An on-chip instrument for white blood cells classification based on a lens-less shadow imaging technique

Abstract

Routine blood tests provide important basic information for disease diagnoses. The proportions of three subtypes of white blood cells (WBCs), which are neutrophils, monocytes, lymphocytes, is key information for disease diagnosis. However, current instruments for routine blood tests, such as blood cell analyzers, flow cytometers, and optical microscopes, are cumbersome, time consuming and expensive. To make a smaller, automatic low-cost blood cell analyzer, much research has focused on a technique called lens-less shadow imaging, which can obtain microscopic images of cells in a lens-less system. Nevertheless, the efficiency of this imaging system is not satisfactory because of two problems: low resolution and imaging diffraction phenomena. In this paper, a novel method of classifying cells with the shadow imaging technique was proposed. It could be used for the classification of the three subtypes of WBCs, and the correlation of the results of classification between the proposed system and the reference system (BC-5180, Mindray) was 0.93. However, the instrument was only 10 × 10 × 10 cm, and the cost was less than $100. Depending on the lens-free shadow imaging technology, the main hardware could be integrated on a chip scale and could be called an on-chip instrument.

Fig 1. CMOS shadow imaging instrument.

(A) Diagram of the CMOS shadow imaging instrument. (B) Diagram of the instrument when working. (C) Photo of the CMOS shadow imaging instrument. (D) Photo of the system when working.

Fig 2. CMOS shadow imaging system.

(A) Diagram of blood smear shadow image captured by this instrument. (B) Photo of blood smear shadow image captured by this instrument. (C) Raw image of the blood smear captured by the instrument. (D) Enlarged image of the red box area in Fig 2C. (E) The same area as Fig 2D captured by a 4× microscope objective.

Fig 3. Generation of the PPED vector.

(A) Image of WBC captured by CMOS shadow imaging instrument. (B) A five-by-five matrix of the WBC image, every pixel of the image would create a matrix. (C) Filtering kernels for detecting four principal edges. (D) Edge flag of four directions. (E) Sixty-four-dimensional feature vector of the WBCs.

Fig 4. Standard PPED feature vectors of the three subtypes of WBC.

(A) PPED vector of neutrophils. (B) PPED vector of monocytes. (C) PPED vector of lymphocytes.

Fig 5. Images of WBCS and the PPED vector at different resolutions.

(A) Cell image with a 10× objective lens. (B) PPED vector of Fig 5A. (C) Same cell image with 4× objective lens. (D) PPED vector of Fig 5C. (E) Same cell image by CMOS shadow imaging instrument. (F) PPED vector of Fig 5E.

Fig 6. Results of characterization of three whole blood specimens.

(A) Comparison of the BC-5180 (Mindray, Shenzhen, Guangdong, China) and CMOS systems for the WBC population in sample 1. (B) Comparison of the BC-5180 (Mindray) and CMOS systems for the WBC population in sample 2. (C) Comparison of the BC-5180 (Mindray) and CMOS systems for the WBC population in sample 3. (D) Comparison of the BC-5180 (Mindray) and CMOS systems for the WBC population in sample 4. (E) Comparison of the BC-5180 (Mindray) and CMOS systems for the WBC population in sample 5. (F) Comparison of the BC-5180 (Mindray) and CMOS systems for the WBC population in sample 6. (G) Comparison of the CMOS and BC-5180 (Mindray) systems for the neutrophil population in six samples. (H) Comparison of the CMOS and BC-5180 (Mindray) systems for the monocyte population in six samples. (I) Comparison of the CMOS and BC-5180 (Mindray) systems for the lymphocyte population in six samples.