Optimization and diagnostic accuracy of computerized tomography with tridimensional spiral technique in the study of craniostenosis

INTRODUCTION: Conventional Computed Tomography (CT) with three-dimensional (3D) reconstructions is considered the most complete and accurate imaging modality to diagnose craniosynostosis. However, the introduction of Spiral CT (SCT) opened new possibilities for 3D studies of the skull in pediatric patients with craniosynostosis. The purpose of our study is two fold: first, to optimize the scanning and imaging parameters to obtain diagnostic images in a single spiral scan; second, to assess the diagnostic accuracy of such images in the identification of normal and abnormal cranial vault sutures. MATERIAL AND METHODS: Seventy-eight pediatric patients (age range: 1-35 months; mean: 11.8 months) with craniosynostosis were submitted to SCT of the head. The images were acquired with the following parameters: 3- and 5-mm nominal slice thickness, 5-6 mm/s table feed (pitch 1-2), 165 mAs and 120 kV. Two different algorithms and increases were used for image reconstructions. A first set of images was reconstructed with 2-mm increases and a soft tissue algorithm: these images were used for brain studies and for 3D reconstructions. A second set of slices was reconstructed with 5-mm increases and a bone algorithm to visualize the sutures of the axial plane. The 3D images were processed with the Shaded Surface Display software with threshold values ranging 120-150 HU. All images were acquired with a single spiral scan lasting less than 30 seconds. Two blinded radiologists analyzed the 3D and the planar images independently to evaluate the course and depth of each cranial suture. The sensitivity, specificity and diagnostic accuracy of both 3D and planar SCT images were evaluated. The frequency of artifacts (the Lego effect, boiled egg, pseudoforamina, movement, and chainsaw artifacts) and their influence on the final diagnosis were studied on 3D SCT images. RESULTS: The diagnostic accuracy rates of 3D SCT images, by suture, were: sagittal 90.7%, metopic 100%, left lamboid 90.9%, right lamboid 93.9%, left coronal 85.7%, right coronal 91.1%. The diagnostic accuracy rates of the axial images, by suture, were: sagittal 90.7%, metopic 95.5%, left lamboid 86.4%, right lamboid 90.9%, left coronal 83.7%, right coronal 91.1%. The interobserver agreement on 3D images was: sagittal 91.1%, metopic 100%, left lamboid 88.9%, right lamboid 91.1%, left coronal 88.9%, right coronal 84.4%. The Lego effect artifact was the most frequent one (82%) and affected image evaluation in 6.3% of cases. CONCLUSIONS: Our results prove that 3D SCT is a very accurate technique for identifying normal and abnormal sutures and presents many advantages over conventional 3D CT in the examination of pediatric patients with craniosynostosis. The quality of 3D SCT images was adequate and the artifacts did not affect the final diagnostic yield significantly.     

Identification of the aberrant hepatic artery with axial spiral CT

PURPOSE: To determine whether axial spiral computed tomography (CT) allows detection of the replaced hepatic artery as part of preoperative planning for pancreatic tumor resection. MATERIALS AND METHODS: Axial spiral CT scans (8-mm section thickness, 4-mm overlapping reconstructions) were obtained in 50 patients with periampullary tumor and were examined by three radiologists. Readers' interpretations were compared with angiographic results. RESULTS: Eight patients had an aberrant hepatic artery. Two of the three readers detected or suspected all of these abnormalities (100% sensitivity), and one reader identified seven of eight aberrant arteries (88% sensitivity). However, readers requested angiographic confirmation in 14 of 24 tests. Sensitivity, specificity, and accuracy were 96%, 87%, and 88%, respectively, for all readers. CONCLUSION: Axial spiral CT may simplify preoperative evaluation of periampullary tumors. However, angiographic support was necessary in most cases in this study. Improvements in CT techniques may eventually allow spiral CT to replace angiography in the examination of these patients.     

