Psoas muscle disorders: MR imaging

Nineteen patients with evidence of psoas and iliopsoas abnormalities on computed tomographic (CT) scans (12 with metastases, three with lymphoma, two with hematoma, and two with abscess) were examined with magnetic resonance (MR) imaging. The abnormal psoas could be identified on both T1- and T2-weighted spin-echo images, although T2-weighted sequences provided better contrast. The psoas muscle can be affected by one of three mechanisms: total replacement, lateral displacement, or medial displacement. In four patients in whom the CT study showed apparent enlargement of a psoas muscle, subsequent MR imaging examinations demonstrated that the psoas muscle was compressed and displaced laterally by a paraspinal mass. MR images provided better contrast between the normal and abnormal psoas than CT scans in nine cases; MR images were inferior to CT scans in two cases because calcifications (one case) and air bubbles within an abscess (one case) were not detectable.

Effects of cross-section structure on the dosimetric response functions for 0.4 to 10.0 MeV neutrons in the ICRU tissue sphere

The effect of the fluctuating cross-section structure in the energy range of 0.4 to 10.0 MeV on the dosimetric response functions of neutrons in the ICRU standard tissue sphere is analyzed. A Monte Carlo method with point-energy cross-section values, including coupled transport for neutrons and secondary charged particles, was used in the direct estimation of the absorbed dose and the dose equivalent. An approach was adopted in which source-energy band-average responses were calculated instead of the more usual approach involving monoenergetic source neutrons. Data were obtained for the newly defined term, ambient dose equivalent, at various depths, as well as the older index quantities. Such data generated were compared with information from other research workers. In general, good agreement was found, with due consideration to the differences engendered by the use of the source-energy band-average approach. Agreement was poorest for very shallow depths, corresponding to outer skin thickness, this being a most difficult depth to calculate accurately. The dosimetric data generated in this study should contribute to the ongoing efforts for the standardization of neutron protection dosimetry.

Neck neoplasms: MR imaging. Part II. Posttreatment evaluation

Thirty-three patients who had undergone prior surgery and/or radiation therapy for malignant neoplasms of the neck were studied with magnetic resonance (MR) imaging. Twenty-seven of these patients were also evaluated with computed tomography (CT). Ten patients were healthy posttreatment volunteers, and 23 had documented tumor recurrence. MR images better demonstrated normal muscular landmarks, especially in patients with obliterated fat planes. Areas of posttreatment fibrosis or scarring were low in signal intensity with all MR pulse sequences. However, in three patients, high signal intensity from postradiation edema of the supraglottic area mimicked neoplasm. In patients with recurrent tumor, MR imaging was superior to CT in defining the relationship of tumor and muscle and in demonstrating vascular anatomy when no intravenous contrast material was given during the CT examination. In two patients tumor and fibrosis were separated on MR images because of signal intensity differences. CT scans, however, showed adjacent bone and cartilage anatomy better. Our data indicate that an MR examination may be helpful in patients in whom CT is indeterminate either because of anatomical distortion or suboptimal demonstration of vascular anatomy.

Soft-tissue tumors: MR imaging

We evaluated the suspected soft-tissue masses of 33 patients using magnetic resonance (MR) imaging. Thirty-two masses were defined, of which ten were malignant and 22 were benign. Specific characteristics that would allow us to distinguish the benign lesions from the malignant ones could not be identified on MR imaging. Lesions located within muscles or in the intramuscular septa were best seen with T2-weighted imaging sequences; those located within the subcutaneous fat were best outlined with T1-weighted imaging sequences. Both imaging sequences were necessary to provide the complete representation of the extent of the mass. We performed comparison studies using computed tomography (CT) in 24 of the cases. Of 92 possible comparisons and in four categories MR imaging yielded results that were superior to those obtained by CT scanning in 30 instances, equaled the results obtained by CT scanning in 62 instances, but never yielded results inferior to those obtained by CT scanning. However, MR imaging failed to demonstrate soft-tissue calcification and soft-tissue gas in one case each.

