Normal MR Research Articles

NORMAL MR ANATOMY AND TECHNIQUES FOR IMAGING OF THE MALE PELVIS

MR imaging has enhanced our ability to evaluate anatomic and pathologic processes in the male pelvis. Its remarkable soft-tissue contrast provides a unique depiction of the internal anatomy of the pelvic organs. Coupled with this superior soft-tissue characterization, its multiplanar capacity allows for greater depiction of tumor extension and staging. This article discusses some general MR techniques and concepts about MR imaging of the male pelvis and the normal MR anatomy and specific MR imaging techniques regarding each of the male pelvic organs.

The peripharyngeal space: Anatomy and normal CT and MR images (In French) : Kahn JL, Bourjat P (Institut d'Anatomie Normale, Hôpital Central, CHU,BP 426, F-67091 Strasbourg Cedex, France). J Radiol 1996;77:87–97

The peripharyngeal space: Anatomy and normal CT and MR images (In French) : Kahn JL, Bourjat P (Institut d'Anatomie Normale, Hôpital Central, CHU,BP 426, F-67091 Strasbourg Cedex, France). J Radiol 1996;77:87–97

Physiologic functional imaging in “functional” visual loss

Neuroimaging with nuclear medicine techniques permits assessment of brain function by measurement of metabolism or blood flow. Such studies complement the anatomic information derived from computed tomography (CT) or magnetic resonance imaging (MRI). We describe two patients with occipital lesions who were initially diagnosed with functional visual loss. Neither CT scan nor MRI adequately demonstrated the source of visual dysfunction; however, single proton emmission tomography (SPECT) scanning in a patient with carbon monoxide poisoning and positron emission tomography (PET) scanning in a patient with post-hypoxic delayed encephalopathy were helpful in confirming the organic substrate of their visual impairment. Functional imaging techniques such as SPECT and PET should be considered in patients with suspected cortical visual loss and normal CT or MR scans.

Normal changes in the MR appearance of the spleen during early childhood.

During the first year of life, the spleen undergoes histologic changes as the lymphoproliferative system matures. The purposes of this study were to describe the normal MR appearance of the spleen during infancy and early childhood and to correlate imaging findings with age-related histologic changes. The spleen was evaluated on 28 abdominal MR studies obtained during the first 23 months of life. Splenic signal intensity was compared to that of the liver. Selected autopsy specimens were compared with the imaging results. The T2-weighted signal intensity of the spleen gradually increased from isointense to hypointense relative to the liver during the first week of life to moderately hyperintense to the liver by 8 months of age. T1-weighted splenic signal intensity gradually decreased. These findings corresponded to histological increases in white-pulp-red-pulp ratios. Before the lymphoid system completely matures, the T2-weighted signal intensity of the normal neonatal spleen appears decreased compared with the moderately hyperintense splenic signal seen in older children and adults. This finding should not be mistaken for disease.

Evaluation of appropriateness of paediatric admission.

<h3>BACKGROUND AND PURPOSE:</h3> The lateral rectus–superior rectus band is an orbital connective tissue structure that has been implicated in a form of strabismus termed sagging eye syndrome. Our purpose was to define the normal MR imaging and CT appearance of this band in patients without strabismus. <h3>MATERIALS AND METHODS:</h3> Orbital MR imaging and CT examinations in 100 consecutive patients without strabismus were evaluated. Readers graded the visibility of the lateral rectus–superior rectus band on coronal T1WI, coronal STIR, and coronal CT images. Readers determined whether the band demonstrated superotemporal bowing or any discontinuities and whether a distinct lateral levator aponeurosis was seen. Reader agreement was assessed by κ coefficients. Association between imaging metrics and patient age/sex was calculated by using the Fisher exact test. <h3>RESULTS:</h3> The lateral rectus–superior rectus band was visible in 95% of coronal T1WI, 68% of coronal STIR sequences, and 70% of coronal CT scans. Ninety-five percent of these bands were seen as a continuous, arc-like structure extending from the superior rectus/levator palpebrae muscle complex to the lateral rectus muscle; 24% demonstrated superotemporal bowing; and in 82% of orbits, a distinct lateral levator aponeurosis was visible. Increasing patient age was negatively associated with lateral rectus–superior rectus band visibility (<i>P</i> = .03), positively associated with lateral rectus–superior rectus band superotemporal bowing (<i>P</i> = .03), and positively associated with lateral levator aponeurosis visibility (<i>P</i> = .01). <h3>CONCLUSIONS:</h3> The lateral rectus–superior rectus band is visible in most patients without strabismus on coronal T1WI. The age effect with respect to its visibility and superotemporal bowing could represent age-related connective tissue degeneration.

