K-edge subtraction imaging for coronary angiography with a compact synchrotron X-ray source

About one third of all deaths worldwide can be traced back to cardiovascular diseases. An interventional radiology procedure for their diagnosis is Digital Subtraction Angiography (DSA). An alternative to DSA is K-Edge subtraction (KES) imaging, which has been shown to be advantageous for moving organs and eliminating image artifacts caused by patient movement. As highly brilliant, monochromatic X-rays are required for this method, it has been limited to synchrotron facilities so far, restraining the feasibility in clinical routine. Compact synchrotron X-ray sources based on inverse Compton scattering, which have been evolving substantially over the past decade, provide X-rays with sufficient brilliance that meet spatial and financial requirements affordable in laboratory settings or for university hospitals. In this work, we demonstrate a first proof-of-principle K-edge subtraction imaging experiment using the Munich Compact Light Source (MuCLS), the first user-dedicated installation of a compact synchrotron X-ray source worldwide. It is shown experimentally that the technique of KES increases the visibility of small blood vessels overlaid by bone structures.

Emergency Room Arteriography: An Updated Digital Technology

Background:

Emergency room arteriography (ERA) is a safe, accurate, simple and cost-effective method of defining arterial injuries. Limitations include the difficulty of evaluating limb vasculature distal to the suspected site of injury. Statscan is a novel, low-dose digital X-ray machine that can rapidly obtain a whole body image in a single scan. Our goal was to evaluate the role of Statscan technology in ERA.

Methods:

A 24 month retrospective review of all patients who underwent a Statscan assisted ERA at the Groote Schuur Hospital Trauma Unit was completed. Indications for ERA included a hemodynamically stable patient with hard signs of a vascular injury in conjunction with the clinical assessment of a threatened limb. Contraindications encompassed instability, massive bleeding or a rapidly expanding hematoma.

Results:

Ten patients underwent Statscan assisted ERA of their lower limbs. Eight had cold, pulseless limbs with impaired neurological examinations. Common femoral, superficial femoral and popliteal artery lacerations were displayed. Three patients had no identifiable injury and were observed. Seven patients underwent operative management for threatened limbs. Two had Statscan evidence of arterial emboli distal to the site of injury leading to further exploration and distal embolectomy.

Conclusions:

Statscan ERA is safe, rapid, simple and accurate. It has the advantage of providing arteriography distal to the site of injury. This directly altered patient care in 20% of cases, primarily by detecting distal arterial emboli. Thirty percent of patients with normal ERA also avoided an unnecessary operation. This study demonstrates a new role for Statscan technology.

[Study on Reduction of Radiation Exposure by Using Carbon Dioxide Angiography Catheter in Vascular Access Intervention Therapy(VAIVT)]

In vascular access intervention therapy (VAIVT), carbon dioxide is used as negative contrast medium for patients with iodine allergy or for those who have vascular access but not started with dialysis yet and have not endangered their remaining kidney function. To capture the movement of jet-injected carbon dioxide during the carbon dioxide angiography, we performed imaging at a rate of 15 frames per second. This method has a higher level of radiation exposure than angiography using an iodine contrast medium. Therefore we developed a catheter with 20 helical side holes in the tip (carbon dioxide angiography catheter), which allows large numbers of tiny bubbles to be generated simultaneously. In our study, we evaluate whether the use of this catheter can reduce the number of frames taken per second thus reducing the radiation exposure. A comparative experiment with existing angiography catheters with no side holes suggested that the use of this carbon dioxide angiography catheter to be useful for reducing the radiation exposure to patients and operators. Moreover, angiography using this catheter is highly useful from viewpoint of improving the stenotic vesselvisibility and reducing the side effects of using carbon dioxide, and we expect that the carbon dioxide angiography method is effective for patients and operators.

Minimally Invasive Monitoring of Chronic Central Venous Catheter Patency in Mice Using Digital Subtraction Angiography (DSA)

Background

Repetitive administration of medication or contrast agents is frequently performed in mice. The introduction of vascular access mini-ports (VAMP) for mice allows long-term vascular catheterization, hereby eliminating the need for repeated vessel puncture. With catheter occlusion being the most commonly reported complication of chronic jugular vein catheterization, we tested whether digital subtraction angiography (DSA) can be utilized to evaluate VAMP patency in mice.

Methods

Twenty-three mice underwent catheterization of the jugular vein and subcutaneous implantation of a VAMP. The VAMP was flushed every second day with 50 μL of heparinized saline solution (25 IU/ml). DSA was performed during injection of 100 μL of an iodine based contrast agent using an industrial X-ray inspection system intraoperatively, as well as 7±2 and 14±2 days post implantation.

Results

DSA allowed localization of catheter tip position, to rule out dislocation, kinking or occlusion of a microcatheter, and to evaluate parent vessel patency. In addition, we observed different ante- and retrograde collateral flow patterns in case of jugular vein occlusion. More exactly, 30% of animals showed parent vessel occlusion after 7±2 days in our setting. At this time point, nevertheless, all VAMPs verified intravascular contrast administration. After 14±2 days, intravascular contrast injection was verified in 70% of the implanted VAMPs, whereas at this point of time 5 animals had died or were sacrificed and in 2 mice parent vessel occlusion hampered intravascular contrast injection. Notably, no occlusion of the catheter itself was observed.

Conclusion

From our observations we conclude DSA to be a fast and valuable minimally invasive tool for investigation of catheter and parent vessel patency and for anatomical studies of collateral blood flow in animals as small as mice.

Automated carbon dioxide digital angiography for lower-limb arterial disease evaluation: safety assessment and comparison with standard iodinated contrast media angiography

INTRODUCTION

Carbon dioxide (CO2) has been validated as a contrast agent in a large series of studies. A particular advantages of CO2 over iodinated contrast medium (ICM) is the absence of nephrotoxicity and allergic reactions. One of the limitations of CO2 angiography is the difficulty of CO2 manual injection due to its compressibility. The manual gas injection does not permit optimal control of the gas output. Development of an automated CO2 injector has overcome these problems.

AIM

This study compares the feasibility, safety, and diagnostic accuracy of automated CO2 digital subtraction angiography (DSA) in comparison with ICM-DSA in the evaluation of critical limb ischemic (CLI) patients.

METHODS

We performed DSA with both CO2 and ICM on 40 consecutive CLI patients and directly compared the two techniques. Sixteen females and 24 males participated in the study (mean age, 71.7 years). We assessed the diagnostic accuracy of CO2 in identifying arterial stenosis in the lower limb, with ICM-DSA used as the gold standard.

RESULTS

The overall diagnostic accuracy of CO2-DSA was 96.9% (sensitivity, 99.0%; specificity, 96.1%; positive predictive value, 91.1%; negative predictive value, 99.6%). Tolerable minor symptoms occurred in 3 patients. No allergic reactions or significant decline in renal function were observed in patients receiving the CO2 injection.

CONCLUSION

Carbon dioxide DSA is a valuable and safe alternative to traditional ICM-DSA for evaluating CLI patients. This modality should be considered as the standard choice for CLI patients undergoing angiographic evaluation who are known to have renal insufficiency or contrast allergy.

