T2-weighted turbo spin-echo images, maximum-intensity projections, and three-dimensional volume-rendering for delineation of pathologies and anatomic details of the inner ear

PURPOSE: The aim of the current study was to compare 3-dimensional T2-weighted turbo spin-echo (TSE) axial slices, maximum-intensity projections (MIPs), and volume-rendered images with respect to the delineation of pathologic findings and anatomic structures of the inner ear. Each of the compared image types was available at 2 different resolutions. MATERIALS AND METHODS: In 64 patients, 3-dimensional T2-TSE images were acquired with a matrix of 128 x 100 and 230 x 230 (field-of-view 90 x 90 mm). Direct axial images, MIPs, and volume-rendered images from the 2 datasets were evaluated in terms of the delineation of pathologic findings and anatomic structures. Analysis was performed by 2 radiologists in consensus. RESULTS: Though axial images acquired with a matrix of 230 x 230 showed more anatomic details than images acquired with a matrix of 128 x 100, pathologic findings (33 in total) were assessable with the same confidence on images of either resolution. Pathologies completely surrounded by fluid were best assessed on axial slices. The delineation of pathologies not embedded in a fluid was almost equally good in axial slices, MIPs, or 3-dimensional volume-rendered images. CONCLUSION: Reading the axial images cannot be replaced by viewing postprocessed reconstructions for initial diagnosis, because only some of the pathologies can be delineated on MIPs and volume reconstructions. However, reconstructions can be valuable for assessing the extent of pathologies and their spatial relation to the anatomic structures.     

Bildanalyse bei der Mehrschicht-Spiral-CT der Lunge mit MPR- und MIP-Rekonstruktionen

PURPOSE: To test, whether axial, coronal and sagittal MIP and MPR reconstructions of diagnostic quality can be obtained from 1-mm collimation MSCT data of the chest for the evaluation of thoracic anatomy and pathology. MATERIALS AND METHODS: 1-mm collimation MSCT scans were obtained with a pitch of 6 in an acrylic phantom and in 20 patients. Axial images were reconstructed with 0.6-mm increment. Multiplanar reformations (MPRs) and sliding thin-slab maximum intensity projections (STS-MIPs) were reconstructed in axial, coronal and sagittal planes. Images were printed in lung windows and evaluated by three readers by using a standardized evaluation scheme. RESULTS: Overall, both methods allowed good visualization of anatomic structures. MIP was superior for visualization of the pulmonary arteries (p < 0.05) while central and peripheral bronchi and the lung parenchyma were better depicted on multiplanar reconstructions. A confident diagnosis of thoracic pathology was feasible using both modalities, however MIPs appeared less usefull for evaluation of gross parenchymal abnormalities, such as pneumonic infiltrates or fibrotic changes. No significant difference in the degree of motion artifacts were detected between both modalities. CONCLUSION: MSCT data sets are ideally suited for generating MPR and MIP reconstructions. While MIPs are superior for the evaluation of thoracic vessels, MPR is advantageous for visualizing central and peripheral bronchi and the pulmonary parenchyma.     

Value of high-resolution MR in patients scheduled for cochlear implantation

Objective: To determine sensitivity and specificity of high-resolution MR imaging and of high-resolution axial CT (HRCT) and to compare the two modalities in predicting the surgical and functional success of cochlear implantation.Material and Methods: The presurgical MR images (2D T2W TSE, 3D T2*W CISS, plain and contrast-enhanced 3D T1W MP-RAGE) and axial HRCT findings of 26 patients were evaluated with regard to the predictive value concerning the success of cochlear implantation.Results: We found a high correlation between MR and HRCT and the success of cochlear implantation. In all 26 patients, the MR-based predictions concerning the success of cochlear implantation were correct. In 10 patients, MR gave additional information to HRCT. In all patients, MR gave sufficient information about the status of the inner ear, inner auditory canal and cochlear nerve to aid the surgeon during the operation.Conclusion: A high-resolution MR protocol consisting of coronal 2D T2W TSE, 3D T2*W axial CISS, plain and contrast-enhanced sagittal T1W 3D MP-RAGE is recommended for the evaluation of candidates scheduled for cochlear implantation. It provides information which cannot be obtained by HRCT.     

