Showing papers in "American Journal of Roentgenology in 1987"

MR signal abnormalities at 1.5 T in Alzheimer's dementia and normal aging

Abstract: The type, frequency, and extent of MR signal abnormalities in Alzheimer's disease and normal aging are a subject of controversy. With a 1.5-MR unit we studied 12 Alzheimer patients, four subjects suffering from multiinfarct dementia and nine age-matched controls. Punctate or early confluent high-signal abnormalities in the deep white matter, noted in 60% of both Alzheimer patients and controls, were unrelated to the presence of hypertension or other vascular risk factors. A significant number of Alzheimer patients exhibited a more extensive smooth "halo" of periventricular hyperintensity when compared with controls (p = .024). Widespread deep white-matter hyperintensity (two patients) and extensive, irregular periventricular hyperintensity (three patients) were seen in multiinfarct dementia. Areas of high signal intensity affecting hippocampal and sylvian cortex were also present in five Alzheimer and two multiinfarct dementia patients, but absent in controls. Discrete, small foci of deep white-matter hyperintensity are not characteristic of Alzheimer's disease nor do they appear to imply a vascular cause for the dementing illness. The frequently observed "halo" of periventricular hyperintensity in Alzheimer's disease may be of diagnostic importance. High-signal abnormalities in specific cortical regions are likely to reflect disease processes localized to those structures.

Mammographic parenchymal patterns and quantitative evaluation of mammographic densities: a case-control study.

Abstract: The classification of breast parenchymal patterns (N1, P1, P2, DY) and the percentage of the breast containing radiographic densities are two highly correlated radiographic measures proposed as predictors of the risk of breast cancer. In this case-control study, 160 cases of breast cancer and 160 matched controls from a mammography referral practice were compared to determine the risk of breast cancer associated with each of these two radiographic measures. The mammographic densities were quantified on caudal projections by means of a compensating polar planimeter. A relative risk estimate of 3.3 (p less than .05) was associated with the P2 + DY patterns compared with the N1 + P1 patterns. Significantly elevated risks of 4.3 to 5.5 also were observed among women whose breasts contained at least 25% mammographic densities, compared with women with less than 25% involvement. These radiographic measures tended to be more predictive of the risk of breast cancer in black women than in white women. Although the precise clinical roles of breast parenchymal patterns and densities have not been defined fully, the results of this study suggest that they are useful in the recognition of women at high risk of breast cancer. We make no claims that the findings of this study are sufficiently developed to be used as a basis for screening strategies.

MR imaging of paragangliomas

Abstract: MR imaging of 15 paragangliomas in 10 patients was compared with CT of 13 of the lesions in eight patients. All lesions were confirmed with angiography. All lesions were detected by MR and CT with the exception of one small glomus tympanicum tumor that was seen only in retrospect with MR. CT better demonstrated subtle osseous changes of the skull base and the relation of the tumor to the middle ear structures. MR better demonstrated the relation of the tumor to the adjacent internal jugular vein and carotid artery. The paragangliomas had a characteristic MR appearance based on their vascularity. Serpiginous areas of signal void representing high vascular flow were interspersed among areas of high signal intensity caused by slowly flowing blood and tumor cells. This "salt-and-pepper" pattern was seen in all lesions greater than 2 cm in maximal dimension. MR was therefore able to accurately characterize the tumors as highly vascular. Multiplanar imaging and good tissue contrast and anatomic detail permitted display of the relations of these neoplasms to surrounding carotid sheath vessels and to intracranial structures better than did CT. In this experience, the MR appearance of paragangliomas was quite characteristic and differed markedly from meningiomas, neuromas, and metastatic disease of the skull base.