Posterior intermalleolar ligament of the ankle: normal anatomy and MR imaging features.

The purposes of this study were to delineate the normal anatomy and MR imaging features of the posterior intermalleolar ligament--a normal ligamentous variant of the posterior portion of the ankle--and to identify normal anatomic characteristics that may account for the role of the ligament in the development of posterior impingement syndrome. The prevalence, size, and shape of the posterior intermalleolar ligament were documented in 36 cadaveric ankles and in 97 MR studies of the ankle in patients with and without symptoms. The posterior intermalleolar ligament was identified in 20 (56%) of the 36 cadaveric feet. It was 1-8 mm wide, and its diameter (anterior to posterior) was 5-8 mm. The ligament often resembled a meniscus, and in one case its anterior lip herniated into the ankle joint. The posterior intermalleolar ligament was detected in 18 (19%) of the 97 MR studies of the ankle. It was visualized on coronal T1- or T2-weighted images as a distinct, hypointense band traversing between the posterior talofibular ligament and the inferior transverse ligament. The posterior intermalleolar ligament is a normal variant of the posterior ligaments of the ankle and is present in a significant number of persons. It is best seen on coronal T1- and T2-weighted MR images. Its meniscuslike shape and occasional extension into the ankle joint may account for the development of posterior impingement syndrome in susceptible persons.

Low field mari and scaphoid fracture

18 consecutive patients suspected of and treated for an acute scaphoid fracture were examined by lowfield MRI. This showed 11 fractures while seven scaphoids were considered normal. T1 weighted images showed a fracture as an area of decreased signal intensity. Two radiologically obvious fractures produced normal MR images. These fractures proved to be the result of old trauma. A wide spectrum of additional traumatic lesions in the wrists, not detected by routine X-ray analysis, were also demonstrated. These included seven fragmented triangular fibrocartilages (TFC), torn scapho-lunate ligaments in four cases and one torn triquetro-lunate ligament. Bone bruises of other carpal bones and seven other carpal fractures were also detected. Low field MRI can be used to show scaphoid fractures and allows diagnosis of additional or simulating lesions.

Imaging of the postoperative neck with emphasis on surgical flaps and their complications.

Radiologists are playing an increasingly important role in the management of patients with head and neck cancer. Imaging is often essential in preoperative planning. It is therefore imperative for the radiologist to be familiar with the wide variety of surgical procedures used as well as the normal CT and MR imaging appearance after such procedures. In addition, familiarity with the appearance of tumor recurrence and postoperative complications is essential. This pictorial essay illustrates the appearance of the normal and abnormal postoperative neck on CT scans and MR images, with an emphasis on reconstructive flaps. Postoperative complications evident on imaging studies are depicted, as is the appearance of tumor recurrence. One lymph node classification system is briefly reviewed as a basis for discussion of neck dissection and other surgical procedures.

Normal bone marrow in the sacrum of young adults: differences between the sexes seen on chemical-shift MR imaging.

Age-related changes in the distribution of fatty and nonfatty bone marrow in the pelvis and femur are well recognized. However, mapping not only of age-related MR appearance of normal bone marrow but also of potential variations in females versus males is necessary to differentiate normal findings from marrow disease. Accordingly, we studied possible sex-related differences in the MR imaging appearance of sacral bone marrow in young adults. A population of 21 healthy men and 21 healthy women (17-42 years old) was prospectively studied with chemical-shift pulse sequences. MR imaging (1.5 T) of the sacrum was done with frequency-selective fat images (SENEX [selective nonexcitation] 300/27) and water images (SENEX 1000/27) by using an elliptical surface coil. Two independent observers compared the signal intensity of sacral marrow with the signal of fatty tissue planes adjacent to the sacrum (fat images) and the signal of gluteus muscle (water images). T2 relaxation times were estimated by using a two-parametric monoexponential fit on SENEX 1000/27 and SENEX 1000/54 images. In both sexes, fat MR images showed a higher fat content and greater heterogeneity in the bone marrow of the lateral masses than in the vertebral bodies of the sacrum (p < .05). Yellow marrow in the lateral masses of the sacrum appeared brighter in men than in women (p < .05). The heterogeneity of fatty marrow did not differ significantly between the sexes. On water MR images, the signal intensity of the sacrum was higher in women (p < .05). T2 relaxation times were longer in nonfatty marrow with a high water signal intensity (41.8 +/- 5.5 msec versus 33.4 +/- 2.6 msec p < .01). Our findings show that the normal appearance of the sacral bone marrow depicted on chemical-shift MR imaging differs between young men and women. Awareness of these differences is important to avoid misinterpretation of normal MR findings seen in patients in this age group.

