Weighted-averaging multi-planar reconstruction method for multi-detector row computed tomography

Development of multi-detector row computed tomography (MDCT) has enabled three-dimensions (3D) scanning with minute voxels. Minute voxels improve spatial resolution of CT images. At the same time, however, they increase image noise. Multi-planar reconstruction (MPR) is one of effective 3D-image processing techniques. The conventional MPR technique can adjust slice thickness of MPR images. When a thick slice is used, the image noise is decreased. In this case, however, spatial resolution is deteriorated. In order to deal with this trade-off problem, we have developed the weighted-averaging multi-planar reconstruction (W-MPR) technique to control the balance between the spatial resolution and noise. The weighted-average is determined by the Gaussian-type weighting function. In this study, we compared the performance of W-MPR with that of conventional simple-addition-averaging MPR. As a result, we could confirm that W-MPR can decrease the image noise without significant deterioration of spatial resolution. W-MPR can adjust freely the weight for each slice by changing the shape of the weighting function. Therefore, W-MPR can allow us to select a proper balance of spatial resolution and noise and at the same time produce suitable MPR images for observation of targeted anatomical structures.     

Abdominal virtual ultrasonographic images reconstructed by multi-detector row helical computed tomography

BACKGROUND: Three-dimensional (3D) images can be generated using thin sections from multi-detector row computed tomography (CT) and computer software, simulating images obtained using conventional ultrasonography (US). This software allows easy diagnosis of abdominal lesions and subsequent treatment of focal liver lesions such as hepatocellular carcinoma (HCC). The present study used newly developed virtual US software for diagnose and treatment of hepatobiliary disease. METHODS: The software was used to create virtual US images in 10 subjects. Radiofrequency ablation (RFA) was performed by virtual US in seven patients with HCC. RESULTS: Slices were easily reconstructed from various angles, and each slice was continuously animated as with conventional US in all subjects. Moreover, when seven patients with HCC were examined using virtual US, HCC nodules were visualized and could be treated with RFA. CONCLUSIONS: Virtual US should prove useful for visualization of HCC nodules that cannot be seen under conventional US. Virtual US is a useful tool for US-guided treatment of HCC.     

Visualization of congenital thoracic vascular anomalies using multi-detector row computed tomography and two- and three-dimensional post-processing

Anomalies of the vascular system are caused by false embryogenesis and are therefore present from birth. Single-detector row spiral computed tomography angiography (CTA) and multi-detector row computed tomography angiography (MDCTA) have gained increasing importance in the non-invasive assessment of vascular pathologies and replace conventional angiography in many cases. High-resolution volumetric datasets that are acquired during a single breath-hold give the possibility of two- (2D) and three-dimensional (3D)-post-processing. Due to post-processing, even complex vascular malformations are visualized in an understandable way. Furthermore, CTA, in contrast to conventional angiography, depicts not only the vascular structures but also allows assessment of the surrounding anatomical structures. We present cases of rare congenital anomalies of the thoracic vessels using MDCT with special respect to 2D- and 3D-post-processing.     

多层螺旋CT血管成像对脊髓Adamkiewicz动脉的显示

Adamkiewicz动脉是脊髓胸腰段重要的供血血管,术前对其解剖结构的了解,有助于术前设计周密的手术方案,能有效降低脊髓缺血性损伤及术后截瘫或下肢瘫的发生。以往利用选择性动脉造影来了解脊髓的血液供应,但属于有创检查,且技术要求高。随着现代医学影像的发展,多层螺旋CT血管成像技术凭借其较高的空间分辨率和时间分辨率,可以在注入对比剂后一次扫描即可完成全部数据的采集,再通过强大的后处理功能可以获得Adamldewicz动脉及起源的节段性动脉的清晰影像。它在显示脊髓Adamkiewicz动脉方面的优势日益突出。本文综述多层螺旋CT血管成像对脊髓Adamkiewicz动脉显示的临床应用价值。     

Left ventricular myocardium segmentation on arterial phase of multi-detector row computed tomography

Rationale and objectives

Variation of left ventricular myocardial volumes correlates closely with ischemic heart diseases. In clinical practice, because physicians and radiologists rely much on myocardial contour to diagnose many different cardiac diseases, automatic segmentation of left ventricular myocardium and quantifying myocardium characteristics is clinically beneficial. This paper presents a hybrid segmentation method for left ventricular myocardium on arterial phase of multi-detector row computed tomography (MDCT) imaging.

