Biomedical subjects
Publications and source records attributed to S J Erickson.
The normal anatomy of the ankle and fore-foot is quite complex and presents a challenge for both MR imaging and interpretation. Many of the critical ligaments and tendons require imaging in several planes for greatest diagnostic accuracy. We hope this article serves as a solid foundation and a reference for the excellent articles that follow.
Periportal halos are defined as circumferential zones of decreased attenuation identified around the peripheral or subsegmental portal venous branches on contrast-enhanced computed tomography (CT). These halos probably represent fluid or dilated lymphatics in the loose areolar zone around the portal triad structures. While this CT finding is nonspecific, it is abnormal and should prompt close scrutiny of the liver in search of an underlying etiology. Periportal halos which may be due to blood are commonly seen in patients with liver trauma. Periportal edema may cause this sign in patients with congestive heart failure and secondary liver congesion, hepatitis, or enlarged lymph nodes and tumors in the porta hepatis which obstruct lymphatic drainage. This CT sign has also been observed in liver transplants (probably secondary to disruption and engorgement of lymphatic channels) and in recipients of bone marrow transplants who might develop liver edema from microvenous occlusive disease. While the precise pathophysiologic basis of periportal tracking has not been proven, it represents a potentially important CT sign of occult liver disease.
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Stellate ganglion blockade, typically performed by using palpable osseous landmarks, is an accepted method in the diagnosis and treatment of sympathetically maintained pain and other conditions. The authors present the results of stellate ganglion injection performed with computed tomographic (CT) guidance. Thirteen CT-guided procedures were performed in seven patients. Lidocaine, bupivacaine, and buprenorphine were used to achieve the blockade. Successful blocks were achieved in all 13 cases as evidenced by production of Horner syndrome and ipsilateral hand temperature elevations. The average ipsilateral and contralateral hand temperature changes following the procedure were 7.5 degrees C and 0.5 degrees C. The ipsilateral hand temperature changes and the differences between the ipsilateral and contralateral hand temperature changes exceeded 1.5 degrees C in every case. Five patients preferred the CT-guided procedure over the conventional technique, and two patients noted no substantial difference between the approaches. With the CT-guided technique, a highly effective sympathetic block is achieved with a substantially reduced volume of anesthetic compared with the conventional approach.
The MR imaging anatomy of the ankle has been well described. The anatomy of the forefoot, however, is not well understood by most radiologists. In many institutions, MR imaging studies are performed by using the head coil with large fields of view so that the appearance of the asymptomatic side can be used for comparison. At our institution, studies of the forefoot are performed with a specialized solenoid coil that allows a field of view of 8 cm with a resultant in-plane spatial resolution of approximately 0.3-0.4 mm. In this report, we present the MR imaging anatomy of the normal forefoot. Pertinent osseous, musculotendinous, and neurovascular structures are shown. Particular emphasis is placed on the compartmental anatomy of the foot, which is best imaged in the coronal plane.
Imaging of the sacral plexus requires evaluation of both intradural and extradural components with cross-sectional techniques. Although CT is useful, individual extradural sacral nerves and the sacral plexus usually cannot be distinguished from adjacent structures. The higher contrast resolution provided by MR imaging allows the region of the sacral plexus to be examined in greater detail. With MR imaging, the constant relationship of the neural components to one another, and the gluteal vessels in their course from the sacrum to the greater sciatic foramen, can be shown consistently. An understanding of the anatomy of this area in multiple planes can aid in more accurate localization of abnormalities involving the sacral plexus. This pictorial essay reviews the MR appearance of the region of the sacral plexus.
Patients with symptoms of sacral plexopathy, radiculopathy, or sciatica may have disease originating in the neural elements, sacrum, bony pelvis, pelvic soft tissues, or gluteal region. As illustrated in our companion article, the sacral plexus and surrounding structures can be visualized in detail with MR imaging. This pictorial essay illustrates the MR findings in a number of abnormalities affecting the sacral plexus. Multiplanar MR examination is particularly helpful in defining neural levels of involvement by disease in this region.
In the past, MR imaging of the ankle and foot has been performed by scanning both extremities simultaneously to provide a normal side for comparison. More recently, unilateral imaging with small local coils has been favored to maximize spatial resolution through use of small fields of view or large matrices. Such clarity of detail, however, demands a greater knowledge of normal anatomy and anatomic variants. We illustrate the MR appearances of a number of variants involving muscle, tendons, ligaments, and osseous structures of the foot and ankle. Familiarity with these findings is essential to prevent errors in the interpretation of MR images.
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Color Doppler sonography can be useful in the evaluation of erectile dysfunction, which can result from psychogenic, endocrinologic, neurogenic, pharmacologic, and vasogenic causes. It is used to determine the integrity of the vascular mechanism. After an intracavernosal injection of a vasodilatory agent, color Doppler sonography is performed to evaluate cavernosal arteries and dorsal vessels. Color flow imaging allows direct visualization of intrapenile anatomy, vascular variants, and disease. It is also helpful in demonstrating transitions in cavernosal and dorsal blood flow. Color Doppler sonography is combined with spectral interrogation of the cavernosal arteries and dorsal veins to help determine peak systolic and end-diastolic velocities. Cavernosal artery size and systolic velocities help diagnose arterial insufficiency. Recent work on cavernosal artery diastolic flow and dorsal vein flow has indicated that color Doppler sonography, when correlated with cavernosographic findings, may be helpful in diagnosing venous incompetence. Temporal variations in transitions in cavernosal artery and dorsal vein flow during various stages of erection are important in the accurate diagnosis of vasogenic impotence.
