MONSTIR: The UCL 32-channel time-resolved imager

MONSTIR in the UCL neonatal intensive care unit (May 2006).

MONSTIR is a novel medical imaging instrument built to exploit a new technique known as optical tomography. This technique involves generating three-dimensional (3D) images of biological tissues using measurements of transmitted light. Absorption of light (visible and near-infrared radiation) by haemoglobin and other natural chromophores enables optical tomography to reveal information about tissue oxygenation, haemodynamics and metabolism, harmlessly and at the bedside. However, when light travels through human tissues it is very strongly scattered, so that an incident beam of light cannot penetrate more than a few millimetres before all photons have been scattered many times.Generating images despite the overwhelming scatter represents a significant challenge, and various technologies have been explored to overcome the effects of scatter. (A summary of the development of near-infrared imaging techniques is available by clicking here). The design of MONSTIR (click here for a detailed technical description) is intended to enable as much information to be extracted as possible from measurements of light transmitted across large thicknesses of tissue. Specifically, the device measures the flight times of photons transmitted between pairs of points on the surface using very short pulses of laser light and 32 parallel time-resolved detectors.

Our efforts to pursue optical tomography as a clinical technique has also involved the development of highly sophisticated image reconstruction algorithms which enable the internal distribution of optical properties to be derived from our experimental measurements. This work has been performed by the group led by Simon Arridge, who have produced a software package known as TOAST which is available for download (click here for details).

Construction of MONSTIR began in 1996, and the first images of tissue-equivalent phantoms were acquired in 1999. Following further validation using phantom studies, research has focused on three specific clinical applications: imaging the neonatal brain, the adult female breast, and muscle. A list of publications describing MONSTIR and the results of experimental investigations (including some which are available for download) is available by clicking here.

The development of MONSTIR and the performance of experimental and clinical studies has been generously supported by grants from the Wellcome Trust, the EPSRC, and the European Commission. For further information about the imaging research at the Biomedical Optics Research Laboratory, including enquiries about possible research opportunities (e.g. undergraduate and M.Sc projects, Ph.D projects, and postodoctoral positions), or if you have any questions or comments related to this website, please contact Jem Hebden.