Magnetic Resonance Imaging Sections Research Articles

Magnetic resonance imaging, computed tomography, and gross anatomy of the canine tarsus.

To describe the normal anatomy of the soft tissues of the canine tarsus as identified on computed tomography (CT) and magnetic resonance imaging (MRI) and to evaluate specific MRI sequences and planes for observing structures of diagnostic interest. Prospective descriptive study. Canine cadavers (n = 3). A frozen cadaver pelvic limb was used to trial multiple MRI sequences using a 1.5 T superconducting magnet and preferred sequences were selected. Radiographs of 6 canine cadaver pelvic limbs confirmed the tarsi were radiographically normal. A 16-slice CT scanner was used to obtain 1 mm contiguous slices through the tarsi. T1-weighted, proton density with fat suppression (PD FS) and T2-weighted MRI sequences were obtained in the sagittal plane, T1-weighted, and PD FS sequences in the dorsal plane and PD FS sequences in the transverse plane. The limbs were frozen for one month and sliced into 4-5 mm thick frozen sections. Anatomic sections were photographed and visually correlated to CT and MR images. Most soft tissue structures were easiest to identify on the transverse MRI sections with cross reference to either the sagittal or dorsal plane. Bony structures were easily identified on all CT, MR, and gross sections. The anatomy of the canine tarsus can be readily identified on MR imaging.

The association between cerebral developmental venous anomaly and concomitant cavernous malformation: an observational study using magnetic resonance imaging

BackgroundSome studies reported that cerebral developmental venous anomaly (DVA) is often concurrent with cavernous malformation (CM). But there is lack of statistical evidence and study of bulk cases. The factors associated with concurrency are still unknown. The purpose of this study was to determine the prevalence of concomitant DVA and CM using observational data on Chinese patients and analyze the factors associated with the concurrency.MethodsThe records of all cranial magnetic resonance imaging (MRI) performed between January 2001 and December 2012 in Beijing Tiantan Hospital were reviewed retrospectively. The DVA and CM cases were selected according to imaging reports that met diagnostic criteria. Statistical analysis was performed using the Pearson chi-square statistic for binary variables and multivariable logistic regression analysis for predictors associated with the concurrent CM.ResultsWe reviewed a total of 165,230 cranial MR images performed during the previous 12 year period, and identified 1,839 cases that met DVA radiographic criteria. There were 205 patients who presented concomitant CM among the 1,839 DVAs. The CM prevalence in DVA cases (11.1%) was significantly higher than that in the non-DVA cases (2.3%) (P<0.01). In the multivariate analysis, we found that DVAs with three or more medullary veins in the same MRI section (adjusted OR = 2.37, 95% CI: 1.73-3.24), infratentorial DVAs (adjusted OR = 1.71, 95% CI: 1.26-2.33) and multiple DVAs (adjusted OR = 2.08, 95% CI: 1.04-4.16) have a higher likelihood of being concomitant with CM.ConclusionsCM are prone to coexisting with DVA. There is a higher chance of concurrent CM with DVA when the DVA has three or more medullary veins in the same MRI scanning section, when the DVA is infratentorial, and when there are multiple DVAs. When diagnosing DVA cases, physicians should be alerted to the possibility of concurrent CM.

Computed anatomical modelling of the optic pathway and oculomotor system using magnetic resonance imaging

This study presents a computer-based tool for three-dimensional (3D) visualization of the optic pathway and oculomotor system using 3D high-resolution magnetic resonance imaging (MRI) datasets from a healthy subject. The 3D models were built as wireframe grids co-registered with MRI sections. First, 3D anatomical models were generated of the visual pathway from the eyeball to the primary visual cortex and of the cranial oculomotor nerves from the brain stem to the extrinsic eye muscles. Second, a graphical user interface allowed individual and group visualization, translation, rotation and zooming of the 3D models in different spatial positions simultaneously with MRI orthogonal cut planes. Educational and clinical applications are also discussed.