多层螺旋CT在颌骨牙齿显示中的临床价值初步探讨

目的：探讨多层螺旋CT（16层）三维（3D）重建技术在显示颌骨牙齿中的临床应用价值。方法：23例患者行多层螺旋CT轴位扫描，层厚2．5mm。采用最大密度投影法（MIP），表面遮盖显示（SSD）和多平面重建法（加艰）3种方式重建图像。将横轴位图像与不同方法重建的图像进行对比。结果：17例不易定位的埋伏阻生牙及多生牙在上颌骨中的位置、数目、牙轴的方向、牙体形态等，均被清晰、准确地显示出来。23例中17例见牙体长轴排列不整齐，倾斜、旋转、重叠，牙齿长轴间距离不等，其中15例共有23颗埋伏牙。横轴位图像能包括全部信息。SSD可以显示牙齿与颌骨的外部轮廓、整体形态以及牙齿排列与颌骨之间的关系。MIP能清楚显示牙齿全貌、牙齿纵向排列关系；MPR则对根尖骨质、根尖与牙槽骨的局部关系显示更清晰。结论：多层螺旋Cr3D重建技术是一种能展示牙齿立体形态影像的新技术。轴位图像、MIP、SSD及MPR联合应用能明确病变性质，立体、直观、多方位提供信息。3D重建技术对埋伏阻生牙及多生牙的定位精确，能清晰显示其形态、唇颊侧或舌侧位置、萌出方向及邻牙关系，3D重建技术可作为颌面外科处理和正畸治疗前的重要检查手段。     

Three-dimensional CT in the diagnosis of spinal trauma: comparison with plain film and two-dimensional CT examinations

To assess the value of three-dimensional (3D) image reconstructions of two-dimensional (2D) data from contiguous non-overlapping slices in the diagnosis of spinal trauma, 21 patients with a total of 36 injured vertebrae and 4 normal controls were examined. Forty plain films in two planes, 40 axial CT scans with multiplanar reformatted (MPR) 2D reconstructions and 40 sets of 3D images (surface rendering technique) were independently evaluated by four readers. The final diagnosis was defined after a panel review of clinical, surgical and imaging findings on all modalities. The 3D image reconstructions were not as accurate as axial CT with MPR 2D reconstructions in the diagnosis of vertebral body (n = 20) and posterior element fractures (n = 35). Dislocation (n = 3) was equally well detected by all imaging modalities. Narrowing of the spinal canal (n = 17) was best assessed by either MPR 2D CT or 3D images. A rotational component was diagnosed more accurately by 3D images, followed by 2D CT and plain films. Thus, 3D images combined with MPR 2D CT reconstructions are an important adjunct for an accurate diagnosis of spinal trauma, especially when a rotational component is suspected.Presented at the 1993 ECR Scientific Assembly Correspondence to: C. H. Buitrago-Téllez     

Visualization of intraaneurysmal flow patterns with transluminal flow images of 3D MR angiograms in conjunction with aneurysmal configurations

BACKGROUND AND PURPOSE: How the complex flow phenomena generated within unruptured cerebral aneurysms relate to the corresponding aneurysmal geometry is unknown. To estimate the interaction between flow patterns and morphologic features of unruptured cerebral aneurysms, we developed a method to visualize intraanuerysmal flow patterns with transluminal flow imaging of 3D MR angiograms in conjunction with aneurysmal configurations. METHODS: Transluminal images of the vessel lumen were reconstructed with use of a parallel volume-rendering algorithm by selecting information on the margin of lumina from the volume data sets of 3D time-of-flight MR angiograms. Transluminal flow images were then created by superimposing flow-related intraluminal information onto transluminal images. Intraaneurysmal flow patterns were evaluated in three cases of unruptured cerebral aneurysms, based on the animated display of transluminal flow images with stepwise extracted intraluminal volume data of signal intensity, in conjunction with the corresponding aneurysmal configurations depicted on 3D MR angiograms. RESULTS: Transluminal flow images showed 3D visualization of flow-related signal intensity distribution obtained from volume data of MR angiograms, so that qualitative information regarding intraaneurysmal flow patterns could be estimated with respect to morphologic features of cerebral aneurysms. CONCLUSION: Transluminal flow images of 3D MR angiograms allowed feasible visualization of intraaneurysmal flow patterns that were studied. More work is required to validate the technique and clarify the significance of being able to visualize intraaneurysmal flow patterns.     

