Pancreas divisum: depiction with multi-detector row CT

PURPOSE: To retrospectively evaluate contrast material-enhanced multi-detector row computed tomography (CT) in the depiction of pancreas divisum. MATERIALS AND METHODS: This study was approved by the investigational review board. Seventy-seven patients (46 men and 31 women; mean age, 51 years) underwent CT with a four-detector row scanner and endoscopic retrograde pancreatography (ERP). Section thickness was 3.2 mm, and the reconstruction interval was 3 mm. Two radiologists independently evaluated the CT data sets with picture archiving and communication system (PACS) workstations equipped with software for two- and three-dimensional postprocessing reformations; the radiologists were blinded to the clinical and ERP data. Pancreas divisum was diagnosed at CT if what the authors termed the "dominant dorsal duct sign" (the caliber of the dorsal duct was larger than that of the ventral duct) was present and if the dorsal and ventral ducts did not appear to communicate with each other at cine review of images. ERP findings were used as the standard of reference for determining the performance (sensitivity, specificity, positive and negative predictive values) of the radiologists' CT interpretations. Interobserver agreement was measured by using kappa statistics. RESULTS: For four of the 77 patients (5%), both radiologists considered that depiction of the pancreatic duct on CT images was not sufficient to enable evaluation of ductal anatomy. These patients were excluded from further analysis. In the remaining 73 patients, ERP demonstrated pancreas divisum in 10 (14%); both observers made the correct diagnosis in nine of these patients. In addition, one radiologist had one false-positive interpretation, whereas the other radiologist had two false-positive interpretations. Thus, for observer 1, the calculated sensitivity was 90% (95% confidence interval [CI], 60%-98%) and the specificity was 98% (95% CI, 91%-100%). For observer 2, sensitivity was 90% (95% CI, 60%-98%) and specificity was 97% (95% CI, 89%-99%). Interobserver agreement was excellent (kappa = 0.93). CONCLUSION: CT scans obtained with multi-detector row scanners and interpreted with PACS workstations enable depiction of pancreas divisum. This assessment is possible only when the pancreatic duct is visualized.     

Right ventricular function in patients with acute pulmonary embolism: analysis with electrocardiography-synchronized multi-detector row CT

PURPOSE: To prospectively assess electrocardiography (ECG)-synchronized multi-detector row computed tomography (CT) for the evaluation of right ventricular (RV) function in patients suspected of having pulmonary embolism (PE). MATERIALS AND METHODS: All patients gave informed consent after the study details, including radiation exposure, were explained; institutional ethical committee approval was obtained. Nonsynchronized multi-detector row CT of the chest was performed in 66 consecutive patients (29 men, 37 women; mean age, 58 years+/-15 [standard deviation]) who were suspected of having PE. ECG-synchronized cardiac multi-detector row CT was performed to assess cardiac function. Dimension ratios for the RV and left ventricle (LV) were measured on nonsynchronized transverse and angulated four-chamber views. Furthermore, the RV end-diastolic and end-systolic volumes were measured on ECG-synchronized multi-detector row CT scans. An independent samples t test was performed to compare the mean value of different groups. An analysis of variance post hoc test was performed to investigate whether the values of the variables varied between groups. RESULTS: PE was detected in 29 of 66 patients. The location of PE was categorized as central (n=17) or peripheral (n=12). The RV/LV dimension ratio was larger on the four-chamber view (P=.002), and RV end-systolic volume was larger (P=.01) and ejection fraction was lower (P=.01) in patients with PE. The RV end-systolic volumes and RV/LV volume ratios, as assessed by using ECG-synchronized multi-detector row CT, showed significant differences (P<.005) between patients with central PE and those with peripheral PE. However, the RV/LV dimensions on nonsynchronized images revealed no significant differences. CONCLUSION: Retrospective ECG-synchronized multi-detector row CT facilitates detection of RV dysfunction, depending on pulmonary embolus location.     

