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Biomedical subjects

P B Dean

Publications and source records attributed to P B Dean.

At least 37 records · Page 2Linked to original sources
PubMed1995

Massive osteoarticular knee allografts: structural changes evaluated with CT.

PURPOSE: To analyze the structural changes seen at computed tomography (CT), particularly the findings that precede insufficiency (fatigue) fractures in massive osteoarticular knee allografts. MATERIALS AND METHODS: The subchondral and cancellous bone of 12 allografts were retrospectively evaluated with repeat transaxial CT (mean follow-up, 53 months). RESULTS: Early cortical graft resorption was followed by slow thickening after 6 months. Formation of resorptive cysts increased the cortical irregularity, which leveled off after 2 years. Late remodeling was evident as a subcortical sclerotic rim, "neocortex." Initially, the cancellous graft bone showed higher attenuation than the host bone; this difference subsided gradually during the first 3 years. Four insufficiency fractures were detected after the 1st postoperative year. Poor remodeling preceded these fractures. CONCLUSION: CT effectively depicted the structural changes during allograft incorporation and was superior to plain radiography for the detection of insufficiency fractures. The use of CT for follow-up of massive osteoarticular knee allografts provides additional information concerning the readiness of the graft for weight bearing.

Adolescent↗
PubMed1994

Incorporation and clinical results of large allografts of the extremities and pelvis.

The results of implantation of 37 large deep-frozen allografts with 29 osteoarticular grafts of the extremities and pelvis following the resection of malignant or aggressive benign bone tumors were evaluated at followup (mean, 6 years; range, 2.5-20 years). The patients had excellent or good results in 62% of all cases according to the Mankin-Waber functional rating score, and a corresponding rating of 81% in the Musculoskeletal Tumor Society Score. Benign versus malignant disease rated 83% and 76%, respectively, in the Musculoskeletal Tumor Society Score, and 67% and 46%, respectively, in the Mankin-Waber score. Radiological and nuclear medicine (single-photon emission computed tomography) studies and histological biopsies indicated that the incorporation, perfusion, and replacement with new bone was only partial and of a low degree. Late degenerative cartilage and sclerotic changes occurred in 20 of 29 cases with osteoarticular grafts. The best functional results were achieved with knee osteoarticular allografts (81%-88%) compared with modest results in the proximal humerus (69%) and hemipelvis (57%) according to the Musculoskeletal Tumor Society Score rating. Chemotherapy did not influence the union or infection rate of the allografts. In the 4 cases (11%) with infection, all grafts could be salvaged, but the functional results were only 63% in the Musculoskeletal Tumor Society Score. The overall complication rate was high (57%); graft-related complications occurred in 43%, including fatigue fractures in 27%. There were no cases of nonunion at the host graft junction. Clinical rejection did not occur. These clinical results may be improved in the future by new technology that uses bone substitutes, growth factors, and bone morphogenetic proteins.

Adult↗
PubMed1990

MR imaging of experimental intramuscular hemorrhage at 0.02 T. Contrast enhancement with Gd-DOTA.

Intramuscular hemorrhage was induced by injecting autologous blood into the paraspinal muscle of 8 rabbits. In order to evaluate the time-dependent changes of hemorrhage observed on MRI, the animals were imaged at different stages of blood resolution at 0.02 tesla (T), and control examined with ultrasound using a 7.5 MHz linear transducer. Six inversion recovery sequences (TR = 1,000 ms. TE = 30 ms, and TI = 18, 48, 148, 201, 302, and 398 ms) were used for the in vivo calculation of T1 relaxation times. IR 1,000 (398)/30 imaging was performed before and after the Gd-DOTA administration. The hemorrhage was evident on MR images throughout the study, especially on the T2 weighted (SE 1,000/100) images. MRI showed the healing lesion longer than ultrasound. The T1 relaxation time increased during the time of resolution. Lesions on days 4 to 7 enhanced in intensity after the injection of Gd-DOTA.

Animals↗
PubMed1989

The present state of screening for breast cancer.

The results to date are convincing enough to justify recommending large scale mammography screening. The International Union Against Cancer (UICC) Workshop on screening for breast cancer in 1986 concluded that "In countries where breast cancer is common and where the necessary resources are available, screening using mammography alone or mammography plus physical examination is applicable as public health policy." The Swedish government has recommended screening with mammography for all women aged 40-74. This recommendation repeatedly emphasizes the necessity of high-quality examinations interpreted by well-trained radiologists. Screening with mammography is bringing breast cancer patients to therapy at a far earlier stage in the development of the disease. This calls for a re-evaluation of therapeutic methods.