Three-dimensional display of the bronchi using helical CT

The purpose of this study was to evaluate the clinical usefulness of three-dimensional (3D) images of the bronchi obtained using helical CT. Thirteen patients with lung cancer, one with tracheal diverticulum, and one with bronchial amyloidosis were examined. The CT scanner employed was the Toshiba Xforce. The helical CT scan cycle consisted of 20 continuous rotations, each requiring 1.5 sec, for a total scanning time of 30 sec. Scans were obtained using a 5-mm X-ray beam width, a 5-mm/1.5 sec couchtop sliding speed, and a 2-mm reconstruction interval. 3D images were reconstructed using a CEMAX VIPstation. The optimal lower and upper threshold CT values for 3D images of the bronchi were -650 and -100 HU, respectively, and 3D images clearly depicted endobronchial lesions. Cartilage crescents were also demonstrated, but longitudinal and circular mucosal folds could not be visualized. In conclusion, 3D images of the bronchi acquired using helical CT were useful in evaluating endobronchial lesions.     

Corticobasal degeneration: a combined clinical, PET and pathological study

OBJECTIVE: The purpose of this study was to evaluate the application of helical CT-generated three-dimensional images of the upper airway. MATERIALS AND METHODS: Thirty patients, 10 healthy and 20 with upper-airway disease, were studied with helical CT (5-mm collimation). Overlapping images at 2-mm intervals were retrospectively generated. In the group of healthy patients, two radiologists in independently compared overlapping with nonoverlapping images, ranked confidence in identifying small airway structures on a scale of 1-5, and tabulated the number of images demonstrating these structures. In the 20 patients with disease, three-dimensional (3D) surface models were rendered on an independent workstation and were reviewed by two radiologists and one otolaryngologist for image quality, appreciation of lesion morphology, and ability to judge lesion extent, using a similar scale. A phantom was used to optimize parameters for the 3D reconstructions. RESULTS: Viewing of the retrospectively generated overlapping images increased by 122% the number of images in which laryngeal and hypopharyngeal structures could be identified (p < .01). Image confidence scores for the radiologists averaged 3.3 for nonoverlapping and 4.0 for overlapping (p < .05). Radiologists and otolaryngologist rated the quality of the 3D images equally. The otolaryngologist's assessment of the value of the models for understanding the lesion morphology was 3.5 compared with the radiologists assessment of 2.5; and for judging the lesion extent, the otolaryngologist's assessment was 3.8 compared with 2.7 for the radiologist, a statistical significance of p < .01. CONCLUSION: Helical CT with the application of overlapping images and 3D reconstructions significantly assists the understanding of upper-airway disease.     

Multiplanar imaging in the preoperative assessment of metallic intraocular foreign bodies. Helical computed tomography versus conventional computed tomography

OBJECTIVE: This study aimed to compare the effectiveness of helical computed tomography (CT) versus conventional CT in the preoperative assessment of metallic intraocular foreign bodies on axial, coronal, and multiplanar reconstruction images in clinical routine. DESIGN: Prospective comparative trial, alternate assignment of consecutive patients. PARTICIPANTS: Eighteen patients with penetrating eye injuries and suspected metallic intraocular foreign bodies were studied. INTERVENTION: Alternate patients were assigned to undergo either helical CT or conventional CT in the axial plane. Both the helical and the conventional data were transferred to a workstation, and reconstructions in the coronal and sagittal planes were performed. Additional direct coronal scanning was performed only when necessary for preoperative assessment. MAIN OUTCOME MEASURES: The quality of the directly obtained axial and coronal, as well as the reconstructed coronal and sagittal images, was assessed for each, imaging method based on the ability to detect and accurately localize foreign bodies. The size of the foreign bodies was measured and compared to the actual diameter. Total examination time and radiation dose delivered to the lens were measured for each imaging method. RESULTS: All foreign bodies were detected by each scanning method on the axial, the coronal, and on the reconstructed planes. The quality of the axial images was similar for helical and conventional CT. The helical technique provided high-quality reconstructed images comparable in quality to the directly obtained coronal planes in conventional CT. Reconstructions by conventional technique were not useful for preoperative assessment. The examination time for the total orbital volume was 18 seconds for helical CT examinations and 52 seconds for conventional CT examinations. Radiation dose delivered to the lens for the complete examination was 35 mGy for helical CT axial scanning, 56 mGy for conventional CT axial scanning, and 63 mGy for conventional CT coronal scanning. CONCLUSIONS: Helical CT multiplanar imaging offers several significant advantages for the preoperative assessment of metallic intraocular foreign bodies compared to the conventional CT technique in clinical practice, including short examination time, reduced motion artifacts, reduced radiation exposure, and the ability to obtain diagnostically useful coronal and sagittal reconstruction images without the need for additional scanning.     

