Biomedical subjects
Publications and source records attributed to D Ling.
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.
A double-blind, parallel group comparison study of Hexabrix and Conray 325 for adult intravenous urography was performed. Sixty patients with a mean age of 54 years were included. Doses of contrast ranged from 0.5-1.1 ml/kg for both groups with a mean of 0.7 ml/kg. Hematology, urinary and biochemical laboratory tests were performed prior to the study in all patients and at 24 hours afterward in nearly half the group. Biochemical laboratory tests were done at 72 to 96 hours in approximately one third of the patients. Hexabrix proved satisfactory for standard urography at a chosen dose of 16 g of iodine (50 ml). There were no statistically significant differences in the diagnostic quality of the urogram in the two groups except for bladder filling. The decreased osmotic diuresis associated with Hexabrix necessitated delayed bladder filming for optimal evaluation. Excellent patient tolerance was achieved with less pain on injection with Hexabrix. There was one death in the Hexabrix group in a patient with multiple medical problems. Although the patient's medical problems appeared well controlled and did not meet specific rejection criteria, they almost certainly played a role in his death. Hexabrix may be useful for adult urography at a lower dose range, eg, 16 g iodine, than is typically used, which also may be cost effective (competitive) given the higher projected cost of the new low osmolar agents.
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.
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.
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.
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.
A new antibiotic, crisamicin A, with in vitro activity against Gram-positive bacteria, B16 murine melanoma cells, and herpes simplex, vaccinia, and vesicular stomatitis viruses, has been isolated from Micromonospora purpureochromogenes subsp. halotolerans. On the basis of 1H and 13C NMR spectroscopic, high resolution field desorption mass spectrometric, and circular dichroism studies of the antibiotic and several of its derivatives, the structure of crisamicin A has been assigned.
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 (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.
Computed tomography (CT) has dramatically changed the imaging of pediatric oncologic disease. CT precisely displays and characterizes cross-sectional anatomic pathology. This provides important information for diagnosing and staging tumors in infants and children. The principles, techniques, and indications for computed tomography in the evaluation of pediatric extracranial tumors are reviewed in this article. Selected applications of computed tomography for pediatric tumors of the mediastinum, chest wall, lung parenchyma, abdomen, pelvis, and extremities are discussed and illustrated.
Two normal volunteers and three patients with CT evidence of fatty infiltration of the liver (two nonuniform, one diffuse) were studied to determine whether magnetic resonance imaging using a pulse sequence designed to differentiate fat and water could be used to detect fatty infiltration of the liver in human beings. The magnetic resonance technique used a modified spin echo technique (simple proton spectroscopic imaging) that was designed specifically to exploit the difference in the rate of precession between the protons in a water molecule and the protons in a fatty acid molecule. Images were obtained using in-phase and opposed techniques and were added or subtracted in order to obtain pure water and pure fat images. Quantitative data showed that fatty liver can be separated from normal liver using the spin echo technique, and that the opposed image of the proton spectroscopic technique is more sensitive to small changes in hepatic fatty content than in-phase images with any echo time.
The authors report their experience with magnetic resonance imaging (MR) in 20 patients with CT-proved lymphadenopathy of the abdomen and pelvis. Signal intensity from abnormal nodes was intermediate between fat and muscle (T1 longer than fat and muscle; T2 equal to or slightly shorter than fat but longer than muscle) and was shown best in the spin-echo mode with a TR of 900 msec. and a TE of 30 msec. Abnormal nodes were identified by their increased size and other morphological changes rather than by tissue characteristics established by signal intensity information. Lymphadenopathy due to lymphoma could not be differentiated from that due to metastases. MR detected all lymphadenopathy originally documented by CT and in addition easily distinguished blood vessels from lymph nodes; on the other hand, CT offered better spatial resolution and could be completed in less time.
Magnetic resonance imaging (MRI) was performed in 20 patients with radiologically or surgically proven abdominal aortic aneurysms using a Siemens Magnetom scanner with a 0.35-T superconductive magnet. On MRI, rapidly flowing blood emits little or no signal and appears black; stagnant blood, turbulent flow, and atheromatous plaques produce signals of various intensities and are imaged as light to medium gray. Of nine patients who underwent surgical repair, MRI correctly demonstrated the origin of the aortic aneurysm in nine and accurately determined the status of the iliac arteries in eight. In two patients in whom intravenous contrast administration was contraindicated, MRI provided the correct diagnosis of a mycotic pseudoaneurysm in one and clearly distinguished the iliac arteries from the surrounding fibrosis in the other. Of 11 patients who did not have surgical repair, MRI findings correlated well with other radiologic studies. MRI was found to be more reliable than sonography in determining the relation between the aneurysm and the renal arteries as well as the status of the iliac arteries. Despite these advantages, the authors still advocate sonography as the screening procedure of choice in patients with suspected abdominal aortic aneurysms because of its lower cost and east of performance. MRI should be reserved for patients who have had unsuccessful or equivocal sonographic examinations.
The CT findings of two cases of primary lymphedema of the lower extremities are presented. CT showed a coarse, nonenhancing, reticular pattern in an enlarged subcutaneous compartment. CT excluded the diagnosis of secondary lymphedema from an obstructing mass by demonstrating a normal retroperitoneum and pelvis. The CT findings are correlated with pedal lymphangiograms.
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This study was designed to investigate the effect of Cued Speech on the speech reception abilities of profoundly hearing-impaired children under seven conditions of presentation: audition; lipreading; audition and lipreading; cues; audition and cues; lipreading and cues; and audition, lipreading, and cues. The 18 subjects had been taught through the use of Cued Speech for at least 4 years. The subjects were presented with specially designed speech tests (syllables and key words in sentences) which had been recorded on color videotape, and they responded in writing. Speech reception scores of over 95% with the key word in sentence materials and over 80% with the syllables were obtained with lipreading plus cues, and with audition, lipreading plus cues. Equally high levels of accuracy in speech reception by such children have not previously been reported. The subjects also demonstrated the ability to use audition with the sentence materials, both in combination with lipreading and with cues, though there were large individual differences under these conditions. Speech reception abilities in the lipreading-plus-audition condition were highly correlated with scores for speech production, whereas language attainments were correlated with reception through Cued Speech. The implications of these findings to the field of aural rehabilitation are discussed.