Biomedical Engineering Reference
In-Depth Information
Figure 10.4
Noncoherent blue lamp is a common choice for photoactivating,
aminolevulinic acid in the USA. The Blu-U (DUSA Pharmaceuticals, Inc.,
Wilmington, Massachusetts, USA) emits light at a bandwidth of approxi-
mately 417 ± 5 nm.
Source
: Courtesy of DUSA Pharmaceuticals, Inc.
clearance was observed between the two incubation time
groups. Clearance rates were highest for head lesions at 100%.
According to this large cohort study, it appeared that PDL at
subpurpuric doses allows an effi cient and less painful means
of accomplishing PDT.
In 2003, Smith and coworkers (81) published a three-arm study
on 36 patients with AKs. One arm received treatment with low
concentration 5-FU, the other two arms received ALA-PDT—
using either a PDL or blue light for photoactivation. A short,
1-hour unoccluded incubation was used. Clearance rates at 4
weeks follow-up were similar for 5-FU and ALA-PDL (79% vs.
80%). Clearance rates of PDT using a blue light source were lower
(60%). Additionally, improvements in global photodamage,
hyperpigmentation, and tactile roughness were observed (81).
Figure 10.5
Pulsed dye lasers may be used as a light source for aminolevulinic
acid-photodynamic therapy to target individual lesions, including actinic kerato-
ses, sebaceous hyperplasia, and solar lentigines.
Source
: Vbeam Perfecta (595 nm)
laser image, courtesy of Candela Corporation, Wayland, Massachusetts, USA.
with diagnoses of Bowen's disease (BD), SCCs, basal cell carcino-
mas (BCCs), and AKs. In terms of AK outcomes, a clearance rate
of 100% was achieved at 24-36 months posttreatment.
The initial phase I clinical study for FDA-approval of ALA in
PDT also utilized an argon-pumped dye laser. Thirty-nine of
the 40 enrolled patients completed the dose-ranging study.
Jeffes and coworkers (82) used 0-30% ALA topically with an
extended incubation time of 14-18 hours. Ninety-one percent
clearance was obtained in thin to well-developed AKs on the
face and scalp that were treated with 30% ALA. Extremity
treatment was not as successful with only 45% clearance of
AKs on the limbs. Hyperkeratotic AKs did not respond well to
therapy, and the small number of treated hyperkeratotic
lesions precluded statistical analysis.
Nakano and coworkers (83) reported on the use of an excimer
laser (630 nm) in patients of darker skin types. Thirty Japanese
patients with AKs were divided into two groups based on
lesion appearance. The fi rst group included subjects with
AK lesions 10 mm or less in diameter with the second group
including larger lesions greater than 10 mm in diameter.
Patients received three ALA-PDT sessions weekly for 3 weeks.
Red Light Sources
The longer wavelength of red light allows deeper tissue pene-
tration. Red light is used frequently during PDT with MAL.
Red light may also be used for photoactivation of PpIX during
ALA-PDT. Several laser and light sources emit wavelengths in
the red light spectrum, usually targeted around 630 nm. These
include the argon pumped dye laser, excimer laser, metal halide
lamps, and red LED lamps.
Red Light from Laser Sources
One of the earliest studies reporting on ALA-PDT was com-
pleted by Calzavara-Pinton et al. (17) using an argon pumped
dye laser (630 nm). In the treatment of 50 facial AK lesions,
20% ALA cream was applied topically for 6-8 hours. The study's
patient population also included a mixed pool of 85 total patients
