Conventional Computed Tomography Scans Research Articles

Development of an ultrafast X-ray computed tomography scanner system: Application for measurement of instantaneous void distribution of gas-liquid two-phase flow

An ultrafast X-ray computed tomography (CT) scanner has been developed. This scanner overcomes problems that occur in a transient or unsettled state, which make the conventional CT scanner inappropriate. To reduce the scanning time, this X-ray CT system uses electronic switching of electron beams for X-ray generation instead of the mechanical motion adopted by conventional CT scanners. The mechanical motion is a major obstacle to improving scanning speed. A prototype system with a scanning time of 3.6 ms was initially developed and confirmed to measure the dynamic events of two-phase flow. However, an increased scanning speed is generally required for practical use in the thermal hydraulics research field. Therefore, an advanced type which can operate under the scanning time of 0.5 ms and can measure two-phase flow with a velocity up to 4 to 5 m/s was developed. © 2000 Scripta Technica, Heat Trans Asian Res, 29(3): 155–165, 2000

Accuracy and significance of computed tomographic scan assessment of hepatic volume in patients undergoing liver transplantation.

A small liver volume is considered to be a poor prognostic factor in cirrhosis, often indicative of advanced liver disease. Radiologic assessment of liver volume before liver transplant is routinely performed in many transplant centers. We sought to assess the accuracy and significance of computed tomographic (CT) scanning in hepatic volumetric analysis by correlating CT-derived estimation of liver volume with that of corresponding liver explants. A chart review of all patients aged 17 years or older undergoing liver transplant at Mount Sinai Medical Center between 1989 and 1995 was performed. Each patient underwent conventional CT scanning with measurement of liver volume (CTLV). Recipient liver volume (RLV) was defined as weight of liver explant after all attached ligaments, portal structures, and gallbladder were dissected free. Expected liver volume was calculated pretransplant based on age, gender, height, and weight. Patients were categorized into three groups based on etiology of liver disease: (1) hepatocellular (e.g., viral hepatitis, alcohol-related), (2) cholestatic (e.g., primary biliary cirrhosis), and (3) cryptogenic. The ratio of CTLV to RLV was used as a measure of the accuracy of CT volumetric analysis. A total of 579 patients was studied (group 1=376, group 2=139, group 3=64). All three groups were statistically similar with regard to age, prothrombin time and total bilirubin. Median CT liver volume was 1308 ml (range: 338-3847), 1651 ml (range: 641-3861), and 1210 ml (range: 348-2575) in groups 1-3, respectively; median ratio of CTLV to RLV was 1.02 (range: 0.50-2.31), 1.05 (range: 0.52-2.22), and 1.05 (range: 0.50-1.56) for groups 1-3, respectively. When RLV was small, it tended to be overestimated by CTLV. In contrast, when RLV was large, it was often underestimated. Clinical features such as history of esophageal variceal bleed, encephalopathy or ascites, and laboratory data did not influence accuracy of CT volumetric analysis. CT-derived estimation of liver volume appears to correlate closely with actual weight of liver explant regardless of the etiology of chronic liver disease. With extremes in CT volumetric analysis, actual liver volume tends to be under- or overestimated. For patients with end-stage liver disease, both CT-derived and actual liver volume are greater in cholestatic than in hepatocellular disorders.

ボイド分布変動測定

An ultra-fast X-ray computed tomography (CT) scanner has been developed for measurement of gas-liquid two-phase flow. This scanner overcomes problems that occur in a transient or unsettled state, which make the conventional CT scanner inappropriate. To reduce the scanning time, this X-ray CT system uses electronic switching of electron beams for X-ray generation instead of the mechanical motion adopted by conventional CT scanners. A prototype system with a scanning time of 3.6 milliseconds was initially developed and confirmed to measure the dynamic events of two-phase flow. However, an increased scanning speed is generally required for practical use in the thermal-hydraulics research field. Therefore, an advanced type which can operate under the scanning time of 0.5 milliseconds and can measure two-phase flow with a velocity up to 4-5 m/s was developed.