Acute renal rejection versus acute tubular necrosis in a canine model: MR evaluation

Findings of magnetic resonance (MR) imaging in acute renal rejection and acute tubular necrosis (ATN) were studied in dogs. On T1-weighted images, corticomedullary differentiation was absent in kidneys undergoing acute rejection. The loss of corticomedullary differentiation in these kidneys was secondary to a decrease in the relative signal intensity of the cortex, indicating prolongation of the T1 relaxation time of the cortex. In contrast, corticomedullary differentiation was preserved on T1-weighted images of autotransplanted kidneys and kidneys with ATN. MR imaging findings correlated with changes in water content in these three groups of kidneys. Kidneys undergoing acute rejection showed a marked increase in water content compared with kidneys in the other two groups. No change in fat content was found in any group.

The safety and efficacy of the use of methotrexate in long-term therapy for rheumatoid arthritis

Twenty-nine patients participated in a prospective study of the safety and efficacy of oral methotrexate in the treatment of refractory rheumatoid arthritis. Patients received a mean dosage of 12.4 mg weekly over a mean duration of 29.1 months. All patients had liver biopsies at baseline, 2 years, and annually thereafter. Patients improved significantly by all clinical measures of efficacy after 1 month; maximum improvement tended to occur after approximately 6 months of therapy. Radiographs showed improvement of erosive disease in 7 of 11 patients measured. There was a significant reduction in mean prednisone dosage. Four patients required an increase in the dosage of methotrexate after prolonged therapy, because of declining clinical response. Toxicity was noted at some time in 26 of 29 patients (90%), but reactions universally became mild and tolerable after adjustment of the dosage. No significant hepatotoxicity was found in 60 sequential liver biopsies, although elevated transaminase levels were noted at some time in 20 of 29 patients (70%).

Percutaneous drainage of prostatic abscesses

Percutaneous catheter drainage of intra-abdominal abscesses currently is a well established technique. We report on 2 anuric patients on maintenance hemodialysis who presented with a prostatic abscess. We elected to use a transperineal, percutaneous drainage technique. Adequate drainage was documented by pelvic computerized tomography scans and followup confirmed satisfactory long-term results.

Uterine neoplasms: MR imaging

Magnetic resonance (MR) studies were performed on 20 healthy volunteers and 41 patients with proved cervical and uterine neoplasms. MR imaging demonstrated normal uterine landmarks in all patients. On T2-weighted images, the normal uterine wall could be differentiated into three distinct layers: a central high-intensity zone, a junctional low-intensity band, and a peripheral medium-intensity area. While most of the normal cervices had only two distinct zones (central high-intensity zone and peripheral low-intensity zone), a small percentage had three layers of signal intensity, similar to the uterine body. Primary cervical and uterine neoplasms could be identified on MR images. In 18 of 22 patients with proved carcinoma, a mass with a signal intensity higher than that of normal cervical lips was seen on T2-weighted images. Endometrial carcinoma was most often identified as expansion of the central high-intensity area; discrete tumor nodules were visible in nine of 15 patients. Mixed müllerian sarcoma appeared as a large pelvic mass with complete obliteration of normal uterine landmarks. MR imaging delineates primary cervical and endometrial carcinoma better than computed tomography does.

The role of lymphangiography in vulvar carcinoma

The records of all patients with vulvar carcinoma seen at Washington University School of Medicine between 1970 and 1983 were reviewed to determine the role of lymphangiography in the management of patients with vulvar malignancy. Forty-three patients were identified who had a preoperative lymphangiogram followed by radical vulvectomy and lymph node dissection. Thirty-two films were available for review. Seventy-seven sets of lymph nodes were obtained from the 32 patients. Overall diagnostic accuracy was 42 of 77 (54.5%), with a sensitivity of three of 19 (15.7%) and a specificity of 39 of 59 (66.1%). Corresponding values for inguinal nodes were 26 of 57 (45.6%), two of 16 (12.5%), and 24 of 41 (58.5%), respectively. Accuracy rates for pelvic nodes were 16 of 21 (76.2%) with a sensitivity rate of one of three (33%) and a specificity of 15 of 18 (83%). Negative scans were more likely to be accurate than positive scans, 88.6% versus 30%. While a negative lymphangiogram may be helpful in predicting the absence of metastases, its poor specificity limits its widespread usefulness.

