Stair-step artifacts with single versus multiple detector-row helical CT

The accuracy of clinical 3D printing in reconstructive surgery: literature review and in vivo validation study

A growing number of studies demonstrate the benefits of 3D printing in improving surgical efficiency and subsequently clinical outcomes. However, the number of studies evaluating the accuracy of 3D printing techniques remains scarce. All publications appraising the accuracy of 3D printing between 1950 and 2018 were reviewed using well-established databases, including PubMed, Medline, Web of Science and Embase. An in vivo validation study of our 3D printing technique was undertaken using unprocessed chicken radius bones (Gallus gallus domesticus). Calculating its maximum length, we compared the measurements from computed tomography (CT) scans (CT group), image segmentation (SEG group) and 3D-printed (3DP) models (3DP group). Twenty-eight comparison studies in 19 papers have been identified. Published mean error of CT-based 3D printing techniques were 0.46 mm (1.06%) in stereolithography, 1.05 mm (1.78%) in binder jet technology, 0.72 mm (0.82%) in PolyJet technique, 0.20 mm (0.95%) in fused filament fabrication (FFF) and 0.72 mm (1.25%) in selective laser sintering (SLS). In the current in vivo validation study, mean errors were 0.34 mm (0.86%) in CT group, 1.02 mm (2.51%) in SEG group and 1.16 mm (2.84%) in 3DP group. Our Peninsula 3D printing technique using a FFF 3D printer thus produced accuracy similar to the published studies (1.16 mm, 2.84%). There was a statistically significant difference (P<10-4) between the CT group and the latter SEG and 3DP groups indicating that most of the error is introduced during image segmentation stage.

Usefulness of coronal reconstruction CT images for quantitative evaluation of the cross-sectional area of small pulmonary vessels

RATIONALE AND OBJECTIVES

Cross-sectional area <5 mm(2) (CSA<5) is a computed tomography (CT) metric that has been used for the evaluation of pulmonary vessel alterations and perfusion. CSA<5 is calculated from three axial slices; thus, whether CSA<5 represents the small pulmonary vessel alterations in the whole lung remains unclear. The purpose of this study was to compare the measurements of CSA<5 using three axial slices and coronal reconstructed slices in the relationship between the measured CSA<5 and pulmonary perfusion measured using lung perfusion scintigraphy.

MATERIALS AND METHODS

This study comprised 28 subjects who underwent both noncontrast CT and lung perfusion scintigraphy. The present study measured CSA<5 using both three axial CT images and coronal reconstruction images and then obtained the percentage of the CSA in right lung to that in whole lung (R/W-CSA<5). Using anteroposterior and posteroanterior projections on technetium-99m macroaggregated albumin (MAA) lung perfusion scintigraphy, we obtained right and total lung counts and calculated the percentage of the right to whole lung counts (R/W-MAA). The correlations of the R/W-CSA<5 calculated using three axial slices (R/W-CSA(A)x<5) and coronal reconstructed slices (R/W-CSA(COR)<5) with R/W-MAA were evaluated using Spearman rank correlation analysis.

RESULTS

Both R/W-CSA(Ax)<5 and R/W-CSA(COR)<5 were significantly correlated with R/W-MAA; however, the correlation coefficient with R/W-CSA(COR)<5 (ρ = 0.842, P < .0001) was greater than that with R/W-CSA(Ax)<5 (ρ = 0.631, P = .0004).

CONCLUSIONS

Coronal reconstruction images appear suitable for quantitative measurement of CSA of small pulmonary vessels.

[Usefulness of subtraction computed tomography angiography employing orbital synchronized helical scanning for diagnosis of lower extremity arteries with vessel wall calcification]

PURPOSE

Massive calcification complicates the diagnosis of the blood vessel lumen in computed tomography angiography (CTA) of the arteries of the lower extremities. The purpose of this study was to evaluate subtraction CTA with the use of orbital synchronized helical scanning (OS-SCTA).

METHOD

Phantom study: We performed OS-SCTA and non-OSCTA of a calcified vessel phantom (ψ2.5 mm), and compared them with a non-calcified vessel phantom as the reference by full width at half maximum (FWHM) and full width at tenth maximum (FWTM) of maximum intensity projection (MIP) images. Clinical study: 58 patients with peripheral artery disease who were referred for angiography also underwent OS-SCTA. OS-SCTA was produced using MIP images. Findings were graded according to three categories: (1) stenosis greater than 50% or occluded; (2) stenosis less than 50%; (3) not detected due to insufficient image quality. OS-SCTA findings were compared with the angiographic findings for each arterial segment.

RESULTS

In the phantom study, FWHM showed no significant difference between OS-SCTA and the reference (P=0.135), whereas FWTM showed a significant difference (P<0.001). FWHM and FWTM showed a significant difference between non-OS-SCTA and the reference (P<0.001), due to misregistration with helical artifacts. In a clinical study comparing OS-SCTA with angiography, the sensitivity and specificity were 93.3% and 95.1% in calcified segments, 91.8% and 93.9% in non-calcified segments, and 92.2% and 94.6% in all segments. There was no significant difference between calcified segments and non-calcified segments (sensitivity: P=0.568, specificity: P=0.549).

CONCLUSION

OS-SCTA is beneficial for the diagnosis of lower extremity arteries with vessel wall calcification, since it shows detection accuracy comparable to that of angiography.

Multidetector-row Computed Tomography of Diffuse Tracheal Disease: Pictorial Review

Diffuse tracheal diseases are uncommon and may mimic asthma or other forms of chronic obstructive lung disease. Bronchoscopy is usually definitive in establishing a diagnosis and assessing the severity of diffuse tracheal disease. However, advances in multidetector-row computed tomography (MDCT) technology allow for rapid acquisition time and generation of high-quality multiplanar reconstructions and virtual bronchoscopic images, making MDCT evaluation of suspected or known tracheal disease the noninvasive examination of choice. The MDCT findings of the various diseases that diffusely affect the trachea may be highly suggestive of 1 particular disease or narrow the differential diagnosis to a few possibilities. Moreover, MDCT imaging of the chest can help identify associated lung disease or complications of diffuse tracheal disease such as pneumonia or atelectasis. This pictorial review illustrates the MDCT appearances of the more common diffuse tracheal diseases.

Technical considerations for lower limb multidetector computed tomographic angiography

Multidetector computed tomography (MDCT) enables imaging of the entire arterial tree non-invasively. Optimal technical considerations for performing MDCT angiography (MDCTA) are essential for accurate diagnosis and atherosclerotic disease stratification. This review article focuses on the various technical aspects necessary for peripheral computed tomographic angiography (CTA) acquisition. Common clinical indications for peripheral MDCTA and the latest scan protocols are described. The essential issue of radiation dose reduction is discussed, along with methods of optimal contrast bolus detection and delivery. Post-processing techniques are also presented. Previously, digital subtraction angiography was the only established reliable imaging technique to quantify atherosclerotic disease load; however, MDCTA may now challenge this old gold standard, along with other non-invasive techniques such as magnetic resonance angiography (MRA).