ACCURACY OF LOW‐FIELD MAGNETIC RESONANCE IMAGING VERSUS RADIOGRAPHY FOR GUIDING INJECTION OF EQUINE DISTAL INTERPHALANGEAL JOINT COLLATERAL LIGAMENTS

Desmopathy of the distal interphalangeal joint collateral ligament is a common cause of lameness in the horse and carries a variable prognosis for soundness. Intralesional treatment has been proposed for improving outcome; however, limited reports describe methods for injecting this ligament. The purpose of this study was to compare accuracy of low-field magnetic resonance imaging (MRI) vs. radiography for injecting the collateral ligament of the distal interphalangeal joint. Equine cadaver digit pairs (n = 10) were divided by random assignment to injection of the ligament by either technique. An observer unaware of injection technique determined injection success based on postinjection MRI and/or gross sections acquired from the proximal, middle, and distal portions of the ligament. McNemar's test was performed to determine statistical difference between injection techniques, the number of injection attempts, and injection of the medial or lateral collateral ligament. Magnetic resonance imaging guided injection was successful more frequently than radiographic-guided injection based on postinjection MRI (24 of 30 vs. 9 of 30; P = 0.0006) and gross sections (26 of 30 vs. 13 of 30; P = 0.0008). At each level of the ligament (proximal, middle, and distal), MRI-guided injection resulted in more successful injections than radiographic guidance. Statistical significance occurred at the proximal aspect of the collateral ligament based on postinjection MRI (P = 0.0143) and the middle portion of the ligament based on gross sections (P = 0.0253). Findings supported future testing of standing, low-field MRI as a technique for delivering intralesional regenerative therapy in live horses with desmopathy of these collateral ligaments.

Comparison of imaging-based gross tumor volume and pathological volume determined by whole-mount serial sections in primary cervical cancer

ObjectiveTo investigate the accuracy of imaging-based gross tumor volume (GTV) compared with pathological volume in cervical cancer.MethodsTen patients with International Federation of Gynecology and Obstetrics stage I–II cervical cancer were eligible for investigation and underwent surgery in this study. Magnetic resonance imaging (MRI) and fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET)/computed tomography (CT) scans were taken the day before surgery. The GTVs under MRI and 18F-FDG PET/CT (GTV-MRI, GTV-PET, GTV-CT) were calculated automatically by Eclipse treatment-planning systems. Specimens of excised uterine cervix and cervical cancer were consecutively sliced and divided into whole-mount serial sections. The tumor border of hematoxylin and eosin-stained sections was outlined under a microscope by an experienced pathologist. GTV through pathological image (GTV-path) was calculated with Adobe Photoshop.ResultsThe GTVs (average ± standard deviation) delineated and calculated under CT, MRI, PET, and histopathological sections were 19.41 ± 11.96 cm3, 12.66 ± 10.53 cm3, 11.07 ± 9.44 cm3, and 10.79 ± 8.71 cm3, respectively. The volume of GTV-CT or GTV-MR was bigger than GTV-path, and the difference was statistically significant (P < 0.05). No significant difference was observed between GTV-PET and GTV-path (P > 0.05). Spearman correlation analysis showed that GTV-CT, GTV-MRI, and GTV-PET were significantly correlated with GTV-path (P < 0.01). There was no significant difference in the lesion coverage factor among the three modalities.ConclusionThe present study showed that GTV defined under 40% of maximum standardized uptake value in PET images was very similar to the pathological volume of cervical cancer. This result should be replicated in a larger number of patients with cervical cancer in a future study of ours.

SAT0053 Advantages of non-invasive imaging techniques in monitoring antigen induced arthritis rat model

BackgroundDisease assessment using magnetic resonance imaging (MRI) in small animal models of rheumatoid arthritis (RA) is not a commonly used method to date. Inflammation and erosion histological scoring remain the...

