Spectrometric measurement in laryngeal cancer

Only early diagnosis of laryngeal cancer can prevent major or mutilating treatment. Recently, autofluorescence endoscopy has been developed to enhance endoscopic information and succeeded in facilitating the detection and demarcation of precancerous lesions, carcinoma in situ and cancer of the larynx. The aim of the present study is to quantify autofluorescence imaging by spectroscopy in order to validate the above mentioned findings. In a prospective study, 42 patients with suspected one-sided precancerous or cancerous lesions of the vocal folds were investigated during microlaryngoscopy. Autofluorescence (AF) was induced by filtered blue light (375-440 nm) of a xenon short arc lamp and processed by a CCD camera system (D-light AF System, STORZ, Germany). Autofluorescence images were gathered in a contact mode. For spectrometric measurements an optical multi channel analyzer (AVS-USB 2000, Avantes, The Netherlands) was applied. The results were compared to pathohistological findings. Under blue light excitation normal mucosa presented a bright green fluorescence. Intensity increased from the ventricular folds to the subglottic area. Averaged spectra of the normal laryngeal mucosa demonstrated different fluorescence maxima at 475, 515, 550, 600 and 630 nm. Highest intensity was measured at 515 nm explaining the green appearance of the autofluorescence picture. In contrast, precancerous as well as cancerous lesions showed a significant decrease in autofluorescence intensity with a reddish-violet color. Highest loss of autofluorescence intensity was measured at 515 nm. At this wave length intensity dropped 70% on average in comparison to the regularly appearing contralateral vocal fold. In contrast to 515 nm, the loss of intensity at 630 nm amounted to 38%. Sensitivity amounted to 97% and specificity to 82%. Comparable to autofluorescence endoscopy a differentiation between precancerous and cancerous lesions could not be detected. The reason for the loss of autofluorescence may predominantly be caused by mucosal thickening but also by changes in metabolism and higher nuclei density.