The effects of misinterpretation of an artefact on multidetector row CT scans in children

BACKGROUND

Artefacts reflect problems with radiographic technique rather than true pathology. These may be misinterpreted as pathology with serious consequences. An artefact caused such problems in one paediatric imaging department.

OBJECTIVE

To determine the incidence, and consequences of misinterpretation, of a CT artefact in a paediatric imaging department.

MATERIALS AND METHODS

A retrospective review of images and reports of paediatric CT scans over a set period with a known artefact was performed. Reports were correlated with reviewers' evaluation of the presence of artefact and reviewed for correct identification of artefact, misinterpretation as pathology, and action taken as a result.

RESULTS

A total of 74 CT scans had been performed over the study period and an artefact detected by reviewers on 32 (43%). Six (18.75%) of these were misinterpreted as pathology, of which three (9.4%) were reported as tuberculous granulomas, two (6.2%) as haemorrhages and one (3.1%) as an unknown hyperdensity. Two patients (6.2%) had subsequent MRI studies performed, and treatment for tuberculosis was continued in one patient (3.1%).

CONCLUSION

No initial report identified the artefact. One-fifth of the scans with the artefact were misinterpreted as pathology and half of these misinterpretations led to further action. Artefacts result in false diagnoses and unnecessary investigations; vigilance is needed.

A NURBS-based technique for subject-specific construction of knee bone geometry

Subject-specific finite element (FE) models of bones that form the knee joint require rapid and accurate geometry construction. The present study introduces a semi-automatic non-uniform rational B-spline (NURBS) technique to construct knee bone geometries from computed tomography (CT) images using a combination of edge extraction and CAD surface generation. In particular, this technique accurately constructs endosteal surfaces and can accommodate thin cortical bone by estimating the cortical thickness from well-defined surrounding bone. A procedure is also introduced to overcome the bifurcation at the femoral condyles during surface generation by combining transverse and sagittal plane CT data. Available voxel- and NURBS-based subject-specific construction techniques accurately capture periosteal surfaces but are limited in their ability to capture endosteal geometry. In this study, the proposed NURBS-based technique and a typical voxel mesh technique captured periosteal surfaces within an order of magnitude of image resolution. The endosteum of diaphyseal bone was also captured with similar accuracy by both techniques. However, the voxel mesh model failed to accurately capture the metaphyseal and epiphyseal endosteum due to the poor CT contrast of thin cortical bone, resulting in gross overestimation of cortical thickness. The proposed technique considered both the local and global nature of CT images to arrive at a description of cortical bone thickness accurate to within 2 pixel lengths.

Cranial CT with 64-, 16-, 4- and single-slice CT systems-comparison of image quality and posterior fossa artifacts in routine brain imaging with standard protocols

Posterior fossa artifacts constitute a characteristic limitation of cranial CT. To identify practical benefits and drawbacks of newer CT systems with reduced collimation in routine cranial imaging, we aimed to investigate image quality, posterior fossa artifacts and parenchymal delineation in non-enhanced CT (NECT) with 1-, 4-, 16- and 64-slice scanners using standard scan protocols. We prospectively enrolled 25 consecutive patients undergoing NECT on a 64-slice CT. Three groups with 25 patients having undergone NECT on 1-, 4- and 16-slice CT machines were matched regarding age and sex. Standard routine CT parameters were used on each CT system with helical acquisition in the posterior fossa; the parameters varied regarding collimation and radiation dose. Three blinded readers independently assessed the cases regarding image quality, infra- and supratentorial artifacts and delineation of brain parenchymal structures on a five-point ordinal scale. Reading orders were randomized. A proportional odds model that accounted for the correlated nature of the data was fit using generalized estimating equations. Posterior fossa artifacts were significantly reduced, and the delineation of infratentorial brain structures was significantly improved with the thinner collimation used for the newer CT systems (p<0.001). No significant differences were observed for midbrain structures (p>0.5). The thinner collimation available on modern CT systems leads to reduced posterior fossa artifacts and to a better delineation of brain parenchyma in the posterior fossa.

Comparison between coronal reformatted images and direct coronal CT images of the swine lung specimen: assessment of image quality with 64-detector row CT

The aims of this study were to compare the image quality of coronal multiplanar reconstruction (MPR) images from axial spiral images with that of direct coronal spiral and sequential images, and to estimate and analyse the effect of an incremental change on the image quality using 64-detector row CT. 12 swine lungs were used. Five kinds of images from each lung specimen were obtained using 64-detector row CT. All images were analysed by categories and grades, and the direct coronal sequential images were used as the reference standard for the image quality. Statistical analysis was performed for the following categories: (i) inter-observer reliability, (ii) interaction between the observers and images, (iii) image analysis, (iv) anatomical structural analysis of each observer, (v) stair-step artefact and (vi) background noise. The overall image quality and the image quality of all anatomical structures of coronal MPR images with 0.67 mm slice increments were inferior to the image quality of the other images; this difference was statistically significant (p<0.05). Stair-step artefact was detected on coronal MPR images, and was more prominent on coronal MPR images with 0.67 mm slice increments than on coronal MPR images with 0.34 mm slice increments. The most severe background noise was detected on the direct coronal sequential images, but there was no significant difference between the direct coronal sequential images and the direct coronal spiral images. Background noise was least prominent on coronal MPR images with 0.67 mm slice increments. The increment process is important for improving the image quality of MPR images even when using 64-detector row CT. Coronal MPR images with 0.34 mm slice increments using 64-detector row CT showed a similar image quality to that obtained from the direct coronal images, and can be used instead. This means that the coronal MPR images obtained with 64-detector row CT could be as useful for evaluating the lung parenchyma as the axial high-resolution CT images.

Identification of the anterior ethmoid arteries on thin-section axial images and coronal reformatted orbit images by means of multidetector row CT

AIM

The aim of this study was to identify anterior ethmoid arteries on thin-section axial images and coronal reformatted images of the orbits using multidetector row computed tomography (CT).

MATERIALS AND METHODS

One hundred and thirty-two patients underwent paranasal CT using a 16-row detector CT (n=59) or a 6-row detector CT machine (n=73) at 1 or 1.25 mm section width, respectively. Coronal images were reformatted at section widths of 3 and 1 mm. The anterior ethmoid arteries were identified for each patient. Differences were assessed using the chi-square test.

RESULTS

All CT images were of approximately average diagnostic quality. Anterior ethmoid arteries were identified in 97.5 and 96.6% at section thicknesses of 1 and 1.25 mm on the axial images, respectively. There was no statistically significant difference in the detection rate (p=0.89). On the coronal images, anterior ethmoid arteries were presented tangentially in 75.4 and 90.2% at section widths of 3 and 1 mm, respectively. The visibility of the anterior ethmoid arteries was rated significantly better on coronal images at a section width of 1 mm than on those at section widths of 3 mm (p<0.001).

