Magnetic resonance imaging as an adjunct to ultrasound in oligohydramnios. Detection of sirenomelia.
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Biomedical subjects
Publications and source records attributed to R F Mattrey.
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Perfluorochemicals (PFCs) are versatile compounds with a variety of applications in industry and in medicine. Their medical applications are in oxygen transport and diagnostic imaging. These agents are the only ultrasound contrast agents capable of altering tissue echogenicity. The bromine atom in perfluoroocytlbromide (PFOB) makes this agent the only PFC visible by computed tomography. PFOB contains many fluorine atoms and no hydrogen, so it can be used for fluorine MR imaging or as a signal void for hydrogen imaging. All of these applications are presently in clinical trials in the United States and Europe. PFOB is an exciting new contrast agent because of its low or insignificant toxicity, its universality across all imaging modalities, and its potential impact upon diagnostic applications.
On the basis of laboratory experiments, we devised a wire-sheath system for MR-guided biopsy and drainage and then evaluated that system in 10 patients. The localizing system consisted of a 20-gauge plastic sheath into which a stainless-steel alloy wire had been inserted. In laboratory studies, we compared this wire-sheath assembly with other materials to determine its optimal visualization on MR images. We then used the same wire-sheath system to perform 16 procedures (in 10 patients), including six biopsies, five diagnostic fluid aspirations, and five catheter drainages of infected and noninfected fluid collections. The laboratory results showed that the wire-sheath assembly cast a 7-mm artifact, was visualized well on all pulse sequences, and was safe within the magnet (minimal attraction). The assembly was visualized well in each patient and provided adequate localization. MR-guided biopsy and drainage can be performed with high-resolution detail by using this wire-sheath system. Potential uses of this system include (1) treatment of lesions that can be seen on MR images only (or that can be seen to significantly better advantage on MR images than on sonograms or CT scans), and (2) treatment of patients in whom avoidance of the radiation delivered by CT is imperative.
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The preliminary results of perfluorocytlbromide (PFOB) emulsion when used as an intravenous contrast agent for hepatosplenic CT imaging in humans are reported. Ten patients were examined using dosages ranging from 1 to 2 g/kg. There was good clinical and biochemical tolerance. Diagnostic dose for liver enhancement seems to be at least 2 g/kg, whereas 1 g/kg was sufficient for splenic enhancement.
Magnetic resonance imaging was used to evaluate seven patients with undescended testes. In six patients the presence or absence of testicular tissue was predicted correctly prior to surgery. Spermatic cord structures, if present, were accurately visualized in all patients.
High-resolution magnetic resonance (MR) imaging with a surface coil was utilized to evaluate the normal scrotum. Scrotal contents, spermatic canal, and inguinal regions were visualized within the same field of view. Differences in signal intensity in the testis, epididymis, tunica albuginea, fluid, fat, and spermatic cord allowed for clear delineation of these structures in detail. The high contrast and spatial resolution of MR imaging, coupled with the wide field of view and absence of ionizing radiation, make MR imaging well suited for evaluation of the scrotum.
The utility of high-resolution magnetic resonance (MR) imaging in studying a variety of intratesticular and extratesticular pathologic conditions was assessed. The high magnetic signal intensity of the testis provided an excellent background for visualization of intratesticular abnormalities. Except for old blood, all intratesticular processes were less intense than testis, especially on T2-weighted images. The visualization of the tunica albuginea is a distinct advantage, allowing its assessment in cases of trauma or testicular tumors. Epididymal and spermatic cord abnormalities were easily recognized. All pathologic conditions were best seen on T2-weighted images acquired in the coronal plane. Balanced images allowed for tissue characterization.
In animals, perfluorochemicals (PFCs) are effective ultrasound (US) contrast agents that produce hepatic, splenic, and tumor enhancement. The use of Fluosol-DA 20%, an emulsion of perfluorodecalin and perfluorotripropylamine, was studied in nine non-critically ill patients with cancer who had liver lesions. US studies without Fluosol were compared with studies obtained 24, 48, and 72 hours after Fluosol infusion. Vital signs and extensive laboratory analyses are performed before and after Fluosol infusion. Liver metastases from colonic, pancreatic, and gastric carcinoma exhibited rim or diffuse enhancement after a Fluosol dose of 1.6 g/kg or greater. Fluosol produced echogenic enhancement of the liver and spleen relative to kidney at a dose of 2.4 g/kg, allowing the detection of nonenhancing lesions. In addition, Fluosol at a dose of 1.6 g/kg or greater allowed detection of lesions not seen before contrast medium was administered in three of the seven patients studied. There was a mild increase in the level of serum glutamic oxaloacetic transaminase in two patients, one given 2.4 and the other 3.2 g/kg of Fluosol. Mild and transient allergic reactions without change in vital signs were experienced by two patients.
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The ability to distinguish bowel from other intraabdominal structures is essential for the accurate diagnosis of intraabdominal disease with MR. Because perfluorochemicals have no protons, they cause no MR signal. Since they are immiscible with water, they create a signal void in bowel independent of bowel contents and thus are suitable as oral contrast agents. Furthermore, they are tasteless and odorless and have no side effects. We evaluated the use of perfluorochemicals by performing MR scans of the abdomen in rats after the oral administration of unemulsified perfluorohexylbromide or perfluoroctylbromide. Since the latter is approved as an investigational drug for oral use in humans, two volunteers were also studied. Both compounds created signal void in the bowel of both rats and human subjects allowing identification of the gastrointestinal tract. The results suggest that these compounds have potential as oral contrast agents for MR imaging.
