PDT: AFTER 2X24 HOURS

Interstitial technique of PDT is used to debulk huge tumours.
The debulking process started hours after illumination by direct cytotoxic effect of PDT into tumour cells and by vascular shutdown
resulting in tumor apoptosis and necrosis.
In order to treat tumours thicker than 1 cm(limit of light penetration depth into the human tissue),the interstitial illumination technique was invented.
By this technique laser fibres with a light diffuser at the tip are implanted into the tumour tissue.
Laser fibres are feed-through needles,which can be placed under image guidance in the tumour(CT,MRI or US).
In large tumours,several fibres can be placed close to each other(12 cm apart) in order to illuminate the entire tumour volume.
Interstitial light delivery allows PDT to be used in the treatment of large,buried tumours and is particularly suitable for those whose surgery would involve extensive resection or for those who are unsuitable for surgery.
Due to the difficult and non precise light dosimetry in the tumout,interstitial PDT is mainly used with palliativeintention,as stated by Xu et al.
The pictures shown are PDT in large tumour of the neck,before (upper picture)and 2x24 hours (lower picture)after laser interstitial illumination.

HPD-PDT SOME TECHNICAL CONSIDERATION

HPD is abbreviation of Hematoporphyrin Derivative
It is a name of a photosensitizer,a chemical compound which will be sensitized and reacted to light.
The pathological cells which retain photosensitizer molecules will be dead due to direct cytotoxic process.
The bloodvessels nurturing the cancer will be shut down.
The necrotic cancer will stimulate the immunity of cancer patient.

The laser:

The machine generates the red visible laser light with a wavelength of 630 nm.The deviation of output wavelength is +/- 5 nm.
The output power of each way (of 3 ways) is from 100 mW to 1000 mw( 1 W),continuously adjustable.
The instability of output power is less or the same of +/- 10 %
The semiconductor laser beam,as the output power is less than 1 Watt,it may lead to three-degree burns on;ly in the situation of focusing or less than 10 mm distance to light extraction end
in using flat-head fiber.

Safety conduct

-Do not look directly at laser beam and its reflex.The visible red light is harmful to eyes.
-All field operator should wear protective glasses
-The protective glasses are specific in its optical density to the laser wavelength which provide enough protection to radiation of 630 nm laser beam
-Patient should wear protective glasses or putting mask on patient's face
-The exposed parts of patient's body should be covered with cloth cover
-Possible explosive matters should be forbidden (alcohol,gasoline,organic solvent.)
-Clothing,gauze and other flammable substances should be removed from the optical path
-A fire extingusher should be placed in the laser area
-Reliable grounding is very important to operation
-Warning labels should be placed to make personsaware of laser operation