Materials and methods

The proposed method utilizes an intensity transformation equation as a preprocessing procedure to enhance contrast and reduce noise in MDCT imaging. By setting the centroid of left ventricle (LV) as an initial seed, the conventional region growing method is employed to identify the endocardial contour of LV cavity for each slice. Then the level-set method (LSM) utilizes the extracted endocardial contour as initial contour to delineate the epicardium of LV. The two extracted contours are integrated to form the region of interest (ROI) of the LV. Finally, the ROIs from all slices are combined to obtain the volume of the whole LV myocardium.

Results

Twenty-two healthy patients who had no symptoms of ischemic heart disease are applied to evaluate the performance of the proposed method. Compared with manual contours delineated by two experienced experts, the contouring results from computer simulation reveal that the proposed method always identifies similar contours as that obtained by the manual sketching.

Conclusion

The proposed method provides a robust and fast automatic contouring for LV myocardium on arterial phase of MDCT. The potential role of this technique may save much of the time required to manually sketch a precise contour with high stability.     

Estimation of aortic time-enhancement curve in pharmacokinetic analysis: dynamic study by multi-detector row computed tomography

This paper presents an introduction to the development of software that provides a physiologic model of contrast medium enhancement by incorporating available physiologic data and contrast medium pharmacokinetics to predict an organ-specific aortic time-enhancement curve(TEC)in computed tomography(CT)with various contrast medium injection protocols in patients of various heights, weights, cardiac output levels, and so on. The physiologic model of contrast medium enhancement was composed of six compartments for early contrast enhancement pharmacokinetics. Contrast medium is injected via the antecubital vein and distributed to the right side of the heart, the pulmonary compartment, the left side of the heart, and the aorta. It then circulates back to the right side of the heart via the systemic circulation. A computer-based, compartmental model of the aortic system was generated using human physiologic parameters and six differential equations to describe the transport of contrast medium. Aortic TEC generated by the computer-based physiologic model of contrast medium enhancement showed validity and agreement with clinical data and findings published previously. A computer-based physiologic model that may help predict organ-specific CT contrast medium enhancement for different injection protocols was developed. Such a physiologic model may have multiple clinical applications.     

Detectability of pancreas divisum in patients with acute pancreatitis on multi-detector row computed tomography

The purpose of this study was to retrospectively assess the diagnostic performance of multi-detector row computed tomography (MDCT) in an evaluation of pancreas divisum using endoscopic retrograde pancreatography (ERP) as the reference standard. We analyzed 41 consecutive patients (14 cases of pancreas divisum and 27 cases of standard anatomy) who had undergone both MDCT and ERP for the evaluation of clinically diagnosed acute pancreatitis between November 2004 and June 2007. The CT reconstruction thickness and interval were both 3 mm. Two radiologists independently reviewed CT data, and the diagnostic confidence in determining the pancreatic ductal anatomy was scored using a five-point scale. CT detectability was correlated with the severity of pancreatitis and the degree of pancreatic necrosis based on the Balthazar index. With consensus, 16 of 41 cases (39.0%) were evaluated as indeterminate. Ductal anatomy was correctly diagnosed in 23 of 41 cases (56.1%). Eight of 14 cases (57.1%) were correctly diagnosed as pancreas divisum. Standard anatomy was identified in 15 of 27 cases (55.6%). The inter-observer agreement was substantial (κ = 0.71). Grade B or more pancreatitis and the presence of pancreatic necrosis significantly influenced the evaluation of ductal anatomy (p = 0.01 and p < 0.01, respectively). Pancreas divisum was correctly diagnosed in the case of grade A acute pancreatitis. The CT detectability of pancreas divisum in patients with grade B or more pancreatitis is still relatively low even in the MDCT era.     

Study of radiation dose to the eye lens by multi-detector row computed tomography of the temporal bone

The exposure of the eye lens caused by multi-detector row computed tomography (MDCT) of the temporal bone is a serious problem. Our aim was to evaluate the radiation dose to the eye lens by different scan baselines (orbitomeatal line; OML, acanthiomeatal line; AML) and examine the difference of the depiction of the temporal bone structures. Measurement of the exposure to the eye lens was performed by means of MDCT of the temporal bone with a radio-photoluminescence glass dosimeter using a rand phantom. Moreover, we studied only one volunteer (58-year-old male) who had no symptom and was not suspected of having any ear abnormalities with a two scan baseline. Visualization of the major anatomical structures of the temporal bone (the tympanic portion of the facial nerve canal, the body of the incus, stapes superstructures, vestibule etc.) was performed on the volunteer. The average absorbed dose was 6.42 mGy by the OML and 1.59 mGy by the AML, respectively. With regard to visualization of the temporal bone structures, all structures were of equal quality with the two scan baseline. With the AML line, the radiation dose to the eye lens was reduced to 75%. Therefore, the authors recommended an AML for use for MDCT of the temporal bone. In clinical practice, the optimization of scanning factor (kVp, mAs etc.) and the use of the radio-protection should be implemented for radiation dose reduction of the eye lens by MDCT of the temporal bone.     