SAT0386 The structural basis of MRI bone erosions- an assessment by micro computed tomography

BackgroundMicro-CT (μCT) allows to directly measure the volume of individual erosions and thus exactly defines the extent of structural damage. Based on our experience with high resolution μCT scanning we...

Diffusion-weighted magnetic resonance imaging as a new diagnostic tool of subclinical IgG4-related acute tubulointerstitial nephritis.

A 47-year-old Caucasian man with a 2-year history of type 1 autoimmune pancreatitis (AIP) was referred to the nephrology clinic because of abnormal kidney imaging. He was asymptomatic and his physical examination was normal. Blood tests gave the following results: γ-glutamyltransferase (γ-GT): 662 IU/L (normal 8–16), alanine aminotransferase: 312 IU/L (normal <45), total bilirubin: 2.0 mg/dL (normal <1.2), lipase: 245 IU/L (normal <75), CA19–9: 100 U/mL (normal <37), IgG4: 310 mg/dL (normal 14–126) and serum creatinine (Scr): 0.8 mg/dL (normal 0.7–1.2). Urine analyses (dipstick, microscopy and 24-h urine collection) did not show any abnormality. Kidney ultrasound examination was normal. Besides a relapse of AIP, magnetic resonance imaging (MRI) and diffusion-weighted (DW) MRI sections showed bilateral cortical lesions in both kidneys (Figure 1a–e), corresponding to areas of restricted water diffusion. Biopsy of the left kidney, as classically advised, demonstrated normal parenchyma. The immunofluorescence study and IgG4 staining were negative (Figure 1f). Corticosteroids were started to treat relapsing AIP. During the follow-up, 1 year later, the patient remained asymptomatic. Biological parameters were normalized, except γ-GT and IgG4 serum levels (202 IU/L and 230 mg/dL, respectively). Renal function remained normal (SCr: 0.9 mg/dL). However, a control DW-MRI did not only show signs of AIP, but also enhanced renal lesions (Figure 2a–c). A second kidney biopsy targeting the bright areas well described by DW-MRI (Figure 2b) was performed on the antero-inferior pole of the right kidney. Light microscopy revealed marked tubular destruction and interstitial inflammation (lymphocytes, eosinophils and IgG4+ plasma cells), consistent with acute IgG4-related tubulointerstitial nephritis (TIN) (Figure 2d). Consequently, corticosteroids were increased to better control the involvement of both organs. Fig. 1. T2-weighted magnetic resonance imaging: (a) Normal kidneys showing the well-delineated renal cortex (closed arrows) from medulla (arrow head). (b) Kidneys during IgG-related TIN characterized by cortical thickening in the anterior and the inferior poles ... Fig. 2. Magnetic resonance imaging performed 1 year later. (a) T2-weighted and (b) diffusion-weighted sections demonstrating slight increased renal lesions (open arrows). (c) Coronal reformat of diffusion-weighted magnetic resonance imaging displays the localization ... IgG4-related TIN is a part of IgG4-related disease [1]. Recognition of this specific type of autoimmune TIN is mandatory to start appropriate therapy early and to prevent any further degradation of renal function [2]. Our observation demonstrates that DW-MRI can be useful in detecting subclinical (inflammatory) stage of IgG4-related TIN.

The contribution of cervical dynamic magnetic resonance imaging to the surgical treatment of cervical spondylotic myelopathy.

Cervical spine is the most kinetic segment of the whole vertebrae. The radiologic imaging methods concern with the morphologic changes but give no functional data. At flexion, spinal cord strains, anterior osteophytic compression increases. At extension, spinal canal gets narrower, cord shortens and gets thicker, compression of posterior ligament gets abberant and cord compression increases. 258 cervical spondylotic myelopathy (CSM) cases were scanned by conventional magnetic resonance imaging (MRI) and additionally dynamic MRI. Contributions of dynamic cervical MRI to the surgical plans and results were evaluated. We had sagittal and axial T2W MR scans at flexion and extension, in addition to the neutral cervical MR imaging. We found that the AP diameter of spinal canal is increased 14.9 % in flexion and decreased 13.4 % in extension relative to the neutral MR imaging. The changes of the cord compression and the transvers area of cord which is the most important prognostic indicator in spinal diseases and also the area of spinal cord and subarachnoid space can be detected via dynamic axial sections of MRI. Dynamic MR images may be helpfull in the decision making for the surgical treatment of CSM.