Pre-operative classification of abdominal aortic aneurysms with spiral CT: the axial source images revisited

OBJECTIVE: The differentiation of supra-, juxta- and high infrarenal abdominal aortic aneurysms (AAA), which is essential for good surgical management, remains problematic. This prospective study assessed the value of highly overlapping vs. contiguous axial spiral computed tomography (CT) reconstructions in the pre-operative assessment of AAA. PATIENTS AND METHODS: Thirty-five patients with abdominal aortic aneurysms were studied with spiral CT (10 mm collimation, pitch 1). Axial reconstructions were performed at 2 and 10 mm increments and compared with surgical findings. Using each protocol, the aneurysms were classified as infra-, juxta- or suprarenal. Observers also assessed visualization of main and accessory renal artery origins and identification of other surgically relevant vascular anomalies. RESULTS: The 2 mm protocol correctly identified 29/31 infrarenal, 3/3 juxtarenal and 1/1 suprarenal aneurysms; two infrarenal aneurysms were overestimated as suprarenal. The 10 mm protocol correctly classified 25/31 infrarenal, 3/3 juxtarenal and 1/1 suprarenal aneurysms; five infrarenal aneurysms were overestimated as juxtarenal (n = 3) or suprarenal (n = 2) and one case was equivocal. Correct classification was thus 94% using the 2 mm protocol and 83% with the 10 mm protocol (P = 0.063). All 70 main renal artery origins were visualized with the 2 mm protocol, while the 10 mm protocol missed six (P = 0.03) The 2 mm protocol identified 10 accessory renal arteries, four of which were missed by the 10 mm protocol. Both protocols demonstrated five surgically relevant venous anomalies. CONCLUSION: Spiral CT with highly overlapping axial reconstructions correctly classified 94% of abdominal aortic aneurysms; overlapping reconstructions were particularly useful in differentiating high infrarenal from juxtarenal aneurysms.     

Spiral CT angiography and surgical correlations in the evaluation of intracranial aneurysms

We investigated the accuracy of spiral computed tomography angiography (CTA) in the detection and study of intracranial aneurysms by comparing CTA with selective angiograms and surgical findings. Twenty-six patients (9 men and 17 women; mean age 53.1 +/- 1.8 years) with suspected intracranial aneurysms were submitted to CTA (1- to 2-mm slices, pitch 1:1, 24 s, RI = 1) after a conventional CT examination showing subarachnoid hemorrhage (SAH) in 19 cases and during neuroradiological investigations performed for other reasons in 7 cases. One hundred twenty to 150 ml iodate contrast agent (0.3-0.4 gI/ml) were injected intravenously at 5 ml/s rate and with 12- to 25-s delay calculated with a preliminary test bolus. Three-dimensional shaded surface display (3D SSD) and maximum intensity projection (MIP) reconstructions were obtained from axial images. Then, within 48 h, all patients were submitted to digital subtraction angiography (DSA), with separate assessment of CTA and DSA findings. Twenty-two aneurysms shown by CTA were confirmed at DSA and surgery (true positives), whereas the vascular lesion was not confirmed at DSA in 2 cases (false positives). The presence of intracranial aneurysms was excluded at both CTA and subsequent DSA in 7 cases (true negatives) and there were no false negatives; sensitivity was 100 %, specificity 77.8 %, and diagnostic accuracy 93.5 %. Computed tomography angiography aneurysm location was confirmed at surgery in all cases, with very high accuracy in assessing the presence of an aneurysm neck (100 %). Computed tomography angiography accurately depicted the aneurysm shape in 20 of 22 cases, but failed to depict its multilobed nature in 2 cases. The mean aneurysm diameter calculated at CTA was 0.99 +/- 0.12 cm vs 1.09 +/- 0.11 cm at surgery (p < 0.01). The present results suggest that the high sensitivity of CTA, if confirmed by further studies, might help in avoiding having to resort to arteriography after negative CTA in SAH patients.     

