Surface Coil Magnetic Resonance Imaging Research Articles

High-Q metasurface signal isolator for 1.5T surface coil magnetic resonance imaging on the go.

The combination of surface coils and metamaterials remarkably enhance magnetic resonance imaging (MRI) performance for significant local staging flexibility. However, due to the coupling in between, impeded signal-to-noise ratio (SNR) and low-contrast resolution, further hamper the future growth in clinical MRI. In this paper, we propose a high-Q metasurface decoupling isolator fueled by topological LC loops for 1.5T surface coil MRI system, increasing the magnetic field up to fivefold at 63.8 MHz. We have employed a polarization conversion mechanism to effectively eliminate the coupling between the MRI metamaterial and the radio frequency (RF) surface transmitter-receiver coils. Furthermore, a high-Q metasurface isolator was achieved by taking advantage of bound states in the continuum (BIC) for extremely high-resolution MRI and spectroscopy. An equivalent physical model of the miniaturized metasurface design was put forward through LC circuit analysis. This study opens up a promising route for the easy-to-use and portable surface coil MRI scanners.

Masquerading Superior Oblique Palsy

We evaluated patients with hypertropia compatible with a diagnosis of superior oblique (SO) palsy to ascertain whether the 3-step test (3ST) can distinguish SO atrophy characteristic of trochlear nerve pathology from masquerading conditions. Prospective cross-sectional study. In an academic practice, we performed quasi-coronal plane, surface coil magnetic resonance imaging in 83 patients clinically diagnosed with SO palsy. We evaluated alignment, SO cross-sectional area, SO contractility, and rectus muscle pulley positions. A total of 57 patients with mean age 39 years (SD = 21 years) had unilateral SO palsy manifested by SO atrophy (22 congenital and 35 acquired). There was normal SO size in 26 patients with an average age of 39 years (SD =16 years) considered masquerades (8 congenital and 18 acquired). Maximum palsied SO cross-section averaged 9.5 ± 3.8 mm2, less than 18.4 ± 3.9 mm2 contralaterally (P < 10-24). In masquerades, maximum hypertropic SO cross-section was 20.7 ± 3.1 mm2, which was not different from the hypotropic SO or the contralesional muscle in SO palsy. Head tilt testing in masquerades was indistinguishable from SO palsy. In SO palsy, central hypertropia averaged 13.2 ± 9.4Δ, increasing to 21.1 ± 14.0Δ in ipsilateral tilt, and decreasing to 4.3 ± 5.3Δ in contralateral tilt. In masquerades, central hypertropia averaged 13.1 ± 8.7Δ, and was 17.7 ± 11.1Δ in ipsilateral and decreasing to 4.9 ± 5.1Δ in contralateral tilt. Upright hypertropia was larger at 17.7 ± 9.9Δ in congenital than 12.0 ± 8.4Δ in acquired SO palsy (P = 0025) but was indistinguishable from congenital masquerades. Contractile change in SO cross-section was bilaterally similar in masquerades. Relevant coordinates of rectus pulleys were similar bilaterally in masquerades. The 3ST pattern characteristic of unilateral SO palsy may be mimicked in all respects by masquerades.

Cross-Sectional Soft-Tissue Composition and the Distribution of Blue Cutaneous Discoloration in the Lower Eyelid after Hyaluronic Acid Injection.

The soft-tissue composition of the eyelid varies from lateral to medial, in that the orbicularis area (in square millimeters) is greatest medially and least laterally, whereas the reverse is true for the preauricularis and postorbicularis fat. The purpose of this study was to describe the relative contribution of tissue types to the volume of the lower eyelid-midface junction. This is an observational cohort study of 11 subjects (20 eyes) without a history of orbital or periorbital surgery or abnormality. Quasi-sagittal surface coil magnetic resonance imaging scans in planes parallel to the long axis of each orbit were obtained during central gaze fixation. Measurements of the tissue area (in square millimeters) of the skin, preorbicularis fat, orbicularis, and postorbicularis fat were obtained in the center, medial, and lateral eyelid regions. Differences in tissue area across the eyelid were assessed. The segmental cross-sectional area and percentage of total segment represented by the orbicularis muscle increased from the lateral (9.4 mm; 21.8 percent) to the central (14.1 mm; 35.0 percent) and to the medial (18.5 mm; 47.0 percent) eyelid (p < 0.01). The inverse pattern was noted for both preorbicularis and postorbicularis fat, each occupying less area (in square millimeters) from lateral to medial (p < 0.01). Skin thickness did not vary significantly across the eyelid. The soft-tissue composition of the eyelid varies from lateral to medial in that the orbicularis increases in area, whereas the reverse is true for the preorbicularis and postorbicularis fat. This anatomical progression may help to explain the stereotypical location of blue discoloration in some patients after hyaluronic acid filler injection.

