0001). An origin from the segment 4 artery was seen in 51.7% of HFAs. Prophylactic HFA coil-embolization prior to 90Y microspheres infusion was performed in 2 patients. Of the patients who underwent radioembolization with a patent HFA, none developed supra-umbilical radiation dermatitis. One patient experienced epigastric pain attributed to post-embolization syndrome and was managed conservatively.

Conclusion

The HFA detection rate of CTHA is superior to that of DSA and 99mTc-MAA SPECT/CT. Complications related to non-target radiation of the HFA vascular territory rarely occur, even in patients undergoing radioembolization with a patent HFA.     

A comparison of 35 mm cine film and digital radiographic image recording: implications for quantitative coronary arteriography. Film vs. digital coronary quantification

To assess potential differences in the intrinsic properties of image recording media and their impact on quantitative coronary arteriography, we used an automatic quantitative arteriography computer program to analyze cine film and digital radiographic images of a radiographic arterial phantom. The phantom consisted of a lucite plate with precision-drilled lumena ranging from 0.5 to 5.0 mm in diameter. Film images were digitized at 2048 X 2048 pixel resolution, and digital radiographic images were acquired at 512 X 512 and 1024 X 1024 resolution. Arterial geometric diameter, percent diameter stenosis, densitometric relative cross-sectional area, and densitometric percent area stenosis were measured. All three techniques were equivalent in measuring diameters with a high degree of overall accuracy (R greater than .992). All methods overestimated diameters below 1.0 mm. Both 512 X 512 and 1024 X 1024 digital images were superior to film for densitometric measurement of relative area (R = .995 vs. R = .940, P = .0032). We conclude that automated analysis of digital radiographic images yields results that are similar in geometric precision but greater in densitometric precision than film analysis.     

CT during selective arteriography: anatomical assessment of unruptured intracranial aneurysms before endovascular treatment

Our aim was to investigate the usefulness of helical CT during selective angiography (CT arteriography) in pretreatment assessment of unruptured intracranial aneurysms. We studied 47 unruptured aneurysms in 34 prospectively recruited patients for whom endovascular embolisation was initially considered. As pretreatment assessment, we performed rotational digital subtraction angiography (DSA) followed by CT arteriography. The findings on axial source images (axial images) and reconstructed three-dimensional CT angiography (3D-CTA) of CT arteriography were compared to those of rotational DSA, with particular attention to the neck of the aneurysm and arterial branches adjacent to it. Information provided by CT arteriography was more useful than that of rotational DSA as regards the neck in 25 (53 %) of 47 cases and as regards branches in 18 (49 %) of 37 aneurysms. On axial images, small arteries such as the anterior choroidal artery were seen in some cases. CT arteriography can provide valuable additional information about unruptured aneurysms, which cannot be obtained by rotational DSA alone. This technique is useful for obtaining anatomical information about aneurysm anatomy and for deciding the therapeutic strategy. Received: 22 May 2000/Accepted: 25 September 2000     

Dynamic and static phantoms for evaluation of digital subtraction angiographic systems

Two types of phantoms were developed with which to evaluate the overall performance of digital subtraction angiography (DSA) systems. A dynamic phantom, called a "fish bone" phantom, consists of polyethylene tubes that simulate blood vessels with various lesions, such as stenoses, ulcers, and aneurysms. With this phantom, washout curves were obtained representing the relationship between iodine content and time. It will be useful for qualitative assessment of DSA images, evaluation of different image-processing schemes, and studies of blood flow analysis. A static phantom, called a "C-D" phantom, can be used for measurement of quantitative contrast-detail (C-D) diagrams and for daily monitoring of DSA systems. This was constructed of tubes of seven different diameters (2.15-0.28 mm) and 14 different concentrations of contrast medium (100%-1.1% Renografin-76 [meglumine and sodium diatrizoate]). The C-D diagrams were determined from an observer performance study using C-D phantom images obtained at four different DSA settings.     