Oblique magnetic resonance imaging of the cardiovascular system

This exhibit demonstrates that cardiac anatomy can be imaged by MRI in oblique planes that are equivalent to views obtained radiographically or at angiocardiography. These MR images may be obtained either by simple patient positioning or by electronic rotation of the imaging axis. The advantages of this technique include its simplicity and its ability to show detailed anatomy noninvasively. Major cardiac structures including chambers, walls, vessels and bronchi are optimally demonstrated in long axis or cross section. This permits estimation of chamber volume, wall thickness, vessel position and variations from normal. Smaller structures are also well visualized. These include the pericardium, papillary muscles, azygos vein and some cross sectional anatomy of the coronary arteries and veins. The valvular structures can be shown during diastole or systole. The ability of MRI to show these cardiac structures due to the intrinsic contrast differences in signal intensity between muscle, fat, flowing blood and lung suggest an important future for MR cardiac imaging in a broad group of congenital and acquired diseases of the heart, pericardium and great vessels.

MRI of extracranial hematomas: preliminary observations

Thirteen patients (16 examinations) with extracranial hematomas (four mediastinum, three pelvis, two calf, two psoas muscle, one liver, one abdominal wall) were examined with magnetic resonance imaging (MRI). With the exception of an acute hematoma (less than 48 hr), which did not have a distinctive MRI appearance, subacute and chronic hematomas (up to 10 months' duration) had areas of high signal intensity on both T1- (TR 500/TE 30) and T2- (TR 1500/TE 90) weighted pulse sequences. The hematomas in 10 of the patients were also evaluated by computed tomography (CT). The MRI findings complemented those seen on CT. Low-intensity parts of the hematoma on both T1- and T2-weighted images corresponded to areas of high attenuation on CT, whereas high-intensity zones correlated with regions of low attenuation. This observation was more apparent on the T1-weighted images. While older hematomas did not exhibit areas of hyperdensity that would allow a specific diagnosis on CT, MRI did demonstrate regions of high signal intensity indicative of hemorrhage.

Anatomy of the perirenal area

The authors comment on the use of the renal bridging septa as a sign in distinguishing compartmentalization of the perinephric space. They also address new concepts regarding the spread of pancreatic effusions and provide information on other anatomic features of the perirenal area.

Prostatic carcinoma and benign prostatic hyperplasia: inability of MR imaging to distinguish between the two diseases

Forty patients with prostatic carcinoma or benign prostatic hyperplasia (BPH) underwent magnetic resonance (MR) imaging of the prostate. In vitro MR images of six prostate specimens were also obtained. The prostatic parenchyma was best evaluated by a T2-weighted spin-echo pulse sequence. The prostate both in patients with prostatic carcinoma and patients with BPH often had an inhomogeneous and nodular appearance on T2-weighted images. While most of the prostatic carcinomas appeared hyperintense relative to muscle and adjacent prostatic parenchyma, some of the hyperplastic nodules had a signal intensity similar to carcinoma. With current imaging techniques, MR imaging cannot differentiate prostatic carcinoma from BPH with certainty.

High resolution CT of the porta hepatis and hepatoduodenal ligament

The authors present a detailed analysis of the sectional anatomy of the porta hepatis and hepatoduodenal ligament, and illustrate the use of high resolution CT in the clinical evaluation of the area.

