16层CT蛛网膜下腔造影

蛛网膜下腔造影后进行CT扫描充分结合了腔道造影和CT断层成像的优势,16层CT同时还提供了优秀的三维重建,使CT蛛网膜下腔造影技术得到了充分的发挥.本文就其中的CT椎管造影和脑室脑池造影的应用技术和效果作一论述.     

Influence of observer experience and training on proficiency in coronary CT angiography interpretation

Purpose

To assess the influence of experience and training on the proficiency in coronary CT angiography (CCTA) interpretation of practitioners with different levels of experience.

Methods and materials

Nine radiologist and cardiologist observers with varying prior CCTA experience ranging from novice to expert independently analyzed two case series of 50 catheter-correlated CCTA studies for coronary artery stenosis (0%, ≤49%, 50–74%, 75–99%, or 100%). Results of the first case series were unblinded and presented along with catheter angiography results to each reader before proceeding to the second series. Diagnostic accuracy on a per-segment basis was compared for all readers and both case series, respectively.

Results

Correlation coefficients between CCTA and catheter angiography initially ranged between good (r = 0.87) and poor (r = 0.26), depending on reader experience, and significantly (p < 0.05) improved in the second case series (range: r = 0.42 to r = 0.91). Diagnostic accuracy was significantly (p < 0.05) higher for more experienced readers (range: 96.5–97.8%) as compared to less experienced observers (range: 90.7–93.6%). After completion of the second case series for less experienced readers sensitivity and PPV significantly (p < 0.05) improved (range: 62.7–67.8%/51.4–84.1%), but still remained significantly (p < 0.05) lower as compared to more experienced observers (range: 89.8–93.3%/80.6–93.3%).

Conclusion

The level of experience appears to be a strong determinant of proficiency in CCTA interpretation. Limited one-time training improves proficiency in novice readers, but not to clinically satisfactory levels.     

First performance evaluation of a dual-source CT (DSCT) system

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90°. We introduce the system concept and derive its consequences and potential benefits for echocardiograph (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient’s heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated. An erratum to this article can be found at     

High-resolution computed tomography (HRCT) in the detection of “early asbestosis”

Two radiologists reviewed in masked fashion 144 standard chest radiographs, previously judged as normal by other readers, within a cohort of asymptomatic shipyard workers exposed to amosite. Among the 144 workers we selected subjects (n = 72) who fitted the following criteria: (1) documented occupational exposure to asbestos; (2) absence of any clinical symptomatology suggestive of asbestosis or of any other lung disease. Thirty-eight of them had standard chest radiogrphs that were confirmed as normal by both our radiologists, while 34 showed suspected pleural plaques or a very slight parenchymal involvement. These 72 subjects underwent high-resolution CT (HRCT): pleural plaques were shown in 33, parenchymal alterations in 7, and both pleural and parenchymal involvement in 13. HRCT findings were strictly correlated to the duration of amosite exposure and to the latency time since first exposure. Sensitivity, specificity and diagnostic accuracy values of standard chest radiographs were calculated with respect to HRCT and found to be, for pleural and parenchymal findings respectively: sensitivity 53% and 19%; specificity 72% and 94%; accuracy 60% and 72%. In conclusion, pleural and/or pulmonary involvement in asbestos-exposed workers can be shown by HRCT before the appearance of any symptomatology and abnormality on chest radiography. Furthermore the HRCT findings are correlated to the duration of exposure and latency time. time. Correspondence to; P. Boraschi     

Suitability of helical multislice acquisition technique for routine unenhanced brain CT: an image quality study using a 16-row detector configuration

Subjective and objective image quality (IQ) criteria, radiation doses, and acquisition times were compared using incremental monoslice, incremental multislice, and helical multislice acquisition techniques for routine unenhanced brain computed tomography (CT). Twenty-four patients were examined by two techniques in the same imaging session using a 16-row CT system equipped with 0.75-width detectors. Contiguous “native” 3-mm-thick slices were reconstructed for all acquisitions from four detectors for each slice (4×0.75 mm), with one channel available per detector. Two protocols were tailored to compare: (1) one-slice vs four-slice incremental images; (2) incremental vs helical four-slice images. Two trained observers independently scored 12 subjective items of IQ. Preference for the technique was assessed by one-tailed t test and the interobserver variation by two-tailed t test. The two observers gave very close IQ scores for the three techniques without significant interobserver variations. Measured IQ parameters failed to reveal any difference between techniques, and an approximate half radiation dose reduction was obtained by using the full 16-row configuration. Acquisition times were cumulatively shortened by using the multislice and the helical modality.     

