Author's reply

DS Krupa Shankar, A Kushalappa, KS Uma, Anjay A Pai

 Department of Dermatology and Pathology, Manipal Hospital, Bangalore - 560 017, India

Correspondence Address:
D S Krupa Shankar
Department of Dermatology, Manipal Hospital, Rustom Bagh, Airport Road, Bangalore - 560 017
India

Sir,

The readers′ interest in our article is appreciated as well as their survey of literature. Here are the parameters: make - union medical laser UML 25; de-bulking in continuous wave an continuous mode 9 w to 12 w depending on size of lesion; terminal vaporization - 6.3 w uper pulse continuous; excisions - 6.3 w super pulse continuous coagulation 6W continuous wave; continuous mode - de-focused; asepsis - 10% povidone iodine 5 minutes prior to procedure; anesthesia - 2% lignocaine with adrenaline through a 30 g needle.

The spot size was 0.3 mm. Irradiances cannot be precisely calculated as the hand piece is a focusing hand piece. Hence the figures below are approximate:

• Power: 0.5 to 25 watts, continuously scalable by one decimal place
• Modes: continuous, super pulse [10 w]
• Repeat: 400 Hz
• Beam diameter: 0.3 mm
• On time: .01, 0.1, 0.2, 0.3, 0.5 sec
• Off time: 0.01 to 0.1 sec in continuous and super pulse modes
• Guide beam: Helium Neon, flux adjustable

Since we used a beam diameter of 0.3 mm, the fluence can be calculated as follows:

• Diameter = 0.3 mm = 0.003 cm,
• Hence radius [r] = 0.0015 cm
• Therefore r ² = 0.00000225
• ∏ r ² = 0.000007065
• Irradiance = Power [w] / Spot size[∏ r ² ] = 4.2 / 0.000007065 = 594479 w/cm ²
• Super pulse is 0.9 milli seconds = 0.0009 sec
• Fluence = irradiance x time = 594479 x 0.0009 = 382J /cm ²

The detailed delivery capabilities of the machine used by us are shown in [Table - 1].

True ultra pulse laser is a combination of very short pulse width and high amplitude and is the patented technology of one particular manufacturer; others marketed under the same name give the pulse width but not the amplitude and are no different from gated super pulse lasers in terms of their tissue effects. True ultra pulse laser is very expensive and cannot be recommended to all readers of our journal for indications where it is not needed. Besides, the haloed pages of our journal cannot be used to further the commercial interests of one manufacturer.

Pulse dye laser is not cited as this article is written to encourage Indian dermatologists to use an affordable device that is somewhat skill dependent and not to digress into the realm of expensive and difficult to maintain technologies.