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 show any remaining geometric distortion in the corrected DSA images. This distortion correction can, if properly applied, be used for high-precision stereotaxic DSA. Received: 16 September 1995 Accepted: 5 January 1996     

Standardized volume rendering for magnetic resonance angiography measurements in the abdominal aorta

Purpose: To compare three methods for standardizing volume rendering technique (VRT) protocols by studying aortic diameter measurements in magnetic resonance angiography (MRA) datasets.

Material and Methods: Datasets from 20 patients previously examined with gadolinium-enhanced MRA and with digital subtraction angiography (DSA) for abdominal aortic aneurysm were retrospectively evaluated by three independent readers. The MRA datasets were viewed using VRT with three different standardized transfer functions: the percentile method (Pc-VRT), the maximum-likelihood method (ML-VRT), and the partial range histogram method (PRH-VRT). The aortic diameters obtained with these three methods were compared with freely chosen VRT parameters (F-VRT) and with maximum intensity projection (MIP) concerning inter-reader variability and agreement with the reference method DSA.

Results: F-VRT parameters and PRH-VRT gave significantly higher diameter values than DSA, whereas Pc-VRT gave significantly lower values than DSA. The highest interobserver variability was found for F-VRT parameters and MIP, and the lowest for Pc-VRT and PRH-VRT. All standardized VRT methods were significantly superior to both MIP and F-VRT in this respect. The agreement with DSA was best for PRH-VRT, which was the only method with a mean error below 1 mm and which also had the narrowest limits of agreement (95% of cases between 2.1 mm below and 3.1 mm above DSA).

Conclusion: All the standardized VRT methods compare favorably with MIP and VRT with freely selected parameters as regards interobserver variability. The partial range histogram method, although systematically overestimating vessel diameters, gives results closest to those of DSA.     

The accuracy and reliability of radiographic methods for the assessment of marginal bone level around oral implants

OBJECTIVES: To determine the accuracy and reliability of radiographic methods for assessment of the marginal bone level around oral implants in human cadavers. METHODS: In three human cadavers two implants were placed according to the Instruction Manual for the Br?nemark System. One implant was installed in the canine and one in the premolar region of the left mandible. For each implant, conventional and digital intra-oral paralleling radiography were performed. Digital images were printed with a Kodak 1200 Distributed Medical Imaging printer on blue transparent film, glossy and plain paper. Furthermore, digital scanographic, panoramic and tomographic images were taken with the Cranex Tome multimodal X-ray unit and printed on Agfa Drystar TM 1 B transparent films. All images were evaluated by five dental specialists. Data were statistically compared with real measurements of the marginal bone level on the human cadavers, performed by the same group of observers. Intra- and inter-observer variability were determined. RESULTS: Digital intra-oral images on glossy paper showed the smallest absolute difference between real and measured bone level, followed by digital intra-oral images on film and on plain paper, conventional intra-oral images on analogue film, panoramic, scanographic and tomographic images on film. The difference between real and radiographic measurements was not statistically significant (P>0.05) for all radiographic techniques. Intra- and inter-observer reproducibility was high for all techniques. CONCLUSIONS: The selected imaging techniques showed an acceptable accuracy for peri-implant bone level measurements with an overall error of less than 0.5 mm. Intra-oral images showed the smallest absolute differences.     

Value of arteriography scanning in lower limb artery evaluation: a preliminary study