Spontaneous rupture of intracranial dermoid tumor in a patient with vertigo. Computed tomography and magnetic resonance imaging findings

SummaryBackgroundCongenital dermoid cysts are very rare, constituting less than 1% of intracranial tumors. Spontaneous rupture of dermoid tumor is a potentially serious complication that can lead to meningitis, seizures, cerebral ischemia and hydrocephalus. Occasionally, dermoid tumors are incidentally discovered on computed tomography (CT) of the brain or magnetic resonance imaging (MRI) following unrelated clinical complaints. They are also discovered during radiologic investigations of unexplained headaches, seizures, and rarely olfactory delusions.Case ReportIn this report we describe a patient complaining of vertigo caused by spontaneous rupture of dermoid cyst, preoperatively diagnosed by CT and MRI. Cranial CT revealed a dense fatty lesion adjacent to the posterolateral parasellar region on the left with multiple small, dense fat droplets scattered in the subarachnoid space corresponding to a dermoid cyst rupture. Cranial MRI sections revealed a lesion with mixed-signal-intensity and multiple hyperintense droplets scattered through the cerebellar surface on the left. No enhancement was found on axial T1-weighted MRI after intravenous Gadolinium administration. Diffusion weighted image (DWI) and apparent diffusion coefficient map studies exhibited explicit restricted diffusion.DiscussionMany studies and literature case reports concerning the rupture of dermoid cyst have been reported. However, multimodal imaging of this rare pathology in the same patient is uncommon. Although dermoid cysts are pathognomonic in appearance on a CT examination, the MRI is also of value in helping to understand the effect of extension and pressure of the mass. DWI is also important for support of the diagnosis and patient follow-up.

Magnetic resonance imaging and histology of ovine hip joint cartilage in two age populations: a sheep model with assumed healthy cartilage

To compare morphologically normal appearing cartilage in two age groups with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) and correlate magnetic resonance imaging (MRI) findings with histology. Twenty femoral head specimens collected from ten lambs (group I) and ten young adult sheep (group II) underwent dGEMRIC and histological assessment. A region of 2 cm(2) with morphologically normal-appearing cartilage was marked with a surgical suture for subsequent matching of MRI and histological sections. The MRI protocol included a three-dimensional (3D) double-echo steady-state sequence for morphological cartilage assessment, a B1 pre-scan with various flip angles for B1 field heterogeneity correction, and 3D volumetric interpolated breathhold examination for T1(Gd) mapping (dGEMRIC). Histological analysis was performed according to the Mankin scoring system. A total of 303 regions of interest (ROI; 101 MRI reformats matching 101 histological sections) was assessed. Twenty-six ROIs were excluded owing to morphologically apparent cartilage damage or insufficient MR image quality. Therefore, 277 ROIs were analyzed. Histological analyses revealed distinct degenerative changes in various cartilage samples of group II (young adult sheep). Corresponding T1(Gd) values were significantly lower in the group of sheep (mean T1(Gd) = 540.4 ms) compared with the group of lambs (mean T1(Gd) = 623.6 ms; p < 0.001). Although morphologically normal, distinct cartilage degeneration may be present in young adult sheep cartilage. dGEMRIC can reveal these changes and may be a tool for the assessment of early cartilage degeneration.

