Computer-assisted lung nodule volumetry from multi-detector row CT: influence of image reconstruction parameters

PURPOSE: To investigate differences in volumetric measurement of pulmonary nodules caused by changing the reconstruction parameters for multi-detector row CT. MATERIALS AND METHODS: Thirty-nine pulmonary nodules less than 2 cm in diameter were examined by multi-slice CT. All nodules were solid, and located in the peripheral part of the lungs. The resultant 48 parameters images were reconstructed by changing slice thickness (1.25, 2.5, 3.75, or 5 mm), field of view (FOV: 10, 20, or 30 cm), algorithm (high-spatial frequency algorithm or low-spatial frequency algorithm) and reconstruction interval (reconstruction with 50% overlapping of the reconstructed slices or non-overlapping reconstruction). Volumetric measurements were calculated using commercially available software. The differences between nodule volumes were analyzed by the Kruskal-Wallis test and the Wilcoxon Signed-Ranks test. RESULTS: The diameter of the nodules was 8.7+/-2.7 mm on average, ranging from 4.3 to 16.4mm. Pulmonary nodule volume did not change significantly with changes in slice thickness or FOV (p>0.05), but was significantly larger with the high-spatial frequency algorithm than the low-spatial frequency algorithm (p<0.05), except for one reconstruction parameter. The volumes determined by non-overlapping reconstruction were significantly larger than those of overlapping reconstruction (p<0.05), except for a 1.25 mm thickness with 10 cm FOV with the high-spatial frequency algorithm, and 5mm thickness. The maximum difference in measured volume was 16% on average between the 1.25 mm slice thickness/10 cm FOV/high-spatial frequency algorithm parameters and overlapping reconstruction. CONCLUSION: Volumetric measurements of pulmonary nodules differ with changes in the reconstruction parameters, with a tendency toward larger volumes in high-spatial frequency algorithm and non-overlapping reconstruction compared to the low-spatial frequency algorithm and overlapping reconstruction.     

Thoracic aorta at multi-detector row CT: motion artifact with various reconstruction windows

The authors assessed motion artifact of the thoracic aorta in 25 patients who underwent multi-detector row computed tomography (CT) with retrospective electrocardiographic (ECG) gating. CT reconstructions centered at four phases of diastole were compared for five different levels of the thoracic aorta. A significant positive correlation was observed between heart rate and motion artifact (r = 0.72, P <.001). The optimal reconstruction phase varied between patients, and this was directly related to heart rate. For patients with a heart rate of 70 beats per minute, the reconstruction phase centered at 75% of the R-R interval had the significantly least motion artifact (P =.004). Conversely, the optimal reconstruction phase for patients with heart rates above 70 beats per minute was centered at 50% of the R-R interval (P =.09).     

Volumetric measurement of pulmonary nodules at low-dose chest CT: effect of reconstruction setting on measurement variability

Objective  

To assess volumetric measurement variability in pulmonary nodules detected at low-dose chest CT with three reconstruction settings.     

Coronary artery bypass grafts: ECG-gated multi-detector row CT angiography--influence of image reconstruction interval on graft visibility

PURPOSE: To evaluate the influence of different reconstruction intervals of retrospectively electrocardiographically (ECG)-gated multi-detector row computed tomographic (CT) angiography on image quality of different segments of various types of coronary artery bypass grafts. MATERIALS AND METHODS: Twenty consecutive patients with 62 grafts underwent retrospectively ECG-gated four-channel multi-detector row CT angiography and conventional coronary angiography. Raw helical CT data were reconstructed at 0%-90% of the cardiac cycle in increments of 10%. Each graft was separated into three segments (proximal segment, graft body, and distal anastomosis). Three graft types were identified according to site of distal anastomosis. Two readers assessed image quality of segments and graft types. Effective radiation dose was calculated. RESULTS: Best image quality of all segments was obtained at a reconstruction interval of 50%-70% of the cardiac cycle. Image quality of the proximal segment did not vary significantly with different reconstruction intervals (analysis of variance, P =.8), whereas image quality of the graft body and distal anastomosis changed significantly with varying reconstruction intervals (P <.001). Distal anastomosis and body of types 1 and 2 grafts were best seen at 60%-70% of the cardiac cycle, whereas distal anastomosis and body of type 3 grafts were best visualized at 50%. Accuracy of CT angiography for detection of graft patency was 94% for reader 1 and 95% for reader 2. Effective dose for CT was 11.4 mSv for both men and women. Mean effective dose for angiography was 2.1 mSv for men and women. CONCLUSION: Optimal selection of reconstruction interval improves image quality of the graft body and of distal anastomosis in particular.     

