MR Arthrography of the Hip

Magnetic resonance imaging (MRI) of the hip has been valuable in the diagnosis of occult osseous abnormalities and of periarticular soft tissue disorders. MRI has been less useful in the evaluation of acetabular labral tears and other intra-articular abnormalities. Image optimization is more technically challenging in the hip than in smaller joints because the overlying soft tissues are thicker, resulting in decreased spatial and contrast resolutions that may not be adequate to distinguish the acetabular labrum from subchondral bone, articular cartilage, and joint capsule. MR arthrography (MRA) extends the capabilities of conventional MRI because contrast solution separates intra-articular structures and outlines abnormalities. In hips with suspected acetabular labral injury, arthrographic MR images demonstrate the location and length of tears and the presence of associated capsular defects. Arthrographic MR images may also enable the accurate diagnosis of cartilage lesions and intra-articular loose bodies. This article illustrates normal arthrographic MR features of the hip as well as pathologic disorders of the acetabular labrum, capsule, and articular cartilage     

螺旋CT三维和多平面重建在髋臼骨折中的应用

目的：探讨螺旋CT三维（3D）和多平面重建（MPR）在髋臼骨折中的临床应用价值。方法：27例髋臼骨折的病人先经营骨盆螺旋CT薄层扫描，并在工作站上作髋臼三维和多平面重建。注重观察髋臼骨折的以及CT表现特征。结果：27例病人共计31个髋臼骨折。除1个T形骨折用三维和多平面重建判断为横行骨折外，其余30个骨折轴位CT、三给和多平面重建均显示。三维和多平面重建能更直观的显示病变的具体情况。结论“螺旋CT三维和多平面重建是轴位CT扫描的有价值的补充手段，在髋臼骨折中有很高的应用价值。     

多层螺旋CT三维重建技术在髋臼骨折中的临床应用

目的　探讨多层螺旋CT(MSCT)三维重建技术在髋臼骨折分型中的临床应用。方法　收集 2 0名髋臼骨折患者共 2 0个髋臼行多层螺旋CT容积扫描。将扫描数据经薄层重建行髋臼三维重建处理 (3D)及多平面重建 (MPR) ,三维重建图像与手术所见相对照。结果　在手术的 17个髋臼中 ,髋臼三维重建图像与手术中骨科医师所见完全一致。结论　MSCT髋臼三维重建图像质量可与大体标本相媲美 ,有利于髋臼骨折术前的正确分型 ,具有很大的优越性及良好的应用前景     

CT of pelvic fractures

Although magnetic resonance imaging has become the dominant modality for cross-sectional musculo-skeletal imaging, the widespread availability, speed, and versatility of computed tomography (CT) continue to make it a mainstay of emergency room (ER) diagnostic imaging. Pelvic ring and acetabular fractures occur as the result of significant trauma secondary to either a motor vehicle accident or a high-velocity fall. These injuries are correlated with significant morbidity and mortality, both from the complications of pelvic ring fractures and from commonly associated injuries. The most commonly used classification of pelvic and acetabular fractures has been based on conventional radiographs that are, in the majority of cases, sufficient to determine the type of injury. However, because of the complexity of pelvic and acetabular fractures, precise pathological anatomy is not easily demonstrated by routine radiographs and in many cases details of fractures are not visible. Moreover, the insufficient co-operation of the patient or the difficulty of maintaining special positions can be overcome by using computed tomography. Spiral computed tomography provides information regarding the extent of the fractures and is complementary to radiography for ascertaining the spatial arrangement of fracture fragments. Spiral computed tomography is an effective tool for understanding complex fracture patterns, particularly when combined with multi-planar reconstruction two-dimensional (MPR 2D) reformatted images or three-dimensional images (3D) images. Including these techniques of reconstruction in routine pelvic imaging protocols can change management in a significant number of cases. Subtle fractures, particularly those oriented in the axial plane, are better seen on MPR images or 3D volume-rendered images. Complex injuries can be better demonstrated with 3D volume-rendered images, and complicated spatial information about the relative positions of fracture fragments can be easily demonstrated to the orthopaedic surgeons. The use of intravenous (i.v.) contrast material allows simultaneous evaluation of osseous and vascular structures within the affected area. Postoperative studies in patients with orthopaedic hardware also benefit from volume-rendered imaging. Volume rendering eliminates most streak artifact and produces high-quality images on which the relationships among hardware, bones, and bone fragments are well demonstrated.     