CONCLUSION

Thin-section axial images and coronal reformatted images using multi-detector row CT mostly depict anterior ethmoid arteries, and are useful to identify anterior ethmoid arteries for preoperative evaluation of paranasal sinuses.

Diagnostic Accuracy of Multislice CT Angiography in Peripheral Arterial Disease

A systematic search of the PubMed and Medline databases of English literature was performed to determine the diagnostic accuracy of multislice computed tomographic (CT; MSCT) angiography in peripheral arterial disease (PAD) compared with digital subtraction angiography (DSA). Studies comparing MSCT angiography with DSA in peripheral vascular disease were included, and the diagnostic value of MSCT angiography in terms of sensitivity, specificity, and diagnostic accuracy was compared and analyzed. Ten studies (19 comparisons) met the criteria and were included for analysis. The pooled sensitivity, specificity, and accuracy rates were 92%, 91%, and 91%, respectively, at all arterial levels; 92%, 94%, and 93%, respectively, at aortoiliac arteries; 96%, 85%, and 92%, respectively, at femoropopliteal arteries; and 91%, 85%, and 87%, respectively, at infrapopliteal arteries. A significant difference was found in the sensitivity of MSCT angiography in PAD between four-slice CT and 16-slice CT, between aortoiliac and femoropopliteal arterial segments, and between femoropopliteal and infrapopliteal arterial segments (P<.05). This review demonstrates that MSCT angiography has a high diagnostic value and could be a reliable alternative to DSA in the diagnosis of PAD.

Isotropic CT examination of abdomen and pelvis diagnostic quality of reformat

RATIONALE AND OBJECTIVES

To evaluate the image quality of axial and coronal reformats obtained from isotropic resolution abdomino-pelvic computed tomography (CT) examinations.

MATERIALS AND METHODS

Thirty consecutive patients with intravenous contrast-enhanced abdomino-pelvic CT examinations (Brilliance 40, Philips Medical Systems, Cleveland, OH) were enrolled for the study. The raw data were reconstructed into two sets of source axial images: 0.9-mm slice widths with 0.45-mm reconstruction interval (isotropic resolution) and 4-mm slice widths with 3-mm reconstruction interval (anisotropic resolution: group A). Isotropic data set was reformatted into axial and coronal stacks (groups B and C, respectively) with 4-mm slice width and 3-mm interval. Three independent readers evaluated stacks A to C using a 3-point scale for resolution of hepatic vessels, edge sharpness of kidneys, respiratory motion artifact, reconstruction artifact, noise, and overall image quality.

RESULTS

There was no statistical difference among the groups A to C for vessel resolution, motion artifact, noise, and overall quality. The scores given to group C were significantly lower than those to groups A and B for reconstruction artifacts. There was no difference among groups A to C for overall impression of image quality. The interreader agreements were excellent for axial images (groups A and B) and moderate for coronal reformats.

CONCLUSION

Isotropic scanning of the abdomen and pelvis allows creation of reformats with similar image quality as similar thickness axial source images. These reformats are of sufficient quality to form the basis of clinical interpretation.

High-Resolution MDCT of Pulmonary Septic Embolism: Evaluation of the Feeding Vessel Sign

OBJECTIVE

The objective of this study was to use high-resolution MDCT to assess the relation of the pulmonary vasculature to septic emboli with particular attention to the feeding vessel sign.

MATERIALS AND METHODS

The MDCT scans of nine patients with septic emboli were retrospectively, blindly evaluated by two observers. A control group of 10 patients with documented pulmonary metastasis and pathologically proven carcinoma also were included. Transverse images, multiplanar reconstructions, and maximum intensity projections were used to analyze nodules and the pulmonary vasculature. The CT scans were obtained with 1- to 1.25-mm collimation on a 4-, 8-, or 16-MDCT scanner. The feeding vessel sign was defined as a vessel coursing directly into a nodule.

RESULTS

The patients with septic embolism had a total of 141 nodules and 52 wedge-shaped opacities. Transverse images showed that 52 (37%) of the nodules and 11 (22%) of the wedge-shaped opacities had a vessel that appeared to enter the nodule, but multiplanar reconstructions (without IV contrast enhancement) and maximum intensity projections (with IV contrast enhancement) showed the vessels passed around the nodules. Twenty-one (15%) of the spherical nodules and seven (13%) of the wedge-shaped opacities exhibited a central vessel entering the lesion in all imaging planes. All of these vessels were traced to the left atrium on transverse images, a finding consistent with pulmonary vein branches. Similar findings were seen in pulmonary metastatic lesions.

CONCLUSION

Although pulmonary septic emboli often appear to have a feeding vessel on conventional cross-sectional images, multiplanar reconstructions show that most of these vessels course around the nodule and that the others are pulmonary veins.

[Artifact of indicators equipped to stereotactic body frame scanned by 16-row MDCT can be resolved]

We found an artifact of the Stereotactic Body Frame's (SBF) indicators when we used diagnostic 16-row multi-detector computed tomography (MDCT) as a simulator. Stereotactic radiotherapy (SRT) requires the accuracy of each millimeter. However, a gap of 3 mm at the maximum along the Z axis was caused by this artifact. We assessed the characteristics and cause of this artifact and searched for an imaging parameter to reduce the artifact in SRT. It was considered that the artifact was formed mainly by a stair-step artifact and cone-beam artifact. We can acquired accuracy, 1 mm minimizing the beam width and pitch (10 mm/0.5625). However, exposure time was extended because minimum pitch was selected. The influence on dose calculation was negligible. We decided to use a default parameter for treatment planning, and this parameter for determining the isocenter. We found the MDCT parameters to get acceptable positional accuracy for SRT with SBF.

Conventional High-Resolution CT Versus Helical High-Resolution MDCT in the Detection of Bronchiectasis

OBJECTIVE

The purpose of this study was to compare conventional high-resolution CT (HRCT) with helical 16-MDCT in the detection of bronchiectasis.

MATERIALS AND METHODS

We retrospectively evaluated 80 patients including 61 with bronchiectasis (mean age, 64 years; range, 22-87 years) and a control group of 19 patients with normal MDCT of the chest. Two sets of images were blindly, randomly analyzed by two observers: contiguous 1-mm slices (MDCT set) and 1-mm slices every 10 mm (HRCT set) derived from the MDCT set. Images were scored independently for presence, extent, and severity of bronchiectasis, followed by a consensus interpretation. Kappa analysis assessed inter- and intraobserver agreement. MDCT was the radiologic gold standard.