PURPOSE: The purpose of this study was to assess the feasability of CT Angiography (CTA) with a single row of detectors and to compare it to digital subtraction angiography (DSA) in the evaluation of lower limb peripheral arterial disease. MATERIAL: and methods. A total of 22 patients underwent 24 lower limb Helical CTA using a Somatom Plus 4A (Siemens) and 24 DSA using an Angiostar unit (Siemens). CT angiography was performed in one acquisition (collimation 3mm/ couch motion 9mm/ interval 2mm) with tube rotation time of 0.75 sec from the aortic bifurcation to the calf. DSA was performed after catheterization of a common femoral artery using the Seldinger technique. Arteries were classified in four categories (normal or stenosis<50%, stenosis>50%, occlusion, aneurysm). VRT images and axial source images were assessed by two independent radiologists whereas digital angiographies were read by a vascular radiologist. RESULTS: Global interobserver agreement was good (Kappa=0.71). The degree of agreement between CTA and DSA ranged from low to excellent (0.25 to 0.97) depending on the artery. CONCLUSION: Lower limb CT angiography is a promising non invasive technique. VRT allows quick evaluation. However, is not accurate enough to replace digital angiography.     

High-spatial-resolution MR angiography of renal arteries with integrated parallel acquisitions: comparison with digital subtraction angiography and US

PURPOSE: To retrospectively compare three-dimensional gadolinium-enhanced magnetic resonance (MR) angiography, performed with an integrated parallel acquisition technique for high isotropic spatial resolution, with selective digital subtraction angiography (DSA) and intravascular ultrasonography (US) for accuracy of diameter and area measurements in renal artery stenosis. MATERIALS AND METHODS: The study was approved by the institutional review board, and consent was obtained from all patients. Forty-five patients (17 women, 28 men; mean age, 62.2 years) were evaluated for suspected renal artery stenosis. Three-dimensional gadolinium-enhanced MR angiograms were acquired with isotropic spatial resolution of 0.8 x 0.8 x 0.9 mm in 23-second breath-hold with an integrated parallel acquisition technique. In-plane diameter of stenosis was measured along vessel axis, and perpendicular diameter and area of stenosis were assessed in cross sections orthogonal to vessel axis, on multiplanar reformations. Interobserver agreement between two radiologists in measurements of in-plane and perpendicular diameters of stenosis and perpendicular area of stenosis was assessed with mean percentage of difference. In a subset of patients, degree of stenosis at MR angiography was compared with that at DSA (n = 20) and intravascular US (n = 11) by using Bland-Altman plots and correlation analyses. RESULTS: Mean percentage of difference in stenosis measurement was reduced from 39.3% +/- 78.4 (standard deviation) with use of in-plane views to 12.6% +/- 9.5 with use of cross-sectional views (P < .05). Interobserver agreement for stenosis grading based on perpendicular area of stenosis was significantly better than that for stenosis grading based on in-plane diameter of stenosis (mean percentage of difference, 15.2% +/- 24.2 vs 54.9% +/- 186.9; P < .001). Measurements of perpendicular area of stenosis on MR angiograms correlated well with those on intravascular US images (r(2) = 0.90). CONCLUSION: Evaluation of cross-sectional images reconstructed from high-spatial-resolution three-dimensional gadolinium-enhanced MR renal angiographic data increases the accuracy of the technique and decreases interobserver variability.     

Validation of fully automatic brain SPET to MR co-registration

Fully automatic co-registration of functional to anatomical brain images using information intrinsic to the scans has been validated in a clinical setting for positron emission tomography (PET), but not for single-photon emission tomography (SPET). In this paper we evaluate technetium-99m hexamethylpropylene amine oxime to magnetic resonance (MR) co-registration for five fully automatic methods. We attached six small fiducial markers, visible in both SPET and MR, to the skin of 13 subjects. No increase in the radius of SPET acquisition was necessary. Distortion of the fiducial marker distribution observed in the SPET and MR studies was characterised by a measure independent of registration and three subjects were excluded on the basis of excessive distortion. The location of each fiducial marker was determined in each modality to sub-pixel precision and the inter-modality distance was averaged over all markers to give a fiducial registration error (FRE). The component of FRE excluding the variability inherent in the validation method was estimated by computing the error transformation between the arrays of MR marker locations and registered SPET marker locations. When applied to the fiducial marker locations this yielded the surface registration error (SRE), and when applied to a representative set of locations within the brain it yielded the intrinsic registration error (IRE). For the best method, mean IRE was 1.2 mm, SRE 1.5 mm and FRE 2.4 mm (with corresponding maxima of 3.3, 4.3 and 5.0 mm). All methods yielded a mean IRE <3 mm. The accuracy of the most accurate fully automatic SPET to MR co-registration was comparable with that published for PET to MR. With high standards of calibration and instrumentation, intra-subject cerebral SPET to MR registration accuracy of <2 mm is attainable. Received 29 May and in revised form 6 October 1999     

