###### Abstract  
Portable Raman spectrometers may offer advantages for clinical medical diagnostics over laboratory instruments by allowing for quick measurements in the field and provision of data suitable for screening analyses. This work evaluates the potential of using available handheld, modular, and laboratory Raman spectrometers for screening normal colon tissues and benign and malignant colon polyps. The Raman spectra of tissue samples and reference biological macromolecules were measured with these instruments and analyzed using curve fitting and multivariate statistics. The spectra of calf thymus DNA measured with portable devices showed suitable signal-to-noise levels and half-widths of the prominent bands. Band positions, resolution, and relative intensities in the Raman spectra of colon tissues and reference compounds varied for the instruments, and the laboratory device demonstrated the best spectral feature. The principal component analysis (PCA) of the spectra obtained with all Raman devices showed well discrimination of normal colon tissue, adenomatous polyp, and adenocarcinoma. Dendrograms of similarity obtained using hierarchy cluster analysis (HCA) for the Raman spectra of all three devices also showed good separation of these samples. The soft independent modeling of class analogy (SIMCA) and support vector machine (SVM) models efficiently classified normal colon tissues and benign/malignant colorectal polyps based on the Raman data from all three devices. Despite its less pronounced spectral characteristics, the handheld Raman spectrometer can be used in early diagnosis of colorectal carcinoma, comparable to the modular and laboratory instruments. portable Raman instruments; early cancer diagnosis; colorectal carcinoma; colon tissues; discrimination analysis +
Footnote †: journal: Medical Imaging  
0000-0001-8000-0001-8000]Z. Z.  
the areas that require rapid results of screening analyses, especially in the case of severe diseases like colorectal carcinoma [2]. Quickly obtaining a test result and determining a preliminary diagnosis can play a decisive role in saving a human life. Modern technologies that can be useful in clinical diagnosis include Raman spectroscopy [3]. This is a non-destructive method of molecular spectroscopy based on measuring the energy of inelastic scattering emitted by pre-excited sample molecules [4]. The Raman spectrum provides chemically specific information about the biological and biochemical components in cellular and tissue environments. It helps to identify and reveal anomalies in the composition and structure of biological tissues [5]. Although Raman spectroscopy principles have been known for almost a century, recent advancements in instrumentation and operation have expanded the potential of this method for use in various environments. It also appears to be a promising diagnostic tool using intrinsic markers and, thus, provides biochemical information without the need for additional fluorescent or radioactive labeling [6]. In research and routine laboratory conditions, Raman spectrometers commonly deal with clinical samples obtained from patients and stored, whether modified or unmodified, for ex vivo analysis only. However, the clinical practice needs Raman equipment for both in vivo and ex vivo configurations, and portable tools are preferable for rapid and non-invasive diagnoses [7; 8; 9]. The term \"laboratory\" in the context of Raman spectrometers defines a system where all necessary components are permanently in the laboratory where the measurements occur. On the other hand, \"modular\" is a portable system where one or more components are located externally and connected to the main body (the spectrometer). Finally, \"handheld\" refers to a miniature system manipulated by holding it in the hands, with all components in one body [10]. The modular variants of Raman spectrometers are suitable for repeating routine analyses at clinical laboratories, and the fiber optic probes permit us to use them for in vivo examinations.