ECG-gated reconstructed multi-detector row CT coronary angiography: effect of varying trigger delay on image quality

PURPOSE: To evaluate the effectiveness of electrocardiographically (ECG)-gated retrospective image reconstruction for multi-detector row computed tomographic (CT) coronary angiography in reducing cardiac motion artifacts and to evaluate the influence of heart rate on cardiac image quality. MATERIALS AND METHODS: Sixty-five patients with different heart rates underwent coronary CT angiography. Raw helical CT data and ECG tracings were combined to retrospectively reconstruct at the defined consecutive z position with a temporal resolution of 250 msec per section. The starting points of the reconstruction were chosen between 30% and 80% of the R-R intervals. The relationships between heart rate, trigger delay, and image quality were analyzed. RESULTS: Optimal image quality was achieved with a 50% trigger delay for the right coronary artery and 60% for the left circumflex coronary artery. Optimal image quality for the left anterior descending coronary artery was equally obtained at 50% and 60% triggering. A significant negative correlation was observed between heart rate and image quality (P <.05). The best image quality was achieved when the heart rate was less than 74.5 beats per minute. CONCLUSION: To achieve high image quality, the heart rate should be sufficiently slow. Selection of appropriate trigger delays and a decreasing heart rate are effective to reduce cardiac motion artifacts.     

Pulmonary nodules on multi-detector row CT scans: performance comparison of radiologists and computer-aided detection

PURPOSE: To compare the performance of radiologists and of a computer-aided detection (CAD) algorithm for pulmonary nodule detection on thin-section thoracic computed tomographic (CT) scans. MATERIALS AND METHODS: The study was approved by the institutional review board. The requirement of informed consent was waived. Twenty outpatients (age range, 15-91 years; mean, 64 years) were examined with chest CT (multi-detector row scanner, four detector rows, 1.25-mm section thickness, and 0.6-mm interval) for pulmonary nodules. Three radiologists independently analyzed CT scans, recorded the locus of each nodule candidate, and assigned each a confidence score. A CAD algorithm with parameters chosen by using cross validation was applied to the 20 scans. The reference standard was established by two experienced thoracic radiologists in consensus, with blind review of all nodule candidates and free search for additional nodules at a dedicated workstation for three-dimensional image analysis. True-positive (TP) and false-positive (FP) results and confidence levels were used to generate free-response receiver operating characteristic (ROC) plots. Double-reading performance was determined on the basis of TP detections by either reader. RESULTS: The 20 scans showed 195 noncalcified nodules with a diameter of 3 mm or more (reference reading). Area under the alternative free-response ROC curve was 0.54, 0.48, 0.55, and 0.36 for CAD and readers 1-3, respectively. Differences between reader 3 and CAD and between readers 2 and 3 were significant (P < .05); those between CAD and readers 1 and 2 were not significant. Mean sensitivity for individual readings was 50% (range, 41%-60%); double reading resulted in increase to 63% (range, 56%-67%). With CAD used at a threshold allowing only three FP detections per CT scan, mean sensitivity was increased to 76% (range, 73%-78%). CAD complemented individual readers by detecting additional nodules more effectively than did a second reader; CAD-reader weighted kappa values were significantly lower than reader-reader weighted kappa values (Wilcoxon rank sum test, P < .05). CONCLUSION: With CAD used at a level allowing only three FP detections per CT scan, sensitivity was substantially higher than with conventional double reading.     