RESULTS

Of the 61 patients with bronchiectasis diagnosed with MDCT, 56 (92%) were positive for bronchiectasis on conventional HRCT. Seven patients had positive MDCT scans only, and two patients had positive HRCT scans only. Of 479 lobes, 59 were positive for bronchiectasis on MDCT and negative on HRCT, and 19 lobes were positive for bronchiectasis on HRCT and negative on MDCT (p < 0.0001). MDCT showed 25 more lobes with cylindric, 11 more lobes with varicose, and four more lobes with cystic bronchiectasis than did HRCT. Sensitivity, specificity, and positive and negative predictive values of HRCT in detecting bronchiectasis were 71%, 93%, 88%, and 81%, respectively. Interobserver agreement for presence, extent, and severity of bronchiectasis ranged from moderate to good for MDCT (kappa values, 0.64, 0.5, and 0.48, respectively) and poor to good for HRCT (kappa values, 0.65, 0.46, and 0.25, respectively).

CONCLUSION

Contiguous helical 16-MDCT with 1-mm collimation is superior to HRCT at 10-mm intervals in showing the presence and extent of bronchiectasis.

Coronal reformations of the chest on 64-row multi-detector row CT: Evaluation of image quality in comparison with 16-, 8- and 4-row multi-detector row CT

PURPOSE

To evaluate image quality of coronal reformations of chest performed on 64-row MDCT in comparison with 16-, 8- and 4-row MDCT.

MATERIALS AND METHODS

Consecutive patients who underwent pulmonary CT angiography using four different MDCT scanners were retrospectively studied with IRB approval: (1) n=30, 64-row MDCT; (2) n=30, 16-row MDCT; (3) n=30, 8-row MDCT; (4) n=30, 4-row MDCT. Coronal reformatted images (2 mm thickness and 2mm intervals for 64-row MDCT; 5 mm thickness and 5 mm intervals for 16-, 8- and 4-row MDCT) were evaluated by consensus reading of two board-certified radiologists who were blinded to scanner type. The image quality of overall chest appearance and individual thoracic structures including heart, aorta and pulmonary arteries was graded using five-point scale. Grades from four different scanners were compared using Kruskal-Wallis test. A second evaluation was performed in 48 randomly selected patients (12 patients for each scanner). Reproducibility was assessed using weighted-kappa analysis.

RESULT

Significant reproducibility was observed between the first and second evaluations in 48 patients both for image quality of overall chest (weighted kappa=0.826) and each thoracic structure (mean weighted kappa=0.803; range, 0.729-0.858). Image quality of overall chest and individual thoracic structures differed significantly among four different MDCT groups, with 64-row MDCT having the highest grades, followed by 16-, 8- and 4-row MDCT (mean grades for overall chest in each scanner: 3.9, 3.0, 2.4 and 1.9, respectively) (P<0.0001 for overall chest and each thoracic structure).

CONCLUSION

When comparing coronal reformations of chest using four different MDCT scanners, the 64-row MDCT had the highest image quality for overall chest appearance and individual thoracic structures, followed by 16-, 8- and finally 4-row MDCT.

Evaluation of thoracic abnormalities on 64-row multi-detector row CT: Comparison between axial images versus coronal reformations

PURPOSE

To evaluate the capability of coronal reformations of chest on 64-row MDCT in demonstrating thoracic abnormalities in comparison with axial images.

MATERIALS AND METHODS

Thirty-eight consecutive patients who underwent pulmonary CTA on 64-row MDCT were retrospectively studied with institutional review board (IRB) approval. Contiguous 2 mm axial and coronal images were reviewed independently with a 1-week interval, by consensus reading of two board-certified radiologists. Overall image quality was graded using a five-point scale. Abnormalities in mediastinum, hilum, pulmonary vessels, aorta, heart, esophagus, pleura, chest wall, and lung parenchyma were scored: 1 = definitely absent, 2 = probably absent, 3 = equivocal, 4 = probably present, 5 = definitely present. Scores on axial and coronal images were compared using weighted kappa analysis.

RESULTS

Overall image quality was not different with statistical relevance between axial and coronal images (mean/median scores; 3.7/4; 3.6/4, respectively, P = 0.286, Wilcoxon signed-rank test). Significant agreement was observed between axial and coronal scores (mean weighted kappa, 0.661; range, 0.362-1). Agreement was almost perfect for pneumothorax, lung and pleural mass, effusion and consolidation (weighted kappa=0.833-1); substantial for pulmonary embolism, trachea, mediastinal lymphadenopathy and non-skeletal chest wall lesion, heart, esophagus, and emphysema (weighted kappa, 0.618-0.799); moderate for atelectasis, mediastinum, hilar nodes, aorta, other lung lesions, skeletal chest wall lesions, linear scarring, nodules > 1 cm, pulmonary artery abnormalities and pleural thickening (weighted kappa, 0.405-0.592); and fair for nodules < 1 cm (weighted kappa = 0.362).

CONCLUSION

Coronal reformations on 64-row MDCT had substantial agreement with axial images for evaluation of the majority of thoracic abnormalities.

CT angiography of peripheral arterial disease

Lower-extremity computed tomographic (CT) angiography (ie, peripheral CT angiography) is increasingly used to evaluate patients with peripheral arterial disease. It is therefore increasingly important for all vascular specialists to become familiar with the strengths and limitations of this new technique. The aims of this review are to explain the principles of scanning and injection technique for a wide range of CT scanners, to explain and illustrate the properties of current image postprocessing tools for effective visualization and treatment planning, and to provide an overview of current clinical applications of peripheral CT angiography.

Three-dimensional visualization of suprarenal aortic stent-grafts: evaluation of migration in midterm follow-up

PURPOSE

To investigate the midterm results of transrenal fixation of abdominal aortic stent-grafts with regard to device migration and encroachment of stent wires on the renal and visceral branches.

METHODS

Imaging data from 18 patients (15 men; mean age 75 years, range 63-84) undergoing transrenal stent-graft fixation for abdominal aortic aneurysm (AAA) were included in the study. Computed tomographic angiographic data acquired within 1 week of stent-graft implantation were compared to the latest follow-up images. Postprocessing methods generated 3-dimensional (3D) maximum intensity projections (MIP) and virtual intravascular endoscopy (VIE) for evaluation of the relationship between suprarenal stents and aortic branches. Aortic neck angulation was measured in each patient for correlation with the incidence of stent migration.

RESULTS

The mean follow-up period was 40 months. 3D image visualizations showed that the stent-graft moved caudally in all patients (range 2.6-14.2 mm), with migration (>10 mm) observed in 4 (22%) patients. Corresponding VIE images documented changes in stent wire encroachment on the aortic branch ostia in 11 patients, including the number and position of crossing stent wires. There was no close relationship between aortic neck angulation and stent migration.