Although magnetic resonance (MR) imaging routinely is used to evaluate the facial nerve, the conventional axial, coronal, and sagittal planes are not optimal for demonstrating the tympanic and mastoid portions of the nerve. A vertical oblique plane for MR imaging of these portions of the facial nerve was evaluated. With this plane, the course of the nerve was effectively demonstrated on MR images and corresponding cryosections. The oblique plane can be used to supplant or supplement conventional planes in imaging of the facial nerve.
The stellate ganglion has not previously been identified by imaging techniques. MR imaging shows the stellate ganglion at the thoracic inlet adjacent to the neck of the first rib, lateral to the longus colli muscle and posterior to the vertebral artery. Although its shape varies somewhat, it can be identified consistently in normal persons.
This study was designed to investigate a variety of sonographic features of ureteric jets in order to define patterns of flow and ranges of flow values in an asymptomatic population. The following features of ureteric jets were measured during a period of up to 30 min in a group of 15 asymptomatic volunteers after oral hydration (the mean value was calculated on each side): peak velocity (mean, 57 cm/sec); jet duration (mean, 4.6 sec); and number of peaks and subpeaks (mean, 2.2). Several flow patterns were observed, including discrete jets, ureteric streaming, and rest periods. For each patient the ratios of values obtained on the left and right sides were calculated for peak velocity (1.00-1.74; mean, 1.26); jet duration (1.00-4.69; mean, 1.83); and jet frequency (1.00-1.21; mean, 1.11). The interjet interval (period between jets) ranged from 2 to 150 sec. Bolus volume and jet frequency showed simultaneous moment-to-moment variation. The frequency and velocity rather than the duration ratios may be of greatest value in identifying patients with normal ureterodynamics. Our findings challenge two current concepts of renal pelvic and ureteral response to changes in urine output: (1) ureters have a fixed maximal discharge rate and (2) bolus volumes do not change until this rate is achieved. Asymmetric moment-to-moment fluctuations observed in jet frequency suggest that prolonged examination may be necessary to confirm normal symmetry of jet frequency in some patients with suspected ureteric obstruction.
The tendon of the long head of the biceps muscle (long bicipital tendon) has a complex course from its muscle belly to its insertion onto the supraglenoid tubercle/glenoid labrum. It is stabilized by numerous tendinous and ligamentous structures and is, in turn, partly responsible for maintenance of normal glenohumeral function. In this report we describe the anatomy of this tendon, correlating high-resolution MR images with cryomicrotome sections. We illustrate typical MR findings in pathologic conditions affecting the long bicipital tendon sheath, the substance of the tendon, and finally the tendon position.
To determine whether orientation in the static field may be responsible for the frequent occurrence of increased signal intensity within normal tendons at magnetic resonance (MR) imaging, seven healthy volunteers were imaged by means of a 1.5-T unit and standard clinical pulse sequences. The wrist, ankle, and shoulder regions were evaluated with local coils. Imaging was performed with tendon orientations ranging from 0 degree to 90 degrees in relation to the constant magnetic induction field (B0). Markedly increased intratendinous signal intensity was observed at the "magic angle" of 55 degrees, intermediate signal intensity was observed at 45 degrees and 65 degrees, and no signal intensity was observed at 0 degree and 90 degrees. Signal intensity was evident only when a short echo time was used. The authors believe that tendon orientation greatly affects tendon signal intensity in vivo. Increased signal intensity due to the magic angle effect may be misdiagnosed as tendinous degeneration, tendinitis, or frank tear.
Fifteen patients (17 feet) with symptoms suggestive of plantar interdigital neuroma underwent magnetic resonance (MR) imaging at 1.5 T with a solenoid forefoot coil with an 8-cm field of view. Surgery was subsequently performed on six feet. Fifteen interdigital masses were identified with MR imaging. Five of these, in feet that underwent surgery, were pathologically confirmed neuromas. In the remaining foot that underwent surgery, flexor tendon injury with probable inflammatory reaction was demonstrated with MR imaging but was interpreted as indeterminate for neuroma. No neuronal was identified at surgery, which otherwise confirmed the MR imaging findings. Neuromas were most conspicuous on T1-weighted images as foci of decreased signal intensity well demarcated from adjacent fat tissue. The lesions were poorly seen on T2-weighted images, where they appeared isointense or slightly hypointense to fat tissue in all cases. Prominent regions of increased signal intensity, presumably representing fluid in intermetatarsal bursae, were seen proximal to 10 of the 15 masses found with MR imaging.
The ankle is stabilized by three sets of ligaments: the medial collateral (deltoid) ligament, the syndesmotic ligamentous complex, and the lateral collateral ligament. Of these three, the lateral collateral ligament is the one most often injured in ankle sprains. Assessment of the extent of injury has classically relied on clinical evaluation; plain film radiographs (including stress views); and, in some acute situations, ankle arthrography and/or peroneal tenography. In this report we illustrate the use of MR in the evaluation of the lateral collateral ligament. The normal anatomy, pitfalls in image interpretation, and findings in cases of ligamentous injury are demonstrated.