Fractional laser‐assisted delivery of methyl aminolevulinate: Impact of laser channel depth and incubation time

Background and Objectives

Pretreatment of skin with ablative fractional lasers (AFXL) enhances the uptake of topical photosensitizers used in photodynamic therapy (PDT). Distribution of photosensitizer into skin layers may depend on depth of laser channels and incubation time. This study evaluates whether depth of intradermal laser channels and incubation time may affect AFXL‐assisted delivery of methyl aminolevulinate (MAL).

Materials and Methods

Yorkshire swine were treated with CO₂ AFXL at energy levels of 37, 190, and 380 mJ/laser channel and subsequent application of MAL cream (Metvix®) for 30, 60, 120, and 180 minutes incubation time. Fluorescence photography and fluorescence microscopy quantified MAL‐induced porphyrin fluorescence (PpIX) at the skin surface and at five specific skin depths (120, 500, 1,000, 1,500, and 1,800 µm).

Results

Laser channels penetrated into superficial (～300 µm), mid (～1,400 µm), and deep dermis/upper subcutaneous fat layer (～2,100 µm). Similar fluorescence intensities were induced at the skin surface and throughout skin layers independent of laser channel depth (180 minutes; P < 0.19). AFXL accelerated PpIX fluorescence from skin surface to deep dermis. After laser exposure and 60 minutes MAL incubation, surface fluorescence was significantly higher compared to intact, not laser‐exposed skin at 180 minutes (AFXL‐MAL 60 minutes vs. MAL 180 minutes, 69.16 a.u. vs. 23.49 a.u.; P < 0.01). Through all skin layers (120–1,800 µm), laser exposure and 120 minutes MAL incubation induced significantly higher fluorescence intensities in HF and dermis than non‐laser exposed sites at 180 minutes (1,800 µm, AFXL‐MAL 120 minutes vs. MAL 180 minutes, HF 14.76 a.u. vs. 6.69 a.u. and dermis 6.98 a.u. vs. 5.87 a.u.; P < 0.01).

Conclusions

AFXL pretreatment accelerates PpIX accumulation, but intradermal depth of laser channels does not affect porphyrin accumulation. Further studies are required to examine these findings in clinical trials. Lasers Surg. Med. 44: 787–795, 2012. © 2012 Wiley Periodicals, Inc.     

Comparison of the thermal tissue effects produced by aged sapphire and silica hemispherical tips

This study evaluated the performance of sapphire and fused silica hemispherical tips under the same exposure conditions. Lesions produced in the chicken breast and a blood field were sectioned for light and transmission polarizing microscopy. Lesion size and thermal damage area were recorded as a function of the tips accumulated exposure. The tips transmission was measured after every 1,000 J of exposure. Fused silica tips lasted for ～5,000 J and experienced significant surface and transmission deterioration. The sapphire hemispherical tips lasted for > 12,000 J with no surface and transmission deterioration. Lesions produced with the fused silica tips generally increased in depth with use, and depths of 6 mm were common. Lesions produced by the sapphire tips were subsurface spherical areas of coagulation with the tissue surface relatively intact. This difference in resulting lesions may be attributed to the higher thermal conductivity of sapphire. © 1994 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Comparison of lymph node yield in robot‐assisted laparoscopic prostatectomy with that in open radical retropubic prostatectomy

Study Type – Therapy (case series)
Level of Evidence 4

OBJECTIVE

? To investigate both the feasibility and the adequacy of pelvic lymph node dissection (PLND) during robot‐assisted laparoscopic prostatectomy (RALP) by comparing lymph node yields obtained during RALP with those obtained during traditional open retropubic radical prostatectomy (RRP).

PATIENTS AND METHODS

? We retrospectively reviewed 1047 patients who underwent radical prostatectomy between 2001 and 2009. ? In all, 626 patients underwent RALP while 421 patients had traditional open RRP. All patients undergoing bilateral PLND were included in our analysis. ? Lymph node yields and lymph node involvement for each surgical approach were calculated and examined. ? PLND‐related complications were analysed.

RESULTS

? Of the 1047 patients, 816 patients underwent bilateral PLND of whom 473 underwent RALP, while 343 underwent RRP. The mean lymph node yields for the RALP cohort (7.1, interquartile range 4–10) was significantly higher (P < 0.001) than for the RRP cohort (6.0, interquartile range 3–8). ? The percentage of patients with nodal involvement was 1.1 for RALP and 2.3 for RRP (P= 0.167). ? Mean age, preoperative PSA values, and pre‐ and postoperative Gleason scores were similar between the two cohorts. ? PLND‐related complications were similar between both cohorts.

CONCLUSIONS

? In patients undergoing RALP, PLND is feasible and provides lymph node yields comparable with those of the standard open approach. ? PLND should be strongly considered in all radical prostatectomy patients when clinically indicated, regardless of surgical technique.