Surface Coil Magnetic Resonance 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.

Can Binocular Alignment Distinguish Hypertropia in Sagging Eye Syndrome From Superior Oblique Palsy?

PurposeAlthough the three-step test (3ST) is typically used to diagnose superior oblique palsy (SOP), sagging eye syndrome (SES) has clinical similarities. We sought to determine if alignment measurements can distinguish unilateral SOP from hypertropia in SES.MethodsWe studied hypertropic subjects who underwent surface-coil magnetic resonance imaging (MRI) demonstrating either SO cross-section reduction indicative of congenital or acquired palsy (SOP group) or lateral rectus muscle sag (SES group). Alignment was measured by Hess screen and prism-cover testing. Multiple supervised machine learning methods were employed to evaluate diagnostic accuracy. Rectus pulley coordinates were determined in SES cases fulfilling the 3ST.ResultsTwenty-three subjects had unilateral SOP manifested by SO atrophy. Eighteen others had normal SO size but MRI findings of SES. Maximum cross-section of the palsied SO was much smaller than contralaterally and in SES (P < 2 × 10−5). Inferior oblique cross-sections were similar in SOP and SES. In both SOP and SES, hypertropia increased in contralateral and decreased in ipsilateral gaze and was greater in ipsilateral than contralateral head tilt. In SES, nine subjects (50%) fulfilled the 3ST and had greater infraplacement of the lateral than medial rectus pulleys in the hypotropic orbit. Supervised machine learning of alignment data distinguished the diagnoses with areas under the receiver operating curves up to 0.93, representing excellent yet imperfect differential diagnosis.ConclusionsBecause the 3ST is often positive in SES, clinical alignment patterns may confound SES with unilateral SOP, particularly acquired SOP. Machine learning substantially but imperfectly improves classification accuracy.

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.

Two-dimensional spatial distributions of the water content of the membrane electrode assembly and the electric current generated in a polymer electrolyte fuel cell measured by 49 nuclear magnetic resonance surface coils: Dependence on gas flow rate and relative humidity of supplied gases

A PEFC (polymer electrolyte fuel cell) with a large power generation area of 140 mm × 160 mm has spatial distributions of the water content of the MEA (membrane electrode assembly) and the electric current produced that depend on the flow rate and relative humidity of the supplied gas. When 49 NMR (nuclear magnetic resonance) surface coils arranged in 7 rows × 7 columns were inserted into the PEFC, two-dimensional spatial distributions of the water content of the MEA and the electric current could be measured from the acquired NMR signals. The water content of the MEA was calculated from the intensity of the NMR signal, and the electric current distribution was determined by an inverse analysis that reproduces the spatial distribution of the resonance frequency of the NMR signals. The PEFC, which was supplied with hydrogen and oxygen at a high humidity of 80 %RH, generated electric power at 130 A over the whole area of the MEA. On the other hand, under a low humidity of 40 %RH and low flow rate conditions, the water content of the MEA became high in the midstream and downstream regions, and a high electric current was generated in these regions.

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.

Co-Registration of Bioluminescence Tomography, Computed Tomography, and Magnetic Resonance Imaging for Multimodal In Vivo Stem Cell Tracking.

We present a practical approach for coregistration of bioluminescence tomography (BLT), computed tomography (CT), and magnetic resonance (MR) images. For this, we developed a customized animal shuttle composed of nonfluorescent, MR-compatible Delrin plastic that fits a commercially available MR surface coil. Mouse embryonic stem cells were transfected with the luciferase gene and labeled with superparamagnetic iron oxide nanoparticles. Cells were stereotaxically implanted in the mouse brain and imaged weekly for 4 weeks with bioluminescent imaging (IVIS Spectrum CT scanner) and magnetic resonance imaging (MRI; 11.7 T horizontal bore scanner). Without the use of software coregistration, in vitro phantom studies yielded root-mean-square errors of 7.6 × 10−3, 0.93 mm, and 0.78 mm along the medial–lateral (ML), dorsal–ventral (DV), and anterior–posterior (AP) axes, respectively. Rotation errors were negligible. Software coregistration by translation along the DV and AP axes resulted in consistent agreement between the CT and MR images, without the need for rotation or warping. In vivo coregistered BLT/MRI mouse brain data sets showed a single diffuse region of bioluminescent imaging photon signal and MRI hypointensity. Over time, the transplanted cells formed tumors as histopathologically validated. Disagreement between BLT and MRI tumor location was greatest along the DV axis (1.4 ± 0.2 mm) than along the ML (0.5 ± 0.3 mm) and the AP axes (0.6 mm) because of the uncertainty of the depth of origin of the BLT signal. Combining the high spatial anatomical information of MRI with the cell viability/proliferation data from BLT should facilitate preclinical evaluation of novel therapeutic candidate stem cells.