Augmented reality in the surgery of cerebral arteriovenous malformations: technique assessment and considerations

BACKGROUND

Augmented reality technology has been used for intraoperative image guidance through the overlay of virtual images, from preoperative imaging studies, onto the real-world surgical field. Although setups based on augmented reality have been used for various neurosurgical pathologies, very few cases have been reported for the surgery of arteriovenous malformations (AVM). We present our experience with AVM surgery using a system designed for image injection of virtual images into the operating microscope's eyepiece, and discuss why augmented reality may be less appealing in this form of surgery.

METHODS

N = 5 patients underwent AVM resection assisted by augmented reality. Virtual three-dimensional models of patients' heads, skulls, AVM nidi, and feeder and drainage vessels were selectively segmented and injected into the microscope's eyepiece for intraoperative image guidance, and their usefulness was assessed in each case.

RESULTS

Although the setup helped in performing tailored craniotomies, in guiding dissection and in localizing drainage veins, it did not provide the surgeon with useful information concerning feeder arteries, due to the complexity of AVM angioarchitecture.

CONCLUSION

The difficulty in intraoperatively conveying useful information on feeder vessels may make augmented reality a less engaging tool in this form of surgery, and might explain its underrepresentation in the literature. Integrating an AVM's hemodynamic characteristics into the augmented rendering could make it more suited to AVM surgery.

4D digital subtraction angiography: implementation and demonstration of feasibility

BACKGROUND AND PURPOSE

Conventional 3D-DSA volumes are reconstructed from a series of projections containing temporal information. It was our purpose to develop a technique which would generate fully time-resolved 3D-DSA vascular volumes having better spatial and temporal resolution than that which is available with CT or MR angiography.

MATERIALS AND METHODS

After a single contrast injection, projections from the mask and fill rotation are subtracted to create a series of vascular projections. With the use of these projections, a conventional conebeam CT reconstruction is generated (conventional 3D-DSA). This is used to constrain the reconstruction of individual 3D temporal volumes, which incorporate temporal information from the acquired projections (4D-DSA).

RESULTS

Typically, 30 temporal volumes per second are generated with the use of currently available flat detector systems, a factor of ∼200 increase over that achievable with the use of multiple gantry rotations. Dynamic displays of the reconstructed volumes are viewable from any angle. Good results have been obtained by using both intra-arterial and intravenous injections.

CONCLUSIONS

It is feasible to generate time-resolved 3D-DSA vascular volumes with the use of commercially available flat detector angiographic systems and clinically practical injection protocols. The spatial resolution and signal-to-noise ratio of the time frames are largely determined by that of the conventional 3D-DSA constraining image and not by that of the projections used to generate the 3D reconstruction. The spatial resolution and temporal resolution exceed that of CTA and MRA, and the small vessel contrast is increased relative to that of conventional 2D-DSA due to the use of maximum intensity projections.

A comparison of radiation exposure between diagnostic CTA and DSA examinations of cerebral and cervicocerebral vessels

BACKGROUND AND PURPOSE

While the number of CTA examinations is continually increasing compared with DSA examinations, there is little comparative dose information about the different imaging techniques. We compared patient radiation exposure resulting from diagnostic CTA and DSA examinations for both cerebral and cervicocerebral vessels.

MATERIALS AND METHODS

An anthropomorphic phantom was irradiated by using typical diagnostic CTA and DSA setups and imaging parameters. For both imaging techniques, the imaging area of cerebral vessels included intracranial vessels only, while the imaging area of cervicocerebral vessels included both cervical and intracranial vessels from the aortic arch to the vertex. The effective dose was determined by using RPLDs. The DSA examination was simulated by using a biplane angiography system, and the CTA examination, by using a 64-row multidetector CT scanner.

RESULTS

For the imaging of cerebral vessels, the effective dose according to ICRP 103 was 0.67 mSv for CTA and 2.71 mSv for DSA. For the imaging of cervicocerebral vessels, the effective dose was 4.85 mSv for CTA and 3.60 mSv for DSA. The maximum absorbed dose (milligray) for skin, brain, salivary glands, and eyes was 166.2, 73.5, 35.6, and 21.8 mGy for DSA and 19.0, 16.9, 20.4, and 14.8 mGy for CTA, respectively. The conversion factors from DAP and DLP to effective dose were calculated.

CONCLUSIONS

The effective dose for CTA assessment of cerebral vessels was approximately one-fifth the dose compared with DSA. In the imaging of cervicocerebral vessels, the effective dose for CTA was approximately one-third higher compared with DSA.

Evaluation of surgical microscope-integrated intraoperative near-infrared indocyanine green videoangiography during aneurysm surgery

The primary aim of this study is to assess the value of intraoperative near-infrared indocyanine green videoangiography (ICGA) during intracranial aneurysm surgery. Altogether, 129 patients harboring 152 intracranial aneurysms were recruited in this study between March 2007 and December 2008 and the clinical data were retrospectively analyzed. Intraoperative ICGA was performed to examine the completeness of the aneurysm clipping and the patency of the parent arteries in all cases. The intraoperative findings were compared with that of postoperative digital subtraction angiography (DSA). On all of the patients, 276 successful ICGA investigations were performed intraoperatively. The image quality and resolution were excellent, allowing real-time assessment of the cerebral circulation. Indocyanine green (ICG) angiographic results could be divided into arterial, capillary, and venous phases, comparable to those observed with postoperative DSA. In all cases, the postoperative angiographic results corresponded to the intraoperative ICGA findings. In three cases, the information provided by intraoperative ICG angiography significantly changed the surgical procedure. Intraoperative ICG videoangiography may be a useful tool in real-time evaluation of the aneurysm clipping. Its simplicity and easy reproducibility all suggest it to be carried out as a routine procedure during aneurysm surgery.

Auto-tracking system for human lumbar motion analysis

Previous lumbar motion analyses suggest the usefulness of quantitatively characterizing spine motion. However, the application of such measurements is still limited by the lack of user-friendly automatic spine motion analysis systems. This paper describes an automatic analysis system to measure lumbar spine disorders that consists of a spine motion guidance device, an X-ray imaging modality to acquire digitized video fluoroscopy (DVF) sequences and an automated tracking module with a graphical user interface (GUI). DVF sequences of the lumbar spine are recorded during flexion-extension under a guidance device. The automatic tracking software utilizing a particle filter locates the vertebra-of-interest in every frame of the sequence, and the tracking result is displayed on the GUI. Kinematic parameters are also extracted from the tracking results for motion analysis. We observed that, in a bone model test, the maximum fiducial error was 3.7%, and the maximum repeatability error in translation and rotation was 1.2% and 2.6%, respectively. In our simulated DVF sequence study, the automatic tracking was not successful when the noise intensity was greater than 0.50. In a noisy situation, the maximal difference was 1.3 mm in translation and 1° in the rotation angle. The errors were calculated in translation (fiducial error: 2.4%, repeatability error: 0.5%) and in the rotation angle (fiducial error: 1.0%, repeatability error: 0.7%). However, the automatic tracking software could successfully track simulated sequences contaminated by noise at a density ≤ 0.5 with very high accuracy, providing good reliability and robustness. A clinical trial with 10 healthy subjects and 2 lumbar spondylolisthesis patients were enrolled in this study. The measurement with auto-tacking of DVF provided some information not seen in the conventional X-ray. The results proposed the potential use of the proposed system for clinical applications.