CONCLUSION

The current study demonstrated that migration occurs at midterm follow-up in transrenally deployed stent-grafts. 3D images were valuable for the assessment of stent migration, as well as its relationship with aortic branch ostia. Long-term follow-up of transrenal fixation deserves to be investigated, especially after observing stent migration relative to aortic ostial encroachment.

Evaluation of pulmonary embolisms using coronal reformations on 64-row multidetector-row computed tomography: Comparison with axial images

OBJECTIVE

To evaluate coronal reformations of the chest on 64-row multidetector-row computed tomography (MDCT) for detection of pulmonary embolisms compared with axial images.

METHODS

Thirty-eight consecutive patients who underwent pulmonary computed tomography angiography (CTA) on 64-row MDCT for a suspected pulmonary embolism were retrospectively studied. Contiguous 2-mm axial and coronal images were reviewed independently. A pulmonary embolism was assessed in the main, lobar, or segmental pulmonary arteries and was scored using a 5-point scale.

RESULTS

A pulmonary embolism was demonstrated in 10% (4 of 38) of axial images and 16% (6 of 38) of coronal images. Interpretation was concordant in 95% to 100% of cases for a main or lobar pulmonary embolism and in 80% to 82% of cases for a segmental pulmonary embolism. Agreement of scores was almost perfect for a a main or lobar pulmonary embolism (mean weighted kappa value = 0.969) and moderate to good for a segmental pulmonary embolism (mean weighted kappa value = 0.560).

CONCLUSION

Coronal reformations of the chest on 64-row MDCT were as informative as axial images for the detection of main, lobar, and segmental pulmonary embolisms.

MDCT Versus Digital Radiography in the Evaluation of Bone Healing in Orthopedic Patients

OBJECTIVE

Assessment of bone healing in orthopedic patients is usually monitored by radiographs in two views. The purpose of our study was to compare multiplanar reconstructions from MDCT data sets with digital radiographs for assessing the extent of bone healing.

MATERIALS AND METHODS

Forty-three orthopedic patients (19 women, 24 men) who underwent MDCT and radiography after arthrodesis, fractures, or spinal fusions were included in our study. MDCT was performed on an MX 8000IDT scanner and served as the gold standard. The technical parameters were adapted to the anatomic region. A bone algorithm for reconstruction was used (3,500/600 H). Multiplanar reconstructions were calculated in two orthogonal planes. All patients underwent digital radiography on a Multix FD system in two views according to standard procedures. Multiplanar reconstructions and radiographs were analyzed by two musculoskeletal radiologists in a consensus interpretation to determine bone healing using a semiquantitative approach.

RESULTS

In 27 patients (63%), MDCT and digital radiography were concordant with regard to the extent of bone healing, whereas in 16 patients (37%) the results were not concordant. In eight patients (19%) digital radiographs underestimated the extent of bone healing, whereas in another eight patients (19%) they overestimated the degree of fusion.

CONCLUSION

MDCT using high-quality 2D reformatting is recommended as the primary imaging technique for the evaluation of bone healing.

Traumatic arterial injuries of the extremities: initial evaluation with MDCT angiography

OBJECTIVE

The purpose of this study was to retrospectively assess the accuracy of MDCT angiography as the initial diagnostic technique to depict arterial injury in patients with extremity trauma.

MATERIALS AND METHODS

Over 36 months, 87 patients (16 females and 71 males; age range, 16-87 years) with clinically suspected arterial injury after extremity trauma underwent 4-MDCT angiography and 67 ultimately underwent surgery. Eighty patients had blunt injuries, and seven had penetrating injuries. The presence of arterial involvement was investigated prospectively by the radiologist in charge and retrospectively by two independent radiologists. Each detected arterial lesion was then characterized as a spasm, stenosis, occlusion, or rupture. The standard of reference was surgery in 67 patients, angiography in two patients, and clinical and radiologic follow-up findings in 18 patients. MDCT angiography was assessed by means of receiver operating characteristic (ROC) curve analysis for lesion detection and Spearman's rank correlation test for lesion characterization. Image quality, lesion depiction, and artifacts were subjectively assessed.

RESULTS

Sixty-two traumatic arterial lesions were confirmed at surgery in 55 patients. MDCT angiography yielded high accuracy in detection (area under the ROC curve [Az] = 0.96; p < 0.001) and characterization (r = 0.94; p < 0.001) of traumatic arterial injuries and in recognizing an underlying dissection (Az= 0.82; p < 0.001). Prospective sensitivity and specificity were 95% and 87%, respectively, and retrospective sensitivity and specificity were 99% and 87%, respectively. MDCT angiography was considered to be sufficient for a reliable diagnosis in 83 patients (p < 0.001). Image quality and lesion depiction on MDCT angiograms were considered to be good and artifacts were considered mild with substantial interobserver agreement (kappa, 0.62-0.69).

CONCLUSION

MDCT angiography provides significant and reproducible technique for the detection and characterization of arterial injuries to the extremities with high image quality and vascular delineation.

Angiographic imaging of the lower extremities with multidetector CT

Multidetector CT (MDCT) has improved imaging of the arteries in the lower extremities. The main advantages of this novel technology are the exceptionally fast scan times, high spatial resolution, increased anatomic coverage, and capability to generate high-quality multiplanar reformations and three-dimensional (3-D) renderings from raw data that can be reprocessed easily and quickly. The applications of MDCT in imaging the lower extremities are multiple and varied. They include the evaluation of peripheral arterial occlusive and aneurysmal disease, the patency and integrity of bypass grafts, and arterial injury owing to trauma. This article describes the techniques of lower extremity MDCT angiography and its use in a few clinical applications.

Multidetector row CT demonstration of inner and middle ear structures

The aim of this study is to evaluate the anatomical details of the inner ear and middle ear, using multidetector row CT. Temporal bone CT scans were obtained using 16-detector row CT scanner (Lightspeed 16, General Electric Medical Systems, Milwaukee, WI) in 30 patients with dizziness, vertigo, or hearing loss. The three-dimensional (3D) images were reconstructed with volume rendering techniques. The 3D images were reviewed by two radiologists and scored by using a three-point quality rating for qualitative assessment of the 23 representative structures of the middle and inner ear. The malleus, incus, and facial nerve canal were identified in all patients. The incudomalleolar joint appeared fused in all patients. The stapes were seen clearly in 27 (90%) of 30 patients except in three patients. Among the three remaining patients, there was one who had effusions in the middle ear cavity. Another patient had left cholesteatoma. The third patient had normal middle ear cavity. The cochlea and the three semicircular canals (anterior, posterior, and lateral) were well demonstrated in 29 (97%) of 30 patients except for one old woman with osteoporosis. Sixteen-detector row CT imaging of temporal bone with advanced 3D reformation yields state-of-the-art anatomical details of the temporal region useful to address anatomical localization issues and ease conceptual structural learning.