Prostate volume measured by magnetic resonance imaging is not a predictor of lower urinary tract symptoms.

Purpose:Prostate volume is frequently utilized to counsel patients presenting to family medicine physicians with voiding complaints. We evaluated the relation between International Prostate Symptom Score (IPSS) and prostate volume measured by phased-array surface coil magnetic resonance imaging (MRI).Methods:We performed an institutional review board (IRB)–approved retrospective study of all patients who received a prostate MRI between 2015 and 2017. Correlation between the overall IPSS, IPSS components, prostate volume stratified by prostate specific antigen (PSA) (<1.4 vs. ≥1.4 g/dL), and race (black vs. white) was examined.Results:In all, 592 patients had prostate MRIs performed between 2015 and 2017. Two hundred and twenty-nine of these patients had IPSS and prostate volume information available in their medical records. The mean age of the cohort was 64.67 (SD = ±7.82) and mean PSA was 7.75 (SD = ±8.3). The mean IPSS was 9.77 (SD ± 7.2), and mean prostate volume was 55.88 cubic cm (SD = ±38.9). The correlation coefficient between prostate volume and IPSS was 0.12789 (P = 0.05). The correlation between prostate volume and IPSS was also not significant in 128 men with prostate volume above 40 cubic cm. Stratifying analysis by race and PSA showed no significant correlation between volume and IPSS. Analysis of the correlation between the different dimension of prostate volume and IPSS revealed significant but weak associations.Conclusions:Even with more precise estimation with MRI, prostate volume does not predict obstruction complaints. This finding is of importance when treating males presenting with voiding dysfunction to primary care.

Decompensated Esophoria as a Benign Cause of Acquired Esotropia

To determine informative clinical and magnetic resonance imaging (MRI) characteristics of patients with symptomatic adult acquired, comitant esotropia due to decompensated esophoria. Retrospective, interventional case series. Setting: Institutional. Patients with decompensated esophoria who developed acute acquired comitant esotropia. Ophthalmic examination, stereopsis, and strabismus measurements at distance and near using prism cover tests in diagnostic gaze positions were performed. Patients underwent high-resolution surface coil MRI of extraocular muscles with target fixation, and MRI of the brain. Strabismus surgery was performed under topical anesthesia with adjustable sutures wherever possible. Paired t testing was used to evaluate postoperative changes with 0.05 considered significant. Clinical and MRI characteristics, and surgical outcome of patients with decompensated esophoria. Eight cases were identified involving subjects of mean age 29 ± 9.4 (range: 20-48) years having gradually progressive intermittent horizontal, binocular diplopia for 10months to 3 years. Mean preoperative esotropia was 31 ± 12 Δ at distance and 29 ± 12 Δ at near, although this was intermittent in 5 patients who exhibited enhanced fusional divergence. Neurologic evaluation and MRI of brain, orbits, and extraocular muscles were unremarkable in all cases. Orthotropia was successfully restored in all by standard or enhanced doses of bimedial rectus muscle recession surgery, improving mean stereoacuity from 535 to 68 arc seconds, although 5 patients exhibited 2-14 Δ asymptomatic residual esophoria. Decompensated esophoria is a benign clinical entity causing acute, acquired, comitant esotropia treatable with enhanced medial rectus recession.