Three-dimensional time-of-flight MR angiography for evaluation of intracranial aneurysms after endosaccular packing with Guglielmi detachable coils: comparison with 3D digital subtraction angiography

The sensitivities and specificities of three-dimensional time-of-flight MR angiography (3D-TOF MRA) and 3D digital subtraction angiography (3D-DSA) were compared for evaluation of cerebral aneurysms after endosaccular packing with Guglielmi detachable coils (GDCs). Thirty-three patients with 33 aneurysms were included in this prospective study. 3D-TOF MRA and 3D-DSA were performed in the same week on all patients. Maximal intensity projection (MIP) and 3D reconstructed MRA images were compared with 3D-DSA images. The diameters of residual/recurrent aneurysms detected on 3D-DSA were calculated on a workstation. In 3 (9%) of 33 aneurysms, 3D-TOF MRA did not provide reliable information due to significant susceptibility artifacts on MRA. The sensitivity and specificity rates of MRA were 72.7 and 90.9%, respectively, for the diagnosis of residual/recurrent aneurysm. The diameters of residual/recurrent aneurysms that could not be detected by MRA were significantly smaller than those of detected aneurysms (mean 1.1 vs mean 2.3 mm). In one aneurysm of the anterior communicating artery (ACoA), the relationship between the residual aneurysm and the ACoA was more evident on MRA than DSA images. MRA can detect the recurrent/residual lumen of aneurysms treated with GDCs of up to at least 1.8 mm in diameter. 3D-TOF MRA is useful for follow-up of intracranial aneurysms treated with GDCs, and could partly replace DSA.     

Noninvasive measurement of intra-aneurysmal pressure and flow pattern using phase contrast with vastly undersampled isotropic projection imaging

BACKGROUND AND PURPOSE: Currently, more reliable parameters to predict the risk of aneurysmal rupture are needed. Intra-aneurysmal pressure gradients and flow maps could provide additional information regarding the risk of rupture. Our hypothesis was that phase contrast with vastly undersampled isotropic projection reconstruction (PC-VIPR), a novel 3D MR imaging sequence, could accurately assess intra-aneurysmal pressure gradients in a canine aneurysmal model when compared with invasive measurements. MATERIALS AND METHODS: A total of 13 surgically created aneurysms in 8 canines were included in this study. Pressure measurements were performed in the parent vessel, aneurysm neck, and 5 regions within the aneurysmal sac with a microcatheter. PC-VIPR sequence was used to obtain cardiac-gated velocity measurements in a region covering the entire aneurysm. The velocity and pressure gradient maps derived from the PC-VIPR data were then coregistered with the anatomic DSA images and compared with catheter measurements. RESULTS: In 7 of the bifurcation aneurysms, the velocity flow maps demonstrated a recirculation flow pattern with a small neck-to-dome pressure gradient (mean, +0.5 mm Hg). In 1 bifurcation aneurysm, a flow jet extending from the neck to the dome with significantly greater pressure gradient (+50.2 mm Hg) was observed. All sidewall aneurysms had low flow in the sac with intermediate pressure gradients (mean, +8.3 mm Hg). High statistical correlation existed between PC-VIPR aneurysmal pressures and microcatheter pressure measurements (R = 0.82, P < .01). CONCLUSION: PC-VIPR can provide anatomic as well as noninvasive quantitative and qualitative hemodynamic information in the canine aneurysm model. The PC-VIPR intra-aneurysmal pressure measurements correlated well with catheter measurements.