Optimization of Multiplanar Reformations from Isotropic Data Sets Acquired with 16–Detector Row Helical CT Scanner

Institutional review board approval and waiver of consent were obtained for the patient component of this retrospective HIPAA-compliant study. By using an anthropomorphic phantom and metal oxide semiconductor field effect transistor detectors, radiation dose was determined for one eight-detector row and two 16-detector row computed tomographic (CT) protocols. A custom phantom was scanned by using the three protocols to identify isotropy. Contrast-to-noise ratios (CNRs) were determined for the same protocols by using a third phantom. Seven patients had undergone isotropic 16-detector row CT of the abdomen and pelvis. Anonymized coronal reformations at various thicknesses were ranked qualitatively by three radiologists. Effective dose equivalents were similar for the eight- and 16-detector row protocols. When transverse and coronal reformations of data acquired in the custom phantom were compared, coronal reformations obtained with the 16-detector row and 0.625-mm section thickness protocol were found to be nearly identical to the transverse image for all sets of line pairs. CNRs were consistently highest on 5-mm-thick coronal reformations (CNR range, 1.2-3.3). For qualitative assessment, 2- and 3-mm-thick coronal reformations were consistently preferred.

Primary Interpretation of Thoracic MDCT Images Using Coronal Reformations

OBJECTIVE

The objective of this study was to evaluate the accuracy and efficiency of primary interpretation of thoracic MDCT using coronal reformations as compared with transverse images.

SUBJECTS AND METHODS

Fifty patients (18 females, 32 males; age range, 15-93 years; mean age, 63.6 years) underwent 4-MDCT of the chest (detector width, 1 mm; beam pitch, 1.5). Contrast material was administered in 20 of the 50 patients. Coronal and transverse sections were reformatted into 5-mm-thick sections at 3.5-mm intervals. All available image and clinical data consensually reviewed by two thoracic radiologists served as the reference standard. Subsequently, three other thoracic radiologists independently evaluated reformatted coronal and transverse images at two separate review sessions. Each image set was assessed in 58 categories for abnormalities of the lungs, mediastinum, pleura, chest wall, diaphragm, abdomen, and skeleton. Interpretation times and number of images assessed were recorded. Sensitivity, specificity, and interobserver concordance were calculated. Differences in mean sensitivities and specificities were evaluated with Wilcoxon's signed rank test.

RESULTS

The most common findings identified were pulmonary nodules (n = 73, transverse images; n = 72, coronal images) and emphysema (n = 45, transverse; n = 40, coronal). The mean detection sensitivity of all lesions was significantly (p = 0.001) lower on coronal (44% +/- 26% [SD]) than on transverse (51% +/- 22%) images, whereas the mean detection specificity was significantly (p = 0.005) higher (96% +/- 5% vs 95% +/- 6%, respectively). Reporting findings for significantly (p < 0.001) fewer coronal images (mean, 63.0 +/- 4.6 images) than transverse images (mean, 91.9 +/- 8.8 images) took significantly (p = 0.025) longer (mean, 263 +/- 56 sec vs 238 +/- 45 sec, respectively).

CONCLUSION

Primary interpretation of thoracic MDCT is less sensitive and more time-consuming using 5-mm-thick coronal reformations as compared with transverse images.

Small-bowel obstruction: coronal reformations from isotropic voxels at 16-section multi-detector row CT

PURPOSE

To retrospectively assess the added value of coronal reformations of the abdomen and pelvis from isotropic voxels by using 16-section multi-detector row computed tomography (CT) for the diagnosis of small-bowel obstruction (SBO).

MATERIALS AND METHODS

This HIPAA-compliant study was approved by the institutional review board of this medical center with a waiver of informed consent. One hundred consecutive patients (40 men and 60 women; mean age, 55 years) suspected of having SBO and abdominal pain underwent 16-section multi-detector row CT with coronal reformations. Twenty-nine patients had a final diagnosis of SBO, and 71 patients did not. Three independent readers blinded to the diagnosis interpreted the CT scout scan, then transverse scans alone, and then transverse plus coronal scans for the presence of SBO and abnormal wall enhancement. Confidence was scored with a 1-5 scale (1 = absent, 5 = present).

RESULTS

Mean sensitivity and specificity of CT scout alone, transverse CT alone, and transverse plus coronal CT for the diagnosis of SBO were 88% and 86%, 87% and 87%, and 87% and 90%, respectively (not significant). In patients without SBO, transverse plus coronal CT enhanced confidence in the exclusion of SBO (P = .01). In patients with SBO, transverse plus coronal CT enhanced confidence in the diagnosis of SBO and identification of abnormal wall enhancement (P = .01).

CONCLUSION

Transverse 16-section multi-detector row CT data sets are an excellent test for the diagnosis of SBO, while the addition of coronal reformations obtained from these isotropic data sets adds confidence to the diagnosis and exclusion of SBO.

The point spread function of spiral CT

Computed tomography (CT) scanners are usually described by their in-plane resolution and slice-sensitivity profile (SSP). Other imaging systems are characterized by their point spread function (PSF). The PSF is an excellent basis for the analysis, design and enhancement of imaging systems. The 3D PSF of CT systems has rarely been considered, and has usually been approximated by a 3D Gaussian. We present mathematical analysis of the PSF of single-slice and multi-slice fan-beam and cone-beam CT, for major reconstruction algorithms. We show that the PSF has a complicated, non-separable 3D shape. It is anisotropic in the xy plane and twisted in the z direction. Furthermore, the PSF is space variant in all three axes. In particular, it rotates as the input impulse function moves in the z direction. The PSF may also have effective discontinuities that can lead to streaking artefacts. Indirect measurements of the PSF can be misleading. We support the theoretical results by direct experimental measurements of the PSF.

Thin-section multiplanar reformats from multidetector-row CT data: Utility for assessment of regional tumor extent in non-small cell lung cancer

PURPOSE

To determine the clinical utility of thin-section multiplanar reformats (MPRs) from multidetector-row CT (MDCT) data sets for assessing the extent of regional tumors in non-small cell lung cancer (NSCLC) patients.

MATERIALS AND METHODS

Sixty consecutive NSCLC patients, who were considered candidates for surgical treatment, underwent contrast-enhanced MDCT examinations, surgical resection and pathological examinations. All MDCT examinations were performed with a 4-detector row computed tomography (CT). From each raw CT data set, 5mm section thickness CT images (routine CT), 1.25 mm section thickness CT images (thin-section CT) and 1.25 mm section thickness sagittal (thin-section sagittal MPR) and coronal images (thin-section coronal MPR) were reconstructed. A 4-point visual score was used to assess mediastinal, interlobar and chest wall invasions on each image set. For assessment of utility in routine clinical practice, mean reading times for each image set were compared by means of Fisher's protected least significant difference (PLSD) test. A receiver operator characteristic (ROC) analysis was performed to determine the diagnostic capability of each of the image data sets. Finally, sensitivity, specificity and accuracy of the reconstructed images were compared by McNemar test.