Knobby Eye Syndrome

ABSTRACTIntroduction: A spherical globe is traditionally assumed, but this study employed magnetic resonance imaging (MRI) to demonstrate frequent occurrence of non-spherical staphylomata in strabismic patients.Methods: High-resolution, surface coil MRI was obtained in multiple image planes in 21 highly myopic subjects (36 eyes) and compared with 17 normal controls (33 eyes). Images were analyzed for axial length, aspect ratio of eye shape, and deflection of muscle paths.Results: All but two high myopes had strabismus. While myopic globes were generally spherical in 10 myopic eyes including both orthotropic subjects, 15 globes exhibited diffuse posterior staphylomata, 16 equatorial staphylomata, and 4 both posterior and equatorial staphylomata. Equatorial scleral ectasias were positioned to contact and elongate paths of horizontal rectus muscles in some gaze positions. Axial length in myopes averaged 28.8 ± 3.8 (SD) mm and did not differ significantly between regular vs. irregular staphylomata. Globe aspect ratios in the coronal, axial, and sagittal planes were significantly greater than normal in myopes (P < 0.005), but correlated significantly with axial length only in the axial and sagittal planes (P < 0.03). While myopes with irregular staphylomata were older at 57 ± 11 years than subjects with spherical globes at 24 ± 8 years (P < 0.0005), other clinical features were similar.Conclusion: Irregular equatorial or posterior staphylomata are common in strabismic axial high myopes, acting, like “cams” affixed to the normally spherical globe so that they may have no mechanical effect until rotating eccentrically against muscles. After rotational contact, staphylomata would nonlinearly increase muscle tension with further duction. Imaging may be clinically informative about this “knobby eye syndrome.”

Natural Orifice Transluminal Endoscopic Partial Prostatectomy: A Real-time Image-guided Focal Extirpative Feasibility Study

To assess the feasibility of focal endoscopic excision of prostate cancer (PCa) under guidance of real-time magnetic resonance imaging (MRI) or magnetic ultrasound fusion (MUF). Using a cadaveric model, multifocal PCa was simulated using 2 MRI-compatible fiducial markers. These were inserted transrectally and used to generate regions of interests (ROIs) on a 1.5-T surface-coil MRI. The first marker was placed in the right mid-peripheral zone (ROI 1), and the second marker was placed in the left seminal vesicle as a referent lesion for subsequent imaging. MRI of the specimen was then obtained. The radiologist created ROIs using fusion biopsy system at each marker. Two additional incidental ROIs were identified in the left transitional zone (ROI 2-suspicious for benign prostatic hyperplasia nodule) and in the right anterior peripheral zone (ROI 3-suspicious for PCa). Holmium laser enucleation of the transitional zone of the prostate was performed to gain access to the peripheral zone lesions. MUF was used during endoscopic laser excision to convey targeting accuracy. The cadaver was then reimaged to determine the adequacy of resection and examined for histopathologic correlation. Real-time MUF imaging identified the target lesions consistently at the locations designated as ROIs. Complete endoscopic resection of ROIs was possible. Repeated MUF imaging and the postprocedure MRI confirmed the completeness of resection. Pathologic examination demonstrated complete excision, intact neurovascular bundles, and posterior prostatic capsule. This approach may represent a new minimally invasive frontier for focal surgical resection of PCa, making histopathologic margin status determination possible.

Magnetic resonance imaging in dissociated strabismus complex demonstrates generalized hypertrophy of rectus extraocular muscles

Dissociated strabismus complex (DSC) is an enigmatic form of strabismus that includes dissociated vertical deviation (DVD) and dissociated horizontal deviation (DHD). We employed magnetic resonance imaging (MRI) to evaluate the extraocular muscles in DSC. We studied 5 patients with DSC and mean age of 25years (range, 12-42years), and 15 age-matched, orthotropic control subjects. All patients had DVD; 4 also had DHD. We employed high-resolution, surface coil MRI with thin, 2mm slices and central target fixation. Volumes of the rectus and superior oblique muscles in the region 12mm posterior to 4mm anterior to the globe-optic nerve junction were measured in quasi-coronal planes in central gaze. Patients with DSC had no structural abnormalities of rectus muscles or rectus pulleys or the superior oblique muscle but exhibited modest, statistically significant increased volume of all rectus muscles ranging from 20% for medial rectus to 9% for lateral rectus (P<0.05). DSC includes various combinations of sursumduction, excycloduction, and abduction not conforming to Hering's law. We have found modest generalized enlargement of all rectus muscles. DSC is associated with generalized rectus extraocular muscle hypertrophy in the absence of other orbital abnormalities.

Extraocular Muscle Compartments in Superior Oblique Palsy.