Complications of percutaneous nephrolithotomy

Abstract: Of 582 patients who underwent percutaneous nephrolithotomy, 4% had complications. The most common complications were fever (23%) and bleeding necessitating transfusion (12%). Extravasation was seen in 7% of patients and transient ureteral obstruction in 6%. Other complications included pneumothorax or hydrothorax, pneumonia/atelectasis, paralytic ileus, nephrostomy-tube dislodgment or urine drainage from the flank lasting more than 1 week, significant infection, urinoma formation, renal pelvic laceration, ureteral avulsion, ureteropelvic or ureteral stricture, bowel injury, or escape of stone fragments into the retroperitoneum. Seven patients (1%) required immediate surgery: four to repair renal pelvic lacerations, one to repair a ureteral avulsion, and two to control bleeding after nephrostomy-tube removal when embolization failed. Four patients required delayed surgery for ureteral or ureteropelvic junction strictures, which may have been caused by a tissue reaction to the stones rather than by the procedure itself. There were two deaths--one from respiratory failure in a patient with severe interstitial pulmonary fibrosis and chronic renal failure and the other from myocardial infarction in an obese diabetic patient with hypertension.

MR imaging of marrow changes adjacent to end plates in degenerative lumbar disk disease

Abstract: MR studies of the lumbar spine in 41 patients were analyzed at 203 disk interspaces to assess the appearance and frequency of bone marrow signal changes in the vertebral bodies adjacent to normal and degenerated disks. Degenerative changes were found at 58 interspaces; an abnormal bone marrow signal was identified in 29 (50%) of these. On spin-echo pulse sequences with short and long repetition times (TRs) and echo times (TEs), an area of relative increased signal intensity was seen in the vertebral body adjacent to the disk in 24 cases (17 were bandlike on both sides of the disk, four were focal on one side of the disk, and three were bandlike and focal on one or both sides of the disk). In one patient decreased signal was noted on both short and long TR/TE imaging. In the other four patients decreased signal was noted on short TR/TE pulse sequences and increased signal was evident on long TR/TE. These marrow changes were not present adjacent to normal disks. The relatively high signal intensity on both short and long TR/TE pulse sequences suggests that the increased signal resulted from the conversion of normal hemopoietic bone marrow to fatty marrow. We conclude that bandlike or focal areas of high signal intensity in the bone marrow adjacent to degenerated intervertebral disks occur commonly on MR images of the spine and must not be confused with signal changes from tumors or infections involving the disk space and adjacent vertebral end plates.

Intensity correction in surface-coil MR imaging

Abstract: The use of surface coils in MR imaging has made it possible to obtain images of superficial structures with improved signal-to-noise ratio relative to conventional circumferential receiver coils [1 -4]. However, the signal intensity distribution in surface-coil images is inherently nonuniform; the decreased sensitivity to signal from more distant regions implies a conresponding decreased sensitivity to noise from those regions. As the total noise detected is uniformly distributed over the image, there is a net increase in the signal-to-noise ratio in the image of regions closer to the coil as compared with the conventional receiver coil [1 , 5]. The resulting range of relative intensity over surface-coil images makes it difficult to display them properly or to analyze them quantitatively. In addition, the local image contrast will decrease proportionally to the average local intensity. We report a method for correcting such surface-coil images so as to produce a uniform relative intensity over the region being imaged.

Evaluation of renal transplant rejection by duplex Doppler examination: value of the resistive index

Abstract: The increasing use and availability of renal transplantation has resulted in a demand for noninvasive methods to study possible complications. One of the most serious adverse reactions is acute rejection, a possibly reversible cause of transplant failure if treated promptly. Differentiation from other causes of acute renal failure frequently is difficult, and the lack of specificity in many imaging studies has been troublesome. Eighty-one patients with renal transplants, including 41 with acute rejection, were examined. Duplex Doppler examination of the intrarenal arteries and a simplified formula, the resistive index ([peak systolic frequency shift--lowest diastolic frequency shift]/[peak systolic frequency shift]), were used to diagnose rejection. With a resistive index greater than 0.90, a 100% positive predictive value was obtained for the diagnosis of acute rejection. A value less than 0.70 was unlikely to be rejection (negative predictive value, 94%). This approach uses a simple analysis of the wave...