Acetabular fractures revisited: a new CT-based classification

The objective of this investigation is to provide a new CT-based classification of acetabular fractures. The axial CT scans of 112 randomly selected acetabular fracture patients admitted to a Level 1 trauma center between January 1998 and December 2000 were analyzed by an experienced orthopedic trauma surgeon and two experienced emergency radiologists. When available, 3D reformatted images were analyzed as well. The fracture pattern for each acetabular fracture with respect to column(s) wall(s) and extension superiorly and/or inferiorly from the acetabulum, when present, was recorded. Fracture comminution was not a defining characteristic. Analysis of the acetabular fracture patterns showed that each fracture fell into one of four broad categories: Category 0--wall only; Category 1--single column; Category 2--both columns, with extension subcategories of (A) no extension, (B) superior extension only, (C) inferior extension only, and (D) both superior and inferior extension; and Category 3--the "floating" acetabulum. The axial CT display of acetabular fracture patterns provides a basis for a classification of acetabular fractures that is simple, unambiguous, readily understood by both radiologists and orthopedic surgeons, and provides clear direction for both diagnosis and surgical treatment planning. Category and subcategory fracture specificity creates a mechanism for intra- and interdepartmental postoperative assessment of any of the individual acetabular fracture types.     

Three-dimensional computed tomography analysis of non-osteoarthritic adult acetabular dysplasia

OBJECTIVE: Little data exists on the original morphology of acetabular dysplasia obtained from patients without radiographic advanced osteoarthritic changes. The aim of this study was to investigate the distribution and degree of acetabular dysplasia in a large number of patients showing no advanced degenerative changes using three-dimensional computed tomography (3DCT). MATERIALS AND METHODS: Eighty-four dysplastic hips in 55 consecutive patients were studied. All 84 hips were in pre- or early osteoarthritis without radiographic evidence of joint space narrowing, formation of osteophytes or cysts, or deformity of femoral heads. The mean age at the time of CT scan was 35 years (range 15-64 years). 3D images were reconstructed and analyzed using recent computer imaging software (INTAGE Realia and Volume Player). Deficiency types and degrees of acetabular dysplasia were precisely evaluated using these computer software. RESULTS: The average Harris hip score at CT scans was 82 points. Twenty-two hips (26%) were classified as anterior deficiency, 17 hips (20%) as posterior deficiency, and 45 hips (54%) as lateral deficiency. No significant difference was found in the Harris hip score among these groups. The analysis of various measurements indicated wide variations. There was a significant correlation between the Harris hip score and the acetabular coverage (p < 0.001). CONCLUSION: Our results indicated wide variety of deficiency type and degree of acetabular dysplasia. Hips with greater acetabular coverage tended to have a higher Harris hip score.     

Fetal abnormalities: evaluation with real-time-processible three-dimensional US--preliminary report