A retrospectively ECG-gated multislice spiral CT scan and reconstruction technique with suppression of heart pulsation artifacts for cardio-thoracic imaging with extended volume coverage

A method for cardio-thoracic multislice spiral CT imaging with ECG gating for suppression of heart pulsation artifacts is introduced. The proposed technique offers extended volume coverage compared with standard ECG-gated spiral scan and reconstruction approaches for cardiac applications: Thin-slice data of the entire thorax can be acquired within one breath-hold period using a four-slice CT system. The extended volume coverage is enabled by a modified approach for ECG-gated image reconstruction. For a CT system with 0.5-s gantry rotation time, images are reconstructed with 250-ms image temporal resolution. Instead of selecting scan data acquired in exactly the same phase of the cardiac cycle for each image as in standard ECG-gated reconstruction techniques, the patient's ECG signal is used to omit scan data acquired during the systolic phase of highest cardiac motion. With this approach cardiac pulsation artifacts in CT studies of the aorta, of paracardiac lung segments, and of coronary bypass grafts can be effectively reduced.     

CT colonography: results and limitations

Meta-analysis of data from studies of CT colonography suggests that it has excellent per-patient average sensitivity and average specificity for detection of adenomatous polyps and cancer. However, while its potential as a screening test is undoubted, there are several current limitations that will need to be overcome before it can be considered seriously by health policy makers. These revolve around issues of generalisability, which is inhibited most by a lack of trained observers and access to CT scanners, and a paucity of data relating to cost-effectiveness. Whether offering CT colonography as an alternative to competing strategies will genuinely enhance compliance also needs further and more detailed attention.     

Thin-section CT of the lung: influence of 0.5-s gantry rotation and ECG triggering on image quality

The aim of this study was to determine if ECG triggering and a shorter acquisition time of 0.5-s rotation decrease cardiac motion artifacts of thin-section CT of the lung. In 25 patients referred for thin-section thoracic CT, 1-mm thin-section slices were performed with a scanning time of 0.5 s with ECG gating, 0.5 s and 1 s during the diastolic phase of the heart at five identical anatomical levels from the aortic arch to lung basis. At each anatomical level and for each lung, cardiac motion artifacts were graded independently on a four-point scale by three readers. Patients were divided into two groups according to their heart rate. A four-way analysis of variance was used to assess differences between the three modalities. Mean cardiac motion artifacts scores were rated 1.23+/-0.02, 1.47+/-0.02, and 1.79+/-0.02, at 0.5 s with ECG gating, 0.5 s without ECG gating, and 1 s, respectively (F=139, p<0.0001). At the four anatomical levels below the aortic arch, the left lung scores were greater than the right lung score for the three modalities. For the modality 0.5 s with ECG gating no difference of scores was found between patients grouped according to their cardiac frequency. The 0.5-s gantry rotation with or without ECG gating scans reduces cardiac motion artifacts on pulmonary thin-section CT images and is mainly beneficial for the lower part of the left lung.     

Redistributed Regional Ventilation after the Administration of a Bronchodilator Demonstrated on Xenon-Inhaled Dual-Energy CT in a Patient with Asthma

We report here on the redistributed regional ventilation abnormalities after the administration of a bronchodilator and as seen on xenon-inhaled dual-energy CT in a patient with asthma. The improved ventilation seen in the right lower lobe and the decreased ventilation seen in the right middle lobe after the administration of a bronchodilator on xenon-inhaled dual-energy CT could explain a positive bronchodilator response on a pulmonary function test. These changes may reflect the heterogeneity of the airway responsiveness to a bronchodilator in patients with asthma.     

Practical approaches to overcoming artifacts in coronary CT angiography

Coronary CT angiography is a novel noninvasive imaging technology that provides a unique view of cardiac and coronary artery pathologies. Despite proper preparation, artifacts and noisy scans can occur and are usually caused by cardiac or respiratory motion or both and obesity. This article formulates a practical approach for salvaging difficult or potentially uninterpretable studies by diagnosing the causes of artifacts and providing an approach for scan improvement with the reconstruction of new data sets. Multiple pictorial examples of scan editing are provided. In addition, tables link the likelihood that a specific cause of an artifact will allow a scan to be salvaged. An approach for interpreting scans with excess noise is also discussed.     