Reproducibility and accuracy of coronary calcium measurements with multi-detector row versus electron-beam CT

PURPOSE: To methodically evaluate the reproducibility and accuracy of coronary arterial calcification measurements by using spiral multi-detector row and electron-beam computed tomography (CT) with a beating heart phantom. MATERIALS AND METHODS: A phantom was built to mimic a beating heart with coronary arteries and calcified plaques. The simulated vessels moved in a pattern similar to that of a beating heart. The phantom operated at a variety of pulse rates (0-140 beats per minute). The phantom was repeatedly scanned in various positions by using various protocols with electron-beam and multi-detector row CT scanners to assess interexamination variability. Statistical analysis was performed to determine significant differences in interexamination variability for various acquisition protocols. RESULTS: Electrocardiographically (EKG) gated volume coverage with spiral multi-detector row CT (2.5-mm collimation) and overlapping image reconstruction (1-mm increment) was found to significantly improve the reliability of coronary arterial calcium quantification, especially for small plaques (P <.05). Mean interexamination variability was reduced from 35% +/- 6 (SD) (Agatston score, standard electron-beam CT) to 4% +/- 2 (P <.05) (volumetric score, spiral EKG-gated multi-detector row CT). CONCLUSION: By coupling retrospective gating with nearly isotropic volumetric imaging data, spiral multi-detector row CT provides better input data for quantification of coronary arterial calcium volume. Multi-detector row CT allows precise and repeated measurement of coronary arterial calcification, with low interexamination variability.     

Coronary artery calcium measurement with multi-detector row CT: in vitro assessment of effect of radiation dose

The authors assessed in vitro the effect of radiation dose on coronary artery calcium quantification with multi-detector row computed tomography. A cardiac phantom with calcified cylinders was scanned at various milliampere second settings (20-160 mAs). A clear tendency was found for image noise to decrease as tube current increased (P <.001). No tendency was found for the Agatson score or calcium volume and mass errors to vary with tube current. Calcium measurements were not significantly affected by the choice of tube current. Calcium mass error was strongly correlated with calcium volume error (P <.001). The calcium mass measurement was more accurate and less variable than the calcium volume measurement.     

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.     

Vascular calcification in ex vivo carotid specimens: precision and accuracy of measurements with multi-detector row CT

PURPOSE: To test the accuracy and precision of multi-detector row computed tomography (CT)-derived measurements of vascular calcification in ex vivo human carotid endarterectomy (CEA) specimens. MATERIALS AND METHODS: Sixteen ex vivo CEA specimens were imaged with multi-detector row CT. Multi-detector row CT-derived calcium scoring algorithms (ie, mineral mass and volume score) were compared with the mass and volume of ashed remnants of the CEA specimens. Bland-Altman analysis was performed to assess the mean (ie, bias) and SD (ie, precision) of differences between multi-detector row CT- and ashing-derived measurements. In addition, conventional Agatston score, volume score, mineral mass, and modified Agatston score were calculated for each specimen by using a number of scanning protocols. Images were obtained at a section thickness of 1.25 mm by using different tube energy settings and tube currents. Specimens were also imaged at different section thicknesses with fixed combinations of tube energy and tube current. To compare measurement variability of scoring methods, coefficients of variation for all protocols were calculated. RESULTS: Both mean multi-detector row CT-derived mineral mass and mean ashing-derived mineral mass were 0.129 g +/- 0.173 (r = 0.99, P <.001). Mean multi-detector row CT- and ashing-derived volumes were 339.94 mm3 +/- 395.4 and 39.48 mm3 +/- 55.76, respectively (r = 0.95, P <.001). Measurement bias relative to the reference ashing values was high (2,800.0%) for volume score and low (2.58%) for mineral mass. Measurement precision was 0.6% for volume score and greater than 0.0005% for mineral mass. Mean coefficients of variation for all CT protocols were 5.0% +/- 4.2 and 4.9% +/- 4.2 for mineral mass and modified Agatston score, respectively, and 16.0% +/- 9.2 and 14.5% +/- 3.9 for conventional Agatston and volume scores, respectively (P <.001). CONCLUSION: Compared with the conventional volume score, multi-detector row CT-derived mineral mass is a less biased and more precise measurement of the mineral content of nonmoving ex vivo CEA specimens. Mineral mass and modified Agatston score are more reproducible than conventional volume and Agatston scores.     