RESULTS

Mean reading times for thin-section sagittal and coronal MPRs were significantly shorter than those for routine CT and thin-section CT (p<0.05). Areas under the curve (Azs) showing interlobar invasion on thin-section sagittal and coronal MPRs were significantly larger than that on routine CT (p=0.03), and the Az on thin-section sagittal MPR was also significantly larger than that on routine CT (p=0.02). Accuracy of chest wall invasion by thin-section sagittal MPR was significantly higher than that by routine CT (p=0.04).

CONCLUSION

Thin-section multiplanar reformats from multidetector-row CT data sets are useful for assessing the extent of regional tumors in non-small cell lung cancer patients.

Multi-detector row CT artifacts that mimic disease

PURPOSE

To determine retrospectively the frequency of two artifact patterns that mimic pathologic lesions on computed tomographic (CT) head images acquired in the axial scanning mode with two different multi-detector row CT systems at the same institution.

MATERIALS AND METHODS

The institutional review board approved this Health Insurance Portability and Accountability Act-compliant study and waived informed consent. The study involved two groups of consecutive patients, a group of 22 (nine men, 13 women; mean age, 56 years; age range, 27-85 years) examined with one multi-detector row CT system with four detector rows, and another group of 13 (seven men, six women; mean age, 69 years; age range, 53-81 years) examined with a different four-detector row CT system. Examinations in each group took place in a 4-week period. CT images were retrospectively evaluated by a neuroradiologist and a physicist for presence, appearance, location (within the image set and on individual images), and size of artifacts. Elimination of artifacts was verified by scanning a water phantom after scanner service and repair.

RESULTS

A pseudolesion, or artifact, was identified in scans of four of 22 patients examined with the first scanner and eight of 13 patients examined with the second scanner. The artifact on images obtained on the first scanner, an approximately 2-cm-diameter faintly hyperattenuating and nonenhancing area with hypoattenuating collar, was found at gantry isocenter on every fourth image. A different pattern was found on images obtained on the second scanner: a 1.1-cm-diameter circular area of hypoattenuation with a faintly attenuating rim, that mimicked a cyst. This artifact was observed also at the CT scanner gantry isocenter on every fourth image. Artifacts disappeared after recalibration (first scanner) or collimator cleaning (second scanner).

CONCLUSION

CT scanning in the axial mode can produce a regularly repeating artifact when data from one detector row of a multi-detector row CT scanner are compromised. Because of the risk of misinterpreting such patterns, routine assessment of each detector element is recommended for multi-detector row CT scanners that are routinely used in the axial scanning mode.

Medical rapid prototyping technologies: state of the art and current limitations for application in oral and maxillofacial surgery

PURPOSE

We describe state-of-the-art software and hardware requirements for the manufacture of high quality medical models manufactured using medical rapid prototyping. The limitations of medical models, the source of artefacts, and their physical appearance are illustrated along with remedies for their removal.

MATERIALS AND METHODS

Medical models were built using predominantly stereolithography and fused deposition modeling at both institutions over a period of 6 years. A combined total of 350 models have been produced for a range of maxillofacial, neurosurgical, and orthopedic applications. Stereolithography, fused deposition modeling, computerized numerical milling, and other technologies are described along with computer software requirements.

RESULTS

A range of unwanted artefacts that create distortions on medical models have been identified. These include data import, computed tomography gantry distortion, metal, motion, surface roughness due to support structure removal or surface modeling, and image data thresholding. The source of the artefact has been related to the patient, imaging modality performance, or the modeling technology. Discussion as to the significance of the artefacts on clinical use is provided.

CONCLUSIONS

It is recommended that models of human anatomy generated by medical rapid prototyping are subject to rigorous quality assurance at all stages of the manufacturing process. Clinicians should be aware of potential areas for inaccuracies within models and review the source images in cases where model integrity is in doubt.

Detection of liver metastases under 2 cm: comparison of different acquisition protocols in four row multidetector-CT (MDCT)

This study compared different acquisition protocols performance to detect small liver metastases (<2 cm). Thirty consecutive patients with histologically proven hepatic metastases were explored by MDCT at the liver equilibrium phase by four successive acquisitions. We compared the following protocols (1-4): 5/30/1.5 (section thickness/table speed/pitch); 5/15/0.75; 5/11.25/0.75; and 2.5/15/1.5 with the same X-ray dose. The gold standard was based on patient radiological follow-up. Evolutive lesions were considered as true positive (TP). The described lesions, not found on the follow-up exams despite tumoral progression, were considered as false positive (FP). Stable lesions could not be considered as metastasis and were eliminated. One hundred and seventy-six lesions were detected: 61 TP and 91 FP. Twenty-four lesions were eliminated. The mean kappa values for protocols 1, 2, 3 and 4 were, respectively, 0.43, 0.68, 0.73 and 0.51 (0.61-0.80: substantial agreement) and the mean areas under the ROC curve were, respectively, 0.76, 0.87, 0.86 and 0.80. The results of protocols 2 and 3 were significantly superior to those of protocols 1 and 4. MDCT protocols using thin sections or an increased table speed are less efficient in detecting small metastases.

How to image from head to pubis for blunt abdominal trauma using GE LightSpeed QX/i

Multislice CT scanners can rapidly produce head-to-pubis images in multitrauma patients. This article summarizes the technical advances that distinguish multislice CT scanners from single-slice helical CT scanners. It is important to understand certain physical principles in order to use this powerful technology to maximum diagnostic advantage while keeping radiation doses at reasonable levels. The CT imaging protocol of our institution is presented along with a discussion of the rationale behind our protocol choices. One of the important advantages in using the total body CT approach is its ability to perform CT angiography of the aorta and multiplanar reformatted images of the spine from a single pass through the torso. Techniques for optimizing reformatted images conclude the article.

Comparison of artifacts on coronal reformation and axial CT pulmonary angiography images using single-detector and 4- and 8-detector multidetector-row helical CT scanners

RATIONALE AND OBJECTIVES

The aim of this study is to compare the degree of stair-step artifact on coronal reformation computed tomographic (CT) pulmonary angiography images obtained using single-detector helical CT (SDCT), four-detector (4-MDCT), and eight-detector multidetector-row CT (8-MDCT) and compare the degree of motion artifact on the corresponding axial CT images.

MATERIALS AND METHODS

Three groups of consecutive patients imaged by means of CT angiography for suspected pulmonary embolus were retrospectively identified by using CT records at our institution: (1) group A (n = 38), SDCT; (2) group B (n = 36), 4-MDCT; and (3) group C (n = 74), 8-MDCT. For each case, coronal multiplanar volume reformation maximal intensity projection images were created by using a standard technique. All images were reviewed in a randomized fashion by two thoracic radiologists who were blinded to the type of CT scanner. Stair-step artifact of pulmonary arteries on coronal reformation images was graded by consensus agreement using a four-point scale (0 = no artifact to 3 = severe artifact). Axial images were assessed for six parameters of motion artifact. The sum of these grades resulted in a total motion score, with a potential range of 0 (no motion) to 12 (severe motion). Statistical analysis was performed using the Mann-Whitney test.