Free-breathing high-pitch 80 kVp dual-source computed tomography of the pediatric chest: Image quality,presence of motion artifacts and radiation dose

ObjectivesTo investigate image quality, presence of motion artifacts and effects on radiation dose of 80 kVp high-pitch dual-source CT (DSCT) in combination with an advanced modeled iterative reconstruction algorithm (ADMIRE) of the pediatric chest compared to single-source CT (SSCT).Materials and methodsThe study was approved by the institutional review board. Eighty-seven consecutive pediatric patients (mean age 9.1 ± 4.9 years) received either free-breathing high-pitch (pitch 3.2) chest 192-slice DSCT (group 1, n = 31) or standard-pitch (pitch 1.2) 128-slice SSCT (group 2, n = 56) with breathing-instructions by random assignment. Tube settings were similar in both groups with 80 kVp and 74 ref. mAs. Images were reconstructed using FBP for both groups. Additionally, ADMIRE was used in group 1. Effective thorax diameter, image noise, and signal-to-noise ratio (SNR) of the pectoralis major muscle and the thoracic aorta were calculated. Motion artifacts were measured as doubling boarders of the diaphragm and the heart. Images were rated by two blinded readers for overall image quality and presence of motion artifacts on 5-point-scales. Size specific dose estimates (SSDE, mGy) and effective dose (ED, mSv) were calculated.ResultsAge and effective thorax diameter showed no statistically significant differences in both groups. Image noise and SNR were comparable (p > 0.64) for SSCT and DSCT with ADMIRE, while DSCT with FBP showed inferior results (p < 0.01). Motion artifacts were reduced significantly (p = 0.001) with DSCT. DSCT with ADMIRE showed the highest overall IQ (p < 0.0001). Radiation dose was lower for DSCT compared to SSCT (median SSDE: 0.82 mGy vs. 0.92 mGy, p < 0.02; median ED: 0.4 mSv vs. 0.48 mSv, p = 0.02).ConclusionsHigh-pitch 80 kVp chest DSCT in combination with ADMIRE reduces motion artifacts and increases image quality while lowering radiation exposure in free-breathing pediatric patients without sedation.     

Does addition of CT pelvic venography to CT pulmonary angiography protocols contribute to the diagnosis of thromboembolic disease?

AIM: To evaluate the contribution which addition of pelvic computed tomography venography (CTV) to a standard CT pulmonary angiography (CTPA) imaging protocol makes to a definitive diagnosis of thromboembolic disease. MATERIALS AND METHODS: One hundred and six consecutive patients over the age of 55 years referred for (CTPA) for suspected pulmonary embolism between June and November 1999 had pelvic CTV performed at the time of the CTPA study. RESULTS: Ninety-six of 106 CTPA studies were technically adequate. In total, 29/96 (29.6%) CTPA studies were positive for pulmonary embolism, 10/96 (10.4%) CTV studies were positive and five of these 10 examinations showed venous thrombus when the CTPA study was negative (n = 4) or equivocal (n = 1). CONCLUSION: Addition of CTV shows residual thrombus in the pelvis in a proportion of patients with positive CTPA studies and demonstrates venous thrombus in a small number of patients with no CT evidence of pulmonary embolism.     

Biphasic spiral CT of the liver: automatic bolus tracking or time delay?

The aim of this study was to evaluate the value of automatic bolus tracking for biphasic spiral CT of the liver in comparison with time delay examinations. Forty patients scheduled for a biphasic spiral CT of the liver randomly were examined either with time delay of 25 s for the arterial phase and 55 s for the portal-venous phase (n = 20), or with an automatic scan start triggered by contrast enhancement in the aorta (n = 20). Examinations were performed with 120 ml of contrast material and a flow rate of 4.0 ml/s. Density measurements of the aorta, of the liver parenchyma, and of the spleen were obtained by means of regions of interest (ROI). The end of the arterial phase was considered when hepatic parenchymal enhancement was greater than 20 HU. In all patients of the group with automatic bolus tracking arterial scanning was completed in the arterial phase of the liver. In 25 % of patients with fixed time delay, however, an enhancement of liver parenchyma during arterial phase greater than 20 HU was observed. During the portal-venous phase there was no significant difference in parenchymal enhancement between both groups. Automatic bolus tracking allows an individualized timing of the arterial phase in biphasic spiral CT of the liver. The timing is more accurate than in time delay scanning. Received: 18 February 2000 Revised: 13 July 2000 Accepted: 19 July 2000     