Treatment Planning of Tangential Breast Irradiation Using a Simulator with CT-Option Compared to a Conventional CT

Treatment planning for breast cancer is often performed using a conventional computed tomography (CT), which does not allow patient positioning in the treatment set-up. Using a simulator with CT option the scanning procedure can be performed in an identical position as the treatment. Aim of the present study was to investigate feasibility and accuracy of a simulator with CT option compared to treatment planning with a conventional CT for breast irradiation. Twenty patients submitted for radiotherapy after breast conserving surgery underwent simulation with the SLS-CT (Elekta Oncology Systems, EOS). Additionally, a planning CT with a diagnostic CT scanner (Somatom Plus, Siemens,) was performed. All the patients were scanned with both modalities and had 3 to 5 slices. For Somatom-CT patients lay flat, for SLS-CT they rested on a breast angle board. The target volume was delineated in the CT scans obtained with both modalities, the planning procedure was carried out using the 3-D planning system Helax-TMS. The median values for SLS-CT (1) and Somatom (2) were: Target volume: 679 cm3 (1) and 670 cm3 (2) for all patients and 1,025 cm3 (1) and 1,100 cm3 (2) for large breasts. Maximal dose in the dose-volume histogram (DVH): 109.3% (1) and 109.7% (2). Lung volume in the 20% isodose: 119 cm3 (1) and 123 cm3 (2). The distance between entrance and exit point in the central axis: 13.8 (1) and 14.6 cm (2). Treatment planning with a CT option is feasible, the simulation procedure can be performed with 1 single device and under identical set-up conditions as the treatment itself. Our data show a tendency towards sparing of irradiated volume with SLS-CT, the clinical relevance cannot yet be determined.

Tolosa-Hunt syndrome: Focus on MRI Diagnosis

Experience with modern neuroimaging techniques, computed tomography (CT) and magnetic resonance imaging (MRI) scans, in the diagnosis of Tolosa-Hunt syndrome (THS) is reviewed. Conventional CT scan remains normal in about two-thirds of these patients. In the reported 22 patients meeting the IHS criteria for a THS diagnosis on whom an MRI study was performed, MRI revealed a convex enlargement of the symptomatic cavernous sinus by an abnormal tissue isointense with gray matter on short TR/TE images and isohypointense on long TR/TE images. This abnormal tissue markedly increases in signal intensity after contrast injection. MRI seems also to be the ideal technique to follow progressive resolution of the abnormal tissue after steroids. Therefore, normal MRI would probably exclude THS, whereas in the appropriate clinical setting of steroid-responsive painful ophthalmoplegia, MRI showing the cavernous sinus abnormality described here suggests a diagnosis of THS. From these data, we propose that the fourth IHS criterion for THS diagnosis, "Exclusion of other causative lesions by neuroimaging and (not compulsory) carotid angiogram" should be changed to "Finding by MRI of specific cavernous sinus abnormalities (with the characteristics described herein) which slowly resolve with steroid treatment".

Micronodules and emphysema in coal mine dust or silica exposure: relation with lung function.

The aim of this study was to investigate the respective effects of micronodules and pulmonary emphysema, detected by computed tomography (CT), on lung function in workers exposed to silica and coal mine dust. Eighty-three subjects exposed to silica (n=35) or to coal mine dust (n=48), without progressive massive fibrosis, were investigated by high-resolution and conventional CT scans to detect micronodules and to quantify pulmonary emphysema by measuring the relative area of the lung with attenuation values lower than -950 Hounsfield units. Sixty-six (54.5%) subjects had evidence of micronodules on CT scans. Smokers had micronodules more rarely than nonsmokers. Significant correlations were found between the forced expiratory volume in one second (FEV(1); % predicted) (r=-0.41, p<0.001), FEV1/vital capacity (VC) (r=-0.61, p<0.001), diffusing capacity of the lung for carbon monoxide (DL,CO) (r=-0.36, p<0.001) and the extent of emphysema. No difference was demonstrated in the linear relationships between the extent of emphysema and the pulmonary function according to the type of exposure or the presence of micronodules on CT scans. This study suggests that micronodules detected by computed tomography have no influence, by themselves, on pulmonary function and that they should only be considered as a marker of exposure.