Soft-tissue masses: histologic basis for decreased signal (short T2) on T2-weighted MR images.

Abstract: Most soft-tissue masses and tumors of various etiologies and histologies have high signal intensity on T2-weighted pulse sequences (long T2). Of 47 soft-tissue masses, seven had a low signal (short T2) on T2-weighted pulse sequences. All seven masses were tumors, and histologic review showed that their composition differed from that of the other 40 lesions with a long T2 in that the seven masses were relatively acellular and had more collagen. The tumors with a short T2 included one malignant and six benign soft-tissue tumors. Malignant fibrous histiocytoma and aggressive fibromatosis showed paradoxical signal intensities in that they showed both long and short T2. All of the tumors with low signal intensity on T2-weighted images had significant fibrous elements and marked hypocellularity. This study suggests that the less commonly encountered short T2 may be seen in both benign and malignant soft-tissue lesions. A part of the explanation for the low signal on T2-weighted sequences appears to be the relative acellularity and abundant collagen of these tumors in comparison with those that have the same histologic diagnoses but show a high signal. The histologic composition of the tumor rather than the histologic diagnosis appears to influence the MR signal on T2-weighted sequences.

Improving MR image quality in the presence of motion by using rephasing gradients.

Abstract: Numerous techniques exist for suppressing ghosting artifacts due to respiratory motion on MR images. Although such methods can remove coherent ghosting artifacts, motion during gradient pulses also leads to poor image quality. This is due to phase variations at the echo caused by changes in velocity from one phase-encoding view to the next. The effect becomes severe for long sampling times and long TE values and can lead to low estimates of T2. We discuss general, robust modifications of the standard gradient or spin-echo sequences by using rephasing gradients that force the phase of constant-velocity moving spins to be zero at the echo. These sequences lead to a significant reduction in motion artifacts and hence improvement in image quality. They can be applied to multislice, multiecho, water/fat, and gating schemes as well. Since motion problems are universal, it would appear that these modified sequences should come into common usage for MR imaging.

Cine MR imaging: potential for the evaluation of cardiovascular function.

Abstract: MR imaging is valuable in defining cardiac anatomy in a variety of cardiac abnormalities. However, evaluation of cardiac function by this technique has been limited by long imaging times and low temporal resolution. New, recently described pulse sequences shorten imaging time considerably and improve temporal resolution. This paper reports our early experience with cine MR imaging of the heart, a technique of gradient-recalled acquisition in the steady state (GRASS) that uses low flip angles and gradient-recalled echoes. Images were obtained in 36 subjects (14 normal volunteers and 22 patients with coronary artery or valvular heart disease) and displayed in a cinegraphic mode for assessment of cardiac function. The acquisition of 10 to 12 levels, covering the whole heart with up to 24 time frames per level, required a maximum imaging time of only 30 min. Because systole and diastole were readily identified, and the contrast between blood and surrounding structures was excellent, systolic wall thickening, wall motion, and motion of the cardiac valves were visualized easily. Regions of myocardial infarcts were clearly visible and characterized by lack of systolic wall thickening and/or diastolic wall thinning. Turbulence caused signal loss within the flowing blood, which usually had higher signal intensity than myocardium. Therefore, turbulent blood flow in valvular regurgitation and in valvular and subvalvular stenosis could be detected. Cine MR imaging is a promising new technique for the evaluation of myocardial and valvular function.

High-resolution sonography of acute appendicitis.

Abstract: During a 7-month period high-resolution sonography was used in the evaluation of 68 patients with an equivocal clinical diagnosis of acute appendicitis. The sonographic findings were correlated with surgical-pathologic outcome in 32 cases and with clinical follow-up in the remainder. This technique was found to be accurate in the diagnosis of acute appendicitis with a specificity of 95%, a sensitivity of 80%, and an accuracy of 90%. The predictive value of a positive test was 91%; that of a negative test was 89%. The results show that high-resolution sonography is indicated to establish the diagnosis of acute appendicitis in patients with equivocal clinical findings.