Hereditary haemorrhagic telangiectasia: study of hepatic vascular alterations with multi-detector row helical CT and reconstruction programs

PURPOSE: To evaluate hepatic alterations in patients affected by Hereditary Haemorrhagic Telangiectasia (HHT) by using multidetectorrow helical CT (MDCT) and new reconstruction programs. MATERIALS AND METHODS: An MDCT multiphasic study of the liver was performed in 105 consecutive patients: 89 considered to be affected by HHT and 16 with suspicion of disease alone. The scan delay was determined by using a test bolus of contrast material. The CT examination was performed with a triphasic technique (double arterial phase and portal venous phase). Multiplanar and angiographic reconstructions were then obtained, and the images checked for the presence of shunts, hepatic perfusion disorders, vascular lesions (telangiectases and large confluent vascular masses), indirect signs of portal hypertension, and anatomical vascular variants. RESULTS: Hepatic vascular alterations were found in 78/105 cases (67/89 patients affected by HHT and 11/16 patients with clinical suspicion alone). Therefore HHT diagnosis was excluded in 5 patients. 78/100 (78%) patients with HHT had intrahepatic vascular alterations: arterioportal shunts in 40/78 (51.2%), arteriosystemic shunts in 16/78 (20.5%), and both shunt types in 22/78 (28.3%). Intraparenchymal perfusion disorders were found in 46/78 (58.9%) patients. Telangiectases were recognised in 50/78 (64.1%) patients. Large confluent vascular masses (LCVMs) were identified in 20/78 (25.6%) patients. Indirect signs of portal hypertension were found in 46/78 (58.9%) cases. Variant hepatic arterial anatomy was present in 38/100 cases (38%). CONCLUSIONS: Multiphasic MDCT and the new reconstruction programs enable the identification and characterisation of the complex vascular alterations typical of HHT.     

Comparison of a dental cone beam CT with a multi-detector row CT on effective doses and physical image quality

The purpose of this study was to compare a dental cone beam computed tomography (dental CBCT) and a multi-detector row CT (MDCT) using effective doses and physical image quality. A dental mode (D-mode) and an implant mode (I-mode) were employed for calculating effective doses. Field of view (FOV) size of the MDCT was 150 mm. Three types of images were obtained using 3 different reconstruction functions: FC1 (for abdomen images), FC30 (for internal ear and bone images) and FC81 (for high resolution images). Effective doses obtained with the D-mode and with the I-mode were about 20% and 50% of those obtained with the MDCT, respectively. Resolution properties obtained with the D-mode and I-mode were superior to that of the MDCT in a high frequency range. Noise properties of the D-mode and the I-mode were better than those with FC81. It was found that the dental CBCT has better potential as compared with MDCT in both dental and implant modes.     

Impaired left ventricular function has a detrimental effect on image quality in multi-detector row CT coronary angiography

AIM: To determine whether there is a relationship between left ventricular (LV) haemodynamic parameters, circulation times, and arterial contrast opacification that might affect the image quality of computed tomography (CT) coronary angiography. METHODS: Thirty-six patients were included in the study: 18 with cardiomyopathy (CM) and LV dilatation of suspected ischaemic aetiology [age 57.9+/-13.7 years, range 30-77 years; 14 male, four female; body mass index (BMI)=27.7+/-4.5, range 25.5-31.8] and 18 controls (age 62.3+/-9.4 years, range 47-89 years; 10 male, eight female; BMI 27.8+/-6.6; range 19.2-33.6). Coronary artery image quality was assessed using a three-point visual scale; contrast medium circulation times, aortic root contrast attenuation, and LV functional parameters were studied. RESULTS: Visually reduced contrast opacification impaired image quality more often in the CM group than the control group (27.4 versus 5.1%). A total of 55.6% CM patients had a contrast transit time ranging from 30-75 s; the number of "unassessable" segments increased with increasing transit time conforming to a fitted quadratic model (R2=0.74). The relationship between LV ejection fraction and contrast attenuation may also conform to a quadratic model (R2=0.71). CONCLUSION: LV haemodynamics influence coronary artery opacification using cardiac CT, and users imaging this subgroup must do so with the knowledge of this potential pitfall. The results indicate the need for further studies examining CT protocols in this clinical subgroup.     