Development of ultra-fast X-ray computed tomography scanner system

The development of an ultra-fast X-ray computed tomography (CT) scanner system has been achieved. This system can operate under the scanning time of 0.5 milliseconds/slice and give 2,000 slices/second. The original object of interest is in a transient or unsettled state of multiphase flow to measure the instantaneous phase distribution. An improvement of scanning speed was required to reduce the effects of motion artifact. The mechanical motion mechanism of a conventional CT scanner is a major obstacle to improve the scanning speed. Therefore, the concept of electrically switching the electron beam is adopted to reduce the scanning time. The present developed system has 60 stationary X-ray tubes and stationary 584 cadmium telluride (CdTe) semiconductor detectors. The excellent performance for the measurement and visualization of dynamic events of multiphase flow is confirmed by measuring moving acrylic resin phantoms and the air-water two phase flow in a tube or a 3/spl times/3 rod bundle. In addition, the system's feasibility for application to the medical field is demonstrated by trial application to the movement of a dog's heart, though the requirement remains to improve the image quality. It was confirmed by a simulation that this improvement will be achieved by increasing the number of projections.

Magnetic resonance imaging (MRI) for localization of the prostatic apex: comparison to computed tomography (CT) and urethrography

Background and purpose: It is necessary to include the entire prostate in the high dose treatment volume when planning radical radiation for patients with prostate cancer. We prospectively compared magnetic resonance imaging (MRI) to computed tomography (CT) and urethrography as means of localizing the prostatic apex. Materials and methods: Thirty patients with clinically localized prostate cancer had a sagittal T2-weighted MRI scan and a conventional axial CT scan performed in the treatment position prior to the start of radiotherapy. Twenty of these patients had a static retrograde urethrogram performed at simulation. The position of the MRI and CT apices were localized independently by two radiation oncologists. In addition, the MRI apex was localized independently by a diagnostic radiologist. The urethrogram apex, defined as the tip of the urethral contrast cone, was easily identified and was therefore localized by only one observer. Results: There was good interobserver agreement in the position of the MRI apex. Interobserver agreement was significantly better with MRI than with CT. There were no systematic differences in the position of the MRI and CT apices. However, the MRI apex was located significantly above and behind the urethrogram apex. There was poor correlation between MRI and CT and between MRI and urethrogram in the height of the apex above the ischial tuberosities. There was 83% agreement between MRI and CT and 80% agreement between MRI and urethrogram in the identification of patients with a low-lying apex. The apex, as determined by MRI, was <2 cm above the ischial tuberosities and therefore potentially under-treated in 17% of the patients. Conclusions: MRI is superior to CT and urethrography for localization of the prostatic apex. All patients undergoing radiotherapy for prostate cancer should have localization of the apex using MRI or a technique of equal precision to assure adequate dose delivery to the entire prostate and to minimize the unnecessary irradiation of normal tissues.

Laryngeal radionecrosis versus recurrent cancer: a clinical approach.

A group of 38 patients was studied by positron emission tomography utilizing fluorine18-labeled deoxyglucose (FDG-PET) scanning to examine the ability to differentiate postirradiation laryngeal recurrent cancer from radionecrosis. The resulting 79% correct diagnosis showed the technique to be far superior to conventional computed tomography scanning (61%) and clinical examination (43%). An algorithmic approach to evaluating and treating patients with radionecrosis and/or recurrent cancer by utilizing FDG-PET scanning is presented.