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.

3.0-T MR Imaging of Intracoronary Local Delivery of Motexafin Gadolinium into Coronary Artery Walls

To develop a technique with clinical 3.0-T magnetic resonance (MR) imaging to delineate local contrast agent distribution in coronary artery walls for potential molecular MR imaging-guided local gene or drug therapy of atherosclerotic coronary artery disease. This animal protocol was approved by the institutional animal care and use committee and was in compliance with the Guide for the Care and Use of Laboratory Animals. For in vitro confirmation, human arterial smooth muscle cells (SMCs) were used to determine capability of SMCs in uptake of motexafin gadolinium (MGd) and its optimal dose. For ex vivo evaluation, a 2-mL mixture of MGd and trypan blue was locally infused into coronary artery walls of six cadaveric pig hearts with MR monitoring and an MR imaging guidewire, surface coils, or both. For in vivo validation, the balloon catheter was placed into coronary arteries of seven living pigs, and the MGd and trypan blue mixture was infused into arterial walls with MR guidance. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of coronary artery walls were recorded by using different coils between pre- and postcontrast infusion, with subsequent histologic confirmation. Paired Student t tests were used to compare average SNRs and CNRs of arterial walls before and after contrast agent infusion with different coils. SMCs could take up MGd with the optimal concentration at 150 µmol/L. Average SNR with the MR imaging guidewire and surface coil combination was significantly higher than that with the MR imaging guidewire only or with surface coils only (P < .05), and average SNR and CNR of postinfusion MR imaging was significantly higher than that of preinfusion MR imaging (P < .05). Histologic analysis was used to confirm successful intracoronary infiltration of MGd and trypan blue within coronary artery walls. MR imaging can be used to delineate locally infused contrast agent distribution in coronary artery walls. This establishes groundwork for development of molecular MR imaging-guided intracoronary therapy.

Anatomic Distribution of Gadolinium Contrast Medium by High-Resolution Magnetic Resonance Imaging After Peribulbar and Retrobulbar Injections

To examine the anatomic distribution of gadolinium contrast medium by high-resolution surface-coil magnetic resonance imaging after peribulbar and retrobulbar injection. Comparative case series in which 4 healthy volunteers were randomized to peribulbar (n = 2) or retrobulbar (n = 2) injection of gadolinium and lidocaine hydrochloride, 2%, without epinephrine. Magnetic resonance imaging was performed before injection and at 5 minutes and 90 minutes after injection. The peribulbar injection technique resulted in contrast medium primarily in the extraconal space, with no gadolinium observed at the orbital apex; surprisingly, a small amount of contrast medium was observed in the pterygopalatine fossa immediately after peribulbar injection. The retrobulbar injection technique resulted in gadolinium signal diffusely enhancing the intraconal space, orbital apex, optic nerve sheath, and optic canal. The signal intensity was clearly observed in the cavernous sinus surrounding the cavernous portion of the internal carotid artery. A small amount of contrast medium was detected in the pterygopalatine fossa. The retrobulbar injection technique localizes to the intraconal space, with access to intracranial and central nervous system structures via the optic canal, superior orbital fissure, and cavernous sinus. In contrast, the peribulbar injection technique produces a mostly extraconal distribution; however, intraconal solution may communicate with the central nervous system via the inferior orbital fissure and pterygopalatine fossa. This novel finding suggests that peribulbar anesthesia has a readily accessible route for central nervous system toxic effects. Magnetic resonance imaging with gadolinium contrast medium administration provides an important methodological advantage over previously described techniques and is a safe, reproducible, and superior method of orbital imaging.