[Development of a prevention of body movement fixation appliance in leg digital subtraction angiography]

In the peripheral angiography to evaluate blood flow below the knee levels in patients with arteriosclerosis obliterans, a motion artifact occurs as a result of body movements of a patient in normal fixation. This sometimes makes a correct evaluation difficult. Therefore, we developed a fixed appliance which can restrain body movement without affecting image quality and blood flow in digital subtraction angiography of a leg. The appliance is filled with the styrofoam of 1 mm diameter in a sealed bag, after air is aspirated from inside the bag. The appliance is stiffened to fit the shape of the crus. We measured signal to noise ratio / contrast to noise ratio / a resolution limit by visual evaluation to examine the influence of the image before and after usage of this appliance. In addition, the blood velocity of the dorsalis artery in ultrasound was measured to examine the effect on the blood flow. As a result, the fixed appliance did not affect blood flow in peripheral angiography to evaluate the clinical significance, the usual 5-point evaluate scale was used. The scale was significantly improved (p <0.01) after usage of this appliance. The newly developed fixed appliance for digital subtraction angiography of a leg is useful to avoid motion artifacts in clinical settings.

A machine learning approach for deformable guide-wire tracking in fluoroscopic sequences

Deformable guide-wire tracking in fluoroscopic sequences is a challenging task due to the low signal to noise ratio of the images and the apparent complex motion of the object of interest. Common tracking methods are based on data terms that do not differentiate well between medical tools and anatomic background such as ribs and vertebrae. A data term learned directly from fluoroscopic sequences would be more adapted to the image characteristics and could help to improve tracking. In this work, our contribution is to learn the relationship between features extracted from the original image and the tracking error. By randomly deforming a guide-wire model around its ground truth position in one single reference frame, we explore the space spanned by these features. Therefore, a guide-wire motion distribution model is learned to reduce the intrisic dimensionality of this feature space. Random deformations and the corresponding features can be then automatically generated. In a regression approach, the function mapping this space to the tracking error is learned. The resulting data term is integrated into a tracking framework based on a second-order MAP-MRF formulation which is optimized by QPBO moves yielding high-quality tracking results. Experiments conducted on two fluoroscopic sequences show that our approach is a promising alternative for deformable tracking of guide-wires.

[The improved design of table operating box of digital subtraction angiography device]

In this paper are analyzed the disadvantages of CGO-3000 digital subtraction angiography table Operating Box. The authors put forward a communication control scheme between single-chip microcomputer(SCM) and programmable logic controller(PLC). The details of hardware and software of communication are given.

[Evaluation of FOV size on cerebral three-dimensional rotational digital subtraction angiography with flat panel detector system]

In interventional neuroradiology, three-dimensional rotational digital subtraction angiography (3D-DSA) is very useful for the spatial grasp of the location and size of an intracranial cerebral aneurysm. The purposes of this study were to evaluate the property of three-dimensional image dependence on the respective field of view (FOV) size in a flat-panel detector (FPD) using vessel phantoms, and to optimize clinically. The indices of three-dimensional image properties such as profile curve (FWHM, FWTM), digital value, and image noise were evaluated using a vessel phantom with a different diameter. As a result, in the case of a 6-inch FOV size of the FPD, the relative diametral rate of change from the actual value of the vessel phantom was least for all FOV sizes. This study demonstrated that the difference in FOV size in 3D-DSA affects the three-dimensional object's reproducibility. Furthermore, as for this 3D-DAS system, three-dimension images such as a VR image might be processed more faithfully, since an FOV size of 6 inches has the highest reproducibility of objects.

Cost impact of diagnostic imaging for lower extremity peripheral vascular occlusive disease

OBJECTIVE

The evaluation of peripheral vascular disease in the primary care setting is routinely performed by contrast-enhanced magnetic resonance angiography (CE-MRA) and digital subtraction angiography (DSA). However, limited data are available on the relative costs and clinical outcomes following these diagnostic procedures. The objective of this study is to assess and compare costs associated with diagnostic imaging in peripheral vascular occlusive disease (PAOD).

METHODS

US veterans (n = 19,209) with CE-MRA or DSA for the assessment of PAOD from fiscal year (FY) 1999 to FY 2004. Main outcome measure(s) using the Department of Veterans Affairs' (VA) costing algorithms, cost, and log-cost of interventions (e.g., revascularization, stent, angioplasty), amputations or mortality rates within 30/90 days and 1 year of DSA or CE-MRA were compared, and adjusted for patient characteristics and disease severity using multivariate regression. Imaging modality selection bias was evaluated with propensity score, instrumental variables, and Heckman methods using untransformed costs and log-costs with smearing retransformation.

RESULTS

Initial CE-MRA imaging was significantly more likely among patients with prior renal disease or bypass surgery [odds ratio (OR) > 2; P < 0.001], and less likely among patients with prior amputation, peripheral vascular disease (PVD), claudication, or other cardiovascular disease (OR < 0.7; P < 0.001). After adjusting for endogenous choice of initial imaging modality, 30-day treatment costs were US$3500-$4300 lower (P < 0.001) for patients with initial CE-MRA. Eighty-two percent of DSA imaging patients had no additional procedures or events within 30 days, and 65% at 90 days. Less than 3.2% (3.6%) of patients had any repeat imaging within 30 (90) days of initial imaging.

CONCLUSIONS

Relative to DSA, CE-MRA imaging was associated with substantial treatment episode savings, beyond the US$950 direct savings in imaging cost per procedure. Substituting CE-MRA for DSA among those not planning or requiring any follow-up procedures within 30 days, could have reduced outpatient imaging costs by up to 55%, and reduced VA system costs by US$13.2 million over the six-year period.

[Clinical application of the three-dimensional CT of the flat-panel digital subtraction angiography system]

OBJECTIVE

To evaluate the clinical value of the three-dimensional (3D) CT module of the flat-panel digital subtraction angiography (DSA) system.

METHODS

A retrospective analysis was conducted among 278 patients receiving examination with rotational 3D-CT of INNOVA 3100 flat-panel DSA system. AW4.3-04 workstation was used to perform the 3D reconstruction and INNOVA CT reconstruction, and the imaging data were analyzed in comparison with the clinical results.

RESULTS

The 3D-CT of the flat panel DSA system displayed the conditions of cerebral aneurysms in 54 cases, cerebral arteriovenous malformation in 25 cases, and the intracranial conditions in 24 cases. The blood supply and tumor vessels were clearly displayed in 57 cases, and the effects of embolization and endovascular stenting were evaluated in 27 and 21 cases, respectively. The rotational 3D-CT was used to evaluate complete embolization in 24 cases, and failed to display the feeding arteries of small tumors in 11 cases. The vascular lesions, biliary tract lesions, and the occurrence of hemorrhage during interventional therapy were observed in 58, 5 and 25 cases, respectively.