Temperature dependence of the normal and inverse magnetoresistance in magnetic multilayers.

The temperature dependence of the giant magnetoresistance (GMR) in ${\mathit{M}}_{1}$/N/${\mathit{M}}_{2}$ multilayers consisting of magnetic ${\mathit{M}}_{\mathit{i}}$ (i=1,2) and nonmagnetic N layers, is discussed with the use of the finite-temperature band theory in which the effect of spin fluctuations is taken into account by means of the static functional-integral method combined with the coherent potential approximation. It is shown that the temperature dependence of the MR ratio, \ensuremath{\Delta}R/R, shows a variety of behaviors depending on the values of ${\mathit{a}}_{1}$ and ${\mathit{a}}_{2}$ where ${\mathit{a}}_{\mathit{i}}$=${\mathrm{\ensuremath{\Delta}}}_{\mathit{i}\mathrm{\ensuremath{\uparrow}}}$/${\mathrm{\ensuremath{\Delta}}}_{\mathit{i}\mathrm{\ensuremath{\downarrow}}}$ and ${\mathrm{\ensuremath{\Delta}}}_{\mathit{i}\mathit{s}}$ is the imaginary part of the coherent potential of an s-spin electron at the interface of the ${\mathit{M}}_{\mathit{i}}$ layer. In the normal MR where ${\mathit{a}}_{1}$&gt;1 and ${\mathit{a}}_{2}$&gt;1 (or ${\mathit{a}}_{1}$1 and ${\mathit{a}}_{2}$1), \ensuremath{\Delta}R/R decreases as the temperature is raised. On the contrary, in the inverse MR where ${\mathit{a}}_{1}$&gt;1,${\mathit{a}}_{2}$1 (or vice versa) and \ensuremath{\Delta}R/R0, it increases although its absolute magnitude decreases. In a multilayer where normal and inverse MR's coexist, \ensuremath{\Delta}R/R may show a maximum or almost constant behavior in a fairly wide temperature range.

MEDIAL AND LATERAL SUPPORTING STRUCTURES OF THE KNEE: Normal MR Imaging Anatomy and Pathologic Findings

The supporting structures of the knee can be divided into several layers: fascial boundaries, the collateral ligaments and tendons, and the joint capsule. MR imaging's ability to demonstrate these findings has helped to validate this anatomic concept. An appreciation for the organization of the medial and lateral compartments facilitates MR imaging interpretation.

Postoperative Changes of Herniated Intervertebral Disc: Normal and Discitis MR Findings

Postoperative Changes of Herniated Intervertebral Disc: Normal and Discitis MR Findings

Spring ligament of the ankle: normal MR anatomy.

The plantar calcaneonavicular or spring ligament is visualized inconsistently and incompletely on routine MR images of the foot. This ligament is a vital stabilizer of the longitudinal arch of the foot, providing support for the head of the talus, which rests on the ligament's central portion. Laxity or rupture of the spring ligament permits plantar flexion of the talus. This motion results in valgus alignment of the calcaneus and a flatfoot deformity (pes planovalgus). Laxity or rupture of the spring ligament can develop in cases of chronic dysfunction of the posterior tibial tendon. In rupture of the posterior tibial tendon, surgical management may include plication of the spring ligament in addition to repair or reconstruction of the tendon to stabilize the medial column of the foot. Thus, the status of the spring ligament can be a significant consideration in preoperative planning. This pictorial essay illustrates the normal MR anatomy of the spring ligament, the planes of imaging required for optimal depiction of the ligament, and the neighboring structures with which the ligament can be confused.

The pelvis after cesarean section and vaginal delivery: normal MR findings.