The effect of MR surface coils on PET quantification in whole-body PET/MR: Results from a pseudo-PET/MR phantom study

The use of magnetic resonance (MR) radiofrequency (RF) surface coils is a prerequisite for high-quality positron emission tomography (PET)/MR imaging. In lack of in-gantry transmission (TX) sources, the exact position of the RF coils is unknown in PET/MR, and may, therefore, lead to false attenuation correction (AC) of the emission (EM) data. The authors assess lesion and background quantification in AC-PET by mimicking different PET/MR imaging situations using a whole-body (WB) PET-only tomograph. Phantom experiments were performed on a PET tomograph with 68 Ge-rod TX sources. First, a 15-cm plastic cylinder was filled uniformly with [18F]-FDG to simulate a head study. Second, a NEMA NU-2001 image quality phantom (35 x 25 x 25 cm3) was filled uniformly with [18F]-FDG to simulate torso imaging. The phantom contained six lesions (10-38 mm diameter, lesion-to-background ratio 6:1) centred around a 5 cm diameter lung insert. EM and TX measurements were acquired with and without MR head (cylinder) and surface (NU-2001 phantom) RF coils in place. The following imaging situations were mimicked in both head and torso phantom studies: (1) PET scan without MR coils in EM and TX for reference, (2) PET scan with coils in both EM and TX, and (3) PET scan with coils in EM but without coils in TX. Two more set-ups were performed for the torso phantom: (4) PET scan with coils in EM only and phantom shifted slightly compared to (3), and (5) PET scan with coils in EM and TX following local displacement of the surface coils. PET EM data (1)-(4) were corrected for attenuation and scatter using cold TX data. Imaging situations (1)-(3) were repeated with the cylinder phantom and head coil in a combined PET/MR prototype system employing template-based AC. Head phantom: In case the MR head coils were not accounted for during AC (3), central and peripheral background activity concentration was underestimated by 13%-19% when compared to the reference setup (1). The effects of MR coil omission during AC was replicated in the repeat study with the combined PET/MR prototype. Torso phantom: All lesions were equally visible on all AC-PET images. The effects of disregarding MR surface RF coils during AC [(3) vs (1)] were 4%, or less. A slightly higher bias was observed when accounting for the RF surface coils that were shifted between EM and TX (5). The effect of coil misalignment and neglect during AC on the quantification of the simulated lungs was insignificant compared to the noise levels in AC-PET. Unaccounted attenuation from MR surface coils causes a regional bias of AC-PET data in body regions near the MR coils. Bias of central regions was more noticeable in smaller-size objects. In torso studies with body surface coils, the visibility of central lesions on PET was unaffected by MR coils following incomplete AC. Coil misalignment of several cm between emission and attenuation images causes an error that was comparable to that arising from unaccounted MR coil attenuation but small compared to the average standard deviation of the activity concentration levels.

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.

Evaluation of correction methods for coil‐induced intensity inhomogeneities and their influence on trabecular bone structure parameters from MR images