CONCLUSION

The 3D-CT module of the flat-panel DSA system can easily display abnormal vascular lesions and provide comprehensive anatomical information to facilitate interventional therapies and complication monitoring.

Diagnostic performance of computed tomography angiography in peripheral arterial disease: a systematic review and meta-analysis

CONTEXT

Computed tomography angiography (CTA) is an increasingly attractive imaging modality for assessing lower extremity peripheral arterial disease (PAD).

OBJECTIVE

To determine the accuracy of CTA compared with intra-arterial digital subtraction angiography (DSA) in differentiating extent of disease in patients with PAD.

DATA SOURCES AND STUDY SELECTION

Search of MEDLINE (January 1966-August 2008), EMBASE (January 1980-August 2008), and the Database of Abstracts of Reviews of Effectiveness for studies comparing CTA with intra-arterial DSA for PAD. Eligible studies compared multidetector CTA with intra-arterial DSA, included at least 10 patients with intermittent claudication or critical limb ischemia, aimed to detect more than 50% stenosis or arterial occlusion, and presented either 2 x 2 or 3 x 3 contingency tables (< or = 50% stenosis vs > 50% stenosis or occlusion), or provided data allowing their construction.

DATA EXTRACTION

Two reviewers screened potential studies for inclusion and independently extracted study data. Methodological quality was assessed by using the QUADAS instrument.

DATA SYNTHESIS

Of 909 studies identified, 20 (2.2%) met the inclusion criteria. These 20 studies had a median sample size of 33 (range, 16-279) and included 957 patients, predominantly with intermittent claudication (68%). Methodological quality was moderate. Overall, the sensitivity of CTA for detecting more than 50% stenosis or occlusion was 95% (95% confidence interval [CI], 92%-97%) and specificity was 96% (95% CI, 93%-97%). Computed tomography angiography correctly identified occlusions in 94% of segments, the presence of more than 50% stenosis in 87% of segments, and absence of significant stenosis in 96% of segments. Overstaging occurred in 8% of segments and understaging in 15%.

CONCLUSION

Computed tomography angiography is an accurate modality to assess presence and extent of PAD in patients with intermittent claudication; however, methodological weaknesses of examined studies prevent definitive conclusions from these data.

Variation of hepatic artery by 3-D reconstruction MDCT scan of liver in Siriraj Hospital

OBJECTIVE

To evaluate the prevalence of hepatic arterial variant in Siriraj Hospital.

MATERIAL AND METHOD

A retrospective study that was approved by ethic committee of Siriraj Hospital. Between August and October 2006, 200 studies of abdominal MDCT were randomly sampled and multi-planar reformatted by using program Vitrea 2. Both axial, two- and three-dimensional images were evaluated for possible variants of hepatic vasculature. The results were classified by Michel classification and analyzed in percentage. Moreover, a small group (23 studies) that had digital subtraction angiography (DSA) was compared to know accuracy and Intercorelation between the two reviewers (Kappa value).

RESULTS

Of 200 studies, 83.5% had type I, 1% type II, 6% type III, 0.5% type IV, 3.5% type V, 1% type VI, 0.5% type VIII, 1% type IX, 0.5% Type X, and 2.5% others type. Accuracy of MDCT for detection hepatic artery variation as compared with DSA was 78.3%.

CONCLUSION

All variation is about 16%. Type III is most common variation of patients in Siriraj Hospital.

[Design and development of the DSA digital subtraction workstation]

According to the patient examination criterion and the demands of all related departments, the DSA digital subtraction workstation has been successfully designed and is introduced in this paper by analyzing the characteristic of video source of DSA which was manufactured by GE Company and has no DICOM standard interface. The workstation includes images-capturing gateway and post-processing software. With the developed workstation, all images from this early DSA equipment are transformed into DICOM format and then are shared in different machines.

Criteria to optimise a dynamic flat detector system used for interventional radiology

An analysis of the relationship between image quality and incident air kerma has been carried out for a dynamic flat detector X-ray system used for interventional radiology. A phantom of polymethyl methacrylate (PMMA) to simulate patients and two different image test objects, Leeds TOR 18FG and NEMA XR 21, were used to evaluate the quality of the obtained images. Measurements were made simulating clinical configuration with different PMMA thicknesses (16, 20, 24 and 28 cm), available fields of view of 22, 31, 42 and 48 cm (diagonal dimension), in the three default fluoroscopy modes and in one of the most used digital subtraction angiography image acquisition modes. The obtained results are being used to help in the optimisation of clinical procedures.

A cone-beam volume CT using a 3D angiography system with a flat panel detector of direct conversion type: usefulness for superselective intra-arterial chemotherapy for head and neck tumors

BACKGROUND AND PURPOSE

The development of flat panel detectors (FPDs) has made cone-beam CT feasible for practical use in a clinical setting. Our purpose was to assess the usefulness of cone-beam CT using the FPD in conjunction with conventional digital subtraction angiography (DSA) for performing superselective intra-arterial chemotherapy for head and neck tumors.

MATERIALS AND METHODS

Twenty-three consecutive patients (43 feeding arteries) were prospectively examined. All of the patients underwent intra-arterial rotational angiography using an FPD system, and the cone-beam CT was reconstructed from the volume dataset. Two radiologists evaluated the quality of the cone-beam CT and then evaluated whether the additional information provided by the cone-beam CT was useful for the interventional procedures.

RESULTS

In 41 (95%) of 43 arteries, the extent of contrast material perfusion was sufficiently visualized on cone-beam CT. In 20 (47%) of 43 arteries, the DSA plus cone-beam CT was superior to the DSA alone regarding the precise understanding of vascular territory of each artery. This information was helpful for predicting the drug delivery for superselective intra-arterial chemotherapy, especially in deeply invasive tumors with multiple feeding arteries.

CONCLUSION

In superselective intra-arterial chemotherapy for head and neck tumors, cone-beam CT with FPD provides useful additional information, which allows interventional radiologists to determine the feeders, as well as the dose of antitumor agent for each feeder.

Use of 120 kilovolt tube potential for digital subtraction angiography and fluoroscopy in an image-intensifier angiographic system: decrease of skin dose in transarterial chemoembolization therapy for hepatocellular carcinoma

In an image-intensifier angiographic system, the tube potential is commonly regulated in ranges from 75 to 90 kV for digital subtraction angiography (DSA) and fluoroscopy in transarterial chemoembolization therapy (TACE) for hepatocellular carcinoma. The purpose of this study was to investigate whether or not a 120-kV tube potential could be used for DSA and fluoroscopy in TACE to decrease the skin dose. Forty-three patients administered TACE were randomly allocated into two groups: TACE was performed using standard-kilovoltage (75- to 90-kV) DSA and fluoroscopy modes (group A; n = 20) or using high-kilovoltage (120-kV) modes (group B; n = 23). The peak skin dose was compared between the groups. One case in group A was excluded from the study because the HCC nodule was not depicted on DSA. The peak skin dose (mGy) for group A was 383.6 +/- 176.5 and that for group B was 265.1 +/- 145.1. The peak skin dose was decreased by 31% in the 120-kV mode, a statistically significant difference (t-test, p = 0.022). We conclude that the use of 120 kV tube potential for DSA and fluoroscopy may be one option for performing TACE while decreasing the skin dose.