PurposeTo investigate changes in volumes of extraocular muscle (EOM) compartments in unilateral superior oblique (SO) palsy using magnetic resonance imaging (MRI).MethodsHigh-resolution, surface-coil MRI was obtained in 19 patients with unilateral SO palsy and 19 age-matched orthotropic control subjects. Rectus EOMs and the SO were divided into two anatomic compartments for volume analysis in patients with unilateral SO palsy, allowing comparison of total compartmental volumes versus controls. Medial and lateral compartmental volumes of the SO muscle were compared in patients with isotropic (round shape) versus anisotropic (elongated shape) SO atrophy.ResultsThe medial and lateral compartments of the ipsilesional SO muscles were equally atrophic in isotropic SO palsy, whereas the lateral compartment was significantly smaller than the medial in anisotropic SO palsy (P = 0.01). In contrast to the SO, there were no differential compartmental volume changes in rectus EOMs; however, there was significant total muscle hypertrophy in the ipsilesional inferior rectus (IR) and lateral rectus (LR) muscles and contralesional superior rectus (SR) muscles. Medial rectus (MR) volume was normal both ipsi- and contralesionally.ConclusionsA subset of patients with SO palsy exhibit selective atrophy of the lateral, predominantly vertically acting SO compartment. Superior oblique atrophy is associated with whole-muscle volume changes in the ipsilesional IR, ipsilesional LR, and contralesional SR; however, SO muscle atrophy is not associated with compartmentally selective volume changes in the rectus EOMs. Selective compartmental SO pathology may provide an anatomic mechanism that explains some of the variability in clinical presentations of SO palsy.

Rectus Extraocular Muscle Size and Pulley Location in Concomitant and Pattern Exotropia

To determine whether rectus extraocular muscle (EOM) sizes and pulley locations contribute to exotropia, we used magnetic resonance imaging (MRI) to measure these factors in normal control participants and in patients with concomitant and pattern exotropia. Prospective case-control study. Nine patients with concomitant exotropia, 6 patients with pattern exotropia, and 21 orthotropic normal control participants. High-resolution surface-coil MRI scans were obtained in contiguous, quasicoronal planes. Rectus pulley locations were determined in oculocentric coordinates for central gaze, supraduction, and infraduction. Cross sections in 4 contiguous image planes were summed and multiplied by the 2-mm slice thickness to obtain horizontal rectus posterior partial volumes (PPVs). Rectus pulley locations and horizontal rectus PPVs. Rectus pulleys were located differently in patients with A-pattern, versus V- and Y-pattern, exotropia. The lateral rectus (LR) pulleys were displaced significantly superiorly, the medial rectus (MR) pulleys were displaced inferiorly, and the inferior rectus pulleys were displaced laterally in A-pattern exotropia. However, the array of all rectus pulleys was excyclorotated in V- and Y-pattern exotropia. The PPV of the medial rectus muscle was statistically subnormal by approximately 29% in concomitant, but not pattern, exotropia (P < 0.05). The ratio of the PPV of the LR relative to the MR muscles in concomitant exotropia was significantly greater than in control participants and those with pattern exotropia (P < 0.05). Abnormalities of EOMs and pulleys contribute differently in pattern versus concomitant exotropia. Abnormal rectus pulley locations derange EOM pulling directions that contribute to pattern exotropia, but in concomitant exotropia, pulley locations are normal, and relatively small medial rectus size reduces relative adducting force.

Rectus Pulley Displacements without Abnormal Oblique Contractility Explain Strabismus in Superior Oblique Palsy