Intravenous cholangiography in the CT era

With the availability of computed tomography (CT), ultrasonography (US), percutaneous transhepatic cholangiography (PTC), and endoscopic retrograde cholangiopancreatography (ERCP), the use of intravenous cholangiography (IVC) has waned. A retrospective study of 69 intravenous cholangiograms performed from 1979 through 1982 assessed the utility of intravenous cholangiography, as well as its effect on patient management, at an institution where CT was highly developed. In no case after normal findings on CT and/or ultrasound examination did IVC make a positive pathologic diagnosis. After abnormal results on CT and/or US examinations, in no case did IVC add to the diagnosis. Finally, after technically suboptimal results of CT and/or US examinations, IVC made only 1 positive pathologic diagnosis. Overall, IVC correctly demonstrated only 5 of 9 cases of common duct stones or strictures. Of the 26 cases with anatomical correlation there were a total of 7 false-positive and -negative IVC examinations. In this series, IVC was rarely useful in the diagnosis of biliary tract disease. Given the high inaccuracy rate of IVC in this study, its use for the exclusion of biliary tract disease is discouraged.

Fatty infiltration of the liver: evaluation by proton spectroscopic imaging

The reliability of proton spectroscopic imaging in evaluating fatty infiltration of the liver was investigated in 35 subjects (12 healthy volunteers and 23 patients with fatty livers). With this modified spin-echo technique, fatty liver could be separated from normal liver both visually and quantitatively. On the opposed image, normal liver had an intermediate signal intensity, greater than that of muscle, whereas fatty liver had a lower signal intensity, equal to or less than that of muscle. In normal livers, the lipid signal fraction was less than 10%, while in fatty livers it was greater than 10% and usually exceeded 20%. With this technique, nonuniform fatty infiltration of the liver can be differentiated from hepatic metastases, and the technique may prove useful in the differentiation of some hepatic disorders.

Thoracic wall involvement by Hodgkin disease and non-Hodgkin lymphoma: CT evaluation

Thoracic computed tomographic (CT) scans of 250 patients with newly diagnosed or recurrent lymphoma revealed thoracic wall involvement in 24 patients (11 with Hodgkin disease, 13 with non-Hodgkin lymphoma). Thoracic wall involvement occurred without contiguous mediastinal or parenchymal involvement in 17 patients. Of these, 13 patients had masses beneath the pectoralis muscles or within the breast, and four had masses arising from the ribs. Five additional patients had mediastinal masses with thymic involvement and parasternal extension through the thoracic wall. Pulmonary parenchymal lymphoma with thoracic wall invasion was noted in the remaining two patients. In five of nine patients receiving radiation therapy, treatment plans were modified by CT demonstration of thoracic wall lymphoma.

The uterus: in vitro MR-anatomic correlation of normal and abnormal specimens

Magnetic resonance (MR) images of 12 fresh uterine specimens obtained with a high-resolution surface coil were correlated with findings on gross and microscopic pathologic examination. The uterine wall can be differentiated into three distinct zones: a central high-intensity zone, a junctional low-intensity band, and a peripheral medium-intensity area. Whereas the endometrium (basale and functionale) corresponded to the high-intensity zone, the myometrium correlated best with the combined width of the areas of low and medium signal intensity. The signal intensity of a leiomyoma varied, depending on its cellularity. Primary endometrial and cervical carcinomas were clearly shown on MR images, as were other abnormalities such as adenomyosis and Nabothian cysts. The potential usefulness of MR imaging in detecting and staging uterine neoplasms is discussed.

The thoracic aorta studied by MR imaging

Thirty-three patients with a variety of disorders of the thoracic aorta (aneurysm, dissection, Marfan syndrome, coarctation/pseudocoarctation, L-transposition, and Takayasu disease) were evaluated with magnetic resonance (MR) imaging. MR imaging delineated the presence and extent of thoracic aortic aneurysms and showed the relationship of the aneurysm to arch vessels; it also demonstrated intimal flaps and individual lumina in types A and B aortic dissection. Dilation of the ascending aorta in Marfan syndrome and focal narrowing of the aorta in coarctation were well visualized. The anteroposterior and side-to-side relationships of the aorta and pulmonary artery in L-transposition were demonstrated, as were aortic wall thickening and branch vessel narrowing in Takayasu arteritis. Initial experience suggests that MR imaging may provide a noninvasive method for evaluating thoracic aortic disease. Limitations include inferior spatial resolution, occasional difficulty in imaging the entire region of interest in one section, lack of signal from calcifications, and inability to monitor critically ill patients.