PURPOSE: To assess the usefulness of real-time-processible three-dimensional (3D) ultrasonography (US) in the evaluation of fetal abnormalities. MATERIALS AND METHODS: The apparatus comprised a conventional US scanner with a specially designed unit for real-time-processible 3D US and a transabdominal 3D probe. A 3D US examination was performed in 19 women with abnormalities of the fetus (13-35 weeks gestation) that had been detected at two-dimensional (2D) US. RESULTS: Thirty-six abnormalities were detected with conventional 2D US, real-time-processible 3D US, or both in 19 fetuses with abnormalities. Seventeen (47%) of the 36 abnormalities were demonstrated and confirmed clearly with real-time-processible 3D US, and nine of these had been seen with 2D US. Eighteen intrafetal abnormalities had been demonstrated clearly with 2D US, but 14 of these could not be demonstrated with real-time-processible 3D US. CONCLUSION: Real-time-processible 3D US is useful for evaluating fetal abnormalities as a supplement to 2D US, particularly for abnormalities of the face, ears, fingers, and anatomic axis, but real-time-processible 3D US is unlikely to be helpful for detecting intrafetal abnormalities except for skeletal abnormalities and some pathologic changes with fluid accumulation.     

股骨头挖除后螺旋CT三维重建在髋臼粉碎性骨折中的应用

目的 探讨股骨头挖除后螺旋CT三维重建在髋臼粉碎性骨折中的应用价值。资料与方法 对27例经普通X线诊断的髋关节骨折患者，应用螺旋CT扫描获得原始轴面图像，在工作站对兴趣区进行染色显影，通过关节解体技术去除股骨头，然后对髋臼采用多平面重建（MPR）及表面遮盖法（SSD）和容积漫游技术（VRT）三维重建。结果 股骨头挖除后三维重建图像能直观显示髋臼骨折的全貌及关节腔内的游离碎骨片及相互之间的解剖关系。结论 股骨头挖除后SSD和VRT三维重建对外科手术前充分了解髋臼损伤情况、手术方案的制定及内固定器械的选择，均有重要的指导作甩。     

MDCT of tendon abnormalities using volume-rendered images

OBJECTIVE: Our objectives were to report tendon abnormalities diagnosed on 3D volume-rendered images from MDCT data and to validate the clinical usefulness of this technique. CONCLUSION: We present 18 tendon abnormalities from 16 patients that were diagnosed on 3D volume-rendered MDCT images generated by commercially available software. Certain abnormalities such as avulsions, partial tears, and dislocations of tendons are clearly shown by this technique. This technique may prove useful in the evaluation of tendon abnormalities when MRI or sonography cannot be used.     

The infant hip: real-time US assessment of acetabular development

Until recently, radiography was the only available means of assessing acetabular development in infants with congenital hip dysplasia. Now that real-time ultrasonography (US) is successfully employed to determine hip position in infancy, it also offers an alternative method for evaluating acetabular development. In a review of 377 US studies of infant hips, the coronal-flexion images, which show a coronal section of the acetabulum with the hip in flexion, were measured to determine the percentage of the femoral head that was covered. Radiographs were measured to determine the acetabular index (angle). Acetabuli with indices exceeding the normal range for the subject's age showed head coverage of less than 33%. The 51 sonograms in this category were all associated with clinical abnormalities, whereas the 107 with coverage greater than 58% were associated with no clinical abnormalities and with consistently normal acetabular indices. The use of US in assessing acetabular development warrants continued investigation.     

螺旋CT三维和多平面重建在髋臼骨折中的应用

目的 探讨螺旋ＣＴ（ＳＣＴ）三维和多平面重建在髋臼骨折中的临床价值。材料与方法 分析１６例髋臼骨折的轴位、多平面ＣＴ及三维ＣＴ表现。结果 表面重建（ＳＳＤ）对１４例超过２ｍｍ的骨折均很好显示,但对于２ｍｍ以下移位显示较差,多平面重建（ＭＰＲ）良好显示髋臼负重区的损伤及稳定性。结论 ＳＣＴ三维重建和ＭＰＲ对复杂的髋臼骨折的术前分类、指示手术入路及估计预后均有重要的临床意义。     

Evaluation of abnormal regional ventilation in patients with lung cancer using three-dimensional display of dynamic 133Xe SPET