Using high-resolution magnetic resonance imaging (MRI), we investigated whether rectus pulleys are significantly displaced in superior oblique (SO) palsy and whether displacements account for strabismus patterns. Prospective case-control study. Twenty-four patients diagnosed with SO palsy based on atrophy of the SO muscle on MRI and 19 age-matched orthotropic control subjects. High-resolution, surface coil MRI scans were obtained in multiple, contiguous, quasicoronal planes during monocular central gaze fixation. Pulley locations in oculocentric coordinates in the following subgroups of patients with SO palsy were compared with normal results in subgroups of patients with SO palsy: unilateral versus bilateral, congenital versus acquired, and isotropic (round) versus anisotropic (elongated) SO atrophy. Expected effects of pulley displacements were modeled using Orbit 1.8 (Eidactics, San Francisco, CA) computational simulation. Rectus pulley positions and ocular torsion. Rectus pulleys typically were displaced in SO palsy. In unilateral SO palsy, on average the medial rectus (MR) pulley was displaced 1.1 mm superiorly, the superior rectus (SR) pulley was displaced 0.8 mm temporally, and the inferior rectus (IR) pulley was displaced 0.6 mm superiorly and 0.9 mm nasally from normal. Displacements were similar in bilateral SO palsy, with the SR pulley additionally displaced 0.9 mm superiorly. However, the lateral rectus pulley was not displaced in either unilateral or bilateral SO palsy. The SR and MR pulleys were displaced in congenital SO palsy, whereas the IR and MR pulleys were displaced in acquired palsy. Pulley positions did not differ between isotropic and anisotropic palsy or between patients with cyclotropia of less than 7° versus cyclotropia of 7° or more. Simulations predicted that the observed pulley displacements alone could cause patterns of incomitant strabismus typical of SO palsy, without requiring any abnormality of SO or inferior oblique strength. Rectus pulley displacements alone, without abnormal oblique muscle contractility, can createthe clinical patterns of incomitant strabismus in SO palsy. This finding supports accumulating evidencethat clinical binocular misalignment patterns are not reliable indicators of contractile function of the SO muscle. Ocular torsion does not correlate with and thus cannot account for pulley displacements in SO palsy.

Functional morphometry demonstrates extraocular muscle compartmental contraction during vertical gaze changes.

Anatomical studies demonstrate selective compartmental innervation of most human extraocular muscles (EOMs), suggesting the potential for differential compartmental control. This was supported by magnetic resonance imaging (MRI) demonstrating differential lateral rectus (LR) compartmental contraction during ocular counterrolling, differential medial rectus (MR) compartmental contraction during asymmetric convergence, and differential LR, inferior rectus (IR), and superior oblique (SO) compartmental contraction during vertical vergence. To ascertain possible differential compartmental EOM contraction during vertical ductions, surface coil MRI was performed over a range of target-controlled vertical gaze positions in 25 orbits of 13 normal volunteers. Cross-sectional areas and partial volumes of EOMs were analyzed in contiguous, quasi-coronal 2-mm image planes spanning origins to globe equator to determine morphometric features correlating best with contractility. Confirming and extending prior findings for horizontal EOMs during horizontal ductions, the percent change in posterior partial volume (PPV) of vertical EOMs from 8 to 14 mm posterior to the globe correlated best with vertical duction. EOMs were then divided into equal transverse compartments to evaluate the effect of vertical gaze on changes in PPV. Differential contractile changes were detected in the two compartments of the same EOM during infraduction for the IR medial vs. lateral (+4.4%, P = 0.03), LR inferior vs. superior (+4.0%, P = 0.0002), MR superior vs. inferior (-6.0%, P = 0.001), and SO lateral vs. medial (+9.7%, P = 0.007) compartments, with no differential contractile changes in the superior rectus. These findings suggest that differential compartmental activity occurs during normal vertical ductions. Thus all EOMs may contribute to cyclovertical actions.

Muscle path length in horizontal strabismus

Sarcomere adaptation has been proposed as a mechanism for the adjustment of rectus muscle length in regulating binocular alignment. The purpose of this study was to investigate whether horizontal rectus muscle paths have abnormal lengths in subjects with intermittent or alternating strabismus. High-resolution, surface coil magnetic resonance imaging was obtained in 2 mm thick axial planes in strabismic patients who had not undergone prior surgery and normal control subjects. The lengths of horizontal rectus muscle paths were measured digitally in central gaze for the fixating eye only and compared. A total of 12 strabismic subjects and 13 controls were included: 8 subjects had esotropia averaging 30(Δ), and 4 had exotropia averaging 47(Δ). The sample had 80% power to detect muscle path length changes of at least the typical surgical doses appropriate to strabismus surgery for correction of the mean deviations in each group, had such changes existed. Mean (± standard deviation) medial rectus path length was 35.0 ± 4.1 mm in controls, not significantly different from 36.3 ± 1.7 mm in exotropia (P = 0.56) or 35.8 ± 2.9 mm in esotropia (P = 0.62). Mean lateral rectus path length in controls was 35.7 ± 4.0 mm, not significantly different from the values of 39.6 ± 3.8 mm in exotropia (P = 0.09) and 37.8 ± 3.3 (P = 0.19) mm in esotropia. Horizontal rectus muscle path lengths are not significantly abnormal in commonly encountered intermittent or alternating esotropia and exotropia.