Volume fast spin-echo imaging of the cervical spine

RATIONALE AND OBJECTIVES: The authors prospectively evaluated a T2-weighted, three-dimensional (3D) volume, fast spin-echo (SE) pulse sequence in assessment of the cervical spine and compared it with standard imaging protocol. MATERIALS AND METHODS: Eighteen patients with neck pain underwent magnetic resonance (MR) imaging at 1.5 T with two-dimensional (2D) fast SE and axial 3D gradient-echo (GRE) protocols and with an additional sagittal T2-weighted volume fast SE protocol. The spinal cord and canal, neural foramina, and intervertebral disks were assessed by two neuroradiologists, and the results were compared with reports from the standard protocol. The quality of the partition (direct sagittal) and reconstructed images were evaluated. RESULTS: No differences existed in the assessment of spinal cord disease or disk herniation with 2D fast SE and volume fast SE imaging. Some mild variation occurred in assessment of the neural foramina. Partition images demonstrated a high level of resolution and contrast, while reconstructed images had consistently lower quality. However, this did not impede detection and grading of disk or spinal abnormalities, which were adequately shown on volume fast SE sagittal images. Neural foramina were well demonstrated on axial reconstructions from volume fast SE imaging. CONCLUSION: Volume fast SE imaging provides information about the spinal cord, canal, disks, and neural foramina that is comparable to the information provided by routine imaging. Its thinner sections and multiplanar reconstruction capability are advantages over 2D imaging. Its greater tissue contrast with better visualization of the cervical cord, greater signal-to-noise ratio, and less susceptibility artifact are advantages over 3D GRE imaging.     

Preoperative 3T MR imaging of rectal cancer: local staging accuracy using a two-dimensional and three-dimensional T2-weighted turbo spin echo sequence

PURPOSE: The purpose of our study was to evaluate the image quality and diagnostic performance of two-dimensional (D) turbo spin echo (TSE) and 3D T2-weighted TSE MR imaging in local staging of rectal cancer at 3T. MATERIALS AND METHODS: 3T phased-array MR imaging was performed in 36 consecutive patients with biopsy-proven rectal cancer. High-resolution 2D TSE images in three planes and 3D TSE images of the rectum were obtained. Two independent observers performed an image quality assessment using eight image quality characteristics. All 2D and 3D datasets were evaluated separately. MR images were prospectively evaluated by two experienced radiologists in consensus with regard to local disease. Total mesorectal excision was used as the standard of reference. The sensitivity, specificity, positive and negative predictive value, and overall accuracy were calculated. Areas under the receiver operating characteristic (ROC) curve (AUC) were determined. RESULTS: Twenty-two patients who underwent a total mesorectal excision were enrolled in this study. Significantly more motion artifacts were present with 3D TSE imaging (P=0.04). The overall sensitivity, specificity, and accuracy of muscularis propria invasion in rectal cancer using 2D T2-weighted images were 100%, 66%, and 95%, respectively. There was a statistical significant greater AUC using 2D T2-weighted images compared to 3D T2-weighted MR images (P=0.04). The ROC curves describing the results of the interpretation of 2D and 3D T2-weighted datasets regarding perirectal tissue invasion showed no statistical significant difference (P=0.41). CONCLUSIONS: In this study, high local staging accuracies with 3T 2D T2-weighted MR imaging were demonstrated. 3D T2-weighted MR imaging cannot replace 2D MR imaging for local staging of rectal cancer. However, 3D MR imaging can be used for visualization of the complex pelvic anatomy for treatment planning purposes.     

Obstructive lesions of the central airways: evaluation by using spiral CT with multiplanar and three-dimensional reformations

The purpose of this study was to assess the accuracy of transverse CT scans as well as multiplanar (MPR) and three-dimensional (3D) reconstructions in the evaluation of obstructive lesions of the central airways. A total of 64 patients were evaluated for the presence of obstructive lesions of the central tracheobronchial tree with transverse spiral CT scans, multiplanar reformations (MPRs), 3D shaded surface displays (3D SSDs) and minimum intensity projections (MIPs). The findings of these modalities were then compared with those obtained at bronchoscopy. The severity, length, and shape of airway narrowing were analyzed comparatively on the four sets of images. Transverse CT scans and MPRs had a similar accuracy (99%) in detecting obstructive airway lesions. The accuracy of both was significantly higher than that of 3DSSDs (90%, p <0.05) and MIPs (81%; p < 0.01). There was no statistically significant difference between the four imaging modalities in the analysis of the morphology of airway stenoses. Symmetric stenoses were similarly analyzed on the four sets of images, whereas MPRs and MIPs failed to depict accurately simple and complex asymmetric stenoses. Transverse CT scans are accurate in the depiction of obstructive lesions of the central airways and may be complemented by MPRs and/or 3DSSDs in their morphologic evaluation.Correspondence to: M. Remy-Jardin     

