L. Venkatraghavan

The assessment of resting perfusion measures (mean transit time, cerebral blood flow, and cerebral blood volume) with magnetic resonance imaging currently requires the presence of a susceptibility contrast agent such as gadolinium. Here, we present an initial comparison between perfusion measures obtained using hypoxia‐induced deoxyhemoglobin and gadolinium in healthy study participants. We hypothesize that resting cerebral perfusion measures obtained using precise changes of deoxyhemoglobin concentration will generate images comparable to those obtained using a clinical standard, gadolinium. Eight healthy study participants were recruited (6F; age 23–60). The study was performed using a 3‐Tesla scanner with an eight‐channel head coil. The experimental protocol consisted of a high‐resolution T1‐weighted scan followed by two BOLD sequence scans in which each participant underwent a controlled bolus of transient pulmonary hypoxia, and subsequently received an intravenous bolus of gadolinium. The resting perfusion measures calculated using hypoxia‐induced deoxyhemoglobin and gadolinium yielded maps that looked spatially comparable. There was no statistical difference between methods in the average voxel‐wise measures of mean transit time, relative cerebral blood flow and relative cerebral blood volume, in the gray matter or white matter within each participant. We conclude that perfusion measures generated with hypoxia‐induced deoxyhemoglobin are spatially and quantitatively comparable to those generated from a gadolinium injection in the same healthy participant.

Summary The use of point‐of‐care ultrasound has increased considerably over the last two decades. It has become a readily available, non‐invasive bed‐side modality for the rapid diagnosis and management of patients in various settings. Point‐of‐care ultrasound for assessing the heart, lung, abdomen, airway and vascular systems is now well established. Transcranial Doppler ultrasound for assessing cerebral blood flow has been in use for many years. In recent years, brain ultrasonography has been shown to be a powerful tool in the rapid bed‐side assessment of cerebral haemodynamics and structural pathology. Brain ultrasound has been shown to be useful in both the emergency department and neurocritical care setting for the non‐invasive assessment of raised intracranial pressure, cerebral autoregulation and diagnosis of intracranial haematoma and other space‐occupying lesions. Point‐of‐care ultrasound is an important alternative technique to routine imaging and invasive monitoring techniques, and results are comparable. Competence is easily attainable without formal radiology training. With technological advancement, applications for the use of brain ultrasound continue to grow. This review discusses the clinical use of point‐of‐care ultrasound in the diagnosis and management of brain injury.