The potential of superparamagnetic ferrite particles as a contrast agent for magnetic resonance (MR) imaging was studied by in vitro MR spectroscopy and in vivo MR imaging in laboratory animals. After aqueous preparations of ferrite particles were administered intravenously, MR spectroscopy showed greatly decreased T2 relaxation times of liver and spleen, with only minimally altered T1, and no changes in lung, kidney, or muscle. Effects occurred within 30 minutes of injection and persisted for more than 6 months. MR imaging with pulse sequences that provide T2-dependent contrast demonstrated that ferrite produced profound signal loss from liver, spleen, and bone marrow. Sequestration of ferrite particles in hepatic reticuloendothelial cells was confirmed by means of light and electron microscopy. Because ferrite has a potent effect on MR signal and exhibits tissue-specific localization, it warrants further study as a contrast agent for MR imaging of the reticuloendothelial system (i.e., liver, spleen, and bone marrow).

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Sixteen patientswith knewn rectal cancer were evaluated and staged with CT and MR, and at surgery.

The potential of superparamagnetic ferrite particles to enhance detection of liver carcinoma at magnetic resonance (MR) imaging was studied with in vitro MR spectroscopy and in vivo MR imaging in animal models. After intravenous administration of ferrite, MR spectroscopy showed selective shortening of T2 relaxation times in normal liver but not in tumor. MR imaging showed that ferrite produced profound signal loss only from normal liver and not tumor; thus, differences in signal intensity between liver and tumor were greatly enhanced, especially on pulse sequences with T2-dependent contrast. Motion artifacts were reduced as well because of less signal from liver. Microscopic analysis showed sequestration of ferrite particles in hepatic reticuloendothelial cells but not in hepatocytes or tumor tissue, and there was no evidence of cellular injury. Ferrite particles efficiently and predictably enhance signal differences between normal liver and tumor and permit considerable latitude in selection of pulse sequence and timing parameters. Thus, they have considerable promise as a tissue-specific MR contrast agent for improved detection of liver carcinoma.

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.

Experimental animal models of hepatitis, fatty liver, and hepatic iron overload were evaluated using a 3.5-kGauss nuclear magnetic resonance (NMR) imaging system. Increases in image intensity measurements and in T2 relaxation times equalled the sensitivity of histologic findings for the detection of early stages of hepatitis. A significant shift in T1 relaxation times characterized the early stages of hepatic necrosis. Liver triglyceride content correlated significantly with increases in NMR intensity measurements (p less than 0.01); however, changes in liver water content had a much greater influence on intensity, T1, and T2. Thus, it may be possible to distinguish hepatitis from benign fatty liver. Liver iron content correlated with decreases in NMR intensity measurements (p less than 0.001), and iron levels as low as 1.2 mg/g were detected. NMR may more specifically identify hepatocellular iron overload than do other techniques that do not distinguish hepatocellular from reticuloendothelial iron.

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Nonferrous needles of pure brass, titanium, or copper, and ferrous needles of different alloys of stainless steel were analyzed for the size, area, and distribution of the image artifact created when the needles were placed in a 0.6-T magnet. Results demonstrated that a stainless steel prototype needle (type 316) would be visible on magnetic resonance images and would provide an artifact similar to that seen in computed tomographic-guided biopsies. Further testing of this prototype included assessment of the effect on the artifact when changes were made in annealing properties, gauge, length, needle-tip geometry, pulse sequence, and orientation relative to the magnetic field. To date, three human liver biopsies have been successfully and safely performed using a stainless steel type 316 needle.