"Stand down for the homeless". Podiatric screening of a homeless population in Cleveland

The reliability of helical CT as sole preoperative diagnostic technique for abdominal aortic aneurysms (AAA) and its accuracy in detecting vascular anomalies in the abdominal region was evaluated retrospectively in 42 patients with asymptomatic AAA > 40 mm. A single breath-holding helical scan was performed with 5 mm slice thickness, during a single injection of contrast medium, resulting in a 20 cm z-axis coverage. Axial images were reconstructed and used to generate high quality multiplanar reformatted images. Digital subtraction angiography (DSA) was performed in the first 18 patients and then in case of associated peripheral vascular disease (6 patients). Helical CT exactly showed, in all cases, the proximal and distal extent of the AAA. The visceral vessels as well as the inferior vena cava and renal veins were always clearly depicted, showing anatomical variants or pathological involvement in 19 patients. DSA gave sufficient details on the distal run-off but did not allow a reliable visualization of the visceral branches, venous anomalies and true extent of AAA. In our experience helical CT should be considered as the sole method for preoperative imaging of AAA. It allows a complete and precise evaluation; it is fast, with low doses of radiations and does not require hospitalization.     

Value of CT-angiography in diagnosis of cerebral sinus and venous thromboses

Dural sinus thrombosis is not uncommon. Due to the nonspecific symptomatology, as well as the manifold etiology, clinical diagnosis may be difficult. In these cases imaging procedures are frequently crucial in deciding how to proceed and how to treat. The aim of our study was to evaluate the diagnostic utility of helical CT in the detection of dural sinus thrombosis. In 20 patients with clinically suspected thrombosis CT angiography was performed. In 6 patients dural sinus thrombosis was diagnosed. In order to acquire also arterial vessels, a short delay of about 22 s after the onset of the application of contrast medium was selected. By this method we found an occlusion of the MCA in two patients with clinically suspected sinus thrombosis. In all patients the transverse slices and the multiplanar reconstructions showed filling defects or an "empty delta" sign. With irregular outlines the thrombus could be depicted over the complete course of the sinus. The MIP reconstructions were particularly helpful in the evaluation of the vessel anatomy and the pathological collateral venous drainage. In three patients MR angiograms were available for comparison. The smaller veins, such as the v. vermis inferior, were less clearly depicted than in CT angiography. CT angiography is a fast and reliable method to exclude or verify a sinus thrombosis. It can be performed immediately after non-enhanced CT. According to our present experience CT angiography is sufficient for the diagnosis of a sinus thrombosis.     

CT scan of the liver

Since its inception, CT scan has had a dominant role in hepatic imaging. Recent advances including helical CT scan and bolus-triggered scan initiation software packages have had a significant impact. Issues regarding volume, rate of administration, and type of intravenous contrast are being distilled. Workstations for three-dimensional data reconstructions are producing images that compete with conventional angiography in certain areas, while angiographically assisted CT scan is being refined in others.     

Intrahepatic portosystemic venous shunt: report of two cases assessed by helical computed tomography

BACKGROUND: Three-dimensional (3D) anatomic analysis was carried out, using helical computed tomography (helical CT), to evaluate its usefulness in two cases of large intrahepatic portosystemic venous shunt (IPSVS). METHODS: Case 1, a 74-year-old man with type-C hepatitis, underwent hepatic angiography to confirm suggested IPSVS of the left hepatic lobe in 1994. Case 2, a 62-year-old woman with liver cirrhosis associated with type-B hepatitis, was hospitalized for evaluation of suspected hepatocellular carcinoma in 1994. Hepatic angiography disclosed a large IPSVS in the right hepatic lobe. Retrospective evaluation of CT showed that the size of this shunt had increased over the 5 years 3D anatomic analysis was carried out, and the shunt vessels were clearly demonstrated. CONCLUSION: 3D anatomic analysis using helical CT was less invasive and useful for evaluating large IPSVS.     

Thoracic MR aortography: imaging techniques and strategies

Three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiography is a promising technique for thoracic aortography that complements electrocardiographically gated T1-weighted spin-echo imaging and cine MR imaging. Axial and left anterior oblique T1-weighted spin-echo images are well suited to measurement of aortic dimensions and evaluation of aortic aneurysms. Sagittal and coronal spin-echo images are helpful in evaluation of vascular rings and aortic dissection. Cine gradient-echo and cine phase-contrast imaging allow dynamic evaluation of aortic and valvular flow. Cine phase-contrast imaging also enables noninvasive quantification of blood flow. Capable of being performed during a single breath hold, 3D gadolinium-enhanced MR angiography provides high-resolution 3D data that can be readily used for projection angiography and multiplanar reformation. This technique enables further demonstration of subtle pathologic conditions. Three-dimensional gadolinium-enhanced MR angiography allows more comprehensive and efficient evaluation of the thoracic aorta.     