Diagnostic value of 3 D CT surface reconstruction in spinal fractures

Our purpose was to evaluate the diagnostic value of three-dimensional (3 D) CT surface reconstruction in spinal fractures in comparison with axial and reformatted images. A total of 50 patients with different CT-proven spinal fractures were analysed retrospectively. Based on axial scans and reformatted images, the spinal fractures were classified according to several classifications as Magerl for the thoraco-lumbar and lower cervical spine by one radiologist. Another radiologist performed 3 D CT surface reconstructions with the aim of characterizing the different types of spinal fractures. A third radiologist classified the 3 D CT surface reconstruction according to the Magerl classification. The results of the blinded reading process were compared. It was checked to see in which type and subgroup 3 D surface reconstructions were helpful. Readers one and two obtained the same results in the classification. The 3 D surface reconstruction did not yield any additional diagnostic information concerning type A and B injuries. Indeed, the full extent of the fracture could be easier recognized with axial and reformatted images in all cases. In 10 cases of C injuries, the dislocation of parts of vertebrae could be better recognized with the help of 3 D reconstructions. A 3 D CT surface reconstruction is only useful in rotational and shear vertebral injuries (Magerl type C injury). Received: 29 May 1995; Accepted: 11 January 1996     

3 Tesla magnetic resonance imaging of the prostate with combined pelvic phased-array and endorectal coils; Initial experience(1)

RATIONALE AND OBJECTIVES: High-resolution magnetic resonance imaging of the prostate at 1.5T has gained acceptance for pretherapeutic staging of prostate cancer. The aim of this study was to evaluate the potential clinical utility of combined pelvic phased-array and endorectal coils at 3T. MATERIALS AND METHODS: Six volunteers were examined on 1.5T and 3T scanners with pelvic phased-array surface coil combined with a disposable endorectal prostate coil. RESULTS: We were able to acquire T2-W fast spin echo images with 1.5 mm slices, field of view 12, matrix 320 x 192, (voxel size 0.35 mm(3)), with excellent anatomic detail and good T2 contrast. A 1.5 mm axial slice thickness permitted high-quality multiplanar reconstructions with clear visualization of small patho-anatomic structures. Dynamic contrast-enhanced gradient echo images showed excellent spatial resolution (voxel size, 0.38 mm(3)) and temporal resolution. With this level of anatomic information in dynamic images we could clearly distinguish between intracapsular and extracapsular contrast enhancement. CONCLUSION: Using modified T2-fast spin echo and dynamic contrast-enhanced gradient echo sequences, we obtained whole gland coverage with 35-38 microm(3) resolution, without interfering artifacts, in reasonable acquisition times and staying well below the specific absorption rate guidelines. The high spatial resolution in the axial plane allowed meaningful multiplanar reconstructions. The initial results show the clinical utility of endorectal 3T for the noninvasive evaluation of the prostate with image features and quality not achievable at 1.5 T.     

Three-dimensional US of the prostate: early experience.

PURPOSE: To assess the feasibility of using a three-dimensional (3D) endorectal transducer at ultrasonography (US) in the prostate gland in a clinical setting. MATERIALS AND METHODS: Sixteen patients underwent 3D imaging of the prostate gland with a 3D endorectal probe following conventional two-dimensional (2D) US and prior to prostatic biopsy. Image acquisition was performed as a volume of data with nearly immediate reconstruction and simultaneous display of sectional anatomy in three orthogonal planes--sagittal plane, transverse or coronal plane, or any arbitrary oblique plane. Images were evaluated for presence of focal lesions, glandular volume, visualization of lateral and anterior portions of the gland, and extraglandular extension of tumor. RESULTS: Three-dimensional US allowed better visualization of the gland and focal lesions, especially on the coronally reconstructed images, which were judged superior to the sagittally or transversely reconstructed images for interpretation in 50% of the patients. Prostatic volumes obtained from 3D US were consistently smaller than volumes obtained from 2D US (20% difference, P = .006). Three-dimensional US was superior to 2D US in depicting tumor presence (nine of 10 right hemispheres, three of eight left hemispheres) and extraglandular extent of disease (three of five hemispheres). CONCLUSION: Three-dimensional endorectal prostatic US appears to be clinically feasible and easy to perform. Added anatomic information from the coronal plane may allow better depiction of tumors and extraglandular spread than is possible with current 2D techniques.     

