Two-photon three-dimensional optical storage memory.

We describe the design and construction of ultrahigh capacity three-dimensional, 3D, optical storage devices that operate by two-photon absorption. The molecular systems and their properties that are used as two photon media for writing and one photon for accessing the stored information within the volume of the device are presented in some detail and the nonlinear two-photon absorption mechanism is briefly visited. The optical system and its components, which facilitated writing and reading, are also described and the bit density, bit error rate, store and access speeds, cycle times, and stability of the materials under various experimental conditions are also topics addressed in this review. The first ever storage of terabyte data in a removable storage disk is described in detail.

The blanching process due to copper vapour laser treatment of port-wine stains.

We describe the causes and speed of transient blanching during copper vapour laser treatment of port-wine stains. Five watts of yellow (578 nm) light from a copper vapour laser was scanned over the lesion using a computer controlled scanning system. The clinical response of the lesion to treatment is transient blanching, followed immediately by erythema. The clinical response of sclerosed vessels is different in that an intravascular coagulum is observed. We measure the time taken for the lesion to blanch using two methods. First, high-speed photography is used to photograph the treatment process. Second, a photodiode measures the light re-emitted from the skin. Using illumination times of 3 to 5 ms and fluences of approximately 10 J cm-2, blanching times varied between 0 and 33 ms. We conclude that the cause of the transient blanching is not thermal denaturation of either collagen or epidermal melanin. Rather it is the rapid expulsion of red blood cells from the treated vessels. Our results have caused us to commence clinical trials using a new treatment protocol aimed at further improving the response of port-wine stains to copper vapour laser treatment.

Mechanism for improving the signal-to-noise ratio in scanning optical microscopes.

We demonstrate an improved signal-to-noise ratio in a scanning optical microscope used to read out information from a magneto-optical data storage layer. By placing a shading band in the return path of the optical system we can reduce noise by as much as 3 dB in certain spatial frequency ranges. The signal-to-noise ratio improvement arises from differences in the signal and noise distributions in the pupil of the optical system. Although the experimental results are shown only in one dimension, the concept is applicable to two-dimensional scanning of low-contrast samples.

Optical data storage readout with quadrant pupil detection.

A novel detection scheme that uses combinations of quadrant signals derived in a pupil of the optical system is described for optical storage devices. The signals arise because of an asymmetry in the reflected light distribution when the focused spot scans data with a nonzero tracking offset. Theoretical and scalar diffraction characterization indicates that the signals may be useful for improved data density by reducing intertrack interference (cross talk). The signals may also be useful for providing a tracking error signal.

The facial distribution of port wine stains on patients presenting for laser treatment.

During a 2-year period, 232 patients with port wine stains presented for laser treatment. They were analyzed for the position of the port wine stain with respect to the right and left ophthalmic, maxillary, and mandibular divisions of cranial nerve V and the right and left cervical plexus. Fifty-one percent of the facial lesions were confined to either the right or left maxillary division, and 72% of the lesions were confined to just one of the eight nerve regions; 5.9% of the lesions occupied regions on both sides of the face, whereas 49.8% were confined to the right side and 44.3% to the left. In comparison with a group of 103 patients studied by Ohtsuka of Japan, there appeared to be significantly more patients in the maxillary division (p less than 0.0001) and significantly fewer patients in the ophthalmic division and in the combination of ophthalmic and maxillary divisions (p less than 0.00001).

A computer controlled scanner for the laser treatment of vascular lesions and hyperpigmentation.

A computer controlled scanner has been used with a copper vapour laser for the treatment of vascular lesions and hyperpigmented lesions. The computer controls the position and speed of travel of the laser spot during treatment. The illumination time is adjustable with a minimum of 1 ms. The light from the laser is scanned over the lesion so that the lesion is 'painted in' in a raster-like scan of arbitrary shape and produces a series of parallel lines 0.6 mm apart.

Copper vapour laser treatment of port-wine stains and other vascular malformations.

