Quantitative tissue oxygen measurement in multiple organs using 19F MRI in a rat model.

Measurement of individual organ tissue oxygen levels can provide information to help evaluate and optimize medical interventions in many areas including wound healing, resuscitation strategies, and cancer therapeutics. Echo planar (19) F MRI has previously focused on tumor oxygen measurement at low oxygen levels (pO(2)) <30 mmHg. It uses the linear relationship between spin-lattice relaxation rate (R(1)) of hexafluorobenzene (HFB) and pO(2). The feasibility of this technique for a wider range of pO(2) values and individual organ tissue pO(2) measurement was investigated in a rat model. Spin-lattice relaxation times (T(1) = 1/R(1)) of hexafluorobenzene were measured using (19) F saturation recovery echo planar imaging. Initial in vitro studies validated the linear relationship between R(1) and pO(2) from 0 to 760 mmHg oxygen partial pressure at 25, 37, and 41°C at 7 Tesla for hexafluorobenzene. In vivo experiments measured rat tissue oxygen (ptO2) levels of brain, kidney, liver, gut, muscle, and skin during inhalation of both 30 and 100% oxygen. All organ ptO(2) values significantly increased with hyperoxia (P < 0.001). This study demonstrates that (19) F MRI of hexafluorobenzene offers a feasible tool to measure regional ptO2 in vivo, and that hyperoxia significantly increases ptO2 of multiple organs in a rat model.

Cerebral palsy in a term population: risk factors and neuroimaging findings.

OBJECTIVE: The purpose of this work was to study risk factors and neuroimaging characteristics of cerebral palsy in term and near-term infants. PATIENTS AND METHODS: Among a cohort of 334,339 infants > or = 36 weeks' gestation born at Kaiser Permanente Medical Care Program in northern California in 1991-2003, we identified infants with cerebral palsy and obtained clinical data from electronic and medical charts. Risk factors for cerebral palsy among infants with different brain abnormalities were compared using polytomous logistic regression. RESULTS: Of 377 infants with cerebral palsy (prevalence: 1.1 per 1000), 273 (72%) received a head computed tomography or MRI. Abnormalities included focal arterial infarction (22%), brain malformation (14%), and periventricular white matter abnormalities (12%). Independent risk factors for cerebral palsy were maternal age > 35, black race, and intrauterine growth restriction. Intrauterine growth restriction was more strongly associated with periventricular white matter injury than with other neuroimaging findings. Nighttime delivery was associated with cerebral palsy accompanied by generalized brain atrophy but not with cerebral palsy accompanied by other brain lesions. CONCLUSIONS: Cerebral palsy is a heterogeneous syndrome with focal arterial infarction and brain malformation representing the most common neuroimaging abnormalities in term and near-term infants. Risk factors for cerebral palsy differ depending on the type of underlying brain abnormality.