Selective intracranial magnification angiography of the rabbit: basic techniques and anatomy

Development of new therapies for stroke requires animal models with well-defined intracranial vasculature. The rabbit as a small animal model has many desirable traits; however, a modern atlas of rabbit angiographic anatomy is not readily available. Improved digital subtraction magnification angiography and superselective small-catheter techniques now allow excellent anatomical definition. Angiographic techniques include selection of the internal carotid artery and subselection with microcatheters that can progress to branches of the circle of Willis and provide high-resolution cerebral angiography. The authors present an overview of current techniques and illustrations of the angiography of cerebral vessels.

3D digital subtraction angiography of intracranial aneurysms: comparison of flat panel detector with conventional image intensifier TV system using a vascular phantom

BACKGROUND AND PURPOSE

Compared with the image intensifier (I.I.)-TV system, the flat panel detector (FPD) system of direct conversion type has several theoretic advantages, such as higher spatial resolution, wide dynamic range, and no image distortion. The purpose of this study was to compare the image quality of 3D digital subtraction angiography (DSA) in the FPD and conventional I.I.-TV systems using a vascular phantom.

MATERIALS AND METHODS

An anthropomorphic vascular phantom was designed to simulate the various intracranial aneurysms with aneurysmal bleb. The tubes of this vascular phantom were filled with 2 concentrations of contrast material (300 and 150 mg I/mL), and we obtained 3D DSA using the FPD and I.I.-TV systems. First, 2 blinded radiologists compared the volume-rendering images for 3D DSA on the FPD and I.I.-TV systems, looking for pseudostenosis artifacts. Then, 2 other radiologists independently evaluated both systems for the depiction of the simulated aneurysm and aneurysmal bleb using a 5-point scale.

RESULTS

For the degree of the pseudostenosis artifacts at the M1 segment of the middle cerebral artery at 300 mg I/mL, 3D DSA with FPD system showed mild stenoses, whereas severe stenoses were observed at 3D DSA with I.I.-TV system. At both concentrations, the FPD system was significantly superior to I.I.-TV system regarding the depiction of aneurysm and aneurysmal bleb.

CONCLUSION

Compared with the I.I.-TV system, the FPD system could create high-resolution 3D DSA combined with a reduction of the pseudostenosis artifacts.

Tumor imaging in small animals with a combined micro-CT/micro-DSA system using iodinated conventional and blood pool contrast agents

X-ray based micro-computed tomography (CT) and micro-digital subtraction angiography (DSA) are important non-invasive imaging modalities for following tumorogenesis in small animals. To exploit these imaging capabilities further, the two modalities were combined into a single system to provide both morphological and functional data from the same tumor in a single imaging session. The system is described and examples are given of imaging implanted fibrosarcoma tumors in rats using two types of contrast media: (a) a new generation of blood pool contrast agent containing iodine with a concentration of 130 mg/mL (Fenestratrade mark VC, Alerion Biomedical, San Diego, CA, USA) for micro-CT and (b) a conventional iodinated contrast agent (Isovue(R)-370 mg/mL iodine, trademark of Bracco Diagnostics, Princeton, NJ, USA) for micro-DSA. With the blood pool contrast agent, the 3D vascular architecture is revealed in exquisite detail at 100 microm resolution. Micro-DSA images, in perfect registration with the 3D micro-CT datasets, provide complementary functional information such as mean transit times and relative blood flow through the tumor. This imaging approach could be used to understand tumor angiogenesis better and be the basis for evaluating anti-angiogenic therapies.

Carbon dioxide digital subtraction angiography-assisted endovascular aortic aneurysm repair in the azotemic patient

OBJECTIVE

This report analyzes the safety and efficacy of carbon dioxide digital subtraction angiography (CO(2)-DSA) for EVAR in a group of patients with renal insufficiency compared with a concurrent group of patients with normal renal function undergoing EVAR with iodinated contrast angiography (ICA).

METHODS

Between 2003 and 2005, 100 consecutive patients who underwent EVAR using ICA, CO(2)-DSA, or both were retrospectively reviewed, and preoperative, intraoperative, postoperative, and follow-up variables were collected. Patients were divided into two groups depending on renal function and contrast used. Group I comprised patients with normal renal function in whom ICA was used exclusively, and group II patients had a serum creatinine >or=1.5 mg/dL, and CO(2)-DSA was used preferentially and supplemented with ICA, when necessary. The two groups were compared for the outcomes of successful graft placement, renal function, endoleak type, and frequency, and the need for graft revision. Comparisons were made using chi(2) analysis, Student t test, and the Fisher exact test.

RESULTS

A total of 84 EVARs were performed in group I and 16 in group II. Patient demographics and risk factors were similar between groups with the exception of serum creatinine, which was significantly increased in group II (1.8 mg/dL vs 1.0 mg/dL P < .0005). All 100 endografts were successfully implanted. Patients in group II had longer fluoroscopy times, longer operative times, and increased radiation exposure, and 13 of 16 patients required supplemental ICA. Mean iodinated contrast use was 27 mL for group II vs 148 mL in group I (P < .0005). Mean postoperative serum creatinine was unchanged from baseline, and 30-day morbidity was similar for both groups. No patient required dialysis. No patients died. Perioperatively, and at 1 and 6 months, the endoleak type and incidence and need for endograft revision was no different between groups.

CONCLUSIONS

CO(2)-DSA is safe, can be used to guide EVAR, and provides outcomes similar to ICA-guided EVAR. CO2-DSA protects renal function in the azotemic patient by lessening the need for iodinated contrast and associated nephrotoxicity, but with the tradeoff of longer fluoroscopy and operating room times and increased radiation exposure.

Synchrotron-based intravenous cerebral angiography in a small animal model

K-edge digital subtraction angiography (KEDSA), a recently developed synchrotron-based technique, utilizes monochromatic radiation and allows acquisition of high-quality angiography images after intravenous administration of contrast agent. We tested KEDSA for its suitability for intravenous cerebral angiography in an animal model. Adult male New Zealand rabbits were subjected to either angiography with conventional x-ray equipment or synchrotron-based intravenous KEDSA, using an iodine-based contrast agent. Angiography with conventional x-ray equipment after intra-arterial administration of contrast agent demonstrated the major intracranial vessels but no smaller branches. KEDSA was able to visualize the major intracranial vessels as well as smaller branches in both radiography mode (planar images) and tomography mode. Visualization was achieved with as little as 0.5 ml kg-1 of iodinated contrast material. We were able to obtain excellent visualization of the cerebral vasculature in an animal model using intravenous injection of contrast material, using synchrotron-based KEDSA.