In postpartum women, pain and fever can indicate serious complications, such as phlegmon or abscess of the parametrium or bladder flap, ovarian vein thrombosis, or uterine dehiscence. The purpose of this study was to ascertain the MR appearance of the normal pelvis after uncomplicated cesarean section and vaginal delivery. Twenty-two patients (14 who had cesarean sections and eight who had vaginal deliveries) were imaged with a superconducting 0.35-T MR system 1-5 days after delivery. Sagittal and axial T1-weighted, proton density-weighted, and T2-weighted spin-echo images were acquired. Phase reconstruction of the axial T1-weighted sagittal images was performed to confirm flow in the ovarian veins. The ovarian veins, parametrium, bladder flap, endometrium, and uterine incision were analyzed on all images. The uterine incision was well seen in all 14 patients who had cesarean section. The signal characteristics of the incision suggested subacute hematoma within the myometrium, and no myometrial defects were seen. In all 13 patients with a low transverse incision, a hematoma of the bladder flap was seen. Patency was confirmed in the majority of ovarian veins (39/44). No evidence of parametrial edema or mass, which can be seen in abscess or phlegmon, was found in any of the 22 patients. The ovarian perivenous fat did not show edema, which can indicate acute ovarian vein thrombosis. Increased signal in the endometrial cavity was seen in all patients; the signal characteristics were similar to those of subacute hematoma, consistent with clinical findings. Normal findings of the postpartum pelvis on MR imaging are subacute hematoma in the uterine incision, bladder flap, and endometrial cavity. Patent ovarian veins are demonstrated in most (89%) cases.

MR imaging in children with dermatomyositis: musculoskeletal findings and correlation with clinical and laboratory findings.

The purpose of this study was to describe the musculoskeletal MR findings in childhood dermatomyositis and to correlate MR findings with indicators of disease activity such as muscle strength and serum levels of muscle enzymes. This prospective study included 24 children: 19 children with dermatomyositis and five control subjects. The diagnosis of dermatomyositis was established by clinical findings and serum levels of muscle enzymes in all patients, electromyography in six patients, and biopsy in four patients. At the time of the initial MR evaluation, patients were classified on the basis of clinical findings as having active (n = 15) or inactive (n = 4) disease. A total of 44 MR evaluations of patients with dermatomyositis were included in the study: 19 initial MR examinations and 12 examinations repeated after 4-6 months of therapy in patients with active disease. An additional 13 examinations were performed on five patients. Conventional T1-weighted (SE 600/20) and T2-weighted (SE 2500/80) spin-echo and fat-suppressed MR images were obtained. The T2-weighted images (TE = 80) were used for comparison. In addition to the visual assessment, ratios between the signal intensity of muscles (gluteus, adductors, quadriceps, and hamstrings) and the signal intensity of subcutaneous fat in the same tomographic section were calculated. All patients with clinically active disease (n = 15) had abnormal findings on MR studies, whereas those with inactive disease (n = 4) had normal MR findings. Signal-intensity ratios of patients with active disease were greater than those in control subjects, whereas the ratios in patients with inactive disease were not different from those in control subjects. After 4-6 months of therapy, the average signal-intensity ratios of treated patients with repeated MR evaluations (n = 12) differed from ratios obtained before therapy in the same patients, but were not different from the ratios in control subjects. Other MR findings observed were perimuscular edema, enhancement of the chemical-shift artifact, and inflammatory changes of subcutaneous fat. Fat-suppressed imaging enhanced visualization of abnormalities. Markedly abnormal signal intensities of muscle were associated with marked elevations of serum levels of muscle enzymes; however, abnormal MR findings were visualized with normal serum levels of muscle enzymes. Findings of active childhood dermatomyositis on T2-weighted MR images include increased signal intensity in affected muscle, perimuscular edema, enhanced chemical-shift artifact, and increased signal intensity in subcutaneous fat. After therapy, signal intensity of muscle returns to normal. These MR findings are enhanced on fat-suppressed images.(ABSTRACT TRUNCATED AT 400 WORDS)

Abnormalities of the posterior inferior cerebellar artery: MR imaging findings.