Magnetic resonance (MR) imaging-based quantitative trabecular bone structure analysis has gained increasing interest in osteoporotic fracture risk assessment and treatment evaluation related to osteoporosis. In vivo MR images of anatomic regions such as the proximal femur and distal tibia are generally acquired with a surface coil in order to obtain sufficient sensitivity and resolution for quantification of the trabeculae. However, these coils introduce intensity inhomogeneities which affect the trabecular bone structure analysis. This work evaluates the applicability of a fully automatic coil correction by nonparametric nonuniform intensity normalization (N3) in the analysis of trabecular bone parameters. The ability to correct for coil-induced intensity inhomogeneity was evaluated ex vivo on proximal femur specimens scanned with both a surface coil and a volume coil, which allowed for a direct evaluation of the performance of the coil correction methods without any major confounding factors. In addition, trabecular bone parameter values were correlated with values from high-resolution peripheral computed tomography (HR-pQCT) scans, and the reproducibility of trabecular bone parameters was evaluated in an in vivo study of repeat hip MR scans. The trabecular bone parameters determined from MR surface coil scans processed with the N3 coil correction method showed significant correlation (p < 0.05) with corresponding values from homogeneous intensity data in the ex vivo study. This can be compared to the correlation without coil correction (p < 0.5), and coil correction using low-pass filtering (LPF) (p < 0.53). The in vivo interscan variability was reduced from 8.9% to 12.8% using LPF-based to 3.6%-8.4% (CV) using N3 coil correction; hence the results showed that N3 is advantageous to LPF-based coil correction. No significant differences in correlation to HR-pQCT data were found for the coil correction methods. The significant correlations with volume coil data and high reproducibility of the N3 processed data imply that N3 coil correction preserve image information while accurately correcting for coil-induced intensity inhomogeneities, which makes it suitable for quantitative analysis of trabecular bone structure from MR images acquired with surface coils.

Urethral diverticula: A review and an update

Likely originating from the periurethral glands, female urethral diverticula (UD) are an uncommon but fascinating clinical entity. UD are variable in their presentation and the diagnosis is sometimes difficult and delayed. Modern imaging modalities such as surface coil and endoluminal magnetic resonance imaging (MRI) have added to the diagnostic armamentarium but have also furthered our understanding of UD. Accurate preoperative characterization of the often complex anatomical patterns seen on these imaging studies including saddlebag and circumferential urethral involvement, as well as complete evaluation of associated voiding dysfunction such as complete evaluation of associated voiding dysfunction such as urinary incontinence often impacts contemporary surgical management.

Advances in imaging head and neck tumours

The intention of this article is to review the recently published studies summarizing new developments in medical imaging for head and neck tumours. Recent technological improvements in imaging have modified the diagnostic approach to these tumours. The main trends can be summarized as follows: improvement in resolution owing to the detection and study of smaller lesions (achieved with magnetic resonance surface coils and parallel imaging); acceleration of data acquisition thus achieving high-quality vascular imaging; improvement in data manipulation and fusion techniques with metabolic imaging from positron emission tomography scanners, permitting more accurate delineation of target volumes for new radiation therapy techniques. In addition, new techniques are emerging leading to a switch from purely anatomical imaging to more functional or metabolic techniques, including dynamic contrast-enhanced approaches to studying tumour perfusion and vascularization, magnetic resonance spectroscopic techniques to assess tissue metabolites, and magnetic resonance diffusion techniques to evaluate free water motion and interstitial space. Finally, new contrast agents have been developed to detect and characterize metastatic lymph nodes, even when they do not match the classical size criteria.

Preoperative Staging of Rectal Cancer with MR Imaging: Correlation with Surgical and Histopathologic Findings

Rectal cancer is a common malignancy that continues to have a highly variable outcome, with local pelvic recurrence after surgical resection usually leading to incurable disease. The success of tumor excision depends largely upon accurate tumor staging and appropriate surgical technique, although the results of recent surgical trials indicate that evaluation of the involvement of the mesorectal fat and mesorectal fascia is even more important than T staging for treatment planning. Magnetic resonance (MR) imaging is increasingly being used to evaluate tumor resectability in patients with rectal cancer and to determine which patients can be treated with surgery alone and which will require radiation therapy to promote tumor regression. High-spatial-resolution MR imaging has proved useful in clarifying the relationship between a tumor and the mesorectal fascia, which represents the circumferential resection margin at total mesorectal excision. Phased-array surface coil MR imaging in particular plays a vital role in the therapeutic management of rectal cancer. At present, phased-array MR imaging best fulfills the clinical requirements for preoperative staging of rectal cancer. However, preoperative evaluation of the other prognostic factor, nodal status, is still problematic, and further studies will be needed to better define the role of MR imaging in this context.