Coronary artery calcium: accuracy and reproducibility of measurements with multi-detector row CT--assessment of effects of different thresholds and quantification methods

PURPOSE: To evaluate the effects of different thresholds and quantification methods on the accuracy and reproducibility of coronary calcium measurements with multi-detector row computed tomography (CT). MATERIALS AND METHODS: A cardiac CT phantom containing predetermined calcified cylinders was scanned. Calcium volume and mass were measured at various threshold values ranging from 80 to 230 HU. In 32 patients, two consecutive CT scans were obtained, and the coronary artery calcium score, volume, and mass were measured by one observer at 130- and 90-HU thresholds. Correlation analysis and analysis of variance were performed to evaluate the measurement errors in the phantom study and the interscan variability in the clinical study. RESULTS: In the phantom, mass measurement error varied with threshold and calcium density (P <.01). Mass error was strongly correlated with volume error (r = 0.91, P <.01) but with a much smaller range. In the clinical study, interscan variability of mass measurements was significantly lower than that with other measurement methods for both patients and individual vessels. For the patients, the mean interscan variability of calcium score, volume, and mass at the 130-HU threshold was 20.4%, 13.9%, and 9.3%, respectively. For all methods, interscan variability was not significantly different between the 130- and 90-HU thresholds (P >.05). CONCLUSION: The mass measurement is more accurate, less variable, and more reproducible in coronary calcium quantification than are measurements with other algorithms. Accurate quantification of calcium in each calcified plaque may require that the threshold be set individually, depending on the calcium density.     

Preoperative T and N staging of colorectal cancer: accuracy of contrast-enhanced multi-detector row CT colonography--initial experience

PURPOSE: To evaluate the accuracy of contrast material-enhanced multi-detector row computed tomographic (CT) colonography for preoperative staging of colorectal cancer. MATERIALS AND METHODS: Forty-one patients with colorectal carcinoma underwent preoperative contrast-enhanced multi-detector row CT colonography. Images were obtained in the arterial (start delay of 35 seconds) and portal venous (start delay of 70 seconds) phases. The arterial phase was focused on the suspected region of neoplasm, whereas the venous phase included the whole abdomen and pelvis. Two radiologists independently evaluated the depth of tumor invasion into the colorectal wall (T) and regional lymph node involvement (N) on transverse CT images alone and in combination with multiplanar reformations (MPRs). Disagreements were resolved by means of consensus. CT findings were compared with pathologic results, which served as the reference standard. Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were assessed. Differences in accuracy for T and N staging were assessed by using the McNemar test. RESULTS: In T staging, overall accuracy was 73% when transverse images were evaluated alone and 83% when they were evaluated in combination with MPRs. This difference was not significant. N staging was associated with an overall accuracy of 59% with transverse images alone and 80% with combined transverse and MPR images (P <.01). CONCLUSION: Contrast-enhanced multi-detector row CT colonography is an accurate technique for preoperative local staging of colorectal tumors.     

Solitary pulmonary nodules: dynamic enhanced multi-detector row CT study and comparison with vascular endothelial growth factor and microvessel density

PURPOSE: To evaluate enhancement dynamics of solitary pulmonary nodules at multi-detector row computed tomography (CT) and to correlate results with extent of tumor angiogenesis in pathologic specimens. MATERIALS AND METHODS: One hundred thirty-one patients with solitary pulmonary nodules underwent unenhanced thin-section CT, followed by dynamic helical CT (throughout the nodule for 30 mm along the z-axis [13 images] and at 20-second intervals for 3 minutes [130 images total]) after intravenous injection of 120 mL of contrast medium. Diagnosis of malignancy or benignancy was assigned in 109 patients, and follow-up imaging suggested benignancy in the remaining 22. CT findings were analyzed for peak attenuation, net enhancement, and enhancement dynamics. In 54 patients with surgical diagnoses, Pearson correlation coefficient was used to correlate enhancement pattern with extent of microvessel density and vascular endothelial growth factor (VEGF) staining. RESULTS: With 30 HU or more of net enhancement as a cutoff value in differentiation of malignant and benign nodules, sensitivity for malignant nodules was 99% (69 of 70 malignant nodules), specificity was 54% (33 of 61 benign nodules), positive predictive value was 71% (69 of 97 malignant readings), negative predictive value was 97% (33 of 34 benign readings), and accuracy was 78% (102 of 131 nodules). Peak attenuation was correlated positively with extent of microvessel density (r = 0.369, P =.006) and VEGF staining (r = 0.277, P =.042). Malignant nodules showed significantly higher VEGF expression (P =.009) than that of benign nodules. CONCLUSION: Dynamic enhancement with multi-detector row CT shows high sensitivity and negative predictive values for diagnosis of malignant nodules but low specificity because of highly enhancing benign nodules. Extent of enhancement reflects underlying nodule angiogenesis.     