Imaging of the wrist at 1.5 Tesla using isotropic three-dimensional fast spin echo cube

Purpose:

To compare three‐dimensional fast spin echo Cube (3D‐FSE‐Cube) with conventional 2D‐FSE in MR imaging of the wrist.

Materials and Methods:

The wrists of 10 volunteers were imaged in a 1.5 Tesla MRI scanner using an eight‐channel wrist coil. The 3D‐FSE‐Cube images were acquired in the coronal plane with 0.5‐mm isotropic resolution. The 2D‐FSE images were acquired in both coronal and axial planes for comparison. An ROI was placed in fluid, cartilage, and muscle for SNR analysis. Comparable coronal and axial images were selected for each sequence, and paired images were randomized and graded for blurring, artifact, anatomic details, and overall image quality by three blinded musculoskeletal radiologists.

Results:

SNR of fluid, cartilage and muscle at prescribed locations were higher using 3D‐FSE‐Cube, without reaching statistical significance. Fluid–cartilage CNR was also higher with 3D‐FSE‐Cube, but not statistically significant. Blurring, artifact, anatomic details, and overall image quality were significantly better on coronal 3D‐FSE‐Cube images (P < 0.001), but significantly better on axial 2D‐FSE images compared with axial 3D‐FSE‐Cube reformats (P < 0.01).

Conclusion:

Isotropic data from 3D‐FSE‐Cube allows reformations in arbitrary scan planes, which may make multiple 2D acquisitions unnecessary, and improve depiction of complex wrist anatomy. However, axial reformations suffer from blurring, likely due to T2 decay during the long echo train, limiting overall image quality in this plane. J. Magn. Reson. Imaging 2011;33:908–915. © 2011 Wiley‐Liss, Inc.     

Three-dimensional reconstruction of skeletal muscle from MRI

Three-dimensional (3D) reconstructions of medical images can provide useful information to the radiologist, enabling delineation and spatial correlation of anatomic structures in one image rather than consecutive two-dimensional (2D) images. Magnetic resonance imaging (MRI) is known to be a powerful technique for evaluation of skeletal muscle pathology and physiology. We investigated the role of 3D reconstruction from MRI images o pathological and healthy muscle, using volume rendering. The ability to easily delineate and recognize normal and injured muscle in the 3D images were dependent upon the original contrast between normal and injured muscle, spatial resolution, and anatomic complexity in the original slices, and also on imaging parameters such as volume averaging.     

Intraoperative evaluation of aneurysmal architecture: comparative study with transluminal images of 3D MR and CT angiograms

BACKGROUND AND PURPOSE: When exposure and visual access in aneurysmal microsurgery are limited, exact intraoperative information must be obtained regarding the whole shape of the aneurysm, property of the aneurysmal wall, vessels hidden behind the aneurysmal sac, and surrounding bony structures of the skull base. We developed a transluminal imaging technique that uses 3D MR and CT angiograms and applied it for intraoperative transparent evaluation of the angioarchitecture of cerebral aneurysms. METHODS: Transluminal images were reconstructed from a perspective volume-rendering algorithm by selecting information on the luminal margin from the whole volume data sets of MR and CT angiograms. The images show the vessel and aneurysmal walls as a series of rings and provide direct visualization of the underlying objects through the spaces between the rings. By connecting a graphic workstation to the operative microscope, data were reconstructed intraoperatively and adjusted to coincide with the operative views by manipulating the projection and visual angle. The aneurysmal angioarchitecture could then be evaluated transparently on the reconstructed transluminal images through the operative approach. RESULTS: Transluminal images provided direct transparent visualization of the aneurysmal architecture, including orifices at the neck, dome, and bleb and the parent arteries though the vessel and aneurysmal walls. The angioarchitecture of the neck complex was evaluated intraoperatively with transluminal 3D MR and CT angiograms through the operative approach before actual aneurysmal neck clipping. CONCLUSIONS: Intraoperative exact evaluation of aneurysmal angioarchitecture with transluminal images would be a feasible and useful adjunct for aneurysmal microsurgery. Merging of data across modalities including 3D MR and CT angiography may improve preoperative or intraoperative evaluation of the angioarchitecture of cerebral aneurysms.     