MR imaging of congenital anomalies of the thoracic veins

Congenital anomalies of the thoracic veins are infrequent but important developmental abnormalities. Thoracic venous anomalies can be classified as systemic or pulmonary. Systemic venous anomalies are often incidental findings, whereas pulmonary venous anomalies are more likely to manifest with cyanosis and to be associated with congenital cardiac abnormalities, especially atrial septal defect. Magnetic resonance (MR) imaging provides excellent delineation of the abnormal vessels and associated cardiac defects. Conventional spin-echo (SE) techniques show blood flow as a signal void and are sufficient for demonstrating the aberrant venous anatomy in most cases. Gradient-echo images show flowing blood as high signal intensity and are useful for clarifying the course of anomalous veins when vessel walls are difficult to visualize on SE images. Phase-contrast images are valuable for ascertaining the direction of blood flow and thus provide a physiologic method of distinguishing the vertical vein of anomalous pulmonary venous return from a left superior vena cava. MR imaging is useful for delineating both the thoracic venous and accompanying intracardiac anomalies and is a valuable, complementary technique to echocardiography, angiography, and computed tomography in the evaluation of patients with these abnormalities.     

The genomic organization of the genes for human lipopolysaccharide binding protein (LBP) and bactericidal permeability increasing protein (BPI) is highly conserved

PURPOSE: The authors evaluated computed tomographic (CT) virtual colography for the detection of simulated polyps under ideal conditions, as well as the effects on lesion conspicuity of (a) collimation, (b) table pitch, and (c) orientation of the colon lumen with respect to the gantry. MATERIALS AND METHODS: Pig colon was resected and cleansed, and polyps with diameters of 3, 7, and 10 mm were created. Each specimen was scanned with collimation of 5 and 7 mm and table pitch of 1.0, 1.6, and 2.0 at angles of 0 degrees, 45 degrees, and 90 degrees to the gantry. The initial two-dimensional (2D) images were reconstructed at 1-mm intervals (2D reconstructions), from which three-dimensional (3D) virtual colography images were generated. Polyp conspicuity on the initial and reconstructed 2D images and the 3D reconstructions was evaluated on a three-point scale: 0 = polyp not depicted, 1 = polyp faintly depicted, and 2 = polyp clearly depicted. RESULTS: The 10-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstructed 2D image and 3D reconstruction without regard to collimation, table pitch, or angle to the gantry. The 7-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstructed 2D image, but conspicuity on 3D reconstructions varied as the imaging parameters varied. The 3-mm-diameter polyp was faintly depicted (grade 1 conspicuity) on the initial and reconstructed 2D images and 3D reconstructions, but conspicuity varied on the 3D reconstructions as the imaging parameters varied. CONCLUSION: CT virtual colography helped detection of small mucosal polyps regardless of the angle of the colon lumen to the gantry at which they were obtained.     

CT angiography of superior mesenteric artery syndrome

OBJECTIVE: Our purpose was to describe the use of CT angiography and three-dimensional (3D) reconstruction in the diagnosis of superior mesenteric artery syndrome in three patients. CONCLUSION: CT angiography combined with 3D reconstructions is a noninvasive technique that may have a complementary diagnostic role similar to that of angiography in patients with a classic clinical presentation suggestive of superior mesenteric artery syndrome. CT angiography combined with 3D reconstructions should be considered in patients who might otherwise require angiography.     

MR angiography of the portal venous system: techniques, interpretation, and clinical applications

Magnetic resonance (MR) angiography is a noninvasive means of assessing the portal venous system that has potential advantages over currently used modalities. Time-of-flight and phase-contrast MR angiography are useful techniques that differ fundamentally in their means of data acquisition but are comparable in their ability to demonstrate normal anatomy as well as abnormalities of the portal venous system. Occasionally, artifacts caused by respiratory motion, implanted metallic devices or surgical clips, in-plane saturation, or areas of complex flow are seen at MR angiography of the portal venous system. However, most artifacts can easily be identified as such and either remedied or ignored. In addition, the suppression of signal from surrounding soft tissues may result in poor detection of parenchymal lesions. The utility of standard projection angiograms and source images can be increased through the use of intravenously administered contrast material and postprocessing techniques such as partial-volume maximum intensity projection reconstructions and shaded surface renderings. In addition to providing information on portal venous anatomy and portosystemic collateral vessels, MR angiography of the portal vein has clinical application in portal venous thrombosis and stenosis, liver transplantation, and the evaluation and planning of surgical and transjugular intrahepatic portosystemic shunts.     