Surface coil in the magnetic resonance imaging of the orbital vessels anatomy

In this paper, we demonstrate a capability of surface coil magnetic resonance imaging in the review of orbital blood vessels anatomy. Surface coil allows a better detection of small anatomic structures including vessels such as ophtalmic artery and its branches, and also orbital veins, particularly superior and inferior ophtalmic veins with accompanying branches. The best results are obtained by the use of T1 sequences with short TE and TR.

Diagnostic accuracy of surface coil magnetic resonance imaging at 1.5 T for local staging of elevated risk prostate cancer

Introduction: Preoperative prostate cancer stage predicts prognosisand affects treatment decisions. The purpose of this study was toestimate the sensitivity and specificity of surface coil magneticresonance imaging (MRI) for prostate cancer stage using surgicalpathologic data as the reference standard.Methods: High-risk patients (≥cT3 or PSA ≥20 ng/mL or Gleason≥8) and selected intermediate-risk patients (clinically bulky diseaseon exam or biopsy, cT2b/c, or Gleason 7 with ≥3 of 5 biopsycores positive in a lobe) routinely received a pelvic MRI at ourinstitution. The images of identified patients were reviewed by oneradiologist who was blinded to clinical information. The radiologistreported presence or absence of tumour within each lobe of theprostate. Extraprostatic extension (EPE), seminal vesicle (SV) invasionand pelvic lymph node (PLN) metastasis were also reported.Radiological findings were compared with prostatectomy pathologyreports.Results: During the study period, about 320 radical prostatectomieswere performed. Of these, 32 had a preoperative surfacecoil pelvic MRI adequate for analysis. Pathologically, 53 of 64(82.8%) prostate lobes contained tumour, 17 (26.6%) lobes hadassociated EPE, 12 (18.8%) had SV involvement and 7 (10.9%) setsof PLNs contained cancer. Magnetic resonance imaging sensitivityand specificity were, respectively, 94.3% and 81.8% for tumourlocation, 82.4% and 87.2% for EPE, 83.3% and 92.3% for SVinvasion and 71.4% and 94.7% for PLN involvement.Interpretation: Surface coil MRI accurately stages many prostatecancer patients with elevated risk of extraprostatic disease. Thismode of imaging may be reasonable at centres that do not haveendorectal coil MRI.Introduction : Le stade du cancer de la prostate avant l’opérationpermet d’établir le pronostic et influe sur les décisions en ce quiconcerne le traitement. Notre étude avait pour objectif d’évaluer lasensibilité et la spécificité de l’imagerie par résonance magnétiqueavec bobine de surface dans l’établissement du stade du cancerde la prostate en utilisant les données pathologiques liées à lachirurgie comme données de référence.Méthodologie : Les patients à risque élevé (tumeur ≥cT3 ou tauxd’APS ≥20 ng/mL ou score de Gleason ≥ 8) et certains patients àrisque intermédiaire (maladie volumineuse sur le plan clinique lorsde l’examen ou à la biopsie, tumeur cT2b/c, ou score de Gleasonde 7 avec au moins 3 carottes biopsiques sur 5 prélevées dans lemême lobe qui soient positives) subissent un examen par IRM defaçon systématique à notre établissement. Les images des patientsinclus dans l’étude ont été examinées par un radiologiste à qui lesdonnées cliniques n’avaient pas été divulguées (examen à l’insu).Le radiologiste signalait la présence ou l’absence de tumeur danschaque lobe prostatique. On a aussi signalé des cas d’extensionextraprostatique, d’envahissement des vésicules séminales et demétastases touchant les ganglions lymphatiques pelviens. Lesobservations radiologiques ont été comparées aux résultats desrapports de pathologie suivant la prostatectomie.Résultats : Pendant l’étude, environ 320 prostatectomies radicalesont été réalisées. De ce nombre, 32 patients avaient subi une IRMpelvienne avec bobine de surface dont les données étaient analysables.À l’examen pathologique, 53 des 64 lobes prostatiques(82,8 %) présentaient du tissu tumoral, 17 lobes (26,6 %), uneextension extraprostatique associée, 12 (18,8 %), un envahissementdes vésicules séminales et 7 (10,9 %), des groupes de ganglionslymphatiques pelviens présentant des traces de cancer. La sensibilitéet la spécificité de l’IRM étaient respectivement, de 94,3 %et de 81,8 % pour l’emplacement de la tumeur, de 82,4 % et 87,2% pour les extensions extraprostatiques, de 83,3 % et 92,3 % pourles envahissements des vésicules séminales et de 71,4 % et 94,7 %pour l’atteinte des ganglions lymphatiques pelviens.Interprétation : L’IRM avec bobine de surface permet d’établir avecexactitude le stade du cancer de la prostate chez de nombreuxpatients présentant un risque accru de maladie extraprostatique.Cette technique d’imagerie pourrait représenter une méthode diagnostiqueraisonnable dans les centres qui ne disposent pas d’IRMavec bobine endorectale.