Tortuous vertebrobasilar arteries causing cranial nerve syndromes: screening by computed tomography.

Considerable concern with cranial nerve syndromes has often required detailed information of the relationship between the vertebrobasilar system and the brainstem. The obvious invasiveness of conventional vertebral angiography poses the question of whether computed tomography (CT) might serve as a satisfactory technique or even as a sufficient diagnostic method. During a 12 month period, 12 of 250 patients with cranial nerve syndromes were diagnosed by CT as having vertebrobasilar ectasia. This communication correlates the clinical symptomatology with angiography and CT and presents evidence that CT alone can prove satisfactory.     

Comparison of image validity between cone beam computed tomography for dental use and multidetector row helical computed tomography

OBJECTIVES: To evaluate and compare the image validity of a cone beam CT machine for dental use (3DX) and the latest medical CT system, multidetector row helical CT (MDCT). METHODS: A dried right maxilla of an Asian adult was used as a phantom. It was cut from the zygomatic process towards the midline, parallel to the midline plane, into eight slices of 2 mm thickness. This phantom was imaged with the 3DX and MDCT machines. Images were evaluated by comparing them with one selected bone slice from the phantom. In this comparison, two types of MDCT images were used: one with the window level (WL) and window width (WW) suitable for observing teeth (MDCT tooth image), and the other appropriate for observing bone (MDCT bone image). Three dentists and one radiographer then used our reported subjective five-level scale to evaluate and compare images generated by the two systems in terms of validity. Cancellous bone as well as enamel, dentin, pulp cavity, periodontal ligament space, lamina dura and overall impression were evaluated. RESULTS: Statistically significant differences (P<0.05) were found for almost all observation items. Our subjective evaluation clarified that 3DX was superior to MDCT in terms of image validity. Few significant intra- or interevaluator errors were found. CONCLUSIONS: Our subjective evaluation of image validity clarified 3DX as being superior to MDCT. Taken together with the low skin dose we previously reported for 3DX, the results demonstrate 3DX to be beneficial for imaging diagnosis of hard tissues in the maxillofacial region.     

Infections of the neck leading to descending necrotizing mediastinitis: Role of multi-detector row computed tomography

Descending necrotizing mediastinitis is an acute, polymicrobial infection of the mediastinum, originating from odontogenic, oropharyngeal and cervical infections. Anatomical continuity of the fascial spaces between the neck and the mediastinum leads to an occasional mediastinal extension of deep neck infection as a serious sequela. An understanding of the anatomy of the deep spaces of the neck and familiarity with the imaging findings in descending necrotizing mediastinitis may allow rapid diagnosis and treatment of this rare and life-threatening complication of deep neck space infection. In this article, we discuss the current role of radiology in diagnosing descending necrotizing mediastinitis, in determining the level of infection and the pathways of spread of infections from the neck to the mediastinum and in planning a successful treatment.     

Comparison of different iodine concentrations for multidetector row computed tomography angiography of segmental renal arteries

The aims of this study were (1) to assess the diagnostic performance of multidetector row computed tomography angiography (CTA) on imaging of renal artery branches and (2) to investigate the effect of different iodine concentrations at constant total iodine load and either constant injection rates or constant iodine administration rates. A number of 120 consecutive patients (71±6 years of age) underwent CTA of renal arteries (collimation 4×1 mm) using the nonionic contrast medium iopromide, and were divided into six equal groups: 1: 150 ml, 240 mg/ml at 4 ml/s; 2: 120 ml, 300 mg/ml at 4 ml/s; 3: 97.3 ml, 370 mg/ml at 4 ml/s; 4: 150 ml, 240 mg/ml at 5 ml/s; 5: 120 ml, 300 mg/ml, 60 ml at 6 ml/s, 60 ml at 3 ml/s; 6: 97.3 ml, 370 mg/ml at 3.3 ml/s. The image quality of the main renal arteries (n=240) and their first-order to fourth-order branches was scored as 0 for no visualization, 1 for only visualization, and 2 for diagnostic. All main renal arteries were diagnostic. First-order branches had score 2 in 38/40, 40/40, 37/40, 38/40, 39/40, and 40/40 patients for groups 1–6, respectively (p=0.34). Second-order branches were imaged best in group 2 (p<0.002)). Third-order branches had score 2 in only 1/40, 5/40, 1/40, 2/40, 0/40, and 2/40 renal arteries. Fourth-order branches were not imaged diagnostically. At a constant total iodine load, the main renal arteries and their first-order branches achieved diagnostic image quality at all iodine concentrations in four-channel multidetector row CTA for the protocols tested. Second-order renal artery branches were imaged best at 120 ml contrast medium with an iodine concentration of 300 mg/ml at 4 ml/s.     