CT-image analysis of resected peripheral adenocarcinomas of the lung less than 1 cm in diameter

Conventional CT (10-mm thick) and helical thin-section CT (2-mm thick) high-resolution images were obtained to study the relationship between the appearance of small peripheral adenocarcinomas of the lung and pathological findings. Eleven cases in which adenocarcinomas less than 1.0 cm in diameter were resected were retrospectively reviewed. Conventional CT images revealed air spaces within pulmonary nodules in 82% of tumors, an ill-defined margin in 91%, and involvement of vessels in 91%. When these findings are observed in pulmonary nodules, thin-section CT should be used for further examination. Helical thin-section CT images showed inhomogeneous internal attenuation (91%), irregularly undulating margins (91%), and vascular involvement (100%).     

Contrast-enhanced magnetisation transfer MRI in metastatic lesions of the brain

Our purpose was to compare prospectively the sensitivity of contrast-enhanced magnetisation transfer (MT) MRI and gradient-echo (GE) T1-weighted images in metastatic disease of the brain. We studied 52 patients with brain metastases, using conventional T1-weighted GE and MT spin-echo (SE) images after the same standard dose of gadolinium. Axial 5-mm reconstructions of GE data were compared with 5-mm MT images in the same plane. Metastases were counted independently by two neuroradiologists. In 12 patients (23%) MT imaging showed more metastases than GE images (P = 0.03). We detected 68 more metastases with the former technique.     

Head and neck vascular anatomy

Conventional computed tomography (CT) and magnetic resonance (MR) angiography provide excellent vascular images; however, every radiologist interpreting routine cross-sectional imaging of the head and neck must recognize normal and abnormal vascular structures. Knowledge of the normal cross-sectional appearance of vessels can help to define spacial anatomy and provide for recognition of abnormal vessels. Intracranially, the major arterial branches of the Circle of Willis are routinely visualized on MR and CT, as are the dural venous sinuses and major tributaries to the deep and superficial venous system. Using a combination of CT and MR images, we demonstrate the normal cross-sectional vascular anatomy of the head and neck and the important anatomic relationships key to accurate imaging analysis.     

Computed tomographic angiography for the evaluation of carotid artery stenosis

BACKGROUND AND PURPOSE: No previous study has compared the reliability of carotid artery measurement provided by axial images, shaded surface display (SSD), and maximum intensity projection (MIP). METHODS: Helical CT and conventional angiography were performed prospectively in 20 patients with atherosclerotic stenosis of the internal carotid artery. Stenosis measurement was performed in a blinded fashion on angiography and CT by two independent examiners. Calcifications were segmented when they were located far enough from the vascular lumen. SSD and MIP were systematically performed for each carotid bifurcation. We measured stenosis using conventional angiography as standard and the different CT reconstructions (axial images, SSD, and MIP) by comparing the stenosis diameter at its narrowest point to the normal internal carotid artery. The degree of stenosis was classified into six groups: no stenosis, mild stenosis (< 30%), moderate stenosis (30% to 70%), severe stenosis (> 70%), near occlusion, and occlusion (100%). No measurement was made in cases of normal artery, near occlusion, and occlusion. RESULTS: Correlations between angiography and the three types of reconstruction were very good. Axial sections correctly classified the carotid arteries in 95% of cases. In 10 carotid arteries, stenosis was not assessable by SSD and MIP because of calcifications. In the remaining carotid arteries, MIP correctly classified the degree of stenosis in 96% of cases, whereas SSD misclassified 21% of cases. CONCLUSIONS: Our study showed that axial images provide a reliable evaluation of carotid artery stenosis. Calcifications are limiting factors in SSD or MIP. When atherosclerotic plaques are not calcified, MIP reconstructions provide a more reliable measurement of the vascular lumen than SSD.