Optimized radiographic spectra for small animal digital subtraction angiography

The increasing use of small animals in basic research has spurred interest in new imaging methodologies. Digital subtraction angiography (DSA) offers a particularly appealing approach to functional imaging in the small animal. This study examines the optimal x-ray, molybdenum (Mo) or tungsten (W) target sources, and technique to produce the highest quality small animal functional subtraction angiograms in terms of contrast and signal-difference-to-noise ratio squared (SdNR2). Two limiting conditions were considered-normalization with respect to dose and normalization against tube loading. Image contrast and SdNR2 were simulated using an established x-ray model. DSA images of live rats were taken at two representative tube potentials for the W and Mo sources. Results show that for small animal DSA, the Mo source provides better contrast. However, with digital detectors, SdNR2 is the more relevant figure of merit. The W source operated at kVps >60 achieved a higher SdNR2. The highest SdNR2 was obtained at voltages above 90 kVp. However, operation at the higher potential results in significantly greater dose and tube load and reduced contrast quantization. A reasonable tradeoff can be achieved at tube potentials at the beginning of the performance plateau, around 70 kVp, where the relative gain in SdNR2 is the greatest.

Angiographic guidewire with measuring markers: design and clinical experience

PURPOSE

We have developed an angiographic guidewire with measuring markers to determine accurately how far a guidewire is inserted within a catheter. We investigated whether use of this guidewire reduces the risk of vascular injury and the fluoroscopic time during guidewire manipulations.

METHODS

Four markers were put on the surface of the guidewire at 80, 100, 110, and 120 cm from the tip. The actual lengths of 54 catheters from seven manufacturers were measured and compared with the nominal lengths. Sixty consecutive patients who underwent angiography were randomized into two groups: in one group guidewires with surface markers were used (marker group) and in the other group, conventional guidewires (control group). For each guidewire insertion, the fluoroscopic time before the guidewire was pushed forward into the vessel lumen was recorded. The number of occasions on which unintentionally the guidewire had already been pushed out of the catheter at the start of fluoroscopy was also evaluated.

RESULTS

The actual lengths of all catheters were greater than the nominal lengths by 1.0-11.0 cm. Mean fluoroscopic time for each guidewire insertion was 3.3 sec in the marker group and 5.7 sec in the control group (p < 0.05). Guidewires were unintentionally pushed out of the catheters without fluoroscopy three times (3.6%), in each case in the control group.

CONCLUSION

The guidewire with measuring markers is effective for enhancing safety and in reducing fluoroscopic radiation during angiographic procedures. It is recommended that operators be aware that actual lengths of catheters may vary significantly from the nominal lengths listed; they should be aware of this with any guidewire, but particularly with the angiographic measuring guidewire.

High precision radiosurgery and technical standards

BACKGROUND

A high degree of precision and accuracy in radiosurgery is a fundamental requirement for therapeutic success. Small radiation fields and steep dose gradients are clinically applied thus necessitating a dedicated quality assurance program in order to guarantee dosimetric and geometric accuracy.

MATERIAL AND METHODS

A detailed analysis of the course of treatment independent of the irradiation technique used results in the so-called chain of uncertainties in radiosurgery (immobilisation, imaging, treatment planning system, definition of regions of interest, mechanical accuracy, dose planning, dose verification). Each link in this chain is analysed for accuracy and the established quality assurance procedures are discussed. A "System Test" was used to check the whole chain of uncertainties simultaneously.

RESULTS

The tests described are compatible with published reports on quality assurance in radiosurgery. In terms of accuracy the weakest link in the chain of uncertainties is stereotactic MR imaging. Geometric overall accuracy measured in the "System Test" is less than 0.7 mm.

CONCLUSION

The established quality assurance routines have clinically been validated. MR imaging dominates geometric overall accuracy in radiosurgery, which can be limited to less than 1 mm by an adequate quality assurance protocol.

Novel approaches to the measurement of arterial blood flow from dynamic digital X-ray images

We have developed two new algorithms for the measurement of blood flow from dynamic X-ray angiographic images. Both algorithms aim to improve on existing techniques. First, a model-based (MB) algorithm is used to constrain the concentration-distance curve matching approach. Second, a weighted optical flow algorithm (OP) is used to improve on point-based optical flow methods by averaging velocity estimates along a vessel with weighting based on the magnitude of the spatial derivative. The OP algorithm was validated using a computer simulation of pulsatile blood flow. Both the OP and the MB algorithms were validated using a physiological blood flow circuit. Dynamic biplane digital X-ray images were acquired following injection of iodine contrast medium into a variety of simulated arterial vessels. The image data were analyzed using our integrated angiographic analysis software SARA to give blood flow waveforms using the MB and OP algorithms. These waveforms were compared to flow measured using an electromagnetic flow meter (EMF). In total 4935 instantaneous measurements of flow were made and compared to the EMF recordings. It was found that the new algorithms showed low measurement bias and narrow limits of agreement and also out-performed the concentration-distance curve matching algorithm (ORG) and a modification of this algorithm (PA) in all studies.

Real-time image equalization for coronary X-ray angiography

Coronary angiograms, which provide detailed images of contrast-filled coronary arteries, also show other large structures such as the diaphragm, spine and adjacent lung field. A real-time image processing method to attenuate these unwanted features is presented. Side-by-side comparisons of images selected from cine runs before and after processing show that the arteries in the processed images can be visualized more easily due to their higher contrast as other structures are made less prominent. It is also shown experimentally that this method allows more quantitative comparisons of the contrast of vessels in different parts of an image.

3D rotational angiography: use of propeller rotation for the evaluation of intracranial aneurysms

We compared two methods of 3D digital subtraction angiography (DSA)--propeller and standard rotation--for the assessment of aneurysmal morphology and its relation to neighboring vessels. Aneurysms were correctly visualized and localized with both techniques. 3D DSA with propeller rotation technique seems to be effective and allows us to reduce the amount of contrast material related to a shortened acquisition time. Technical progress including propeller rotation allows a larger range of rotation and faster rotational speeds.

Heparin and air filters reduce embolic events caused by intra-arterial cerebral angiography: a prospective, randomized trial

BACKGROUND

Intra-arterial cerebral angiography is associated with a low risk for neurological complications, but clinically silent ischemic events after angiography have been seen in a substantial number of patients.

METHODS AND RESULTS

In a prospective study, diffusion-weighted magnetic resonance imaging (DW-MRI) before and after intra-arterial cerebral angiography and transcranial Doppler sonography during angiography were used to evaluate the frequency of cerebral embolism. One hundred fifty diagnostic cerebral angiographies were randomized into 50 procedures, each using conventional angiographic technique, or systemic heparin treatment throughout the procedure, or air filters between the catheter and both the contrast medium syringe and the catheter flushing. There was no neurological complication during or after angiography. Overall, DW-MRI revealed 26 new ischemic lesions in 17 patients (11%). In the control group, 11 patients showed a total of 18 lesions. In the heparin group, 3 patients showed a total of 4 lesions. In the air filter group, 3 patients exhibited a total of 4 lesions. The reduced incidence of ischemic events in the heparin and air filter groups compared with the control group was significantly different (P=0.002). Transcranial Doppler sonography demonstrated a large number of microembolic signals that was significantly lower in the air filter group compared with the heparin and control groups (P<0.01), which did not differ from each other.

CONCLUSIONS

Air filters and heparin both reduce the incidence of silent ischemic events detected by DW-MRI after intra-arterial cerebral angiography and can potentially lower clinically overt ischemic complications. This may apply to any intra-arterial angiographic procedure.