螺旋CT扫描在牙齿正畸中的临床应用价值

目的 探讨螺旋CT三维(3D)重建技术在牙齿正畸中的临床应用价值。方法 41例牙齿正畸的患者行螺旋CT轴面扫描，层厚3．0mm。采用最大密度投影法(MIP)，表面遮盖法(SSD)和多层面重建法(MPR)3种方式重建图像。将横轴面图像与不同方法重建的图像之间相互比较。结果 41例中37例见牙体长轴排列不整齐，倾斜、旋转、重叠，牙齿长轴间距离不等，其中25例共有36颗埋伏牙。横轴面图像包括全部信息。SSD显示牙齿与颌骨的外部轮廓、整体形态以及牙齿排列与颌骨之间的关系。MIP清楚显示牙齿全貌、牙齿纵向排列关系，显示颌骨内埋伏牙36颗，通过旋转角度显示埋伏牙位置、形态，其中位于牙列的腭侧29颗，唇侧7颗。MPR对根尖骨质、根尖与牙槽骨的局部关系显示更清晰。结论 螺旋CT3D重建是1种能展示牙齿立体形态影像的新技术。轴面图像、MIP、SSD及MPR联合应用能明确病变性质，立体、直观、多方位提供临床医师所需信息，有利于治疗方案的选择。     

Flat-panel-detector-based volumetric CT: performance evaluation of imaging for skeletal structures of small animals in comparison to multislice CT

OBJECTIVES: The aim of this study was to compare the image performance of silicon-based flat-panel-detector-based volumetric computed tomography (fpVCT) to multislice spiral computed tomography (MSCT) for the visualization and detail detectability of skeletal structures in rodents of different development stages. MATERIALS AND METHODS: Rodents of different development stages were imaged with fpVCT (GE prototype with circular gantry with two 1024 x 1024, 200-microm pixel size, amorphous silicon/Cesium lodid (Csl) flat-panel detector) and eight-slice MSCT (LightSpeed Ultra). Imaging parameters (80 kVp, 100 mA) and the position of the rodents were identical in both techniques. Image quality, detail detectability, and contour of skeletal structures were judged by two observers in consensus using a 4-point scale (1 = unsatisfactory...4 = good). Findings were displayed and evaluated in axial slices, multiplanar reconstructions (MPR), maximum intensity projections (MIP) and volume rendering technique (VRT) in both modalities. Mean and standard of error of mean were calculated. RESULTS: In axial slices, visualization and detail detectability of very subtle skeletal structures, e.g., the basis of the skull was better in fpVCT than in MSCT (4 vs. 2 points). The MPRs of fpVCT showed less artifacts and more details than those of the MSCT. The MIPs and VRTs of the fpVCT demonstrated best image quality in all rodents of different development stages, whereas MSCT showed significant artifacts. CONCLUSION: fpVCT outperformed MSCT in imaging of small rodents. Due to the truly isotropic volume data set with high spatial resolution, fpVCT is a powerful tool in evaluating detailed skeletal structures.     

Flat panel detector angiographic CT for stent-assisted coil embolization of broad-based cerebral aneurysms

BACKGROUND AND PURPOSE: The purpose of this work was to evaluate angiographic CT (ACT) in the combined application of a self-expanding neurovascular stent and detachable platinum coils in the management of broad-based and fusiform intracranial aneurysms. MATERIALS AND METHODS: Eleven patients harboring wide-necked intracranial aneurysms were treated with a flexible self-expanding neurovascular stent and subsequent aneurysm embolization with platinum microcoils. ACT was performed after the interventional procedure to analyze stent position and the relationship of coils to the stent. Postprocessing included multiplanar reconstructions (MPRs) and maximum intensity projections (MIPs). ACT volume datasets were postprocessed for soft tissue visualization. RESULTS: Accurate stent placement with subsequent coil occlusion of the aneurysms was feasible in all of the patients. Similar to nonsubtracted digital subtraction angiography (DSA) images, radiopaque platinum stent markers showed excellent visibility in ACT as well. The stent struts themselves, hardly visible in nonsubtracted DSA, were visible in MPRs and MIPs of ACT in all of the patients. In aneurysms larger than 10 mm in diameter, accurate stent assessment at the level of the coils was limited due to beam hardening artifacts. Postprocedural ACT in all of the patients did not reveal any evidence of procedure-related intracranial hemorrhage. CONCLUSION: ACT provides cross-sectional, 3D visualization of endovascular stents otherwise hardly visible with plain fluoroscopy. ACT enables us to accurately determine stent position, which may be helpful in complex stent-assisted aneurysm coiling procedures. However, in aneurysms larger than 10 mm in diameter, beam hardening artifacts caused by the endoaneurysmal coil package impair visibility of the stent. Further data are necessary to evaluate the usefulness of ACT in stent-assisted aneurysm coiling.     

