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Biomedical subjects

R M Friedenberg

Publications and source records attributed to R M Friedenberg.

At least 19 recordsLinked to original sources

The acceleration of gallstone destruction with synchronous biliary lithotripsy and contact dissolution in vitro using three cholesterol-solubilizing solvent.

In the first-known application of its kind, shockwave lithotripsy and contact-solvent dissolution of large, calcified gallstone burdens were performed simultaneously with three chemical solvents, each tested separately in an in vitro model, with the combined effects on gallstone eradication examined. Two solvents, ethyl propionate and isopropyl acetate, were chosen for their solubilizing ability and potentially high level of patient safety. The third solvent, a 70%:30% mixture of methyl tert-butyl ether (MTBE) and dimethyl sulfoxide (DMSO), was chosen for its known ability to accelerate the dissolution of calcium-containing gallstones. All stones were matched for size, weight, and number. Gallstone lithotripsy performed in ethyl propionate was significantly more effective (P less than .02) in the production of fragments less than 2 mm when compared with bile; lithotripsy with isopropyl acetate and the MTBE/DMSO mixture showed no statistically significant effect. Biliary lithotripsy performed in an ethyl propionate medium may enhance gallstone dissolution and the production of small fragments (diameter less than 2 mm).

Acetates

NMR angiography of coronary vessels with 2-D planar image scanning.

On the basis of the principles of the time-of-flight method and the 3-D angiogram obtained by the 2-D planar image scanning technique using 90 degrees RF pulses with short repetition time, we have obtained a coronary angiogram around the heart including the coronary arteries and veins. The cine NMR imaging technique is also incorporated in synchronizing ECG R waves to reduce the motion artifact and at the same time to induce the saturation effect on the static samples. Images of the large bulk blood flow corresponding to the heart chamber and descending aorta are further removed by postprocessing. The final 3-D angiogram is then formed by stacking the 2-D images and contrast is further enhanced by the maximum ray tracing algorithm.

Algorithms

Noninvasive evaluation of hepatic fibrosis using frequency demodulation of ultrasound signals.

A new ultrasound image can be produced by frequency demodulation (FM) of the conventional ultrasound signal. This new FM image appeared to produce a more accurate representation of the fine structure of the liver. The individual features of the FM image were correlated with hepatic portal fibrosis and cirrhosis on liver biopsy in 34 patients with minimal hepatic fat and sinusoidal collagen. An overall ultrasound score correlated with portal fibrosis (r = 0.788; P less than 0.001). We conclude that the FM image may be helpful in measuring and following the progression of hepatic fibrosis in patients with chronic liver disease.

Biopsy

Frequency-demodulated US: evaluation in the liver. Work in progress.

Frequency modulated (FM) imaging is a new ultrasound (US) modality that uses pulse-echo signal instantaneous frequency in addition to the conventional envelope information. Eight features of the FM image in nondiseased livers are described. The technique is evaluated in a study of 34 patients with biopsy-proved diffuse liver disease. Visual grading of FM US image features shows good correlation with levels of biopsy-graded hepatic fibrosis. Patients with diffuse parenchymal liver disease often exhibit evidence of the abnormality when FM liver imaging is used, while such evidence is not as well demonstrated with conventional envelope (AM) imaging.

Humans

Intravenous digital subtraction angiography (DSA) of hemodialysis access fistulae.

Hemodialysis access fistulae or grafts are subject to a variety of complications, including thrombosis, stenoses, and aneurysm or pseudoaneurysm formation. The usual radiologic methods to evaluate these problems consist of retrograde venous angiography or standard femoral or brachial arteriography. Both are invasive, and may traumatize the artery or graft. Six patients with internal blood access were studied using digital subtraction angiography; five using a central venous injection and one with direct graft injection. Preliminary results indicate that intravenous digital subtraction angiography (IV-DSA) can depict the anatomy of access fistula with adequate spatial resolution. Pathologic entities (stenoses, aneurysms) can be demonstrated, as well as other findings of uncertain clinical significance (kinks and webs). In addition, hemodynamic data can be inferred from the near-physiologic sequence of vessel opacification. Methods are in development that will allow determination of absolute blood flow in pertinent vessels via IV-DSA. There were no complications in this small series, and all examinations were performed on outpatients utilizing standard technique.

Adult

Growth changes in the thoracic aorta of the piglet following patch angioplasty.

Patch repair of the thoracic aorta using prosthetic graft material in neonates and infants has been advocated, but long-term results have not confirmed that the residual aorta grows. In this study five piglets had portions of aortic tissue excised, ranging from 38% to 72% of the aortic wall. Each pig underwent patch angioplasty repair of the thoracic aorta with prosthetic graft material. Piglets achieved full growth at approximately six months. Aortic catheterization and contrast angiography were done in each animal before it was killed. Growth and histologic study of the aorta was documented at postmortem examination. There were no blood pressure gradients at rest or with isoproterenol hydrochloride (Isuprel)-epinephrine challenge in four of the five piglets. In one animal that underwent a 72% resection of the aortic circumference, a 20-mm gradient was present at rest. It was concluded that the thoracic aorta in piglets will grow adequately to allow patch grafting of up to 70% of the aortic circumference.

Animals

Digital subtraction ductography.

Digital subtraction techniques used in the examination of eight patients with salivary and nasolacrimal disease are described. Pleomorphic adenoma, ductal stricture, extrinsic masses, parotid-otic fistula, and a radiolucent calculus were demonstrated. The procedures are more easily performed than film techniques, and pathology is better demonstrated by digital ductography than on a film examination. Image subtraction, reregistration, and window manipulation allowed clear demonstration of ducts about the head and neck, overcoming limitations imposed by inherently high object contrast. Digital subtraction ductography is an important nonvascular application of digital imaging technology.

Adult

Digital tomography: description and preliminary clinical experience.

Digital tomography was performed in 30 patients using a new prototype system with a PET-Scope image tube. Twenty-eight exposures are obtained during a single revolution of the x-ray source over the volume of tissue to be imaged. The sum of the radiation produced by the 28 exposures is about equivalent to a single routine exposure of the part imaged. The data accumulated can provide up to 200 tomographic sections at intervals of 5 mm. Reconstruction time for each section is 3 sec. The raw images may be reconstructed as often as desired. Algorithms are being developed to allow axial and sagittal reformations. Further work is required to improve spatial resolution and contrast and to develop algorithms to allow subtraction of blurred images above and below the reconstructed site. The authors believe that digital tomography may eventually replace most routine tomograms.

Adult

Various applications of corpus cavernosography.

The authors believe corpus cavernosography is an important aid in the evaluation of metastatic lesions, priapism, impotence, atrophy and fibrosis of the penis, and trauma to the penis. By visualizing the emptying of the contrast material from the cavernous spaces into the veins draining the penis, it is possible to assess the length of time that the contrast material remained in the organ.

Humans

Schistosomiasis.

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Blood Vessels