Adult↗
PubMed1988

X-linked myopathy with excessive autophagy: a new hereditary muscle disease.

We report on 3 brothers with a myopathy that also affected their maternal grandfather and great-uncle. Characteristic features are onset in early childhood, very slow progression, normal life expectancy, weakness of proximal limb muscles, especially in the legs, elevation of serum creatine kinase, and no cardiac or intellectual involvement. In biopsy material muscle fibers are almost never necrotic but show excessive autophagic activity and exocytosis of the phagocytosed material. We suggest that this family has an undescribed type of congenital myopathy, for which we propose the name X-linked myopathy with excessive autophagy.

Adult↗
PubMed1988

Experimental acute pancreatitis: MR relaxation time studies using gadolinium-DTPA.

Spin-lattice (T1) and spin-spin (T2) relaxation times of normal and sodium taurocholate-induced pancreatitis (38 rats) were determined in vitro using a 10.7-MHz magnetic resonance (MR) spectrometer. The increase in pancreatic T1 time in acute hemorrhagic pancreatitis correlated well with the elevated water content of the organ. Gadolinium-DTPA did not affect significantly the relaxation times of normal pancreas in vitro during 1 t 20 min postinjection, but it decreased the elevated T1 times of inflamed pancreas almost to baseline values. MR imaging studies of rat pancreas in vivo (8 rats, 0.35-T resistive magnet) indicated that the swollen pancreas and associated edema were depicted using a T2-weighted SE sequence. Fifteen minutes postinjection of gadolinium-DTPA a homogeneous enhancement of inflamed pancreas was detected. The differentiation of pancreatic necrotic foci from surrounding viable tissue and edema could not be detected on Gd-DTPA-enhanced MR images after 15 min postinjection although microscopical workup indicated these different tissue constituents in the pancreas.

Acute Disease↗
PubMed1988

Paramagnetic contrast enhancement at 0.02 T: an experimental study using Gd-DOTA in normal and hydronephrotic kidneys.

Both normal and experimentally hydronephrotic rabbits were imaged at 0.02 T using partial saturation (PS 160/30) and inversion recovery (IR 1000/200/40) sequences. The signal intensity of normal renal medulla and cortex markedly increased after the injection of 0.1 mmol/kg of Gd-DOTA. In the unilateral total hydronephrosis the dilated renal pelvis did not contrast enhance after 15 and 35 min of Gd-DOTA injection. The enhancement pattern was similar in 1- and 3-week-old hydronephrosis. The effect of Gd-DOTA on renal T1 times at 0.02 T was studied using rats. Fifteen minutes after the Gd-DOTA injection (0.1 mmol/kg) the T1 times of excised rat kidneys decreased from 311 to 90 ms. The authors conclude that the enhancement of the MR signal of the kidney by Gd-DOTA at an ultralow magnetic field (0.02 T) is similar to its enhancement at higher fields (greater than 0.15 T).

Animals↗
PubMed1988

Does dilution of contrast media affect contrast enhancement? An experimental study in rats.

The effect of contrast media (CM) dilution on contrast enhancement was studied using CM representing four structurally different molecular types at osmolalities ranging from 135 to 1340 mosm/kg. Diatrizoate (ionic monomer), iopamidol (nonionic monomer), ioxaglate (ionic dimer), and iodecol (nonionic dimer) were each given at a dose of 500 mgI/kg and at concentrations of both 300 and 150 mgI/mL. Contrast media concentrations were measured using iodine 125I. Tissue blood volumes were determined using human serum albumin labeled with 131I. For each of the four CM at each of the two concentrations and after each of five time intervals following injection (0, 15, 40, 120, and 300 seconds), five rats were killed (total = 200 rats). Blood and 14 other tissues were studied. Dilution of the CM did not lead to any lower iodine tissue concentrations, iodine distribution volumes, plasma volumes, or hematocrit. The authors conclude that lowering CM osmolality by dilution with water should improve tolerance without affecting CT contrast enhancement.

Animals↗
PubMed1988

Comparative pharmacokinetics of gadolinium DTPA and gadolinium chloride.

