Movement-Artefact-Free Measurement of T1 in the Human Eye to Determine Oxygenation of the Vitreous Humour

Nicholas G. Dowell¹, Edward H. Hughes², Paul S. Tofts¹

Accurate and precise T₁ mapping of the eyeball is difficult due to eye movement and image distortions. An accurate measure of T₁ could provide a non-invasive determination of eye oxygenation since T₁ times are subtly increased by reduced partial pressure of oxygen (pO₂) of the vitreous humour in the eye. Poor oxygenation leads to retinopathy and, in patients with low pO₂ at the retina, a vitrectomy may be performed, where the vitreous humour is extracted and replaced by saline. However, there is no clear evidence that an increase in pO₂ is actually achieved by this procedure and MRI would provide an important validation for ophthalmologists. We have developed a technique, using a TrueFISP acquisition sequence, which provides eye images with no movement artefacts, no image distortion and good SNR. This permits the measurement of T₁ (and hence pO₂) from the vitreous humour of the human eye. Furthermore, we show that asking a subject to fixate on a single point can control eye movement but the need to blink limits fixation to < 5 s. Consequently, we will provide an audio/visual cue that warns the subject when they must fixate. This approach to eye imaging could dramatically improve imaging of the eye and retina.