Effects of pneumoperitoneum and body position on the morphology of the caudal cava vein analyzed by MRI and plastinated sections

Pneumoperitoneum and patient positioning are essential factors during laparoscopic surgical procedures. They cause hemodynamic and anatomical changes in several abdominal organs among which the caudal cava vein (CCV) is involved. Hemodynamic changes in this vein (decreased venous return) have been described in the porcine model, but how the vein morphology and size is affected at different abdominal levels is unknown. We sought to assess the morphological and morphometrical changes in the CCV of the pig caused by pneumoperitoneum and the reverse Trendelenburg position by in vivo magnetic resonance imaging (MRI). Six pigs were scanned via MRI under four situations: S1, control (no pneumoperitoneum); S2, control in the reverse Trendelenburg position; S3, pneumoperitoneum (14 mmHg); and S4, pneumoperitoneum in the reverse Trendelenburg position. MRI and plastinated body sections were used to evaluate the topography, morphology and cross-sectional area of the CCV. Two portions of the CCV were differentiated: a prehepatic portion (located between the vertebral levels L1-T15) with flat and irregular morphology, and a hepatic portion (between T14-T11) that was almost rounded. The reverse Trendelenburg position caused an increase in the lumen affecting mainly the prehepatic portion, while pneumoperitoneum caused a decrease in the total vascular lumen, exerting a greater effect on the hepatic portion. The combination of both situations resulted in a further decrease in the vascular area and global morphological changes. The pneumoperitoneum and reverse Trendelenburg position caused morphological and morphometrical changes in the prehepatic and hepatic portions of the CCV, which should assist in gaining a better understanding of the hemodynamic changes described in the literature.

Prostate: Registration of Digital Histopathologic Images to in Vivo MR Images Acquired by Using Endorectal Receive Coil

To develop and evaluate a technique for the registration of in vivo prostate magnetic resonance (MR) images to digital histopathologic images by using image-guided specimen slicing based on strand-shaped fiducial markers relating specimen imaging to histopathologic examination. The study was approved by the institutional review board (the University of Western Ontario Health Sciences Research Ethics Board, London, Ontario, Canada), and written informed consent was obtained from all patients. This work proposed and evaluated a technique utilizing developed fiducial markers and real-time three-dimensional visualization in support of image guidance for ex vivo prostate specimen slicing parallel to the MR imaging planes prior to digitization, simplifying the registration process. Means, standard deviations, root-mean-square errors, and 95% confidence intervals are reported for all evaluated measurements. The slicing error was within the 2.2 mm thickness of the diagnostic-quality MR imaging sections, with a tissue block thickness standard deviation of 0.2 mm. Rigid registration provided negligible postregistration overlap of the smallest clinically important tumors (0.2 cm(3)) at histologic examination and MR imaging, whereas the tested nonrigid registration method yielded a mean target registration error of 1.1 mm and provided useful coregistration of such tumors. This method for the registration of prostate digital histopathologic images to in vivo MR images acquired by using an endorectal receive coil was sufficiently accurate for coregistering the smallest clinically important lesions with 95% confidence.

Methods for registration of magnetic resonance images of ex vivo prostate specimens with histology

To evaluate two methods of scanning and tissue processing to achieve accurate magnetic resonance (MR)-histologic correlation in human prostate specimens. Two prostates had acrylic paint markers injected to define the plane of imaging and serve as internal fiducials. Each was placed on a polycarbonate plane-finder device (PFD), which was adjusted to align the imaging and cutting planes. Three prostates were aligned by use of a plane finder key (PFK), a polycarbonate plate that locks the specimen in a cylindrical carrier. Markers were injected for registration analysis. Prostates were imaged, then sectioned. Imaging software was used to create registration maps of the MR and histology images. Measurements between control points were made and compared. Accurate correlation was achieved between MR and histologic images. The mean displacement (MD) between the corresponding registration points using the PFD technique ranged from 1.11-1.38 mm for each section. The MD for all sections was 1.24 mm. The MD using the PFK technique ranged from 0.79-1.01 mm for each section, and the MD across all sections for the PFK was 0.92 mm. We describe two methods that can achieve accurate, reproducible correlation between MR imaging and histologic sections in human prostatectomy specimens.

