A Low-Cost, Portable, Multi-Cancer Screening Device Based on a Ratio Fluorometry and Signal Correlation Technique

Abstract

The autofluorescence of erythrocyte porphyrins has emerged as a potential method for multi-cancer early detection (MCED). With this method's dependence on research-grade spectrofluorometers, significant improvements in instrumentation are necessary to translate its potential into clinical practice, as with any promising medical technology. To fill this gap, in this paper, we present an automated ratio porphyrin analyzer for cancer screening (ARPA-CS), a low-cost, portable, and automated instrument for MCED via the ratio fluorometry of porphyrins. The ARPA-CS aims to facilitate cancer screening in an inexpensive, rapid, non-invasive, and reasonably accurate manner for use in primary clinics or at point of care. To accomplish this, the ARPA-CS uses an ultraviolet-excited optical apparatus for ratio fluorometry that features two photodetectors for detection at 590 and 630 nm. Additionally, it incorporates a synchronous detector for the precision measurement of signals based on the Walsh-ordered Walsh-Hadamard transform (WHT)_w and circular shift. To estimate its single-photodetector capability, we established a linear calibration curve for the ARBA-CS exceeding four orders of magnitude with a linearity of up to 0.992 and a low detection limit of 0.296 µg/mL for riboflavin. The ARPA-CS also exhibited excellent repeatability (0.21%) and stability (0.60%). Moreover, the ratio fluorometry of three serially diluted standard solutions of riboflavin yielded a ratio of 0.4, which agrees with that expected based on the known emission spectra of riboflavin. Additionally, the ratio fluorometry of the porphyrin solution yielded a ratio of 49.82, which was ascribed to the predominant concentration of protoporphyrin IX in the brown eggshells, as confirmed in several studies. This study validates this instrument for the ratio fluorometry of porphyrins as a biomarker for MCED. Nevertheless, large and well-designed clinical trials are necessary to further elaborate more on this matter.

Keywords: Walsh–Hadamard transform; cancer screening; lock-in amplifier; porphyrins; ratio fluorometry.

Figure 1

Schematic of the ARPA-CS design, including both the optical path and electronic design block diagram.

Figure 2

Schematic of the ARPA-CS optoelectronic circuit design.

Figure 3

A Walsh function (top left) and its shifted version (bottom left). The corresponding sequency spectra of these signals are depicted on the right.

Figure 4

Algorithm for implementing an LIA using (FWHT)_w in conjunction with cyclic shift.

Figure 5

Distribution of maximum amplitude occurrences for Walsh functions for the order ranges of (top left) 0–1023, (bottom left) 1–1022, and (right) 10–100.

Figure 6

(left) Approximating amplitude of noisy Walsh signal using (WHT)_w and (right) performance of (WHT)_w against white noise (SNR: −12 dB to 20 dB).

Figure 7

ARPA-CS photograph: (left) complete assembled device ready for operation and (right) sample chamber during irradiation.

Figure 8

ARPA-CS graphical user interface.

Figure 9

Excitation and emission spectra of riboflavin. Point A on the spectrum indicates the excitation wavelength, while points B and C represent emission wavelengths.

Figure 10

Calibration curve of riboflavin measured at 590 nm, based on data from 10 samples.

Figure 11

Linear regression analysis of SBR as a function of the Walsh sequency index.