Orthopedic hardware complications diagnosed with multi-detector row CT

PURPOSE: To retrospectively evaluate multi-detector row computed tomography (CT) for the depiction of orthopedic hardware complications in the spine and appendicular skeleton. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval; patient informed consent was not required. Results of 114 multi-detector row CT studies performed because of possible hardware complications in 109 patients (57 men, 52 women; mean age, 44 years; age range, 12-82 years) were available for analysis. The CT studies were retrospectively reviewed and compared with clinical or surgical outcomes, which were used as the reference standard. In another experiment, detection of hardware complications on radiographs and multi-detector row CT images was compared between two readers for selected cases (18 positive and 26 negative) by using receiver operating characteristic (ROC) methods. RESULTS: For 91 (80%) of 114 multi-detector row CT studies, the complication status could be determined on the basis of clinical or surgical outcomes. Twenty-three multi-detector row CT studies were confirmed to be positive (revealing 10 cases of nonunion, five cases of hardware malplacement, three cases of hardware loosening, three perihardware fractures, and two chronic infections), and 57 were confirmed to be negative. There were three false-positive and eight false-negative multi-detector row CT studies. With clinical or surgical outcomes as the reference standard, the sensitivity, specificity, and positive and negative predictive values of multi-detector row CT were 74% (23 of 31 studies), 95% (57 of 60 studies), 88% (23 of 26 studies), and 88% (57 of 65 studies), respectively. Results of ROC analysis indicated that detection of hardware complications was much lower with radiography than with multi-detector row CT (area under ROC curve, 0.84 vs 1.00; F = 4.69, df = 1, 43; P < .05). CONCLUSION: Multi-detector row CT is an effective tool for depicting orthopedic hardware complications.     

64 Slice multi-detector row cardiac CT

Cardiac imaging is feasible with multi-detector row (MDCT) scanners. Coronary arterial anatomy and both non-calcified and calcified plaques are depicted at CT coronary angiography. Vessel wall pathology and luminal diameter are depicted, and secondary myocardial changes may also be seen. Diagnostic capacity has increased with technological advancement, and preliminary investigations confirm the utility of 64-MDCT in low- and intermediate-risk patients who present to the emergency department with acute chest pain. The clinical indications, 64-MDCT technique, and MDCT findings in coronary artery disease are reviewed.     

CT colonography: single- versus multi-detector row imaging

PURPOSE: To compare respiratory artifacts, colonic distention, and polyp detection at computed tomographic (CT) colonography by using single- and multi-detector row helical CT systems. MATERIALS AND METHODS: A total of 237 consecutive patients received subcutaneously administered glucagon and underwent prone and supine CT colonography with single-detector row CT (n = 77) and multi-detector row CT (n = 160), followed by colonoscopy. Examination results were graded for colonic distention, respiratory artifacts, and polyp depiction by two radiologists working independently. RESULTS: Suboptimal colonic distention was significantly more common with single-detector row CT and was present in at least one segment in 52% (40 of 77 patients) of examinations versus only 19% (30 of 160 patients) with multi-detector row CT (P <.001). Mild respiratory artifacts were present in 61% (47 of 77 patients) of single-detector row CT examinations versus only 16% (26 of 160 patients) of multi-detector row CT examinations (P <.001). Depiction of polyps larger than 10 mm was 89% (eight of nine polyps) for single-detector row CT and 80% (eight of 10 polyps) for multi-detector row CT (P >.05). CONCLUSION: CT colonography performed with multi-detector row CT significantly improved the demonstration of colonic distention and depicted fewer respiratory artifacts compared with single-detector row CT. No significant differences in the depiction of polyps larger than 10 mm were demonstrated between single- and multi-detector row CT for a small number of polyps. Studies with a larger prevalence of clinically important polyps are needed for further evaluation of differences in polyp detection.     

Breath-hold three-dimensional CT of the liver with multi-detector row helical CT

PURPOSE: To compare image quality on transverse source images and coronal and sagittal reformations to determine the feasibility of using single-breath-hold three-dimensional liver computed tomography (CT) with multi-detector row helical CT in patients suspected of having hepatic metastases. MATERIALS AND METHODS: Fifty-three patients underwent the protocol. Coronal and sagittal reformations were constructed. Images were reviewed for duration of scan acquisition and length and adequacy of z-axis coverage. Reformations were scored for visualization of portal and hepatic vein branches, liver edge sharpness, cardiac pulsation and respiratory motion artifacts, noise due to mottle, and overall impression. RESULTS: Mean z-axis coverage was 207 mm +/- 33 (SD) (range, 145-280 mm), with a mean acquisition time of 10.96 seconds +/- 1.78 (range, 7.73-14.93 seconds). In 44 (83%) patients, the entire liver was imaged on a single helical scan. Artifact from cardiac motion was not identified on the transverse source images in any patient but was identified on coronal images in eight (15%) and on sagittal images in seven (13%). Similarly, noise due to mottle was not identified on the transverse source images but was identified on coronal images in seven (13%) patients and on sagittal images in six (11%). CONCLUSION: It is feasible to perform single-breath-hold three-dimensional liver CT with multi-detector row helical CT technology. Reformations provide a unique perspective with which to view the liver and may improve diagnostic capacity.     