Multimodal wavelet embedding representation for data combination (MaWERiC): integrating magnetic resonance imaging and spectroscopy for prostate cancer detection

Recently, both Magnetic Resonance (MR) Imaging (MRI) and Spectroscopy (MRS) have emerged as promising tools for detection of prostate cancer (CaP). However, due to the inherent dimensionality differences in MR imaging and spectral information, quantitative integration of T(2) weighted MRI (T(2)w MRI) and MRS for improved CaP detection has been a major challenge. In this paper, we present a novel computerized decision support system called multimodal wavelet embedding representation for data combination (MaWERiC) that employs, (i) wavelet theory to extract 171 Haar wavelet features from MRS and 54 Gabor features from T(2)w MRI, (ii) dimensionality reduction to individually project wavelet features from MRS and T(2)w MRI into a common reduced Eigen vector space, and (iii), a random forest classifier for automated prostate cancer detection on a per voxel basis from combined 1.5 T in vivo MRI and MRS. A total of 36 1.5 T endorectal in vivo T(2)w MRI and MRS patient studies were evaluated per voxel by MaWERiC using a three-fold cross validation approach over 25 iterations. Ground truth for evaluation of results was obtained by an expert radiologist annotations of prostate cancer on a per voxel basis who compared each MRI section with corresponding ex vivo wholemount histology sections with the disease extent mapped out on histology. Results suggest that MaWERiC based MRS T(2)w meta-classifier (mean AUC, μ = 0.89 ± 0.02) significantly outperformed (i) a T(2)w MRI (using wavelet texture features) classifier (μ = 0.55 ± 0.02), (ii) a MRS (using metabolite ratios) classifier (μ = 0.77 ± 0.03), (iii) a decision fusion classifier obtained by combining individual T(2)w MRI and MRS classifier outputs (μ = 0.85 ± 0.03), and (iv) a data combination method involving a combination of metabolic MRS and MR signal intensity features (μ = 0.66 ± 0.02).

Normal Feline Brain: Clinical Anatomy Using Magnetic Resonance Imaging

The purpose of this study was to provide a clinical anatomy atlas of the feline brain using magnetic resonance imaging (MRI). Brains of twelve normal cats were imaged using a 1.5 T magnetic resonance unit and an inversion/recovery sequence (T1). Fourteen relevant MRI sections were chosen in transverse, dorsal, median and sagittal planes. Anatomic structures were identified and labelled using anatomical texts and Nomina Anatomica Veterinaria, sectioned specimen heads, and previously published articles. The MRI sections were stained according to the major embryological and anatomical subdivisions of the brain. The relevant anatomical structures seen on MRI will assist clinicians to better understand MR images and to relate this neuro-anatomy to clinical signs.

Elastic registration of multimodal prostate MRI and histology via multiattribute combined mutual information

By performing registration of preoperative multiprotocol in vivo magnetic resonance (MR) images of the prostate with corresponding whole-mount histology (WMH) sections from postoperative radical prostatectomy specimens, an accurate estimate of the spatial extent of prostate cancer (CaP) on in vivo MR imaging (MRI) can be retrospectively established. This could allow for definition of quantitative image-based disease signatures and lead to development of classifiers for disease detection on multiprotocol in vivo MRI. Automated registration of MR and WMH images of the prostate is complicated by dissimilar image intensities, acquisition artifacts, and nonlinear shape differences. The authors present a method for automated elastic registration of multiprotocol in vivo MRI and WMH sections of the prostate. The method, multiattribute combined mutual information (MACMI), leverages all available multiprotocol image data to drive image registration using a multivariate formulation of mutual information. Elastic registration using the multivariate MI formulation is demonstrated for 150 corresponding sets of prostate images from 25 patient studies with T2-weighted and dynamic-contrast enhanced MRI and 85 image sets from 15 studies with an additional functional apparent diffusion coefficient MRI series. Qualitative results of MACMI evaluation via visual inspection suggest that an accurate delineation of CaP extent on MRI is obtained. Results of quantitative evaluation on 150 clinical and 20 synthetic image sets indicate improved registration accuracy using MACMI compared to conventional pairwise mutual information-based approaches. The authors' approach to the registration of in vivo multiprotocol MRI and ex vivo WMH of the prostate using MACMI is unique, in that (1) information from all available image protocols is utilized to drive the registration with histology, (2) no additional, intermediate ex vivo radiology or gross histology images need be obtained in addition to the routinely acquired in vivo MRI series, and (3) no corresponding anatomical landmarks are required to be identified manually or automatically on the images.