THREE-DIMENSIONAL COMPUTED TOMOGRAPHY FOR PLANNING UROLOGIC SURGERY

The development and marketing of new volumetric computed tomography (CT) scanners in 1990 made it possible to perform three-dimensional (3-D) imaging of the abdomen without artifacts and with clarity similar to that achieved in the musculoskeletal and central nervous systems by conventional scanners. 6 Before 1990, all CT scanners had x-ray tubes that were connected to the machine's gantry by electrical cables. This limited the excursion of the tube in any one direction because continuous rotation would wind the cables into a knot. Thus, conventional CT scanning is performed by executing a series of individual CT scan slices during which patients are instructed to hold their breath. Between scans the table is moved forward a certain distance and the process is repeated. If the breath holds are not identical, the imaged organ or region contains gaps or skip areas. This limitation is termed respiratory misregistration. The technical advantage that made volumetric CT possible was the development of a continuously rotating x-ray tube with slip rings. Slip rings are a pair of matched rings on the tube and gantry that can rotate past one another without limit. This allows for continuous rotation of the tube and the ability to perform a continuous x-ray exposure as the patient is moved forward through the CT gantry. The resulting exposure forms a path that looks like a or helix; hence, today volumetric CT scanning often is referred to as spiral or helical CT. Spiral CT acquires data in a region of interest using a single continuous x-ray exposure that is fast enough to be executed during a single breath hold, as the patient moves through the gantry, so that misregistration is eliminated. An entire body region is imaged and a continuous volume of CT data obtained. The resulting volumetric CT data set can be used to create axial images at a desired slice thickness and at a desired increment. Standard axial images from CT of the urinary tract have been shown to be helpful in the diagnosis and staging of renal masses and are now routinely used for evaluation of renal lesions. 15,16 However, the same CT data can be reformated in multiple planes or in three dimensions. Although newer 3-D reconstruction techniques retain more data than did older reformatted display methods, 3-D images cannot contain more information than appropriately filmed axial images from the same source data set. Thus, with the possible exception of CT angiography and future developments in virtual endoscopy, 3-D images, by themselves, are of limited diagnostic utility. However, 3-D imaging of the urinary tract is useful in surgical planning, because it allows surgeons to visualize 3-D anatomic relationships clearly. 3-D images created from the same CT data sets for diagnosis and staging of renal masses have been used to create color-coded 3-D surface renderings of renal masses and surrounding structures for surgical planning of partial nephrectomy. 1 A preliminary investigation and one published case report 9 have shown that this technique can help the urologist locate small renal masses and can help delineate the relationship between a mass and the urinary collecting system during operative planning. Currently, in addition to standard CT, conventional preoperative assessment of a patient before a partial nephrectomy may include aortography and selective renal angiography to determine the number, location, and pattern of branching of renal vessels. Intravenous pyelography also may be indicated to evaluate the anatomic relationship of any renal masses to the intrarenal collecting system and proximal ureter. Someday, 3-D rendering of the same CT data set used to diagnose the tumor may be able to display the relationship between the tumor and the renal parenchyma, vasculature, and collecting system, thus obviating the need for these additional tests.

Development of an Ultra-fast X-ray Computed Tomography Scanner System. Application for Measurement of Instantaneous Void Distribution of Gas-Liquid Two-Phase Flow.

An ultra-fast X-ray computed tomography (CT) scanner has been developed. This scanner overcomes problems that occur in a transient or unsettled state, which make the conventional CT scanner inappropriate. To reduce the scanning time, this X ray CT system uses electronic switching of electron beams for X-ray generation instead of the mechanical motion adopted by conventional CT scanners. The mechanical motion is a major obstacle to improve scanning speed. A prototype system with a scanning time of 3.6 milliseconds was initially developed and confirmed to measure the dynamic events of two-phase flow. However, an increased scanning speed is generally required for practical use in the thermalhydraulics research field. Therefore, an advanced type which can operate under the scanning time of 0.5 milliseconds and can measure two-phase flow with a velocity up to 4∼5 m/s was developed.