The purpose of this essay is to review the normal MR appearance of the posterior inferior cerebellar artery (PICA) and to illustrate the MR findings of representative PICA abnormalities. Because of beam-hardening artifacts, the lower posterior fossa is difficult to evaluate with CT. MR imaging is not hampered by these artifacts. Moreover, the superb sensitivity of MR and its multiplanar imaging capability permit excellent diagnostic accuracy in this region. The PICA is well suited for evaluation on routine MR images, particularly because of the inherent contrast (signal void) of large arteries due to rapid flow. MR imaging has greatly improved our ability to noninvasively diagnose abnormalities of cerebral blood vessels and their resultant manifestations. Some of the diseases that affect the PICA include neoplasms, aneurysms, arteriovenous malformations, and occlusions. The MR images in this essay illustrate the normal appearance of the PICA, as well as these pathologic features. T1-weighted (e.g., 600/15 [TR/TE]), proton density-weighted (e.g., 2000/20), and T2-weighted (e.g., 2400/80) MR images were obtained in axial, sagittal, and coronal planes. The PICA can be evaluated with MR angiography also, although the relatively small size and tortuosity of the artery may preclude adequate visualization.

The ulnar tunnel at the wrist (Juionʼs canal); Normal MR anatomy and variance

The ulnar tunnel at the wrist (Juionʼs canal); Normal MR anatomy and variance

Bone-marrow oedema syndrome and transient osteoporosis of the hip. An MRI-controlled study of treatment by core decompression.

Bone-marrow oedema syndrome (BMOS) of the hip gives a characteristic MRI pattern, in association with severe pain, non-specific focal loss of radiological density and a positive bone scan. In our MRI-controlled study, nine patients with non-traumatic BMOS in ten hips all had core decompression. Bone-marrow pressure measurements and intraosseous venography in five cases showed pathological values. All patients had immediate relief of pain, with return of MRI signals to normal after three months. Regular review was continued for at least 24 months with serial clinical radiological and MRI assessment. At a mean follow-up of 33 months all patients remained free of pain with normal radiographs and MR scans. The histological evaluation of undecalcified sections obtained from eight core decompressions confirmed the presence of bone-marrow oedema, with necrotic and reparative processes involving bone and marrow similar to those of early avascular necrosis but with no evidence of 'osteoporosis'. These findings support the assumption that BMOS may be the initial phase of non-traumatic avascular necrosis. In most patients BMOS will have a self-limiting course, but the duration of symptoms may be reduced by core decompression treatment.

MR imaging of the brain in patients with AIDS: value of routine use of i.v. gadopentetate dimeglumine.

A prospective study was conducted to explore the value of routine administration of IV gadopentetate dimeglumine for MR imaging of the brain in patients with AIDS. Over a 19-month period, MR images of the brain in 51 consecutive AIDS patients were obtained routinely both with and without IV gadopentetate dimeglumine. Unenhanced and contrast-enhanced images from the resulting 63 studies were viewed together. Findings were classified into one or more of three categories: normal, mass or focal lesions, or white matter disease. The number of focal or mass lesions was recorded. Lesion conspicuity on the unenhanced and enhanced images was compared. Ventricular enlargement was also graded. Available medical records and laboratory data of the patients were reviewed. Of the 63 MR studies reviewed, 39 (62%) were abnormal. In no case was a normal unenhanced MR study rendered abnormal after the administration of gadopentetate dimeglumine. Overall, T2-weighted images showed twice as many focal or mass lesions than contrast-enhanced T1-weighted images did. Most lesions detected on the T2-weighted images did not show enhancement with contrast material. White matter disease was the most common abnormality detected. The group of patients with white matter disease also had the highest occurrence of ventriculomegaly. Our study does not support the routine use of gadopentetate dimeglumine for MR imaging of the brain in patients with AIDS. Our experience emphasizes the importance of a normal T2-weighted image.

Effect of dental metals on magnetic resonance imaging (MRI)

The aim of this research was to examine the effects of metals used in dentistry upon magnetic resonance imaging (MRI). Ten disk-shaped samples of metals have been used in this study. Each sample has been set into a volunteer who had produced a normal MR image when tested. The subject was imaged in the sagittal, frontal and coronal plane with a 0.1 T MRI device and results examined for MR defects. Au, Ag, Au-Ag-Pd and amalgam produced no defect. Ni-Cr, Co-Cr and SUS304 expressed small amounts of MR defects, but SUS405, Pd-Co-Ni and Sm-Co expressed large defects. Those metals which create MR image degradation must not be used for fixed prosthesis or orthodontic devices both of which could easily be made from other metals. If the MR image degrading metals are to be used in dentistry, their application should be restricted to removable prosthesis.