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A Spence

Publications and source records attributed to A Spence.

7 recordsLinked to original sources
PubMed1992

Measurement of blood-brain barrier permeability in a tumor model using magnetic resonance imaging with gadolinium-DTPA.

Sequential MR imaging with gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) and sequential measurements of plasma Gd-DTPA concentration by inductively coupled plasma atomic emission spectroscopy (ICP-AES) were used to estimate the blood-to-tissue transport coefficient (Ki) in the 36B-10 rat glioma model. For these measurements, tissue Gd-DTPA concentration was estimated from tumor enhancement by correlation with calibration measurements obtained by ICP-AES analysis of tumor tissue. The 14 animals for which Ki was calculated can be grouped into those imaged at 11 days following tumor implantation, at 13-18 days, and at 20 days. The mean (+SEM) Ki values for these groups were 1.1 + 0.24, 9.2 + 0.8, and 13.4 + 1.7 ml/kg-min, respectively. These results correspond well with published data obtained by quantitative autoradiography. It is concluded that frequent sequential imaging and a graphical approach to Ki calculation are promising methods for determining the blood-to-tissue transport coefficient noninvasively by contrast-enhanced MRI.

Animals↗
PubMed1988

Improved localization of infratentorial ependymoma by magnetic resonance imaging: implications for radiation treatment planning.

Ependymomas of the posterior fossa extend into the upper cervical spinal cord in approximately one-third of cases. Unfortunately, the posterior fossa and upper cervical cord region is often poorly seen on computed tomography (CT), making radiotherapy planning difficult. We report five cases of posterior fossa ependymoma with extension into the cervical cord where magnetic resonance imaging (MRI) demonstrated the caudal extent of tumor more clearly than CT. The extent of tumor depicted by MRI in each case correlated well with the operative findings. Higher doses of radiotherapy to the entire tumor volume are associated with improved survival in infratentorial ependymoma; however, the radiation tolerance of the cervical spinal cord is close to the dose necessary to control posterior fossa ependymoma, making limitation of radiation field volumes important. MRI may provide a method of precisely defining caudal tumor extent of posterior fossa ependymomas so that limited volume, high dose radiotherapy can be more safely administered to these patients.

Brain Neoplasms↗
PubMed1978

Fast-neutron irradiation of glioblastoma multiforme. Neuropathological analysis.

Various modes of therapy, alone or in combination, have had little effect in improving the survival of patients with glioblastoma multiforme. Recently, in a pilot study, 34 patients with glioblastoma were treated by fast-neutron-beam irradiation of the whole brain. Following treatment, the patients became steroid-dependent and pursued a gradual downhill course with increasing obtundation. Although there was no improvement in the length or quality of survival of these patients, neuropathological studies in the 13 patients who came to autopsy showed the following: 1) extensive coagulative necrosis of much of the tumor mass; 2) dense infiltration by collagenous connective tissue; 3) minimal phagocytic reaction; 4) marked reduction in the amount of viable tumor; 5) abnormal astrocytic proliferation, which may represent either astrocytoma or a radiation-induced bizarre gliosis, and 6) areas of gliosis and white matter degeneration in the brain stem, remote form the tumor site. These observations suggest that continued efforts to further refine this mode of therapy for glioblastoma are warranted.

Adult↗