内耳奇形の３次元ＣＴ所見 聴力残存例を中心に

Up to now the diagnosis of inner ear anomalies has been largely dependent on pathohistological studies. In clinical practice, however, imaging diagnostics are inevitably used to characterize inner ear anomalies. Imaging diagnostics has evolved through a number of steps: simple roentgenography, tomography, computed tomography (CT), high resolution CT and magnetic resonance imaging (MRI). Over the course of development of MRI and imaging diagnostics, pros and cons of these methods have been discussed. We have applied three-dimensional helical CT scanning (3D-CT), which has recently been put to use in clinical diagnosis, to observe shortening of the cochlear turn, which could not be visualized with conventional two-dimensional CT scanning (2D-CT). Case #1, a 17-year-old male, had an inner ear anomaly of the Mondini type, with hearing of 40dB HL in the frequency range for conversation. 2D-CT indicated an anomaly of the cochlea, but failed to reveal its detailed structure. On the contrary, 3D-CT clearly indicated that a part of the cochlear turn was missing. Case #2, a 35-year-old female, had fluctuating hearing levels in the left ear and hearing of 80-40dB HL in the frequency range for conversation. While 2D-CT suggested only a relatively minor anomaly of the inner ear without showing the developmental status of the cochlea in detail, 3D-CT pointed out a shortened cochlear turn. In this way, 3D-CT permitted identification of the cause of deafness, which could not be defined by 2D-CT. These observations suggest that 3D-CT is useful as a method of diagnosing inner ear anomalies and deafness of unknown cause.

Utility of low mA 1.5 pitch helical versus conventional high mA abdominal ct

The objective of this study was to evaluate the utility of a low mA 1.5 pitch helical versus conventional high mA conventional technique in abdominal computed tomography (CT). Twenty-five patients who had both a conventional high mA (>300) and a 1.5 pitch low mA (80–125) helical CT within 3 months were selected for inclusion in the study. Patients were excluded who had a significant change in pathology between the two studies. The other parameters (injection rate, contrast type and volume, and filming window/level) were constant. The studies were randomized and blinded to five separate experienced readers who graded the studies by a variety of normal anatomical structures and pathological criteria. Overview questions also assessed noise, resolution, contrast, and overall quality. The abdominal wall/retroperitoneum and hiatal hernias were statistically better visualized on the conventional high mA studies. However, for all other normal anatomical and pathological sites, there was equivalent or better visualization on the helical versus the conventional CT examinations. The resolution of the helical studies was graded statistically better than the high mA conventional CT scans as was the amount of noise present on the images. While there was some advantage for conventional high mA CT with respect to contrast enhancement and low contrast sensitivity, these differences were not statistically significant. It appears from the data of this study that a low mA technique in evaluating the abdomen may be a useful option in performing routine abdominal CT. The radiation dose savings to the patient is significant and there appears to be little degradation of image quality using a low mA 1.5 helical versus mA conventional CT technique.

Comparison of technetium-99m sestamibi and indium-111 octreotide imaging in a patient with ewing's sarcoma before and after stem cell transplantation

We report the use of two novel nuclide agents, Technetium-99m (99Tc)sestamibi (MIBI) and indium-111 (In-111) octreotide, in comparison with conventional computed tomography (CT) imaging in a patient with metastatic Ewing's sarcoma (ES) before and after high dose chemotherapy with autologous peripheral stem cell transplantation (PSCT). MIBI is taken up actively by metabolically active tumor cells. Octreotide, a somatostatin analog, binds specifically to somatostatin receptors.The patient was a 20-year-old male with recurrent metastatic ES to the lung. Before and sequentially after high dose chemotherapy and PSCT, the patient was imaged with MIBI. Whole body planar and single photon emission computed tomography (SPECT) images were obtained after the injection of 30 mCi of 99Tc MIBI. Prior to PSCT the patient was imaged with 6 mCi In-111 pentreotide.Conventional CT scans also were performed. Initial CT revealed pulmonary metastasis in the right lower lobe along with multiple left pleural-based lesions. These lesions were visualized clearly with MIBI. Octreotide detected only the left lung involvement. Sequential MIBI scans after PSCT correlated with tumor reduction in the right lung field and tumor progression in the left lung as well as the development of new pulmonary metastasis. These findings were confirmed on CT.MIBI imaging was highly concordant with CT scanning in the detection of metastatic ES. MIBI scanning holds promise for the direct detection of a variety of human malignancies, and may prove useful as a rapid whole body imaging modality.