Reduced Signal Intensity on MR Images of Thalamus and Putamen in Multiple Sclerosis: Increased Iron Content?

Abstract: High-field-strength (1.5-T) MR imaging was used to evaluate 47 patients with definite multiple sclerosis and 42 neurologically normal control patients. Abnormal, multiple foci of increased signal intensity on T2-weighted images, most prominent in the periventricular white matter, were apparent in 43 of 47 MS patients and in two of 42 control patients. A previously undescribed finding of relatively decreased signal intensity most evident in the putamen and thalamus on T2-weighted images was seen in 25 of 42 MS patients and correlated with the degree of white-matter abnormality. In the normal control patients a prominently decreased signal intensity was noted in the globus pallidus, as compared with the putamen or thalamus, correlating closely with the distribution of ferric iron as determined in normal Perls'-stained autopsy brains. The decreased signal intensity (decreased T2) is due to ferritin, which causes local magnetic field inhomogeneities and is proportional to the square of the field strength. The...

Carotid cavernous fistulae: indications for urgent treatment.

Abstract: Angiographic and clinical data from 155 patients with carotid cavernous fistulae were retrospectively reviewed to determine angiographic features associated with increased risk of morbidity and mortality. These features included presence of a pseudoaneurysm, large varix of the cavernous sinus, venous drainage to cortical veins, and thrombosis of venous outflow pathways distant from the fistula. Clinical signs and symptoms that characterized a hazardous carotid cavernous fistula included increased intracranial pressure, rapidly progressive proptosis, diminished visual acuity, hemorrhage, and transient ischemic attacks. Cortical venous drainage from the carotid cavernous fistula is secondary to occlusion or absence of the normal venous outflow pathways and is associated with signs and symptoms of increased intracranial pressure and an increased risk of intraparenchymal hemorrhage. Angiographic demonstration of a cavernous sinus varix, with extension of the sinus into the subarachnoid space, is associated wi...

Neonatal hydronephrosis in the era of sonography

Abstract: During a 6-year period (1979-1985), 142 neonates with significant hydronephrosis were seen. Seventy-eight percent of the cases were discovered on fetal screening during obstetric sonography. Maternal/fetal intervention was virtually never indicated and most babies were asymptomatic. The most common conditions found were obstruction of the ureteropelvic junction (41%), obstruction of the distal ureter (usually primary megaureter) (23%), upper-pole hydronephrosis associated with duplex anomalies (13%), and posterior urethral valves (10%). Seventeen neonates with multicystic dysplastic kidney were seen (three per year or one for every eight with hydronephrosis). In comparison, during the 30-year period, 1947-1977, 146 neonates with significant hydronephrosis were seen. Most cases were discovered because the patients had signs and/or symptoms--either an abdominal mass (an enlarged kidney or bladder) or urosepsis. The three most common conditions were obstruction of the ureteropelvic junction (22%), posterior ...

Study of movement disorders and brain iron by MR.

Abstract: Heavily T2-weighted high-field MR images provide a unique opportunity for the evaluation of the extrapyramidal motor system. The images are affected by the presence of small amounts of naturally occurring paramagnetic substances—principally iron—that delineate the neostriatum (caudate and putamen), globus pallidus, red nucleus, substantia nigra, and dentate nucleus, primarily by a decrease in signal secondary to the T2* effect. Movement disorders are associated with either increased or decreased signal or both in these structures, depending on the pathologic process. In the initial evaluation of 113 patients with a variety of movement disorders, good correlation of imaging abnormalities can be made with a simplified schema of the extrapyramidal pathways and a system of classification of abnormal movements, parkinsonism/tremor, dystonia, chorea, myoclonus, and hemiballismus. Parkinsonisms are characterized by abnormalities of the cortico-ponto-cerebello-dentato-rubro-thalamo-cortico-spinal tract or the nigrostriatal tract. Dystonias are characterized by abnormalities of the neostriatum predominantly affecting the putamen. Choreas are also characterized by abnormalities of the neostriatum but predominantly affecting the caudate nucleus. Hemiballismus is characterized by lesions affecting the subthalamic nucleus or associated pathway.