High-resolution magnetic resonance imaging of rotator cuff tears using a microscopy coil: noninvasive detection without intraarticular contrast material

The aim of this study was to evaluate the feasibility of high-resolution magnetic resonance imaging (MRI) using a microscopy coil for the diagnosis of rotator cuff tears by comparing the method to conventional MRI and MRI arthrography. A total of 68 shoulders were prospectively studied using a 1.5-T MRI unit. Conventional MRI scans were obtained with a surface coil and high-resolution MRI scans with a microscopy coil. MRI arthrography was performed in 28 shoulders using a surface coil. MRI evaluation of tears of rotator cuff tendons was compared with arthroscopic findings and surgical results. The surgery revealed 40 full-thickness tears, 13 partial-thickness tears, and 15 intact cuffs. In all, 35 (88%) full-thickness tears were correctly diagnosed on conventional MRI and 40 (100%) on high-resolution MRI. MR arthrography delineated 11 of 12 (92%) full-thickness tears. Altogether, 5 (38%) of the partial-thickness tears were detected on conventional MRI, and 12 (92%) were clearly demonstrated on high-resolution MRI. MRI arthrography depicted three (60%) of five partial-thickness tears. High-resolution MRI showed higher sensitivity than conventional MRI (P < 0.05) and had values equivalent to those of MRI arthrography for diagnosing partial-thickness tears. High-resolution MRI with a microscopy coil is a feasible, noninvasive technique for diagnosing rotator cuff tears.

A total variation based approach to correcting surface coil magnetic resonance images

Abstract Magnetic resonance images which are corrupted by noise and by smooth modulations are corrected using a variational formulation incorporating a total variation like penalty for the image and a high order penalty for the modulation. The optimality system is derived and numerically discretized. The cost functional used is non-convex, but it possesses a bilinear structure which allows the ambiguity among solutions to be resolved technically by regularization and practically by normalizing the maximum value of the modulation. Since the cost is convex in each single argument, convex analysis is used to formulate the optimality condition for the image in terms of a primal–dual system. To solve the optimality system, a nonlinear Gauss–Seidel outer iteration is used in which the cost is minimized with respect to one variable after the other using an inner generalized Newton iteration. Favorable computational results are shown for artificial phantoms as well as for realistic magnetic resonance images. Reported computational times demonstrate the feasibility of the approach in practice.

3-T MRI with phased-array surface coil in the local staging of rectal cancer

This study sought to evaluate the diagnostic accuracy of surface-coil 3T magnetic resonance (MR) imaging in the preoperative study of patients with rectal cancer. Thirty patients with histologically proven rectal cancer underwent surface-coil 3T MR imaging with sagittal, paracoronal and para-axial T2-weighted turbo spin echo (TSE) sequences. Slice thickness was 3 mm without gap, field of view 24 cm, matrix 400 × 512. Images were assessed for infiltration of the rectal wall, perirectal fat and pelvic structures. Tumours were staged according to the TNM system, and the MR imaging results were correlated with histopathology. In the patients who underwent MR imaging before and after radiotherapy (group 1), the diagnostic accuracy of 3T MR imaging was 88% for T2, 94% for T3 and 88% for T4 cancers. In those who underwent surgical treatment without preoperative radiotherapy (group 2), the diagnostic accuracy was 90% for T2, 87% for T3 and 87% for T4 cancers. The high signal-to-noise ratio coupled with a large field of view enables surface-coil 3T MR imaging to achieve high levels of diagnostic accuracy in the local staging of rectal cancer, and in particular in assessing infiltration of mesorectum and mesorectal fascia.