Intensive-care unit lung infections: The role of imaging with special emphasis on multi-detector row computed tomography

Nosocomial pneumonia is the most frequent hospital-acquired infection. In mechanically ventilated patients admitted to an intensive-care unit as many as 7-41% may develop pneumonia. The role of imaging is to identify the presence, location and extent of pulmonary infection and the presence of complications. However, the poor resolution of bedside plain film frequently limits the value of radiography as an accurate diagnostic tool. To date, multi-detector row computed tomography with its excellent contrast resolution is the most sensitive modality for evaluating lung parenchyma infections.     

Comparison between 3-T magnetic resonance imaging and multi-detector row computed tomography for the preoperative evaluation of rectal cancer

OBJECTIVE: To compare prospectively between 3-T magnetic resonance imaging (MRI) and multidetector row computed tomography (MDCT) for the local staging of rectal cancer. MATERIALS AND METHODS: During a recent 8-month period, both 3-T MRI with a phased array coil and MDCT scanner were used to preoperatively examine 31 consecutive patients. Preoperatively, the 3 experienced reviewers independently assessed the MRI and MDCT findings for the depth of tumor invasion into the rectal wall (T). Regional lymph node metastasis (N) was assessed by the 3 reviewers working in consensus. For T staging, we used a modified T staging ( 0.05). CONCLUSIONS: For local staging of rectal cancer, 3-T MRI is more accurate than MDCT for determining the depth of tumor invasion and the extent of lymph node metastasis.     

Assessment of left ventricular volumes using multi-detector row computed tomography (MDCT): phantom and human studies

PURPOSE: Multi-detector row CT (MDCT) is a new noninvasive modality for coronary artery imaging. Using the same MDCT data obtained for coronary artery assessment, left ventricular (LV) volumes such as end-diastolic (ED) and end-systolic (ES) volumes (EDV and ESV, respectively) and ejection fraction (EF) can potentially be assessed when ED and ES datasets are extracted. The purpose of this study was to evaluate the feasibility of MDCT in the assessment of LV volumes. METHODS: Using a pulsating heart phantom (EDV = 143 ml, ESV = 107 ml, stroke volume = 36 ml, EF = 25%) and MDCT, EDV and ESV were measured and EF was calculated. Clinical materials consisted of 11 consecutive human subjects who underwent MDCT. MDCT data were acquired during a single breathhold, using an intravenous injection of contrast medium. Left ventriculography (LVG) was performed in all patients as a gold standard. LV-EF was calculated by measuring ESV and EDV in all patients. RESULTS: In the phantom study, LV volumes were: EDV = 137 ml, ESV = 101 ml, stroke volume = 36 ml, and EF = 26%. Close correlations were observed between MDCT values and LVG values (EDV: r = 0.95, ESV: r = 0.98, EF: r = 0.93, p < 0.001). CONCLUSION: MDCT was useful for th e assessment of LV volumes and EF in various patients with CVD.     

Evaluation of retroperitoneal hemorrhage by computed tomography before and after translumbar aortography.

Twenty patients were prospectively studied by computed tomography (CT) before and after undergoing translumbar aortography (TLA). Changes indicative of retroperitoneal bleeding were depicted by CT in all 20 patients despite the predominantly small size of the hematomas. CT scans obtained within two hours after TLA demonstrated: (a) thickening of the diaphragmatic crura, (b) enlargement of the left psoas muscle, and (c) obscuration of the aortic outline by soft-tissue density. Follow-up scans at 24 hours (10 patients) and one week (3 patients) revealed marked decrease in abnormalities, suggesting rapid resorption of the hematoma.     

Ectasia of the intracranial arteries diagnosed by computed tomography

Summary The megadolichobasilar anomaly may be diagnosed by CT as an extra-axial lesion in the cerebellopontine angle. It enhances in a tubular fashion after intravenous injection of contrast. Hydrocephalus resulting from obstruction of CSF circulation may be demonstrated.