MR imaging of the prostate gland: normal anatomy

Abstract: MR images of the male pelvis in 55 subjects were analyzed retrospectively for depiction of the zonal anatomy of the prostate gland as related to different repetition (TR) and echo (TE) times, slice thickness, plane of imaging, chronologic age of the patient, and different magnetic field strengths. With imagers operating at 0.35 and 1.5 T, T2-based tissue-contrast images were needed for the demonstration of the internal anatomy of the prostate gland. The display of zonal anatomy was improved when continuous 0.5-cm slices were used. Evaluating sequential sections, the peripheral, central, and transition zones could be differentiated. The peripheral zone showed higher signal intensity than either the central or transition zone and was discerned in the coronal, sagittal, and transverse planes. The central zone was of low signal intensity and was well displayed in the coronal and sagittal planes. The central zone was seen in 31 of the 32 young men (aged 25-35 years) but in only eight of the 23 older men (aged 40 years and older). The transition zone had intrinsic MR parameters similar to the central zone, and the two could be distinguished from each other only by the knowledge of their respective anatomic location. The low-intensity transition zone blended with the periurethral glands and the preprostatic sphincter. The transition zone was of homogeneous low signal intensity in young men but varied in size and signal intensity in older men. Such a detailed display of the prostate zonal anatomy offers a unique potential for the evaluation of prostatic physiology and disease.

Renal adenocarcinoma: CT staging of 100 tumors.

Abstract: The preoperative CT scans of 100 pathologically proven renal adenocarcinomas were retrospectively reviewed to assess the accuracy of CT for staging the tumor. Regardless of tumor stage, perinephric extension was assessed with a sensitivity of 46% and a specificity of 98%. The sensitivity of CT in detecting venous invasion (either venous enlargement or thrombus) was 78%, with a specificity of 96%. For detection of metastatic adenopathy, CT had a sensitivity of 83% and specificity of 88%. Adjacent organ invasion was correctly identified in 60% of patients, with a specificity of 100%. Overall, CT correctly staged 91% of patients. If errors associated with perinephric invasion were excluded, CT staging accuracy improved to 96%. CT is useful in staging renal adenocarcinoma. If the renal vein is not well seen, angiography or sonography may be necessary to determine the presence of venous tumor extension.

CT evaluation of Crohn's disease: effect on patient management.

Abstract: CT scans from 80 consecutive patients with clinically symptomatic Crohn's disease were reviewed retrospectively to determine the effect of CT diagnosis on patient management. The initial clinical impression and any subsequent change in patient management because of the CT findings were noted. In 22 (28%) of the 80 patients, significant previously unsuspected findings led to a change in medical or surgical management. These included 12 patients with fistulae, four with abscess, two with avascular necrosis of the femoral head, two with sacral osteomyelitis, and single cases of pelvic inflammatory disease and femoral vein thrombosis.

MR imaging of the carpal tunnel: normal anatomy and preliminary findings in the carpal tunnel syndrome

