Martha C. Nelson

Magnetic resonance appearance of peripheral nerve sheath tumors

Magnetic resonance imaging (MRI) was used to evaluate 22 histologically proven peripheral nerve sheath tumors, approximately two-thirds of which arose in the lower extremity. The histologic distribution was as follows: 12 schwannomas, 7 neurofibromas, and 3 malignant peripheral nerve sheath tumors (2 of which occurred in patients with neurofibromatosis). Most lesions demonstrated an intermediate to moderately bright signal on T1-weighted images and were minimally inhomogeneous. All lesions were moderately bright on proton-density-weighted images and bright on T2-weighted images, again with variable inhomogeneity. The extent of the tumor was best assessed on proton-density- and T2-weighted images. Smooth margins were noted in 19 lesions. Of the 3 remaining lesions, 2 were malignant (but had been subjected to biopsy prior to MRI), and the other lesion was a plexiform neurofibroma. MRI accurately determined the relationship between the lesion and the adjacent neurovascular structures and muscles, thereby assisting surgical management. On MRI, 5 lesions demonstrated coexistent subtle muscle atrophy along the longitudinal axis of surrounding or distally innervated musculature. This latter finding, together with the presence of a tumor in the vicinity of a large nerve trunk, suggests a peripheral nerve sheath neoplasm.

Potential for unnecessary patient exposure from the use of storage phosphor imaging systems

It is possible to use storage phosphor radiography (SR) devices in a manner that results in excess exposure to the patient without the operators knowledge. Because these SR systems have an automatic correction for the final optical density (OD) of the image, the technologist and radiologist will not be able to use excessive blackness of the image as a sign of overexposure. Tests reported here demonstrate that it is possible to obtain images of a chest phantom that appear acceptable with a 32 times difference in exposure (maximal exposure .86 R). It is possible to obtain exposures of a pelvis phantom that appear acceptable up to the tube limit of our machine (4.8 R). Tests of the Fuji AC-1 demonstrate that it will accept a much wider range of exposures than the AGFA ADC prototype which permits only a 7 times difference in exposure before the image is degraded.

Case report 560

A 75-year-old white woman presented with a 40-year history of a slowly growing bony mass on the anterior surface of the left tibia. Several months prior to admission she suffered minor trauma to the leg and since then, she has had increasing pain and some paresthesia in her foot. Physical examination revealed a fixed, nontender 7 cm x 15 cm bony mass on the anterior surface of the left tibia. The neuro-vascular status of her foot was intact. Roentgenograms and tomogram of the left tibia showed a large, sessile lobulated juxta-articular mass of dense cortical bone, without obvious cortical invasion, soft tissue mass, or periosteal reacton. No cleavage plane was seen between the lesion and the cortex of the tibia (Fig. 1 A and B). A C T scan confirmed these findings (Fig. 2). Angiography showed the lesion to be fairly vascular without the typical features of malignant growth. A bone scan showed increased uptake of tracer in the lesion (Figs. 3 A and B, 4). The patient then underwent a surgical procedure.

Isolated popliteal vein entrapment

We present two cases of isolated popliteal vein entrapment caused by the lateral head of the gastrocnemius muscle confirmed by both venography and magnetic resonance imaging of the knee.

Case report 448

Osteome osteoide de la 6eme cote gauche avec reaction inflammatoire de la plevre adjacente et hyperostose des cotes adjacentes

Image processing in digital mammography

Digital mammography is likely to replace conventional mammography within a few years. In anticipation of this, our group has been exploring the implications of image processing in digital mammography. Some of our findings are reported here.

Case report 554

Report of a case of osteonecrosis at multiple sites in a 31-year-old white man, after corticosteroid treatment

Intraforaminal schwannoma of the sacrum

Correspondence to: A.D. Aaron, Department of Orthopaedic Surgery, Georgetown University Medical Center, 3800 Reservoir Road NW, Washington, DC 20007, USA tremity numbness or weakness, bowel or bladder complaints, or t rauma was elicited. Physical examination disclosed midline tenderness over the lumbar and sacral region. Al though the neurological examination revealed normal muscle strength, reflexes and sensation, left-sided radiating leg pain could be invoked with straight leg raising. The clinical signs and symptoms were consistent with a herniated nucleus pulposus. Plain radiographs of the lumbar spine were normal. An anteroposterior view of the pelvis demonstrated a well-demarcated radiolucent lesion near the midline o f the sacrum, which was outlined with a thin sclerotic border (Fig. 1). Computer ized axial tomography (CT) revealed a lucent le-

Image optimization procedures for the Fuji AC-1

The Fuji AC-1 is a popular system for digital radiography with great potential, but for many the initial implementation of the system in a radiology service is frustrating experience for lack of effective support and a clear operational manual. Adjusting the image processing settings for site specific image optimization has been, for most users, difficult and confusing. The effect of each of the image processing parameters available on the Fuji AC-1 is not easily understood by users of the machine. The application manual that comes with the machine briefly defines the parameters and gives recommended settings for different types of examinations, but the manual does not provide the user with adequate information or a suggested method to allow the user to easily optimize the image for that users site. This paper defines in more precise terms the meaning of the various parameters and suggests a method of procedure to optimize the parameters to each radiologists preference. The results are based on experiments and measurements we performed with a Fuji AC-1 +. This information should assist the radiologist to use a more systematic method of image quality improvement rather than the somewhat random trial and error process that current users have described.

Storage phosphor images in the neonatal intensive care unit: a multiobserver preference study

Attempts to implement digital chest imaging in the Neonatal Intensive Care Unit at Georgetown University have proven unsuccssful. This paper explores some of the reasons for this. Based on our experience we will also make suggestions of how to best use the storage phosphor system, should one wish to implement it.