Radiation fibrosis: differentiation from recurrent tumor by MR imaging

Magnetic resonance (MR) images of 21 patients who had undergone radiation therapy were analyzed and compared with those of 15 patients who had untreated tumors. T2-weighted images (TR = 1,500 msec, TE = 90 msec) were most helpful in distinguishing recurrent tumor from radiation fibrosis. Radiation fibrosis, like muscle, usually remained low in signal intensity on T2-weighted images, while tumor demonstrated higher signal intensity. In no patient was the signal intensity of tumor the same or less than muscle on the T2-weighted images. However, relatively high signal intensity on T2-weighted images is not specific for tumor recurrence and may be seen in acute radiation pneumonitis, infection, hemorrhage, and even pulmonary radiation fibrosis.

Detection of hepatic metastases by proton spectroscopic imaging. Work in progress

Fourteen patients with hepatic metastases underwent magnetic resonance (MR) imaging using both the conventional spin-echo (SE) technique and the opposed phase of the proton spectroscopic imaging method. The opposed image showed more lesions than the conventional SE image in five patients and provided better contrast between the liver parenchyma and metastases in two patients. Four of these seven patients had associated fatty infiltration of the liver. When compared with the computed tomography (CT) scan, the opposed image either showed more lesions or provided better contrast in six patients, four of whom had fatty infiltration. More significantly, the MR image showed several 1-cm lesions not shown by the CT scan in one patient. Our study discloses the possible explanations for the increased sensitivity of the opposed image in detecting hepatic metastases.

Hepatic metastases studied with MR and CT

Examinations of the liver using magnetic resonance (MR) and computed tomography (CT) were performed on 50 patients with hepatic metastases. MR and CT were comparable in their ability to detect metastases, which generally appeared hypointense compared with normal liver parenchyma on T1-weighted MR images and hyperintense on T2-weighted images. The MR imaging techniques that were most reliable in detecting metastases were inversion recovery and a relatively T2-weighted, spin-echo technique (TR = 1,500 msec, TE = 60 msec). We conclude that CT, because of its shorter imaging time, greater spatial resolution, and lower cost, should remain the preferred screening test for hepatic metastases. MR imaging should be reserved for patients with equivocal CT findings and for patients in whom there is persistent clinical suspicion of hepatic metastases despite a negative CT examination.

Magnetic resonance imaging of mediastinal and hilar masses: comparison with CT

Magnetic resonance imaging (MRI) was compared to computed tomography (CT) of the mediastinum and/or hila in 37 patients with bronchogenic carcinoma (35 unresectable for cure) and 11 patients with other masses. Spin-echo pulse sequences using a short pulse repetition rate (TR) and short echo delay (TE) were most helpful for detection of abnormal soft-tissue mediastinal and hilar masses. The accuracy of MRI and CT in staging bronchogenic carcinoma for curative resectability/nonresectability was comparable. CT staged 35 of 37 cases appropriately, while MRI correctly staged 36 of 37 cases. Several pitfalls in MRI evaluation of the mediastinum were identified. By MRI the esophagus may be misinterpreted as an enlarged retrotracheal lymph node unless serial scans are studied. Scattered calcifications in enlarged mediastinal and hilar lymph nodes due to old granulomatous disease are not detectable by MRI. Small adjacent lymph nodes shown individually by CT may appear as a single enlarged lymph node by MRI due to partial-volume averaging. Small lung nodules may be undetected by MRI due to respiratory motion and partial-volume averaging. Certain patients are unsuitable for MR scanning. Because of the requirement for patient selection and the identified pitfalls of MRI, CT remains the radiologic procedure of choice in the staging of patients with bronchogenic carcinoma and the evaluation of other mediastinal and hilar masses at present. However, because of the ability to show blood vessels without an intravascular contrast agent, MRI is useful in evaluating patients with potential contrast allergy and solving diagnostic problems not solved by CT.