Spontaneous Closure of Large Base Idiopathic Full Thickness Macular Hole

Spontaneous closure of idiopathic full thickness macular hole is a rare case as it occurs in only 3.5% while awaiting vitrectomy surgery. There are few pathologies associated with it such as vitreomacular traction (VMT) and posterior vitreous detachment. We report a case in a 74-year-old man who presented with right eye painless, progressive blurring of vision with idiopathic stage 4 full thickness macular hole which was confirmed on optical coherence tomography. It closed spontaneously after sometimes while waiting for surgery. It is important to monitor closely for the possibility of spontaneous closure based on the optical coherence tomography findings.

First photon detection in time-resolved transillumination imaging: a theoretical evaluation.

First photon detection, as a special case of time-resolved transillumination imaging, is studied through the derivation of the temporal probability density function (pdf) for the first arriving photon. The pdf for different laser intensities, media and second and later arriving photons were generated. The arrival time of the first detected photon reduced as the laser power increased and also when the scattering and absorption coefficients decreased. The pdf for an imbedded totally absorbing 3 mm inhomogeneity may be distinguished from the pdf of a homogeneous turbid medium similar to that of human breast in dimensions and optical properties.

Spatial resolution in fast time-resolved transillumination imaging: an indeterministic Monte Carlo approach.

The spatial resolution achievable in time-resolved optical transillumination imaging through a turbid (scattering and absorbing) medium has been reassessed theoretically. The temporal point spread function was constructed assuming a delta function input pulse, a approximately 50 mm thick medium and a small detector with zero risetime. Temporal profiles were derived from an indeterministic Monte Carlo simulation for different time scales. From the temporal point spread function (TPSF), an analytic edge response function from which the spatial resolution was determined was derived. Previous analytical methods for determining the spatial resolution are approximations for very short flight times (sub-100 ps time region). The results show that a spatial resolution of about two millimetres is possible under ideal signal-to-noise ratio conditions and with detector gate times of the order of ten picoseconds. If this predicted spatial resolution can be achieved in an imaging system, it may be possible to improve the diagnosis of breast tumours.

An indeterministic Monte Carlo technique for fast time of flight photon transport through optically thick turbid media.

A time-resolved indeterministic Monte Carlo (IMC) simulation technique is proposed for the efficient construction of the early part of the temporal point spread function (TPSF) of visible or near infrared photons transmitted through an optically thick scattering medium. By assuming a detected photon is a superposition of photon components, the photon is repropagated from a point in the original path where a significant delay in forward propagation occurred. A weight is then associated with each subsequently detected photon to compensate for shorter components. The technique is shown to reduce the computation time by a factor of at least 4 when simulating the sub-200 picosecond region of the TPSF and hence provides a useful tool for analysis of single photon detection in transillumination imaging.

Detection of gunshot residues in routine CTs.

The forensic assessment of non-fatal gunshot wounds often proves to be difficult as wounds have usually been cleaned and protected with a sterile bandage by the time of the examination. The aim of our investigation was to test the possible application of computed tomography (CT) for the forensic assessment. Doing so raised the questions whether gunshot residues in the soft tissues, detected by means of 3-dimensional CT, can be used as evidence of a close-range shot and whether conclusions can be drawn pertaining to the range of the shot or the type of bullet used based on the distribution of the radiologically detectable material? In this experimental study 39 shots were fired at fresh pig skin and it was possible to distinguish shots fired from distances of more than 10 cm and contact shots independent of the type of bullet. For unjacketed lead bullets, radiopaque material could be seen in the depth of the entrance would for firing distances up to 10 cm. In individual cases, CT data and the 3-D reconstruction could provide valuable information in the forensic assessment of patients with gunshot wounds.