An intravenous injection of 153Gd-labeled gadolinium-DTPA or gadolinium chloride was given to 60 rats, which were killed either 15, 40, 120, 300, 900, or 3600 seconds later. Tissue concentrations of gadolinium in the blood, liver, spleen, stomach, pancreas, renal cortex, renal medulla, lungs, heart, adrenals, gluteal muscle, fat, skin, thymus, brain, thyroid, and parathyroids were measured. Five animals were killed at each time interval with gadolinium-DTPA, and at each of the latter four time intervals (15 and 40 seconds excluded) with gadolinium chloride. The pharmacokinetics of gadolinium-DTPA and chloride differ markedly in terms of tissue concentration, distribution volumes, and the time course of these parameters. Gadolinium, when injected as a chloride, evidently forms insoluble carbonate and phosphate precipitates in the blood, which are taken up by the reticuloendothelial system. The distribution of gadolinium-DTPA on dynamic MRI should closely parallel the distribution of iodinated contrast media on dynamic computed tomography.

Animals↗
PubMed1987

The control of breast cancer through mammography screening. What is the evidence?

There are few forms of cancer that can be effectively controlled. Now that there is sufficient evidence demonstrating that mortality from breast cancer can be reduced with the help of mammography screening, we are faced with the challenge of applying this method on a large scale. What are the major practical problems? The medical profession and decision makers must be made familiar with nature of the recent achievements and with their practical implications. The personnel who will be responsible for undertaking screening have to be adequately trained before screening gets under way. Women should understand the benefits that they can gain from mammography screening so that they will be sufficiently motivated to attend. This can be achieved by sincere, periodic information through the mass media. It is important that every woman eligible for screening understand that her risk of dying from breast cancer will be half as much if she participates in screening as it would be if she fails to participate. She should also be aware that the smaller cancers detected at screening can often be removed by breast conserving surgery without the need for mastectomy. Because mammography does not prevent breast cancer, women must be aware of the fact that mammography has to be repeated at regular intervals if the benefits of screening are to be maintained. Additionally, breast self-examination should be practiced in the interval between screens. Finally, decision makers will have to realize that screening with mammography can, in the long run, lead to reduction of health service costs. It is obvious that the expenses involved in taking care of a patient with advanced breast carcinoma can be very high. As it has been clearly demonstrated that properly performed screening will significantly decrease the number of advanced, costly breast carcinomas, a large proportion of these expenses will be saved in the population invited to screening. Because screening itself drains economic resources, the costs of screening outweigh the savings until the number of advanced cancers decreases; however, after this occurs the expenses of screening will be far less than the savings. The savings arise from the smaller number of advanced, costly cases. The results to date are convincing enough to justify recommending large-scale mammographic screening. The Swedish government has recommended screening with mammography for all women aged 40-74. This recommendation repeatedly emphasizes the necessity of high quality examinations interpreted by well-trained radiologists.

Breast Neoplasms↗
PubMed1986

Renal vein ethanol concentration during ablation of renal cell carcinoma.

Absolute ethanol is an effective embolizing material for the ablation of renal cell carcinoma with a balloon catheter. We have measured the renal vein ethanol concentration during embolization in 9 patients in order to determine whether toxic levels are achieved. Total occlusion of the embolized arteries was obtained using an average of 12.9 ml (range 8-18) ethanol. Renal vein ethanol concentration varied from trace amounts to 0.79%. There was a significant correlation of the maximum renal vein concentration with the ethanol dose per tumor size. The authors conclude that the renal vein ethanol concentration remains sufficiently low to be harmless when a proper balloon occlusion is used. The optimum ethanol dose may be a function of tumor size.

Angioplasty, Balloon↗
PubMed1986

The frequency of hyperamylasemia after ERCP with diatrizoate and iohexol.

The frequency of hyperamylasemia was examined in 88 consecutive patients undergoing ERCP (endoscopic retrograde cholangio-pancreaticography) using either meglumine diatrizoate at 306 mgI/ml., or iohexol at 240 mgI/ml. There was no difference in the incidence of hyperamylasemia between these two groups of patients, nor did any other factors appear to influence its occurrence. The authors conclude that acute hyperamylasemia after ERCP is a complication of relatively minor importance unlikely to be reduced by the use of low osmolality contrast media.

Adult↗