Preliminary studies were carried out of regional ventilation in lung cancer using three-dimensional (3D) display of dynamic pulmonary 133Xe single photon emission tomography (SPET). Transaxial equilibrium and washout images were obtained from SPET data acquired with an acquisition time of 30 s using a triple-detector SPET system in 39 patients with lung cancer. After reconstructing colour-illuminated, surface-rendered 3D images of equilibrium and 3-min washout (WO3), a single 3D fusion display was created from these two different time-course image sets, in which the 3D WO3 image indicating 133Xe retention was visible through the 3D equilibrium image delineating lung contours. The extent of retention was assessed using the 133Xe retention index, defined as the ratio of summed pixels of the segmented WO3 data to those of the segmented equilibrium data. 133Xe SPET was highly sensitive and specific for the presence of regional ventilation abnormalities associated with endobronchial tumour or bronchial compression due to enlarged lymph nodes. These abnormalities were demonstrated irrespective of the presence or absence of secondary changes distal to the tumour on the chest computed tomography scan. The geometrically realistic 3D fusion display enhanced anatomic localization of the regional ventilation abnormalities compared to the information from multislice tomograms, and the 133Xe retention index correlated well with %FEV1 (r = 0.828). This topographic 3D display for 133Xe SPET allows better perception of anatomic localization and extent of 133Xe retention. It will be useful for assessing regional ventilatory function in patients with lung cancer.     

Acetabular fractures revisited: part 2, a new CT-based classification

OBJECTIVE: The objective of this investigation was to provide a new CT-based classification of acetabular fractures. MATERIALS AND METHODS: The axial CT scans of 112 randomly selected acetabular fractures in patients admitted to a level 1 trauma center between January 1998 and December 2000 were analyzed by an experienced orthopedic trauma surgeon and two experienced emergency radiologists. When available, 3D reformatted images were analyzed as well. The fracture pattern for each acetabular fracture, with respect to column walls and extension beyond the acetabulum, when present, was recorded. Fracture comminution was not a defining characteristic. RESULTS: Analysis of the 112 acetabular fracture patterns showed that each fracture fell into one of four broad categories. Category 0 included wall fractures only. Category I included acetabular fractures limited to a single (anterior or posterior) column. Category II fractures included those involving both the anterior and posterior columns; category II fractures were further subdivided into those with no fracture extension beyond the acetabulum, those with superior or inferior extension, and those with both superior and inferior extensions beyond the acetabulum. Category III fractures included only the "floating" acetabulum, which is defined as an acetabular fracture in which the acetabulum is separated from the axial skeleton both anteriorly and posteriorly. CONCLUSION: The axial CT display of acetabular fracture patterns provides a basis for a classification of acetabular fractures that is simple, unambiguous, readily understood by both radiologists and orthopedic surgeons and provides clear direction for both diagnosis and surgical treatment planning. Category and subcategory fracture specificity creates a mechanism for intra- and interdepartmental postoperative assessment of any of the individual acetabular fracture types.     

MR imaging of the chest using a contrast-enhanced breath-hold modified three-dimensional gradient-echo technique: comparison with two-dimensional gradient-echo technique and multidetector CT

