Time-resolved fluorescence spectroscopy for the diagnosis of oral lichen planus

Abstract

Background: Lichen planus (LP) is a T-cell mediated autoimmune disorder of unknown aetiology that affects the skin, nails, oral and genital mucous membranes. Conventionally, oral LP (OLP) is diagnosed through clinical assessment and histopathological confirmation by oral biopsy.

Aim: To explore the use of time-resolved fluorescence spectroscopy (TRFS) to detect fluorescence lifetime changes between lesional OLP and perilesional normal mucosa.

Methods: In this pilot study, measurements of lesional and perilesional buccal and mouth floor mucosa were conducted in vivo with a TRFS system. Histopathological findings were consistent with OLP in 8 out of 10 patients biopsied. Two patients with histopathological diagnoses of frictional hyperkeratosis and oral candidiasis, respectively, were excluded from the study.

Results: Our preliminary data show that lifetime values in the 360-560 nm spectral range indicate a significant differentiation between normal and diseased tissue. In contrast to the standard oral biopsy procedure, this technique is noninvasive, painless, time-efficient and safe.

Conclusions: Future studies are needed to better elucidate the diagnostic capability of TRFS and to further explore the sources of fluorescence contrast. This pilot study suggests that, based on fluorescence lifetime parameters, TRFS is a very promising technology for the development of a novel OLP diagnostic technique.

Figure 1

A schematic of the system, depicting the time-resolved fluorescence spectroscopy (TRFS) and multispectral (ms)-TRFS modules. F₁, 390/40 nm; F₂, 466/40 nm; F₃, 542/50 nm; F₄, 629/53 nm (not used in the current study); DM₁, 370 nm dichroic mirror; DM₂, 425 nm; DM₃, 515 nm; DM₄, 610 nm; M, moving mirror that controls the operating module (i.e. if positioned between DM1 and DM2, then TRFS measurements are implemented, otherwise ms-TRFS measurements are acquired).

Figure 2

Time-resolved fluorescence spectroscopy (TRFS) measurements from the eight patients considered in this study. (a) Normalized and (b) absolute values of the integrated autofluorescence intensity, and (c) corresponding lifetime values. (d) Section from an oral lichen planus (OLP) punch biopsy sample (haematoxylin and eosin, original magnification × 200). (e) Section from a normal perilesional tissue punch biopsy sample (haematoxylin and eosin, original magnification × 200). The difference in the spectra between diseased and normal tissues in the spectral region 370–420 nm can be attributed to the relative absence of subepithelial collagen and elastin in (d) OLP compared with (e) normal perilesional tissue, as captured by the typical 300 μm penetration depth of the 337 nm excitation light. (f) Hyperkeratotic patch with focal erosions involving the right buccal mucosa. The error bars correspond to mean ± SD.

Figure 3

Multispectral fluorescence lifetime measurements. (a) The derived lifetime values at three specific spectral bands. (b) Lifetime values as estimated by the data acquired from both systems at three spectral bands and for both normal and oral lichen planus (OLP) tissues. The error bars correspond to mean ± SD.

Figure 4

Lifetime differentiation between perilesional normal mucosa and oral lichen planus (OLP) lesional tissues. (a,b) Differentiation at (a) the 390/40 nm and (b) the 466/40 nm spectral bands as derived from data acquired by the time-resolved fluorescence spectroscopy (TRFS) system. (c,d) The corresponding differentiation as derived from data acquired by the multispectral (ms)-TRFS system.