Solitary pulmonary nodule: characterization with combined wash-in and washout features at dynamic multi-detector row CT

PURPOSE: To prospectively assess the accuracy of combined wash-in and washout characteristics at dynamic contrast material-enhanced multi-detector row computed tomography (CT) in distinguishing benign from malignant solitary pulmonary nodules. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. The study included 107 patients (62 men, 45 women; mean age, 55 years; range, 22-81 years) with a solitary pulmonary nodule. After unenhanced CT (2.5-mm collimation) scans were obtained, dynamic CT was performed by using a helical technique (series of images obtained throughout the nodule, with 2.5-mm collimation, at 30, 60, 90, and 120 seconds and 4, 5, 9, 12, and 15 minutes) after intravenous injection of contrast medium (120 mL). Tissue diagnosis was made in 70 nodules, and follow-up images showed benignancy in the remaining 37 (no change in size, n = 32; decrease in size, n = 5). CT findings were analyzed in terms of wash-in and washout of contrast medium. Sensitivity, specificity, and accuracy for malignant nodules were calculated by considering both the wash-in and washout characteristics at dynamic CT. RESULTS: There were 49 malignant and 58 benign nodules. When diagnostic criteria for malignancy of both wash-in of 25 HU or greater and washout of 5-31 HU were applied, sensitivity, specificity, and accuracy for malignancy were 94% (46 of 49 nodules), 90% (52 of 58 nodules), and 92% (98 of 107 nodules), respectively. Of 58 benign nodules, 27 showed less than 25 HU wash-in, 14 showed persistent contrast enhancement without washout and with wash-in of 25 HU or greater, and 11 showed washout greater than 31 HU and wash-in of 25 HU or greater. CONCLUSION: Evaluation of solitary pulmonary nodules by analyzing combined wash-in and washout characteristics at dynamic contrast-enhanced multi-detector row CT showed 92% accuracy for distinguishing benign nodules from malignant nodules.     

Acute aortic syndromes: Role of multi-detector row CT

Acute thoracic aortic syndromes encompass a spectrum of emergencies including aortic dissection, intramural haematoma, penetrating atherosclerotic ulcer and aneurysm rupture. All these life-threatening conditions require prompt diagnosis and appropriate management. To date multi-detector row Computed Tomography represents a valuable diagnostic tool especially in the emergency setting. This paper focus on the use of multi-detector row Computed Tomography in the evaluation of acute thoracic aortic syndromes and illustrates the key imaging findings related to each disease.     

Laparoscopic splenectomy: multi-detector row CT for preoperative evaluation

PURPOSE: To prospectively evaluate multi-detector row spiral computed tomography (CT) for determination of splenic volume, splenic vascular anatomy, and presence of accessory spleens and parenchymal lesions in patients who were undergoing laparoscopic splenectomy. MATERIALS AND METHODS: Twenty-two patients who were candidates for laparoscopic splenectomy underwent multiphasic multi-detector row CT. Two observers evaluated splenic volume with two hand-tracing editing modalities. Variability between the two observers was calculated with a reliability coefficient (Cronbach alpha). A linear regression equation for each modality was generated to identify the correlation between the two observers. Multi-detector row CT angiography was evaluated for assessment of splenic vascular anatomy. Presence and number of both accessory spleens and parenchymal lesions were recorded. RESULTS: Mean splenic volume was 1,050 and 1,046 mL, respectively, for observers A and B by using each-section editing (technique 1) and 1,067 and 1,068 mL for observers A and B by using distanced editing (technique 2). For each editing modality, alpha reliability coefficient was higher than 0.99. Both techniques 1 and 2 were very highly predictive of specimen weight and had R2 values of greater than 0.99 (P <.001). CT angiograms correctly showed polar arteries in all cases and the presence of the arteria pancreatica magna in one case. Multi-detector row CT demonstrated the presence, number, and size of all accessory spleens and of focal parenchymal lesions. CONCLUSION: Multi-detector row CT volumetric and anatomic evaluation provided accurate and reproducible information.     

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.     

Subsegmental pulmonary emboli: improved detection with thin-collimation multi-detector row spiral CT

PURPOSE: To compare different reconstruction thicknesses of thin-collimation multi-detector row spiral computed tomographic (CT) data sets of the chest for the detection of subsegmental pulmonary emboli. MATERIALS AND METHODS: A multi-detector row spiral CT protocol for the diagnosis of pulmonary embolism was used that consisted of scanning the entire chest with 1-mm collimation within one breath hold. In 17 patients with central pulmonary embolism, the raw data were used to perform reconstructions with 1-mm, 2-mm, and 3-mm section thicknesses. For each set of images, each subsegmental artery was independently graded by three radiologists as open, containing emboli, or indeterminate. RESULTS: For the rate of detection of emboli in subsegmental pulmonary arteries, use of the 1-mm section width yielded an average increase of 40% when compared with the use of 3-mm-thick sections (P <.001) and of 14% when compared with the use of 2-mm-thick sections (P =.001). With the use of 1-mm sections versus 3-mm sections, the number of indeterminate cases decreased by 70% (P =.001). Interrater agreement was substantially better with the use of 1-mm and 2-mm sections than with the use of 3-mm sections. CONCLUSION: For the diagnosis of subsegmental pulmonary emboli at multi-detector row CT, the use of 1-mm section widths results in substantially higher detection rates and greater agreement between different readers than the use of thicker sections.     