Safe working zones using the minimally invasive lateral retroperitoneal transpsoas approach: a morphometric study

The minimally invasive lateral retroperitoneal transpsoas approach is a recent technique developed for lumbar interbody fusion and discectomy. The proximity of the retroperitoneal vessels and ventral nerve roots to the surgical pathway increases the risk of injury to these anatomical structures. A precise knowledge of the regional anatomy of the lumbar plexus is required for safe passage through the psoas muscle. Preoperative examination of the axial MRI images will allow the surgeon to observe the neural structures at the operative levels and confirm that abdominal vessels do not obstruct the lateral disc space. The objective of this study was to determine the anatomic position of the ventral nerve roots and the retroperitoneal vessels in relation to the vertebral body in the degenerative spine and to delineate a safe working zone using magnetic resonance imaging (MRI). We retrospectively evaluated lumbar spine MRI in 78 patients (from L1-L2 to L4-L5). The total number of lumbar vertebrae measured was 304 levels. Sagittal MRI sections were used to measure disc height (anterior, middle, posterior). Axial MRI sections were used to measure the sagittal and transversal vertebral endplate diameters, the overlap between ventral nerve roots and the posterior border of the lower endplate of the vertebral body, and the overlap between the retroperitoneal vessels and the anterior border of the lower endplate of the vertebral body. The safe zone was subsequently calculated. It was defined as the relative lower endplate vertebral body sagittal diameter that is anterior to the nerve root and is posterior to the retroperitoneal vessels. The safe working zone was 75.3% of the lower endplate of the vertebral body sagittal diameter at L1-L2, 59.5% at L2-L3, 51.9% at L3-L4 and 37.8% at L4-L5 levels. This area significantly decreases from L1-L2 to L4-L5 (p<0.05). Compared with L1-L2, L2-L3 levels, the more anterior position of the nerve root and the more posterior position of the retroperitoneal vessels at the L4-L5 level causes a significant reduction of this area. Compared with the L3-L4 level, we observed that the safe zone decrease was simply secondary to the more anterior position of the nerve roots at the L4-L5 level. Preoperative planning and safe zone delineation are a simple method to assess the relative position of neural and vascular anatomic structures in relation to the surgical area. This method can help spine surgeons to prevent perioperative complications.

A magnetic resonance spectroscopy driven initialization scheme for active shape model based prostate segmentation