MR imaging and proton spectroscopy of the breast: how to select the images useful to convey the diagnostic message

PURPOSE: The purpose of this study was to propose a short way to summarise a breast magnetic resonance (MR) examination including a precontrast and contrast-enhanced dynamic study and proton spectroscopy (1H-MRS) in order to convey the diagnostic message. MATERIALS AND METHODS: At the Department of Radiology of the Policlinico San Donato (University of Milan), breast MR is routinely performed at 1.5 T as follows: 36-slice axial 2D short-time inversion-recovery (STIR) sequence; 128-partition 3D gradient-echo coronal sequence (1-mm3 siotropic voxel) before and after rapid automatic intravenous injection of 0.1 mmol/kg of Gd-DOTA (one precontrast and four postcontrast phases). Postprocessing includes temporal subtraction (postcontrast minus precontrast), maximum intensity projections (MIPs), percent enhancement-to-time curves for small regions of interest, and axial and/or sagittal multiplanar reconstructions. Single-voxel 1H-MRS is acquired to characterise focal lesions. Applying this protocol, more than 1,200 images are generated for each examination. We select only four MIPs of an early subtracted dynamic phase: one axial similar to craniocaudal x-ray mammographic views, one coronal, and two lateral similar to lateral 90 degrees x-ray mammographic views. For each lesion described in the report, we select five items, including three images, one graph, and one table: STIR image, precontrast and subtracted postcontrast images (morphology), percent enhancement-to-time curves and a table of raw data generating the curves (dynamics). If 1H-MRS has been performed, we add other five items: two postprocessed spectra (metabolism) and three images localising the volume of interest. Only the selected items are printed on films and attached to the report. RESULTS: The selected items range usually from four (no detected lesion) to 14 (one lesion, studied also with 1H-MRS), to 44 (five lesions, one of them studied also with 1H-MRS). The percentage of items presented with the report if compared with the total number of generated images is equal to 0.33% (4/1,200), 1.17% (14/1,200), and 2.83% (34/1,200), respectively. CONCLUSIONS: Breast MR imaging and 1H-MRS can be effectively summarised presenting only a minimal fraction of all generated images.     

Evaluation of the middle and inner ear structures: comparison of hybrid rendering, virtual endoscopy and axial 2D source images

Recent developments in 3D reconstructions can enhance the quality and diagnostic value of axial 2D image data sets with direct benefits for clinical practice. To show the possible advantages of a hybrid rendering method [color-coded 3D shaded-surface display (SSD)- and volume rendering method] with the possibility of virtual endoscopy we have specifically highlighted the use in relation to the middle and inner ear structures. We examined 12 patients with both normal findings and postoperative changes, using image data sets from high-resolution spiral computed tomography (HRSCT). The middle and inner ear was segmented using an interactive threshold interval density volume-growing method and visualized with a color-coded SSD rendering method. The temporal bone was visualized using a transparent volume rendering method. The 3D- and virtual reconstructions were compared with the axial 2D source images. The evaluated middle and inner ear structures could be seen in their complete form and correct topographical relationship, and the 3D- and virtual reconstructions indicated an improved representation and spatial orientation of these structures. A hybrid and virtual endoscopic method could add information and improve the value of imaging in the diagnosis and management of patients with middle or inner ear diseases making the understanding and interpretation of axial 2D CT image data sets easier. The introduction of an improved rendering algorithm aids radiological diagnostics, medical education, surgical planning, surgical training, and postoperative assessment. Received: 22 July 1998; Revised: 15 April 1999; Accepted: 19 April 1999