Over a 2-year period more than 1350 treatment sessions have been conducted with yellow 578 nm light from a copper vapour laser on a variety of vascular malformations. Of these sessions half were of port-wine stains, from 297 patients. The light is applied by scanning a 1 mm optical fibre approximately 2 mm above the lesion along the lines of Langer. We use a maximum scan rate of 3 s/cm2, which is the highest rate at which minimal blanching can be produced. Up to 6.5 watts of light has been used, and a typical energy fluence is 20 to 30 J/cm2. Topical melanin suppressing creams are used before and after treatment, in order to maximise the effectiveness of the treatment. Non-vasoconstricting anaesthetics are always used. Repeat treatments are 3 months apart. The scan rate we used was directly correlated with the light intensity. The degree to which the colour of the port-wine stains lightened after the first treatment was also well correlated with the scan rate (p less than 0.0005). The faster the scan rate, the greater the colour reduction. This provides some supporting evidence for the short illumination time that theoretical models have indicated as "ideal". The lightening was more marked for patients whose lesion colour was initially dark (p less than 0.0005). Those whose skin had a high melanin content (Maori, Polynesian and Asian) responded more slowly than others. Thirty-six patients have had a greater than 70% reduction in the size of their lesions after an average of four treatments. Ten patients have responded poorly after at least four treatments (10% of all those who have had four or more treatments). The occurrence of scarring, hyperpigmentation and hypopigmentation was low in comparison with that reported previously from the green light of argon ion lasers.

Computed temperature distributions around ectatic capillaries exposed to yellow (578 nm) laser light.

We have numerically modelled the thermal effects of yellow (577 or 578 nm) light illumination on the ectatic blood vessels of port wine stains. We investigated the effect of the laser treatment parameters of light irradiance and illumination time on the extent of coagulation (coagulation thickness) of the endothelial cells of the ectatic vessels. We assumed that this coagulation is dependent on heating the cells to a critical temperature (coagulation temperature). We iteratively adjusted the treatment parameters so that the model vessels had a maximum temperature that did not exceed the boiling point of blood. Given the likely range of variation of coagulation temperature, coagulation thickness and vessel size, coagulation temperature was found to have the greatest effect on the treatment parameters. Variations in coagulation thickness had less influence, and the diameter of the ectatic vessel (typically in the 30-80 microns diameter range) had the least effect. The treatment parameters that have been shown clinically to cause purpura (e.g. 6-7 cm-2 in 360 microseconds) were also studied. The purpura seen by some workers using pulsed dye lasers is most likely to be the result of vaporisation of blood leading to the rupture of the vessel. We conclude that, in order to achieve coagulation with these short laser pulses, the choice of irradiance is critical.

Histology of port wine stains after copper vapour laser treatment.

We report histological changes in four patients with port wine stains treated with 578 nm yellow light from a high power copper vapour laser. Histology showed that selective damage occurred to the ectatic blood-vessels in the dermis, without haemorrhage and damage to non-vascular structures, and without scarring. The initial damage to the overlying epidermis was not permanent, and the damaged ectatic vessels returned to normal size or were completely necrosed and replaced by collagen.

Thermal profiles of blood vessels heated by a laser.

Thermal profiles of ectatic capillaries, modelled on those found in port wine stain birthmarks, are calculated by a method of finite differences. Yellow 578nm light is assumed to illuminate these vessels. The coagulation of endothelial cells is assumed to occur when the cells are heated to at least 70 degrees C. We model this by asking that a point 6 microns above the top of the vessel lumen attains a temperature of 70 degrees C. We constrain the parameters to prevent heating of blood above 100 degrees C, so as to avoid vapourisation. The treatment parameters of dose and illumination time are varied until they produce thermal profiles that show the model's coagulation conditions. being treated and are rather longer than the thermal relaxation time of the vessel and also much longer than the pulses of pulsed dye lasers.

Reconstruction of the lower lip.

Carcinoma of the lip arises in the strip of exposed mucosa between the mucocutaneous junction and the point of contact of the lips. Removal of the entire area at risk usually prevents recurrence or the development of a second primary tumor. A classification of lower lip involvement is presented, the various modes of treatment are reviewed, and surgical techniques for providing a pouting lower lip vermilion are described.

The vascular anatomy of the pectoralis major myocutaneous flap.

The vascular anatomy of the pectoralis major muscle and overlying skin and subcutaneous tissue was investigated in seventeen cadaver specimens by cannulation of the arterial supply and injection of contrast medium. A rich anastomosis between the internal mammary artery and the pectoral branch of the thoraco-acromial artery and between the pectoral branch and the lateral thoracic artery was demonstrated. In 36% of cases a major axial cutaneous vessel, originating close to the thoraco-acromial artery, was shown to extend caudad. The lateral thoracic artery, in addition to the pectoral branch, contributed significantly to the vascularity of the pectoralis major muscle and was the main blood supply to the female breast. The skin overlying the muscle was abundantly supplied from the muscle vasculature. Both the major arteries were enclosed within the muscle's fascial envelope. A technique for developing a standard pectoralis major myocutaneous island flap is described. Our studies show that a hemichest flap incorporating all the skin of the chest over the muscle is feasible.