Abstract: MR imaging was performed through the carpal tunnel in 18 wrists of nine normal volunteers and compared with cryomicrotome sections from cadaver wrists. MR reliably imaged the flexor retinaculum and carpal bones and thus defined the borders of the carpal tunnel. In all cases the median nerve was seen as an ovoid structure of moderate signal intensity and was easily distinguished from the flexor tendons of the hands running in the carpal tunnel. The tendons were separated from each other by their tendon sheaths, and this allowed for identification of the various tendons. Anatomic variations encountered in the normal volunteers included anomalous positioning of the origin of the lumbrical muscles within the carpal tunnel in two, persistent median arteries in two, and interposition of the median nerve between the flexor pollicis longus and the superficial flexor tendon to the index finger in one. Preliminary observations in 10 wrists of patients with carpal tunnel syndrome include segmental and diffuse swelling of the median nerve in six, distortion of the nerve in one, and thickening of the tendon sheaths in one. We conclude that MR imaging accurately and reliably displays the normal anatomy of the carpal tunnel and can detect morphologic changes in patients with carpal tunnel syndrome.

Cholangiographic findings in hepatic artery occlusion after liver transplantation.

Abstract: Because the hepatic artery provides the only blood supply to the biliary tree of a liver allograft, posttransplantation arterial occlusion may result in a biliary complication. Cholangiograms were reviewed retrospectively in 31 transplant patients who had proved complete or partial occlusions of the hepatic artery (thrombosis in 29 and marked stenosis in two). Cholangiograms were abnormal in 26 (84%). The most common abnormality, seen in 16 patients, was nonanastomotic contrast leakage from the donor intra- or extrahepatic bile ducts. Strictures of the donor biliary tree occurred in 14 patients, four of whom also had a nonanastomotic bile leak. In 12 of the 14, the strictures were nonanastomotic. Other findings included poor filling of the intrahepatic bile ducts, generalized donor ductal dilatation and irregularity, and intraductal filling defects. Sixteen (89%) of 18 transplants with nonanastomotic contrast leakage had occlusions of the hepatic artery. Of 21 transplants with nonanastomotic strictures, 12 (57%) had occlusions of the hepatic artery. Only two (10%) of 20 transplants with biliary anastomotic strictures had arterial occlusion. We conclude that liver transplant recipients who exhibit nonanastomotic contrast leakage or nonanastomotic strictures on cholangiography should be evaluated for occlusion of the hepatic artery as the probable cause.

CT and MR of the temporomandibular joint: comparison with autopsy specimens

Abstract: CT and MR imaging have been advocated for use in the diagnosis of disorders of the temporomandibular joint. A systematic comparison of these imaging techniques has not been made. We performed direct sagittal CT and sagittal MR on 15 fresh temporomandibular joint autopsy specimens and compared our diagnoses with cryosectional findings in a blinded fashion. We found no statistically significant differences between these procedures in detecting bony abnormalities or disk position. However, a side-by-side comparison between the CT and MR images demonstrated that MR depicted the soft-tissue anatomy of the joint with greater detail than did CT. Thus, MR clearly displayed the disk when it was positioned either superiorly or anteriorly, whereas CT only showed the disk adequately when it was positioned anteriorly. MR further showed the configuration of the disk and the borderlines between the disk and its attachments; these relationships could not be assessed from CT images. This experimental study indicates that MR is superior to CT for depiction of soft-tissue changes, whereas CT is superior in showing osseous abnormalities. Clinical confirmation of these results is necessary before one method can be definitively recommended over the other for clinical studies.

Percutaneous ethanol injection in the treatment of liver neoplasms

Abstract: The effectiveness of percutaneous ethanol injection therapy was investigated in 30 patients who had hepatocellular carcinoma (18 had a single lesion and 12 had multiple lesions). In patients who had a single lesion, ethanol injection was especially effective. Histopathologic examination, performed in nine cases in this group, showed that the tumor was completely necrotic in six cases, 90% necrotic in two cases, and 70% necrotic in the remaining case. In eight other cases with a single tumor, follow-up angiography showed complete disappearance of the tumor stain. In the other case, CT showed the nonenhanced low-density area. In the 12 patients with multiple lesions, ethanol injection was performed as part of an integrated treatment plan. Eleven were still alive at the end of the study (the mean follow-up period was 5.8 months). We conclude that ethanol injection may be a valuable treatment for hepatocellular carcinoma.