Pancreas: optimal scan delay for contrast-enhanced multi-detector row CT

PURPOSE: To prospectively determine optimal scan delays for multiphasic contrast medium-enhanced imaging of the pancreas with multi-detector row computed tomography (CT). MATERIALS AND METHODS: This study was approved by an institutional review committee, and patients gave written informed consent. One hundred ninety-one patients underwent three-phase CT of the pancreas after receiving intravenous contrast medium with a fixed duration injection of 30 seconds. Patients were prospectively assigned among four groups with scan delays of 25, 45, and 65 seconds (group 1); 30, 50, and 70 seconds (group 2); 35, 55, and 75 seconds (group 3); and 40, 60, and 80 seconds (group 4). Mean CT numbers of abdominal aorta, spleen, pancreatic parenchyma, superior mesenteric artery and vein, splenic vein, and hepatic parenchyma were measured, and increases in contrast enhancement on enhanced images were assessed. Qualitative analysis was performed with a four-point scale. RESULTS: Abdominal aorta and superior mesenteric artery enhanced at a mean of 35 seconds from the start of injection (both P < .001). Pancreatic parenchyma enhanced most intensely at 35-45 seconds (P < .001) with a peak enhancement at the mean of 40 seconds. Liver parenchyma enhanced most intensely at 55-65 seconds with a peak at 60 seconds (P < .001). The mean time to peak enhancement was 45 seconds for the splenic vein and 55 seconds for the superior mesenteric vein. Qualitative results were in good agreement with quantitative results (both P < .001). CONCLUSION: With the injection protocol used in this study, optimal scan delays for imaging the pancreas were 30-35 seconds for the abdominal aorta and the superior mesenteric artery, 35-45 seconds for the pancreas, 45 seconds for the splenic vein, and 55 seconds or later for the liver.     

Isoattenuating pancreatic adenocarcinoma at multi-detector row CT: secondary signs

PURPOSE: To assess the frequency of isoattenuating pancreatic adenocarcinoma with multi-detector row computed tomography (CT) and determine whether there are specific secondary signs that aid in detection. MATERIALS AND METHODS: Fifty-three patients with pancreatic adenocarcinoma underwent contrast material-enhanced biphasic multi-detector row CT with curved planar reformation. Tumors were initially deemed isoattenuating or hypoattenuating to normal pancreatic parenchyma on the basis of visual inspection, and the degree of attenuation was confirmed by calculating the mean attenuation differences between normal pancreatic parenchyma and tumor (tumor-pancreas contrast) during the pancreatic phase. Indirect signs of pancreatic tumor were tabulated in patients with an isoattenuating tumor. RESULTS: Of the 53 patients, six (11%) had isoattenuating tumors with a mean tumor-pancreas contrast of 9.25 HU +/- 11.3 during the pancreatic phase and 4.15 HU +/- 8.5 during the portal venous phase. The secondary signs of pancreatic tumor in these six patients included an interrupted pancreatic duct (n = 5), dilated biliary and pancreatic ducts (n = 1), atrophic distal pancreatic parenchyma (n = 3), and mass effect and/or convex contour abnormality (n = 3). The mean tumor-pancreas contrast for the remaining 47 patients was 74.76 HU +/- 35.61 during the pancreatic phase. CONCLUSION: With no visible tumor-pancreas contrast for isoattenuating tumors, indirect signs such as mass effect, atrophic distal parenchyma, and an interrupted duct sign are important indicators for the presence of tumor.     

CT dose optimization when changing to CT multi-detector row technology

The purpose of this article was to review the strategies to control patient dose in adult and pediatric computed tomography (CT), taking into account the change of technology from single-detector row CT to multi-detector row CT. First the relationships between computed tomography dose index, dose length product, and effective dose in adult and pediatric CT are revised, along with the diagnostic reference level concept. Then the effect of image noise as a function of volume computed tomography dose index, reconstructed slice thickness, and the size of the patient are described. Finally, the potential of tube current modulation CT is discussed.     

多层螺旋CT技术在胰腺检查中的应用

目的：探讨多层螺旋CT技术在胰腺检查中的价值。方法：对正常志愿60例，胰腺炎16例，胰腺癌28例行多层螺旋CT检查。结果：多层螺旋CT清晰显示胰腺解剖结构和毗邻关系，双期扫描明显提高胰腺炎和胰腺癌CT诊断及胰腺癌可切除性的判断。结论：多层螺旋CT在胰腺疾病的诊断中有很高的价值。