Segmentation of the prostate boundary on clinical images is useful in a large number of applications including calculation of prostate volume pre- and post-treatment, to detect extra-capsular spread, and for creating patient-specific anatomical models. Manual segmentation of the prostate boundary is, however, time consuming and subject to inter- and intra-reader variability. T2-weighted (T2-w) magnetic resonance (MR) structural imaging (MRI) and MR spectroscopy (MRS) have recently emerged as promising modalities for detection of prostate cancer in vivo. MRS data consists of spectral signals measuring relative metabolic concentrations, and the metavoxels near the prostate have distinct spectral signals from metavoxels outside the prostate. Active Shape Models (ASM's) have become very popular segmentation methods for biomedical imagery. However, ASMs require careful initialization and are extremely sensitive to model initialization. The primary contribution of this paper is a scheme to automatically initialize an ASM for prostate segmentation on endorectal in vivo multi-protocol MRI via automated identification of MR spectra that lie within the prostate. A replicated clustering scheme is employed to distinguish prostatic from extra-prostatic MR spectra in the midgland. The spatial locations of the prostate spectra so identified are used as the initial ROI for a 2D ASM. The midgland initializations are used to define a ROI that is then scaled in 3D to cover the base and apex of the prostate. A multi-feature ASM employing statistical texture features is then used to drive the edge detection instead of just image intensity information alone. Quantitative comparison with another recent ASM initialization method by Cosio showed that our scheme resulted in a superior average segmentation performance on a total of 388 2D MRI sections obtained from 32 3D endorectal in vivo patient studies. Initialization of a 2D ASM via our MRS-based clustering scheme resulted in an average overlap accuracy (true positive ratio) of 0.60, while the scheme of Cosio yielded a corresponding average accuracy of 0.56 over 388 2D MR image sections. During an ASM segmentation, using no initialization resulted in an overlap of 0.53, using the Cosio based methodology resulted in an overlap of 0.60, and using the MRS-based methodology resulted in an overlap of 0.67, with a paired Student's t-test indicating statistical significance to a high degree for all results. We also show that the final ASM segmentation result is highly correlated (as high as 0.90) to the initialization scheme.

Evaluation of the two bundles of the anterior cruciate ligament with 1.5 tesla magnetic resonance imaging

Studies on the anatomy of the anterior cruciate ligament (ACL) have shown that the normal ACL consists of two functional bundles named as anteromedial (AM) and posterolateral (PL) bundles. In this study, we evaluated the AM and PL bundles of the ACL using 1.5 tesla magnetic resonance imaging (MRI), which is routinely used in clinical practice. The study included 150 patients (96 females, 54 males; mean age 33.4+/-11.6 years; range 18 to 59 years) who did not have any signs of ACL insufficiency and whose knees were examined by MRI for other reasons. Standard magnetic resonance images (77 right, 73 left) were evaluated independently by an orthopedist and a radiologist in terms of distinguishable ACL bundles. The angle between the ACL (and each bundle) and the tibial plateau was measured on sagittal and coronal sections. Arthroscopic surgery was performed in 64 patients (42.7%) for primary diagnoses and arthroscopic and MRI findings were compared. Magnetic resonance imaging showed an intact ACL in all the patients. The ACL was assessed as a single bundle in the axial, coronal, and sagittal planes in 93 patients (62%). A double-bundle appearance was noted in 57 patients (38%), involving all three planes in 14 patients (9.3%), axial and coronal planes in 41 patients (27.3%), coronal and sagittal planes in one patient (0.7%), and only coronal plane in one patient (0.7%). On MRI sections showing a single bundle ACL, the mean angle between the ACL and the tibial plateau was found as 55.3 degrees in the sagittal plane, and 70.3 degrees in the coronal plane. On sections with a double-bundle appearance, the mean angles between the AM bundle and the tibial plateau were 70.1 degrees and 55.1 degrees in the coronal and sagittal planes, respectively. The corresponding angles for the PL bundle were 81 degrees and 53.5 degrees . The incidence of double bundle ACL appearance in coronal, sagittal, and axial MRI sections was not influenced by sex and side (p>0.05). The number of bundles identified in each plane did not show a significant difference between the two observers (p>0.05). During arthroscopic surgery, both bundles were identified with normal integrity and function of the ACL in all the patients. Of these, MRI could depict a double-bundle appearance in one or more planes in only 42.2% of the patients. Even though standard 1.5 tesla MRI, routinely used in clinical practice, has a very high success rate in demonstrating the ACL, it can visualize the two-bundle structure only in about one-third of the patients.