OBJECTIVE: The purpose of this study was to assess the feasibility of performing MR imaging of the chest using a fat-suppressed gadolinium-enhanced modified three-dimensional (3D) gradient-echo technique with a volumetric interpolated breath-hold (VIB) sequence compared with using a standard two-dimensional (2D) breath-hold gradient-echo technique. MR images obtained using both techniques were compared with multidetector CT (MDCT) scans. SUBJECTS AND METHODS: Paired gadolinium-enhanced 2D gradient-echo and 3D gradient-echo VIB images were acquired in 15 consecutive patients with suspected intrathoracic abnormalities. MDCT scans were available for comparison in 12 patients. Two reviewers independently analyzed the MR images obtained using the two techniques for overall quality, the degree of artifacts, and visibility of mediastinal or parenchymal abnormalities. The detectability of lesions on the 3D gradient-echo VIB images and 2D gradient-echo images was compared with the detectability of lesions on CT scans obtained in nine patients. RESULTS: In all cases, the MR images obtained using the 3D gradient-echo technique with the VIB sequence were rated superior to those obtained using the 2D gradient-echo technique for quality, depiction of mediastinal structures, and clarity of pulmonary vessels and central airways. On the 3D gradient-echo VIB images, the degree of phase artifacts was lower (p < 0.001), but the degree of pixel graininess was higher (p < 0.05). Detectability, confidence and conspicuity levels, and marginal delineation of the pulmonary lesions were rated higher statistically on the 3D gradient-echo VIB images than on the 2D gradient-echo images. Of the 31 solid pulmonary abnormalities depicted on MDCT, 27 (87.1%) were detected on the 3D gradient-echo VIB images, and 21 (67.7%) were seen on the 2D gradient-echo images (p < 0.05). The 3D gradient-echo VIB images showed all 14 mediastinal lesions (100%) seen on MDCT, whereas the 2D gradient-echo images showed 12 (85.7%) of the 14 lesions (p > or = 0.05). CONCLUSION: The gadolinium-enhanced modified 3D gradient-echo technique with the VIB sequence provides MR images that are superior in quality, have significantly fewer artifacts, and have a higher sensitivity for the detection of intrathoracic lesions compared with images obtained using the standard 2D gradient-echo technique.     

3D planar reformation of vascular central axis surface with biconvex slab.

Curved multi-planar reformation (curved MPR) is one of the commonly used vascular visualization methods in clinics. It re-samples and visualizes the vascular central axis surface (VCAS), which is a curved surface passing through the vascular central axis (VCA) or vessel centerline. The rotation of the VCAS along the VCA generates a set of 2D images. In this paper, we introduce a 3D curved MPR method, VCAS planar reformation (VPR) by a convex hull, called a biconvex slab. The entire vessel is enclosed within a biconvex slab and rendered in one image by volume rendering, such as MIP or X-ray. The method is applied to computed tomographic angiography (CTA) data sets. The resulting image is clear and free from obstruction by bones and other adjacent organs.     

Development of a method for reconstructing three-dimensional data from axial, sagittal, and coronal MR images

Magnetic resonance (MR) imaging is useful for the diagnosis of brain atrophy and intracranial abnormalities. We have developed a method of automated volumetry to evaluate the degree of brain atrophy for the diagnosis of dementia. Whole-brain MR images with thin slices without gaps are required for segmentation and volumetry. However, obtaining such images requires that the patient remain at rest for a prolonged period, thereby reducing the throughput of MR imaging examinations. Therefore, a method is needed for the reconstruction of isotropic three-dimensional (3D) data using routine axial, sagittal, and coronal MR images with 30% gaps and measurement of brain volume. The method of reconstructing 3D data consists of four processes: 1) segmentation of the brain region on axial, sagittal, and coronal MR images using the region-growing technique; 2) setting data to a 3D domain; 3) registration by manual operation; and 4) interpolation between the data based on linear interpolation. In clinical MR images, the differences between this method and the conventional technique were less than 10%. These results demonstrate that this technique is able to construct 3D data from axial, sagittal, and coronal MR images.     

Acetabular labrum: abnormal findings at MR imaging in asymptomatic hips

PURPOSE: To determine the prevalence of abnormalities of the acetabular labrum in asymptomatic hips by means of magnetic resonance (MR) imaging and to correlate such abnormalities with age and the portion of the labrum. MATERIALS AND METHODS: MR imaging was performed in 71 asymptomatic hips that were radially sectioned perpendicular to the acetabular labrum at 30 degrees intervals. RESULTS: The shape of the labrum was triangular in 80% (304 of 382) of the labral segments, round in 13% (49 of 382), irregular in 7% (27 of 382), and not identified in 1% (two of 382). A homogeneous low signal intensity was observed in 56% (212 of 382). The frequencies of labral irregularity or its absence and of high signal intensity increased both with subject age and with a more anterior anatomic labral location. CONCLUSION: In asymptomatic hips, abnormal findings regarding the shape and signal intensity of the acetabular labrum can be detected by means of MR imaging. The fact that the findings vary according to age and labral portion should be considered in interpreting MR images in patients suspected of having a labral lesion.     