[Clinical study with angiography system using a flat panel detecter]

We have been using an X-ray angiography system that incorporates a flat panel detector (FPD) since December 2001. This system is equipped with the scintillator-type FPD PaxScan 4030A from Varian Medical Systems, and for objective comparison of the image intensifier (I.I.) and FPD, the system is constructed so that these detectors can be used alternatively. Using this system and other X-ray angiography systems, visual studies have been conducted on the digital subtraction angiography (DSA) images acquired by FPD and I.I. We have found from the clinical images that the FPD is superior to the I.I. in depiction of fine blood vessels as well as of physical characteristics. Fluoroscopy images acquired by the FPD were not entirely satisfactory, however the improvement made in its performance now permits equal use of the FPD and I.I. systems.

Vascular Guide Wire Navigation with a Magnetic Guidance System: Experimental Results in a Phantom

PURPOSE

To investigate the efficacy of a second-generation prototype magnetic guidance system in complex vessel phantoms versus conventional navigation in simulated interventional radiology procedures and to analyze procedure and fluoroscopy times.

MATERIALS AND METHODS

The magnetic guidance system consists of two focused-field permanent magnets on each side of the body that create a 0.1-T navigation field and is integrated with a modified C-arm single-planar digital angiography system. Forty-nine navigations in a glass phantom and 80 navigations in a three-dimensional liver phantom were performed with a magnetically tipped floppy 0.014-inch guide wire and a conventional 0.014-inch microcatheter system. Rates of success and fluoroscopy and procedure times were quantified for both techniques. For the liver phantom experiment, the Mann-Whitney U test was used. For the glass phantom experiment, the Wilcoxon matched pair test was used with the Hodges-Lehmann estimator.

RESULTS

In the glass phantom experiments, 42 of 49 turns were successfully performed with both methods. Procedure time to reach a target did not differ significantly between methods, while fluoroscopy time was significantly different when compared with that of the magnetic guidance system (P <.01). Navigation in the liver phantom was successful in 80 of 80 turns with the magnetic guidance system and in 76 of 80 turns with conventional navigation. With the support of the magnetic guidance system, procedure time and fluoroscopy time were significantly different from those with conventional navigation (P <.001).

CONCLUSION

The magnetic guidance system allows the precise navigation of a magnetic guide wire in complex vessel phantoms with significantly shorter fluoroscopy and procedure times.

[Value of multidetector computed tomography and digital subtraction angiography in assessment of arterio-venous fistula for hemodialysis--own experiences]

The aim of the study was to compare the utility of multidetector computed tomography (MDCT) in assessment of arterio-venous fistula (AVF) for hemodialysis (HD) in comparison with the "golden standard" which is digital subtraction angiography (DSA).

MATERIAL AND METHODS

The group consisted of 14 pts (9 males and 5 females, mean age 56.8 years +/- 14.3) on HD for 5 to 104 months, clinically suspected for failure of AVF. In all 14 subjects we performed MDCT and DSA of the arterio-venous fistula (AVF). MDCT exams were conducted on a 16 slice LightSpeed16 GE scanner, and on a Marconi Dual MX 8000. We assessed AVF from subclavian artery to the right atrium of the heart. DSA examinations were performed on GE Advantx LCA by Seldinger method. MDCT images were analysed on GE Advantage Workstation 4.1 with different reconstruction techniques: MPR (multiplanar reformation), MIP (maximum intensity projection), VE (virtual endoscopy), VR (volume rendering) and advanced vessel analysis for quantitative assessment of the vasculature.

RESULTS

MDCT showed 31 pathologies of AVF in 13 patients. Only one patient did not have any significant abnormalities. DSA was normal in 5 pts and demonstrated 14 pathologies in further 9 patients. MDCTproved to be more useful than DSA in diagnosis of the following abnormalities: thrombosis, intramural calcifications and thickness of AVF wall (respectively MDCT/DSA--8/1; 2/1; 6/0).

CONCLUSION

In summary, MDCT is more useful diagnostic method than DSA in assessment of AVF morphology. Its high sensitivity and specificity makes this method especially useful in assessment of complicated AVF.

Synchrotron radiation in radiology: radiology techniques based on synchrotron sources

The characteristics of synchrotron X-ray sources--quite different from those of conventional sources--are exploited by several new imaging techniques. These techniques expand the capabilities of conventional radiology and find interesting application in special cases. We briefly review the basic principle, applications and limitations of the most important of them: monochromatic mammography, two-wavelength digital subtraction angiography, phase-contrast/edge-enhancement imaging, diffraction-enhanced imaging and microtomography.

[Angiography]

The clinical usefulness of three dimensional images was widely recognized. The three dimensional digital subtraction angiography (3D-DSA) well demonstrated anatomical structures of cerebral arteries with high special resolution. This 3D observation allowed high quality planning for aneurysmal coil packing and neck clipping. Because of the bony structure and curvy arterial anatomy in the skull base region, 3D-CTA and MRA was sometimes distureved the demonstration of the anatomical relationship adjacent to the aneurysm. However, 3D-DSA not only demonstrated arterial anatomy, but also analyzed of vascular structure, quantifiably. And it was useful in radiation dose reduction by reduction of DSA exposure number. We believe that 3D-DSA should provided useful information for planning of surgical and endovascular treatment in the field of cerebro-vascular disease.

Multi-Slice CT Angiography in Diagnosing Total Versus Near Occlusions of the Internal Carotid Artery

BACKGROUND AND PURPOSE

To determine the accuracy of multislice computed tomographic (CT) angiography in diagnosing total versus near occlusions of the internal carotid artery (ICA).

METHODS

Fifty-seven ICA total or near occlusions identified by catheter angiography were studied with multislice CT angiography 1 to 3 days after catheter angiography. CT angiography in diagnosing total versus near occlusions was analyzed by 2 radiologists independently. The results were compared with those of catheter angiography.

RESULTS

Catheter angiography depicted 31 total occlusions, including 10 without a stump, 19 with a stump <2 cm, and 2 with a stump >2 cm. Among them, 22 had a downward extent of the retrograde ICA flow at or above the carotid siphon, 8 at the carotid canal, and 1 at the distal cervical ICA. Catheter angiography depicted 26 near occlusions, including 21 with a tight stenosis at the proximal third cervical ICA, 1 at the middle third, and 4 at the carotid canal or siphon. CT angiography correctly depicted all total and near occlusions. In total occlusions, the length of the stump and the retrograde flow were all accurately described by CT angiography. In near occlusions, the sites of tight stenoses were also correctly identified by CT angiography.

CONCLUSIONS

Multislice CT angiography had an excellent correlation with catheter angiography in diagnosing total versus near occlusion of the ICA. It may be considered as a substitute of catheter angiography in confirming the ultrasonographic results in diagnosing total versus near occlusions of the ICA.

CO2 digital subtraction splenoportography with the "skinny" needle: experimental study in a swine model

PURPOSE

To evaluate the safety and the effectiveness of CO2 splenoportography with the "skinny" needle.