Diagnostic accuracy of surface coil magnetic resonance imaging at 1.5 T for local staging of elevated risk prostate cancer

Preoperative prostate cancer stage predicts prognosis and affects treatment decisions. The purpose of this study was to estimate the sensitivity and specificity of surface coil magnetic resonance imaging (MRI) for prostate cancer stage using surgical pathologic data as the reference standard. High-risk patients (>/=cT3 or PSA >/=20 ng/mL or Gleason >/=8) and selected intermediate-risk patients (clinically bulky disease on exam or biopsy, cT2b/c, or Gleason 7 with >/=3 of 5 biopsy cores positive in a lobe) routinely received a pelvic MRI at our institution. The images of identified patients were reviewed by one radiologist who was blinded to clinical information. The radiologist reported presence or absence of tumour within each lobe of the prostate. Extraprostatic extension (EPE), seminal vesicle (SV) invasion and pelvic lymph node (PLN) metastasis were also reported. Radiological findings were compared with prostatectomy pathology reports. During the study period, about 320 radical prostatectomies were performed. Of these, 32 had a preoperative surface coil pelvic MRI adequate for analysis. Pathologically, 53 of 64 (82.8%) prostate lobes contained tumour, 17 (26.6%) lobes had associated EPE, 12 (18.8%) had SV involvement and 7 (10.9%) sets of PLNs contained cancer. Magnetic resonance imaging sensitivity and specificity were, respectively, 94.3% and 81.8% for tumour location, 82.4% and 87.2% for EPE, 83.3% and 92.3% for SV invasion and 71.4% and 94.7% for PLN involvement. Surface coil MRI accurately stages many prostate cancer patients with elevated risk of extraprostatic disease. This mode of imaging may be reasonable at centres that do not have endorectal coil MRI.

Bilateral Abnormalities of Optic Nerve Size and Eye Shape in Unilateral Amblyopia

To evaluate the optic nerve (ON) size and globe shape in amblyopic eyes using high-resolution magnetic resonance imaging (MRI) and to compare these values with those of the sound fellow eye and of normal control eyes. Prospective case-control study. Thirty-four amblyopic patients and 60 normal control patients were evaluated using surface coil MRI. Retrobulbar ON cross-section, maximum globe cross-section, globe noncircularity (globe major axis/minor axis), axial length (AL), and the ratio of AL to ON (AL/ON) were measured. Corrected logarithm of the minimum angle of resolution acuity of all 34 amblyopic eyes averaged 0.43 +/- 0.30. The mean retrobulbar ON cross-section was 9.7 +/- 2.4 mm(2), 9.5 +/- 2.3 mm(2), and 10.7 +/- 2.6 mm(2) for amblyopic, fellow, and normal ONs, respectively. Although amblyopic and fellow ONs had similar cross-sections, both were significantly (P = .02) subnormal. AL/ON was 2.7 +/- 1.2 mm(-1), 2.7 +/- 1.0 mm(-1), and 2.3 +/- 0.5 mm(-1), respectively. Although AL/ON significantly exceeded normal in amblyopic eyes (P = .01), there was no significant difference between amblyopic and fellow eyes. Globe noncircularity of amblyopic eyes (1.17 +/- 0.07; P = .002) and fellow eyes (1.15 +/- 0.04; P < .001) was significantly greater than that of control eyes (1.11 +/- 0.04), but amblyopic and fellow eyes did not differ significantly. Unilateral amblyopia is associated with bilaterally, but also with subclinically hypoplastic ONs, greater than normal AL/ON, and abnormally noncircular globe cross-section. These factors evidently do not determine which of the 2 eyes will become amblyopic. Reduced circularity of amblyopic and fellow eyes may reflect optical causes of amblyopia or bilateral dysregulation of globe shape secondary to amblyopia.