Internal derangements of the temporomandibular joint: comparison of assessment with three-dimensional gradient-echo and spin-echo MRI

Our purpose was to assess the diagnostic accuracy of three-dimensional (3D) gradient-echo (GRE) MRI in the diagnosis of internal derangements of the temporomandibular joint (TMJ). We studied 140 joints in 70 patients with TMJ internal derangements. We obtained 3D-GRE and spin-echo (SE) images in the closed-mouth position; the images were reviewed for disc displacement as well as bone and cartilage abnormalities. The 3D-GRE and SE images were interpreted independently by different radiologists. The sensitivity and specificity of 3D-GRE imaging for assessing mediolateral disc displacement was 100 %, whereas the sensitivity and specificity of sagittal SE images were 82 % and 72 %, respectively (P < 0.001). The 3D-GRE images also demonstrated more bone abnormalities (in 112 condyles or 80 %) than did SE images (in 79 condyles or 56 %) (P < 0.001). Furthermore, 3D-GRE imaging revealed articular cartilage abnormalities in 46 condyles (33 %) that were not visible on SE images. The frequency of pain was significantly higher in joints with bone and cartilage abnormalities (P < 0.05 and P < 0.001, respectively). For assessment of disc displacement, 3D-GRE images were superior to sagittal SE images alone, and comparable to combined sagittal and coronal SE images, while for bone and cartilage abnormalities, they were superior to sagittal and coronal SE images. Received: 8 July 1996 Accepted: 7 November 1996     

Technical and analytical advances in pulmonary ventilation SPECT with xenon-133 gas and Tc-99m-Technegas

This paper describes the recent advances in technical and analytical methods in pulmonary ventilation SPECT studies, including a respiratory-gated image acquisition of Technetium-99m (99mTc)-labeled Technegas SPECT, a fusion image between Technegas SPECT and chest CT images created by a fully automatic image registration algorithm, and a three-dimensional (3D). display of xenon-133 (133Xe) gas SPECT data, and new analytical approaches by means of fractal analysis or the coefficient of variations of the pixel counts for Technegas SPECT data. The respiratory-gated image acquisition can partly eliminate problematic effects of the SPECT images obtained during non-breath-hold. The fusion image is available for routine clinical use, and provides complementary information on function and anatomy. The 3D displays of dynamic 133Xe SPECT data are helpful for accurate perception of the anatomic extent and locations of impaired ventilation, and the assessment of the severity of ventilation abnormalities. The new analytical approaches facilitate the objective assessment of the degrees of ventilation abnormalities.     

Interactive continuously moving table (iCMT) large field-of-view real-time MRI.

Continuously moving table (CMT) MRI is a new method that is capable of generating 3D, seamless, large field-of-view (FOV) images by acquiring readouts along the patient superior-inferior axis as the subject is translated through the scanner. For applications that require artifact-free images, such as arterial-phase contrast-enhanced (CE) angiography of the legs, a major challenge is to match the MR data acquisition and patient table motion with the dynamics of blood flow in the region of interest (ROI). Instead of restricting the CMT to predetermined constant table speeds, we adopted a more general approach in which the table motion is decoupled from the phase-encoding order. In our approach the table moves adaptively and in response to operator-provided feedback obtained from viewing real-time preview (or fluoroscopic) images. This interactivity is accomplished by integrating high temporal-spatial resolution encoding of the table position with real-time hybrid-space filling and image reconstruction. Experimental results obtained using our prototype interactive CMT (iCMT) system on a peripheral vascular phantom and five healthy volunteers demonstrate the feasibility of this robust and rapid imaging method for acquiring 3D large-FOV continuous images with patient-specific adaptive table motion profiles.