HIV-associated human herpesvirus 8-positive primary lymphomatous effusions: radiologic findings in six patients.

To define the imaging features of body cavity-based lymphoma (BCBL) related to the acquired immunodeficiency syndrome. This is a peculiar type of non-Hodgkin lymphoma harboring infection by human herpesvirus 8 (HHV-8) and displaying a peculiar tropism for the serous body cavities. At diagnosis of BCBL, six consecutive patients were investigated with radiography of the chest and conventional computed tomography (CT) of the chest and abdomen. For all patients, clinical features and results of biologic characterization of the lymphoma were also available. In all patients, chest radiographs displayed bilateral or unilateral pleural effusion in the absence of parenchymal opacities or mediastinal enlargement. CT scans confirmed chest radiographic findings and revealed a slight thickening of the parietal pleura in all patients and a pericardial thickening in four patients. CT also depicted pericardial and abdominal effusions in five and two patients, respectively, in the absence of solid tumor masses or parenchymal abnormalities. BCBL must be included among the differential diagnoses of serous effusions detected radiologically in individuals infected with the human immunodeficiency virus (HIV). Since the combination of serous effusion, slight serosal thickening, and absence of solid masses is compatible with, though not specific for, BCBL in the context of HIV infection, radiologic findings need to be complemented by a detailed biologic and virologic characterization of tumor cells.

Imaging funzionale per diffusione (DWI) e ischemia cerebrale in fase acuta: Potenzialità diagnostiche e confronto con metodiche convenzionali

Stroke is the third leading cause of death and is a major cause of long-term disability. Neuroprotective treatment within a 4-hour «therapeutic window» has proved highly efficacious in reducing morbility and mortality in animal model. It is with this background that the need for emergent diagnosis and therapy of acute stroke in strongly suggested. Computed tomography (CT) shows the parenchymal changes of acute stroke too late to be helpful, and its role has been primarily to evaluate the possibility of intracerebral or subarachnoid hemorrhage. While conventional magnetic resonance (MR) imaging can demonstrate parenchymal abnormalities 4–6 hours after ischemia, newer techniques such as diffusion-weighted MR imaging (DWI) hold promise that a diagnosis of ischemia can be made within minutes after the acute event. In this article compares different aspects of hyperacute cerebral ischemia depicted at diffusion-weighted imaging before infarction is depicted at conventional MR or CT scans. DWI techniques may improve stroke diagnosis and may contribute to advances in treatment.

Preoperative Sizing of Grafts for Transfemoral Endovascular Aneurysm Management: A Prospective Comparative Study of Spiral CT Angiography, Arteriography, and Conventional CT Imaging

Purpose: To define the impact of spiral computed tomographic angiography (CTA) with image reconstruction on graft selection for Transfemoral Endovascular Aneurysm Management (TEAM) by comparing it to conventional computed tomography (CT) and contrast arteriography. Methods: Twenty-one candidates for TEAM were included. The diameters of the superior and inferior aneurysm necks and lengths between the graft attachment sites were measured using the three imaging techniques. These measurements and their consequences on graft selection were studied. Results: The difference in length sizing between spiral CTA and arteriography never exceeded 1 cm; however, lengths measured by conventional CT scanning resulted in underestimation of graft length in 91% of patients. Graft diameters were chosen too small in 62% of the patients when based on arteriographic diameter measurements. A graft of similar diameter was selected by spiral CTA and conventional CT scanning in 81% of the patients, while minor oversizing by conventional CT scanning was found in 14%. Conclusions: Neither conventional CT scanning nor arteriography is adequate as a sole preoperative radiological investigation for TEAM graft sizing. Spiral CTA with image processing produces all information required for selection of tho-optimal graft size and should be regarded the method of first choice for this purpose.