Radiographic characteristics of skull fractures resulting from child abuse

Abstract: Radiographic characteristics of skull fractures in 39 cases of documented child abuse were compared with skull fractures in 95 cases of accidental injury to determine if differential features could be identified. All children were less than 2 years old. Emergency room and hospital records for these patients were also reviewed. The results of this study show that clinical features did not provide any clues as to whether the children had been injured by abuse or by accident. However, it was found that multiple fractures, bilateral fractures, and fractures crossing sutures occurred significantly more often in abuse cases than in accidental injury. When such fractures are present, abuse should be suspected.

Primary adrenocortical carcinoma: CT evaluation with clinical correlation

Abstract: Clinical histories and CT findings were reviewed in 38 patients with primary adrenocortical carcinomas. The primary tumors exhibited central areas of low attenuation representing tumor necrosis (n = 26), irregular contrast enhancement (n = 16), detectable calcification (n = 9), and a thin, capsulelike rim surrounding the tumor (n = 7). Tumors metastasized to liver (n = 9), lung (n = 5), and lymph nodes (n = 5). In eight of nine cases of liver metastasis the primary tumor arose in the left adrenal gland. Evidence of endocrinopathy was present in each of nine patients with lesions 6 cm or less in diameter, but in only two of seven adults with lesions exceeding 15 cm in diameter. We conclude that, contrary to established concepts, adrenocortical carcinoma may present as a smooth, homogeneous, functioning mass 6 cm or less in diameter on CT.

Sonographic guidance in diagnostic and therapeutic interventions in the pleural space.

Abstract: One hundred eighty-seven diagnostic and therapeutic interventional procedures in the pleural space were performed by using sonographic guidance. These consisted of diagnostic aspiration (118), drainage of malignant and nonmalignant effusions (41), empyema drainage (17), pleural sclerotherapy with tetracycline or bleomycin (7), and pleural biopsy (4). Diagnostic aspiration was performed with 20-gauge needles, and therapeutic and empyema drainages were performed by trocar technique with either a 7-French Sacks catheter or a specially designed empyema drainage catheter. Pneumothoraces were seen in 3% of the patients, and most of these were treated by the radiologist with placement of a Heimlich valve. We conclude that the use of sonography allows rapid localization of pleural fluid collections and instant monitoring of drainage of noninfected fluid collections and empyemas.

The accuracy of CT in the staging of carcinoma of the prostate.

Abstract: Previous studies have reported the accuracy of CT in distinguishing stages of prostatic carcinoma, but they lack uniform surgical proof of histopathologic stage. We evaluated CT scans in 32 patients who underwent radical prostatectomy to assess its role in the preoperative staging of prostatic carcinoma. Two experienced radiologists blindly interpreted CT scans of the pelvis; they looked for evidence of tumor beyond the prostatic capsule and involvement of the seminal vesicles (stage C) or involvement of pelvic lymph nodes (stage D). Sixty-four interpretations in 32 patients yielded a specificity of 75% for predicting stages A or B disease (local disease), a sensitivity of 50% for the prediction of stages C or D, and an overall accuracy of staging of 67%. Interpretation errors were due to an inability to detect lymph node metastases, errors in evaluating the seminal vesicles, and errors in interpreting densities surrounding the prostate gland. Our data suggest that CT should not be used to influence decisions concerning surgical vs nonsurgical treatment in patients with clinically staged local disease and is only useful when unsuspected metastatic nodal disease is detected.

The biophysical basis of tissue contrast in extracranial MR imaging.

Abstract: So that radiologists can understand better the differences between tissues that determine MR image contrast, the biophysical basis of proton-MR tissue contrast is reviewed. Differences in the molecular sizes of water, fat, and protein macromolecules affect the rate of molecular motion, which in turn influences relaxation times. Differences in the physical state of water within tissues determine the extent to which the motion of water is restricted by binding to hydrophilic macromolecules (e.g., protein), which in turn causes variable amounts of T1 and T2 shortening. Understanding these concepts and knowing the location in the body of free water, cellular tissues, fat, collagen, bone, and tissue iron improve the radiologist's ability to extract useful information from MR images.