METHODS

A flexible, 22 gauge needle ("skinny" needle) was introduced into the exteriorized spleens of five pigs. After checking the intrasplenic positioning with CO2 injection, increasing doses of CO2 (10-60 cm3) were injected using a dedicated CO2 injector with digital imaging. The puncture sites were observed during and after CO2 injections, and after removal of the needle. The spleens were then removed for gross and microscopic examination.

RESULTS

In all animals digital subtraction CO2 splenoportograms showed the splenic, extra- and intrahepatic portal veins, and the most distal portion of the superior mesenteric vein. No CO2 extravasation occurred in the spleen. There was no significant bleeding from the puncture site after removal of the needle. Gross and microscopic examination revealed no evidence of splenic rupture or intrasplenic hematoma.

CONCLUSION

CO2 splenoportography with the "skinny" needle is a safe and simple method of visualizing the portal vein and its branches. Careful appraisals of the clinical usefulness of the method will be needed in various clinical settings.

Space–time relationship in continuously moving table method for large FOV peripheral contrast-enhanced magnetic resonance angiography

Data acquisition using a continuously moving table approach is a method capable of generating large field-of-view (FOV) 3D MR angiograms. However, in order to obtain venous contamination-free contrast-enhanced (CE) MR angiograms in the lower limbs, one of the major challenges is to acquire all necessary k-space data during the restricted arterial phase of the contrast agent. Preliminary investigation on the space-time relationship of continuously acquired peripheral angiography is performed in this work. Deterministic and stochastic undersampled hybrid-space (x, k(y), k(z)) acquisitions are simulated for large FOV peripheral runoff studies. Initial results show the possibility of acquiring isotropic large FOV images of the entire peripheral vascular system. An optimal trade-off between the spatial and temporal sampling properties was found that produced a high-spatial resolution peripheral CE-MR angiogram. The deterministic sampling pattern was capable of reconstructing the global structure of the peripheral arterial tree and showed slightly better global quantitative results than stochastic patterns. Optimal stochastic sampling patterns, on the other hand, enhanced small vessels and had more favourable local quantitative results. These simulations demonstrate the complex spatial-temporal relationship when sampling large FOV peripheral runoff studies. They also suggest that more investigation is required to maximize image quality as a function of hybrid-space coverage, acquisition repetition time and sampling pattern parameters.

[An experience of the clinical study with angiography system using a Flat Panel Detector]

We had the chance of clinical studies by new proto-type Digital Subtraction Angiography (DSA) System with the Flat Panel Detector (FPD). That system has two types of detector, FPD and I.I.-CCD camera, and we can compare with image quality in clinical. We measured and discussed about the physical characteristic data of both detectors. Up to physical characteristic evaluation, FPD has good MTF and SNR performance, comparing with I.I.-CCD camera. In clinical evaluation, DSA image of FPD was superior to that of I.I.-CCD camera by visual comparison of medical doctors. Finally we discussed about the feasibility of replacement of detectors. We expect that DSA system will accept FPD in near future.

[The role of digital subtraction angiography in the diagnosis of renal artery injury]

In 3806 patients with vasorenal hypertension the results of kidney angiographic investigation were analyzed. In order to study the efficacy of application of intravenous digital substructional angiography (DSA), the data, obtained in 1621 patients using this method, were compared with such in general group of patients. Informativeness of DSA had constituted 88.9%. Accompanying chronic disease of intestine, excessive body mass, nephrosclerosis are complicating interpretation of obtained results in 10.1% of observations. Possible conduction of ambulatory investigations, decrease traumaticity, invasiveness, duration of procedure, shortening of financial expense constitute the main advantages of DSA. Application of method is recommended in all patients with vasorenal hypertension in ambulatory environment.

Standardized evaluation of CT angiography with remote generation of 3D video sequences for the detection of intracranial aneurysms

Computed tomography (CT) angiography is a well-known imaging technique commonly applied to both the detection and therapy planning of intracranial aneurysms. For this purpose, current studies predominantly focus on three-dimensional (3D) representations of CT angiographic volumes obtained with varying visualization approaches on different computers. Interactive manipulation performed by users individually is an important prerequisite for data analysis. However, this leads to inconsistent and barely reproducible 3D visualization results. Furthermore, the quality of any 3D representation depends on the applied visualization strategy (eg, maximum-intensity projection, shaded-surface display, direct volume rendering). To overcome these limitations, the authors present a novel method for standardized visualization of CT angiographic volumes, consisting of three steps: (a) transfer of the image data to a remote high-end graphics workstation, (b) automatic 3D visualization with high-resolution direct volume rendering, and (c) consecutive video generation performed according to a standardized protocol. The recorded video sequences are transferred for evaluation to a local desktop computer. In the experimental setup, high-quality videos based on 3D visualizations were produced in less than 60 minutes per patient. Although aneurysms above the skull base are usually visualized with excellent quality, the analysis of aneurysms at the skull base is still difficult.

[Patient absorbed dose in coronary angiography determined by the flat panel digital detector X-ray system]

The INNOVA 2000, an all-digital cardiovascular X-ray system with flat panel detector, is equipped with a monitoring function that makes it possible to track a patient's absorbed dose by displaying the real-time presumed absorbed dose. We verified this dose monitoring system and evaluated how it is affected by various parameters. We also compared the INNOVA 2000 to a conventional machine, the Advantx LC. The average absorbed dose of the INNOVA 2000 was 1,066 mGy, while that of the Advantx LC was calculated to be 2,028 mGy. Dose reduction with the INNOVA 2000 was 76% at Low mode and 52% even at Normal mode. The INNOVA provides an advantage in lowering absorbed dose, even considering that it has a rectangular image intensifier (I.I.) versus the Advantx LC's round I.I. This comparison was made by cine and digital angiography.

Fine-needle percutaneous transhepatic parenchymal portal venography by using carbon dioxide: a pilot study in pigs

Our purpose was to evaluate the feasibility and safety of carbon dioxide (CO(2)) in fine-needle percutaneous transhepatic parenchymal portal venography and its potential clinical applications. Three Belgian landrace pigs received fine-needle percutaneous transhepatic parenchymal portal venography by using CO(2) as a contrast agent. Under fluoroscopic and B-mode ultrasonic guidance, right or left lobe of liver was punctured with a 22-G Chiba needle, through which CO(2) was injected with a dedicated CO(2) injector at injection rate of 20 ml/s for 20 ml, 40 ml/s for 40 ml, 40 ml/s for 60 ml, and 40 ml/s for 80 ml, respectively. The portal venograms were obtained by use of digital subtraction angiography (DSA) system with animal in supine position. In one pig transarterial portal venography was performed, in addition, using iodinated contrast agent. The portal vein was visualized in each run of venography. Optimal images of portal tree structure up to four-order branches were obtained in all those with CO(2) injection rate of 40 ml/s, which appeared much better in quality than those obtained by cranial mesenteric arteriography with iodinated contrast agent. No extravasation of CO(2), liver laceration, or any other complication occurred during the procedures. The technique we proposed demonstrated optimal portography, which appeared to be safe, minimally invasive, less time-consuming, cost-effective, and easy to perform, with great potential in clinical applications.