螺旋CT泌尿系统重建成像在血尿诊断上的临床应用

目的:对螺旋CT泌尿系统重建成像在泌尿系统疾病特别是血尿原因检查方面的临床价值做进一步探讨。材料和方法:对152例病人进行螺旋CT泌尿系统成像(血尿患者138例),其中非增强螺旋CT肾输尿管成像72例,排泄性CT泌尿系造影80例重建成像进行分析,包括:①结合临床检查结果确定诊断;②对照轴扫图像和影像检查资料主要是IVP,对重建成像效果和临床价值进行评价。结果:非增强肾输尿管成像72例中,发现输尿管结石45例(3例合并肾结石),膀胱结石7例;膀胱癌(1例合并肾盂癌)9例,腹膜后病变导致输尿管狭窄9例;未见明确异常7例。80例SCTU中,肾实质肿瘤侵犯肾盂22例,肾盂癌5例,慢性肾盂肾炎2例,输尿管病变18例,后腹膜及盆腔肿瘤压迫输尿管7例,膀胱肿瘤7例,先天畸形5例,结核2例,肾脓肿3例,未见明确异常4例。SCTU与IVP对照,两者对泌尿系解剖部位的显示(肾盂,输尿管,膀胱)大致相当。所有IVP所提示的病变,SCTU均能发现。11例IVP不能确定者于SCTU明确诊断。结论:螺旋CT泌尿系统重建成像技术具有较高的临床应用价值,有望取代IVP成为血尿原因检查的首选方法。     

Standardized CT examination of the multitraumatized patient

The aim of this study was to develop a standardized non-helical-CT protocol including head, body and proximal extremities in order to achieve a good time efficiency and diagnostic accuracy in the initial radiological evaluation of the multitraumatized patient. A total of 111 circulatory stable blunt trauma patients, brought in to a trauma level II–III hospital, were examined according to a standardized CT protocol. After examining the head with contiguous 10-mm slices without IV contrast medium injection, the trunk was examined with 10-mm slices every 30 mm through thorax–abdomen–pelvis with IV contrast medium enhancement (occasionally modified). All data in the medical reports were collected and used as “end-point”, and the outcome of the CT examination was compared with this final diagnosis. Mean examination time was 20 min (range 12–32 min). In total, 55 head injuries, 89 thoracic injuries, 27 abdominal/pelvic injuries and 62 fractures were found. Computed tomography correctly identified the injuries, except one brain stem injury, one contusion/rupture of the heart, one hepatic injury, two intestinal injuries, eight vertebral injuries and one joint dislocation. A standardized non-helical-CT examination of the head and body may be achieved in 20 min. Its diagnostic accuracy was high, except for vertebral column injuries, which is why we recommend it as the method of choice for initial radiological examination of multitraumatized patients. When available, helical scanning would improve both examination speed and accuracy. Received 28 April 1997; Revision received 27 February 1998; Accepted 3 March 1998     

Multidetector helical CT of the liver for tumor detection and characterization

Multidetector-row CT (MDCT) scanners have been recently introduced into clinical practice. Major attributes that are improved are the z-axis coverage speed and the longitudinal resolution. These improvements translate into rapid hepatic imaging and allow new imaging protocols. Thin sections can now be used on a routine basis in single-breath-hold technique. This results in improved lesion detection and the nearly isotropic image acquisition provides high-resolution multiplanar reformations. Furthermore, the ability to scan through the entire liver in 10 s or less allows acquisition of two separate sets of CT images of the liver within the time generally regarded as the hepatic arterial dominant phase in monoslice CT; thus, MDCT may demonstrate three clear separate distinct hepatic circulatory phases with a triple-pass technique. Multidetector-row CT with the improvements in morphological and functional information compared with single-slice CT enables a comprehensive approach to hepatic imaging within a single examination.