The Essential Guide to Medical Thermal Film: How It Works, Key Features, and Best Practices
I. Introduction to medical thermal dry image film
Medical thermal dry image film is a graphic recording medium composed of a blue polyester substrate coated with a thermal layer and a protective layer. It generates images in thermal printers based on the differential thermal effects of the thermal print head. Currently, medical thermal dry image film is widely used in medical imaging applications such as CT scans, MRI, CR, and DR for recording purposes, serving as a basis for physician diagnosis and treatment. Typically composed of a polyester PET base, a thermal layer, and a protective layer.
II. Characteristics of medical thermal dry image film
1. Medical thermal dry image film employs nano-scale ink-absorbing coating, waterproof coating, and three-color gradient black technology to reprocess specialty paper into a medical imaging printing medium. It features water resistance, light shielding, and heat tolerance, ensuring decades of preservation. Simultaneously employing lossless high-grayscale image transmission technology, it can print various medical images with clarity, environmental friendliness, and strong compatibility. The membrane structure characteristic of medical film photography is that the silver halide grains are over-flow grains with small, spherical shapes. Compared to over-flow grains, they have a smaller surface area, absorb more light, and have a faster photosensitivity.
2. Medical thermal dry image film The front surface is coated with emulsion, while the back features an anti-halation layer. This film suits diverse medical imaging applications such as tomography, digital subtraction, and ultrasound imaging. It accommodates both high-temperature machine processing and room-temperature manual processing. When paired with contrast-enhancing screens, it delivers sharp images that accurately reveal pathological changes and abnormalities in the human body. This film supports high-temperature machine processing and cleaning, as well as room-temperature manual processing and cleaning.
III. Precautions for medical thermal dry image film
1. Optimal storage conditions: Temperature 18–24°C, humidity 50–60% RH. When removing or repacking medical film, prevent artificial artifacts and static discharge caused by folding, compression, or friction between films. Keep hands clean and dry when handling, or wear dedicated gloves. Avoid contact with wet hands. 90-second continuous high-temperature rapid production process: Development temperature 30–35°C, time 23–30 seconds.
2. Room-temperature cleaning production process: Development temperature 20°C, time 5 minutes; Fixing 5–8 minutes; Cleaning 15–30 minutes; Air-dry. Medical X-ray film structure. Characterized by smaller, rounder silver halide particles with reduced surface area compared to flow particles, enabling greater radiation absorption and faster sensitivity. Under safety illumination from 15W bulbs, maintain an illumination distance of over 1.2 meters from the film, with cumulative exposure time not exceeding 10 minutes.
3. Storage: Medical thermal dry image film must be stored in a dry, cool location (recommended temperature: 10–20°C; relative humidity: 30%–60%). Protect from moisture, cold, sustained high temperatures, all toxic gases, X-rays, gamma rays, or any other penetrating radiation. Store vertically to prevent harmful pressure effects on the film.
IV. Thermosensitive Film Principle
Medical thermal dry image film processing involves a specialized cold-processing technique where a thermal layer is applied to the film substrate. The color-forming layer consists of a binder, a color developer, and a latent dye (or latent colorant), separated by micro-chains, with the chemical reaction in a “latent” state. When thermal paper comes into contact with a heated print head, the color developer and latent dye in the printed area undergo a chemical reaction, changing color to form images.
When thermal materials are exposed to temperatures above 70°C, the thermal coating begins to change color. The mechanism behind this color change must be examined from a compositional perspective. The coating of thermal materials primarily contains two thermosensitive components: one is a colorless dye or colorless dye; the other is a color developer. This type of thermal material is also known as a two-component chemothermally sensitive recording material.
Commonly used latent dyes include crystalline violet lactone (CVL), the fluorescein system, latent benzoylmethylene blue (BLMB), or the spirofuran system based on triphenylmethane phthalate. Common developers include: p-hydroxybenzoic acid and its esters (PHBB, PHB), salicylic acid, 2,4-dihydroxybenzoic acid, or aromatic sulfoxides.
Unstable images on thermal materials will naturally fade because the color reaction in thermal materials is reversible. Colored products decompose spontaneously to varying degrees, causing the image color to gradually lighten until the image completely disappears. Therefore, prolonged storage, extended exposure to light or heat, as well as environmental factors like high temperatures, humidity, or contact with adhesive tape can accelerate the decomposition of color products and hasten image fading. Naturally, the rate of fading also depends on the quality of the thermal paper itself. Thus, medical thermal dry image film should be kept away from heat sources and humidity.
V. Function of medical thermal dry image film
Medical medical thermal dry image film enables direct thermal printing of digitally stored medical imaging data processed by computers. It faithfully reproduces various medical imaging results processed by computers, eliminating the traditional production processes of developing, fixing, and washing silver halide products. This completely resolves environmental damage caused by waste chemicals from washing, production, and processing. medical thermal dry image film offers advantages such as low fog, high image clarity, high density, vivid colors, and ease of use. It is also compatible with renowned brands of medical thermal printers in export markets.
VI. Usage of medical thermal dry image film
Due to its imaging principle, medical thermal dry image film requires specialized thermal printers. Currently, the core technology for thermal printers—the research, development, production, and manufacturing of thermal print heads—is concentrated in developed countries like Japan and the United States. Domestically, there are no factories capable of producing thermal print heads, resulting in persistently high prices for both thermal printers and print heads. Many film manufacturers and large distributors embed chip recognition functions in their thermal printers, limiting them to printing only their own films to control distribution.