Perfluoroctylbromide (PFOB), a perfluorocarbon macrophage-labeling contrast agent, was applied to computed tomographic imaging of septic and aseptic arthritis models in rabbits. Marked enhancement of induced pyarthrosis was observed in both the knee and the sacroiliac joint. Moderate enhancement was noted in tetracycline-induced synovitis of the knee. Sterile synovitis of the sacroiliac joint and simple knee joint effusion showed no enhancement. These results suggest that PFOB is a useful contrast medium for the diagnosis of and distinction between septic and sterile arthritis.
Diagnostic and therapeutic radiologic experience with six patients who had oriental cholangiohepatitis is described. These patients combined had 10 prior operations. Postoperatively each had recurrent cholangitis, numerous stones, concretions, and/or bile duct strictures. Diagnostically, sonography was valuable in the detection of intra- and extrahepatic stones and extrahepatic dilatation of ducts. An important pitfall in sonography was poor visualization of intrahepatic ductal dilatation (due to echogenic sludge filling the ducts) in most patients. CT was helpful diagnostically in all respects. Interventional procedures used postoperatively included percutaneous transhepatic intrahepatic stones, and flushing techniques. Most patients were treated during multiple sessions as outpatients. Cholangitis was the only complication from the procedures. Sectional imaging and interventional radiology perform valuable diagnostic and therapeutic roles in the pre- and postoperative management of patients with oriental cholangiohepatitis.
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Fluosol-DA 20% (Fluosol) and perfluoroctylbromide (PFOB), 2 types of perfluorocarbon emulsions (PFCs), were evaluated as sound contrast agents in imaging acute myocardial infarction (MI) in dogs. Operative ligation of a coronary artery was performed in 9 dogs. PFC was administered 2 days after occlusion. One dog received Fluosol, 10 ml/kg body weight, 2 dogs received 20 ml/kg, and 2 received 25 ml/kg; 2 dogs received PFOB, 20 ml/kg, and 2 dogs received 25 ml/kg. Just before and 2 days after PFC administration, real-time, 2-dimensional ultrasound examination of the heart was performed in the short-axis view from apex to base. No enhancement was seen at the 10-ml/kg dose, but significant mild echogenic enhancement of all MIs occurred after 20 ml/kg. Moderate to marked enhancement was noted after 25 ml/kg. The enhancement was either diffuse throughout the MI or localized to the rim. Initial studies suggest that the mechanism of enhancement is related, at least in part, to the accumulation of PFC-filled macrophages within the MI.
Quantification of myocardial infarct (MI) size is of prognostic importance in patients with acute ischemic damage. Evaluation of the efficacy of interventions for salvage of ischemic myocardium depends on the accurate estimation of the ischemic area and a knowledge of the natural progression of the infarct. Computerized transmission tomography (CTT) is a reliable in vivo technique for estimating infarct size. We serially studied 8 dogs over approximately 1 month after occlusion of the left anterior descending coronary artery using both ungated and prospectively electrocardiogram-gated CTT. Scans were obtained 20 minutes after occlusion and then several more times until the dogs were killed. Using the ungated CTT scans, infarct size increased from 0 to 4 days (+ 65 +/- 20%, mean +/- standard error of the mean, p less than 0.05), then progressively decreased. The initial perfusion defect overestimated the eventual MI size at 1 month by 33 +/- 15% (p less than 0.05). The MI size at necropsy correlated well (r = 0.98, p less than 0.001) with CTT MI size determined just before sacrifice. Non-infarcted left ventricular (LV) muscle mass increased significantly (27 +/- 7% greater at 1 month compared with day 0, p less than 0.01) over time, presumably representing compensatory LV hypertrophy. The LV muscle mass at necropsy correlated well (r = 0.94, p less than 0.001) with CTT LV muscle mass just before sacrifice.(ABSTRACT TRUNCATED AT 250 WORDS)
Thrombi of the left ventricle are common sequelae to acute anterior myocardial infarctions that involve the apex of the heart and produce akinetic or dyskinetic wall thickening patterns. While infarctions of the right ventricle are being increasingly recognized in the setting of inferior myocardial infarcts, little data on in vivo clot formation in the right ventricle of the heart are available in these patients. In the current study we were able to demonstrate a right ventricular mural thrombus using gated computed tomography of the heart. Although an abnormality in the right ventricle extending from the septal margin of the ventricle into the outflow tract could be identified with standard blood pool computed tomographic images and from cross sectional echocardiograms, only with cardiac gating could the relationship between the mass (thrombus) and the noncontractile section of the right ventricular myocardium be clearly identified. We conclude that cardiac gating may help in the evaluation of cardiac masses, and in particular cardiac thrombi. This will be particular valuable in the setting of recent or remote infarction, as the relationship between wall-motion abnormalities and thrombus formation has been well documented.