RESULTS

Stair-step artifacts were significantly higher for SDCT (mean, 2.9; median, 3) compared with 4-MDCT (mean, 2.2; median, 2; P < .0001) and 8-MDCT (mean, 1.5; median, 1; P < .0001). Total motion scores were significantly higher for SDCT (mean, 9.3) compared with 4-MDCT (mean, 8.4; P = .03) and 8-MDCT (mean, 6.8; P < .0001).

CONCLUSION

Stair-step artifacts are significantly higher with SDCT compared with MDCT. For MDCT, eight-detector scanners produce images with significantly less artifact than four-detector scanners.

3D reconstruction techniques made easy: know-how and pictures

Three-dimensional reconstructions represent a visual-based tool for illustrating the basis of three-dimensional post-processing such as interpolation, ray-casting, segmentation, percentage classification, gradient calculation, shading and illumination. The knowledge of the optimal scanning and reconstruction parameters facilitates the use of three-dimensional reconstruction techniques in clinical practise. The aim of this article is to explain the principles of multidimensional image processing in a pictorial way and the advantages and limitations of the different possibilities of 3D visualisation.

Multislice CT Virtual Intravascular Endoscopy for Abdominal Aortic Aneurysm Stent Grafts

PURPOSE

To investigate the optimal scanning protocols of multislice computed tomographic (CT) angiography in aortic stent graft placement observed on virtual intravascular endoscopy (VIE).

MATERIALS AND METHODS

A human aorta phantom was built with a commercial aortic stent graft placed in situ. The phantom was housed in a perspex container and filled with contrast medium with CT attenuation similar to that used in the patient's abdominal scanning. CT was performed with a four-slice multislice CT scanner with section thickness of 1.3 mm, 2 mm, and 3.2 mm, pitch of 0.75, 1, and 1.5, and reconstruction interval of 50% overlap and no overlap. Stair-step artifacts were quantified by measuring the SD of signal intensity on surfaced shaded VIE images in three different locations: superior mesenteric artery (SMA), renal ostium, and aortic aneurysm.

RESULTS

Image quality of VIE images was independent of section thickness and pitch values in the level of renal ostium and aortic aneurysm (P >.05), whereas it was determined by the section thickness and pitch in the level of SMA (P <.05). Aortic branch origin became irregular or distorted when section thickness increased to 3.2 mm or pitch reached 1.5.

CONCLUSION

A scanning protocol of section thickness of 2 mm, pitch 1, and reconstruction interval of 1 mm is recommended in aortic stent graft placement because it allows fewer stair-step artifacts and better visualization of the aortic stent wires observed on VIE.

Tracheal and central bronchial aerodynamics using virtual bronchoscopy and computational fluid dynamics

Virtual bronchoscopy reconstructions of the airway noninvasively provide useful morphologic information of structural abnormalities such as stenoses and masses. In this paper, we show how virtual bronchoscopy can be used to perform aerodynamic calculations in anatomically realistic models. Pressure and flow patterns in a human airway were computed noninvasively. These showed decreased pressure and increased shear stress in the region of a stenosis.

Occlusive arterial disease of abdominal aorta and lower extremities

The purpose of this study was to evaluate helical CT angiography in the assessment of occlusive arterial disease of abdominal aorta and the lower extremities. Sixteen patients underwent both transcatheter angiography and helical CT. Helical CT was inconclusive in 6.2% of segments whereas angiography was inconclusive in 5%. The overall sensitivity of helical CT was 91% and specificity 93%. Segmental analysis found a sensitivity of 43% in infrapopliteal arteries, and a specificity of 86%.

Computed Tomography Angiography

Multidetector-row computed tomography (MDCT) is an essential diagnostic modality for many clinical algorithms. This is particularly true with regard to the evaluation of cardiovascular disease. As a result of increased image acquisition speed, improved spatial resolution, and greater scan volume, MDCT angiography (computed tomography angiography [CTA]) has become an excellent noninvasive imaging technique, replacing intra-arterial digital subtraction angiography for most vascular territories. The clinical success of CTA depends on precise synchronization of image acquisition with optimal vascular enhancement. As technology continuously evolves, however, this task can be challenging. It remains important to have a fundamental knowledge of the principles behind technical parameters and contrast medium administration. This article reviews these essential principles, followed by an overview of current clinical applications.

Multidetector row computed tomography of the aorta and peripheral arteries

MDCT represents a significant advance on SDCT and the advantages it brings are particularly clear in CTA applications. It allows cost effective assessment of longer segments of vascular territories to be imaged with higher spatial, contrast, and temporal resolution. It has replaced SDCT as the new CT standard and its technical abilities are rapidly approaching the temporal resolution of EBCT. With 3-D post processing tools its main benefit is in imaging studies customized to the patient's pathology, with greater measurement accuracy and reliable longitudinal assessment. MDCTA is increasingly applied not to individual vascular territories but to a complete assessment dictated by the pathology, such as the entire aorta and branch vessels in aneurysm evaluation and the aorta and the coronary arteries in dissection cases or the vascular and non-vascular chest in acute chest pain. Greater accuracy of vessel assessment will lead to a refinement of interventional and surgical techniques for an individual patient and facilitates conservative management of conditions that can be reliably monitored non-invasively and the development of intervention criteria. MDCTA will continue to increase its major role in peripheral vascular evaluation in the future though its reliability in assessing small vessels below the knee and in the foot remains to be conclusively proven to obviate the need for diagnostic catheter angiography.

Sixteen-Row multislice computed tomography: basic concepts, protocols, and enhanced clinical applications

Since its introduction, spiral computed tomography (CT) technology underwent a continuous and fast technical and clinical development. In particular, spatial and temporal resolutions were constantly increased during the last decade. The main breakthrough for clinical application was the introduction of multislice technology, first with 2-row and 4-row equipment and more recently with 16-row scanners. A high-resolution sub-millimeter CT dataset can be acquired easily, although with an increased x-ray exposure for the patient. The high speed of the scan requires up-to-date and careful protocol optimization. Scanner technology and geometry affect image formation procedure and imaging protocols should be adapted accordingly. The technical foundations of spiral CT imaging and the main scan and reconstruction parameters are described in this article. Updated protocols and clinical examples of the latest applications are also discussed.

Impact of multislice CT on imaging of acute abdominal disease

The increased speed, greater coverage, and thinner slices of MSCT are exciting developments in radiology, and these feature should only improve with newer generation multislice scanners. The impact of this technology on abdominal imaging has just begun.