New needle for MR-guided aspiration cytology of the head and neck.

Abstract: CT-guided aspiration cytology is valuable in the work-up of many deep head and neck lesions [1]. Since MR imaging is rapidly replacing CT as the imaging study of choice for evaluating many areas of head and neck pathology, the ability to perform MR-guided aspiration cytology is becoming increasingly important. Attempts at MR-guided biopsy with conventional stainless steel CT needles result in images with unacceptably large image artifacts that obscure underlying anatomy. A needle for MR-guided biopsies of the liver first developed by Mueller et al. [2] has decreased the number of artifacts and is ideal for relatively thick MR sections of the liver. The decreased artifact of the liver needle necessary for thicksection liver studies is still too large to locate small lesions in areas of complex head and neck anatomy where higher resolution and thinner MR sections are necessary. Other investigators are studying nonferrous plastic sheaths with larger diameters for MR-guided percutaneous drainage procedures [3]. Finally, new field-echo imaging techniques with narrow flip angles, which probably will be the most practical pulse sequences for MR-guided biopsy because of their speed, tend to accentuate magnetic susceptibility artifacts of all needle types because of the increased T2 sensitivity of gradient refocusing techniques [4]. We describe a new MR needle with fewer artifacts on both spin-echo and gradient-echo sequences that is ideal for MRguided aspiration cytology of head and neck lesions using high-resolution, thin-section MR imaging. Materials and Methods

MR imaging of the aortic root and proximal coronary arteries.

Abstract: Six patients who had recently undergone selective coronary and left ventricular angiography were prospectively examined with MR to show the aortic root and proximal coronary arteries. The examinations were performed with a superconductive 1.5-T instrument with spin-echo sequences and ECG-gated multiple slices of 5-mm thickness. The location and plane direction of the scan were guided by findings on initial coronary MR scout scans and by a review of the angiograms. In four of the six patients both coronary orifices and the proximal centimeters of both coronary arteries were identified. In the remaining two, only the left proximal coronary artery was seen. Although segments of more peripherally located portions of the main coronary arteries and branches were detectable, a prospective and conclusive identification without knowledge of the angiographic anatomy would have been extremely difficult. Differential diagnostic problems, such as erroneous interpretation of pericardial recesses and coronary veins, were observed. Unsuccessful demonstration of the right coronary artery orifice in two cases coincided with more peripherally located occlusion of the vessels on the angiogram. MR with spin-echo sequences appears to be unsatisfactory for diagnosis of coronary arteriosclerotic disease, but it may be useful in other conditions that result in significant coronary dilatation, such as fistulae and aneurysms.

Malignant nerve-sheath neoplasms in neurofibromatosis: distinction from benign tumors by using imaging techniques.

Abstract: Malignant peripheral nerve-sheath neoplasms frequently complicate neurofibromatosis causing pain, enlarging masses, or neurologic deficits. However, similar findings sometimes also occur with benign nerve neoplasms. Our study was done retrospectively to determine if imaging techniques can differentiate malignant from benign nerve tumors in neurofibromatosis. Eight patients with symptomatic neoplasms (three benign, five malignant) were studied by CT in eight, MR in six, and 67Ga-citrate scintigraphy in seven. Uptake of 67Ga occurred in all five malignant lesions but not in two benign neoplasms studied. On CT or MR, all eight lesions, including three benign neoplasms, showed inhomogeneities. Of five lesions with irregular, infiltrative margins on CT or MR, four were malignant and one was benign. Of three lesions with smooth margins, one was malignant and two were benign. One malignant neoplasm caused irregular bone destruction. Accordingly, CT and MR could not generally distinguish malignant from benign les...