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Biomedical subjects

S Bravo

Publications and source records attributed to S Bravo.

11 recordsLinked to original sources
PubMed1991

Histologic basis for increased extraocular muscle enhancement in gadolinium-enhanced MR imaging.

Minimal to mild enhancement of skeletal muscles is normally seen on gadolinium-enhanced magnetic resonance images. The enhancement of the extraocular muscles is much more intense than that of other skeletal muscles. The authors investigated the structural features of extraocular muscles that contribute to this increased enhancement. After comparing samples of extraocular muscle and quadriceps muscle, the authors concluded that the rich vascularity and the prominence of extravascular space most probably cause extraocular muscles to demonstrate intense enhancement on gadolinium-enhanced images.

Gadolinium DTPA↗
PubMed1991

Developing spinal column: gadolinium-enhanced MR imaging.

Enhancement characteristics of the normally developing spinal column were examined in magnetic resonance (MR) images obtained in 58 children aged 7 days to 9 years. With a 1.5-T imager, short-repetition-time spin-echo images were obtained before and after the administration of 0.1 mmol/kg gadopentetate dimeglumine. Enhancement of normal bone marrow was seen in all patients aged less than 7 years; it was marked only in patients aged less than 2 years. Enhancement of normal cartilage, seen in all patients aged less than 1 1/2 years, may be the most striking feature of enhanced MR images of the infant spine. Enhancement of both bone marrow and cartilage in children appears to be due to the unusual prominence of vasculature, associated with permeability of the capillary endothelium and a plentiful extravascular space. Although marked and diffuse enhancement of vertebral bodies in adults is often thought to indicate a pathologic marrow state, caution must be used before the same criteria are applied to children.

Age Factors↗
PubMed1991

Evolution of the infant spinal column: evaluation with MR imaging.

The appearance of the normal lumbar spinal column was examined in spinal magnetic resonance images obtained in 50 pediatric patients aged 2 years or less. The ossification centers of the developing vertebral bodies, the cartilage, and the disks were studied with a 1.5-T imager by using both short- and long-repetition-time spin-echo sequences. Many of the structures of the spine were noted to undergo dynamic changes in appearance, both in signal intensity and in morphologic characteristics, with growth. The vertebrae and cartilage, especially, transform markedly in infancy and proceed through three characteristic stages of evolution. Stage I, from birth to 1 month of age, is characterized by markedly hypointense ossification centers and hyperintense, prominent cartilage. Stage II, from approximately 1 to 6 months of age, is characterized by increasing signal intensity in the ossification centers, progressing from the endplates in, and decreasing prominence of the cartilage, Stage III, from approximately 7 months of age on, is characterized by increasingly rectangular and centrally intense vertebral bodies and diminishing cartilage. The variability of the signal intensities, with that of muscle used as the standard, and morphologic characteristics of different components of the spine at different stages of development can create significant confusion. Careful analysis, however, permits one to follow the evolution of the lumbar spine and to date it on the basis of its appearance.

Cartilage↗
PubMed1990

Low dose rate radiotherapy for transplantable gliosarcoma in the rat brain.

Interstitial brachytherapy with low energy radionuclides is becoming widely used in conjunction with external beam radiotherapy in the treatment of primary malignant gliomas of the brain. Few radiobiological studies have been carried out with low dose rate brachytherapy for brain tumors. Since we have recently developed a non-invasive low dose rate radiotherapy model for the treatment of transplantable 9L gliosarcoma growing in the rat brain, we carried out a series of radiobiological studies to determine the dose rate effect on the tumor and normal brain tissue. Using TCD50 (the radiation dose to control 50% tumor control) as the endpoints, we obtained the results indicating that the tumor control rate was highly dependent on the dose rate and the total dose delivered to the tumor. The TCD50 of dose rates ranging from 100 cGy/min, 120 cGy/hr, and 40 cGy/hr were 25 Gy, 80 Gy, and 100 Gy, respectively. The normal tissue effects were most pronounced with high dose rate irradiation (100 cGy/min). The LD50 for high dose rate irradiation to the whole brain was 29 Gy. In contrast, the majority of animals treated with low dose rate radio-therapy behaved quite normal up to a year follow-up. The late histopathological changes of the irradiated brain usually consisted of vascular and white matter necrosis, although the extent of such changes showed a considerable individual variation within the long-term survivors.

Animals↗
PubMed1989

Effects of intratumoral injection of I-125 iododeoxyuridine on Ehrlich ascites carcinoma.

Intratumoral injection of I-125 iododeoxyuridine (IUdR), saline solution, and oil suspension was investigated using Ehrlich ascites tumors in the thighs of mice. The oil suspension was more effective in tumor growth delay than was the saline solution. Single injection of the oil suspension at the dose of 12.5 microCi resulted in 21.5 days growth delay, whereas 50 microCi of the saline solution resulted in 11.5 days growth delay relative to control growth delay. At 40 days after treatment, higher radioactivities were observed in the tumor and the skin of the mice treated with the oil suspension, which represented the prolongation of I-125 IUdR oil suspension within the tumor. No normal tissue toxicities were observed.

Animals↗
PubMed1989

Spinal lesions: quantitative and qualitative temporal evolution of gadopentetate dimeglumine enhancement in MR imaging.

Seventy gadolinium-enhanced magnetic resonance imaging studies were reviewed, and 36 were selected for quantitative and qualitative analysis of the temporal evolution of contrast medium enhancement of spinal lesions. In the extradural space, lesions often showed mild increase of enhancement on delayed images, but enhancement was always visible on immediate postcontrast images. In the intradural extramedullary space, tumor nodules demonstrated most prominent enhancement on early images, although subtle, strandlike enhancement of the nerve roots showed some delayed uptake of contrast medium on later images. In the intramedullary space, enhancement often increased on delayed images, although this increase was usually mild. For clinical purposes, immediate postcontrast imaging should be sufficient to depict the majority of spinal lesions, regardless of location. However, selected cases, such as necrotic spinal cord tumors, will require delayed imaging.

Contrast Media↗