Intravenous three-dimensional CT portography using multi-detector row CT in patients with hepatic cirrhosis: evaluation of scan timing and image quality

PURPOSE: To evaluate the scan timing and image quality of intravenous three-dimensional (3D) CT portography using multi-detector row CT (MDCT) and to assess the influence of patients' body weight on enhancement of the portal vein (PV). METHODS: One hundred nine patients with hepatic cirrhosis underwent triple-phase contrast enhanced CT using MDCT. The early, portal, and late phases were started at 30 sec, 60 sec, and 90 sec, respectively, after the beginning of intravenous injection of contrast medium (300 mgI/mL, 100 mL total). The CT value of the PV was assessed in the three phases: precontrast, portal phase, and late phase. 3D-portography of the MIP image was evaluated by three-point scale based on vessel visualization. The relationship between these data and body weight was investigated. RESULTS: The mean CT value of PV at 60 sec was 172.01+/-25.94 HU, which was significantly higher than that at 90 sec. Good or excellent 3D-CT portography was obtained in 97/109 patients (89%). Heavy patients tended to show less opacification of PV. CONCLUSIONS: Intravenous 3D-CT portography using MDCT at a 60 sec delay provided adequate PV images for patients with hepatic cirrhosis. Enhancement of PV was affected by patients' body weight.     

Detection of intracranial aneurysms: multi-detector row CT angiography compared with DSA

PURPOSE: To prospectively compare the effectiveness of multi-detector row computed tomographic (CT) angiography with that of conventional intraarterial digital subtraction angiography (DSA) used to detect intracranial aneurysms in patients with nontraumatic acute subarachnoid hemorrhage. MATERIALS AND METHODS: Thirty-five consecutive adult patients with acute subarachnoid hemorrhage were recruited into the institutional review board-approved study and gave informed consent. All patients underwent both multi-detector row CT angiography and DSA no more than 12 hours apart. CT angiography was performed with a multi-detector row scanner (four detector rows) by using collimation of 1.25 mm and pitch of 3. Images were interpreted at computer workstations in a blinded fashion. Two radiologists independently reviewed the CT images, and two other radiologists independently reviewed the DSA images. The presence and location of aneurysms were rated on a five-point scale for certainty. Sensitivity and specificity were calculated independently for image interpretation performed by the two CT image readers and the second DSA image reader by using the first DSA reader's interpretation as the reference standard. RESULTS: A total of 26 aneurysms were detected at DSA in 21 patients, and no aneurysms were detected in 14 patients. Sensitivity and specificity for CT angiography were, respectively, 90% and 93% for reader 1 and 81% and 93% for reader 2. The mean diameter of aneurysms detected on CT angiographic images was 4.4 mm, and the smallest aneurysm detected was 2.2 mm in diameter. Aneurysms that were missed at initial interpretation of CT angiographic images were identified at retrospective reading. CONCLUSION: Multi-detector row CT angiography has high sensitivity and specificity for detection of intracranial aneurysms, including small aneurysms, in patients with nontraumatic acute subarachnoid hemorrhage.     

Coronary artery calcification: effect of size of field of view on multi-detector row CT measurements

The effect of the size of the field of view (FOV) on coronary artery calcium measurements at multi-detector row computed tomography (CT) was assessed. Coronary multi-detector row CT was performed with an identical protocol in 100 consecutive subjects. CT images were reconstructed at different FOV sizes (210, 260, and 310 mm). Calcified coronary lesions were detected in all three image sets in 52 subjects. The FOV sizes tested for multi-detector row CT coronary screening had a negligible effect on coronary artery calcium measurements (P >/=.06). However, risk stratification decreased by one level in seven of 52 subjects when the FOV increased from 210 or 260 to 310 mm.