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Peter F. Kelly, D.P.M., F.A.C.F.A.S.  
  
Diplomate, American Board of Podiatric Surgery  
Fellow, American College of Foot and Ankle Surgeons


PHOTODYNAMIC THERAPY "PDT"  
  
MECHANISM OF OPERATION   
 
1. Requires an injection, dissemination and systemic absorption of  
	protoporphyrins   
2. Malignant cells take up the protoporphyrin   
	These can be visualized under UV light  
	Patient must remain away from all light during this treatment  
		session and have a photosensitivity up to six weeks
		post treatment  
3. Laser radiation is applied at a specified frequency, usually red light  
	area.  
	and for a specified time - result is Joules to tissue  
4. Wavelength depends on protoporphyrin  
5. Results in a singlet oxygen produced which destroys malignant tissue  
	selectively   
  
BIOSTIMULATION "BIOSTIM"    
 
1. A few milliwatts hitting mitochondria stimulating thermal mechanism.    
2. No heat is produced.    
3. Mitochondrial chromophores.  
4. This is FDA investigational.  
5. Applied to wound healing, to nerve regeneration, and chronic pain-- 
	analgesic.  
6. Elicits a systemic effect  
7. 0 milliwatts, tunable dye, helium-neon, 12 joules per week for 30  
	weeks  
8. Applied to rheumatoid arthritis, trigeminal neuralgia, osteoarthritis,  
	sciatica, diabetic neuropathy.  
9. Has 60 to 85% of pain relief  
10. 5-hydroxyindolacetic acid, 5-HIAA produced  
	Urinary HIAA output increase correlated with pain relief  
11. Systemic effects:    
	stimulation of human lymphocytes  
	Decreased pain and inflammation of distant ion irradiated sites  
	Increased urinary 5-HIAA, product of serotonin metabolism  
12. Dose:  
	50 milliwatts, tuneable dye or helium-neon laser,   
	12 joules per week for 30 weeks.  
13. Proposed mechanism:    
	absorption of light by photoreceptor or chromophore in the  
	mitochondria activates the respiratory chain, resulting in a 
	cellular response.  
14. Primary process:  
	a. Electron train excitation   
	b. acceleration of electron transfer in redox pairs (activates and  
	stimulates).  
	c. Transfer of excitation energy from oxygen   
		to singlet oxygen (oxidative effect inhibiting healing).  
	d. Respiratory chain components are probably the primary  
	photoacceptors.  
	e. Flavins, cytochromes, cytochrome oxidase.  
	f. Respiratory chain in a unitary dynamic system can be acted  
	upon at various points causing change in the whole state of  
	response.  

Summary:    

1. Effects are dose dependent.  Higher energies seem to be damaging.	  
2. Coherent light is preferred versus non-coherent.  
3. Narrowed band monochromatic light preferred, i.e. helium-neon  
	coherent and monochromatic light  
4. Competing wavelengths cancel the effects, therefore coherent light is  
	preferred.  
5. Transcutaneous irradiation penetrates deeply enough to   
	produce generalized effect in many cases.  
6. 4 joules/cm2 penetrates approximately 1 cm.  
7. Local radiation with systemic effects.  
	i.e., 5-HIAA production from serotonin metabolism.  
8. Depends upon the physiological status of cell before radiation.  
9. The biostimulation effect is not always possible.