Imaging of the hepatobiliary tract.

Over the past two decades, ultrasonography and computed tomography (CT) have emerged as the principal imaging methods for diagnostic examination of the liver and biliary tree. The other noninvasive imaging techniques, including magnetic resonance imaging (MRI), oral cholecystography, and nuclear scintigraphy, are used for difficult diagnostic problems, and invasive studies, such as angiography and direct cholangiography (transhepatic or retrograde), are increasingly used for treatment. Recent Technical Advances Advances in electronics have improved diagnostic imaging. Perhaps the most important advance in liver imaging has been the introduction of helical or spiral CT scanning.1 With conventional CT scanners, the CT table remains . . .

Imaging modalities for aortic endografting.

One of the most fundamental and influential differences between conventional surgery and endovascular grafting for aortic aneurysm is the central role of imaging in every aspect of management. This review summarizes five imaging techniques for aortic endografting: intravascular ultrasound, contrast angiography, conventional computed tomography (CT), spiral CT with image processing, and magnetic resonance angiography (MRA). External ultrasound and intravascular ultrasound have important relevance to endovascular aortic surgery. Artifacts of arteriography include magnification, thrombus effect, fore-shortening of tortuosity, loss of luminal detail, parallax error, and projection errors. Conventional CT scans have artifacts and difficulties also. Diameter measurement by CT suffers from methodology errors and observer variability. If conventional CT and angiography are used for endovascular aortic graft planning, both should be obtained since neither alone provides sufficient data. The use of spiral CT scanning and computerized image processing has clearly aided the preoperative definition of aneurysm morphology both in terms of dimensional accuracy and by adding diagnostic information. MRA is capable of producing three-dimensional images, axial sections, and longitudinal projections in any plane. It can detect blood flow without contrast medium, but gadolinium enhances MRA by avoiding the "signal dropout" artifact. Technology exists to provide new forms of imaging for endovascular surgery that combines three-dimensional models with on-line image data in a process called "data fusion." This may offer improved ease and accuracy for conducting endovascular procedures in the future.

Imaging Modalities for Aortic Endografting

One of the most fundamental and influential differences between conventional surgery and endovascular grafting for aortic aneurysm is the central role of imaging in every aspect of management. This review summarizes five imaging techniques for aortic endografting: intravascular ultrasound, contrast angiography, conventional computed tomography (CT), spiral CT with image processing, and magnetic resonance angiography (MRA). External ultrasound and intravascular ultrasound have important relevance to endovascular aortic surgery. Artifacts of arteriography include magnification, thrombus effect, foreshortening of tortuosity, loss of luminal detail, parallax error, and projection errors. Conventional CT scans have artifacts and difficulties also. Diameter measurement by CT suffers from methodology errors and observer variability. If conventional CT and angiography are used for endovascular aortic graft planning, both should be obtained since neither alone provides sufficient data. The use of spiral CT scanning and computerized image processing has clearly aided the preoperative definition of aneurysm morphology both in terms of dimensional accuracy and by adding diagnostic information. MRA is capable of producing three-dimensional images, axial sections, and longitudinal projections in any plane. It can detect blood flow without contrast medium, but gadolinium enhances MRA by avoiding the “signal dropout” artifact. Technology exists to provide new forms of imaging for endovascular surgery that combines three-dimensional models with on-line image data in a process called “data fusion.” This may offer improved ease and accuracy for conducting endovascular procedures in the future.