RADIOGRAPHIC AND IMAGE PROCESSING TECHNIQUES NOTES.pdf

RIT104: RADIOGRAPHIC AND IMAGE PROCESSING TECHNIQUES (UNIT II NOTES) X-RAY FILM: X-ray film is a specialized photographic film used for capturing images with X-rays. It is available in two types: double-coated and single-coated. Double-coated film has a radi...

RIT104: RADIOGRAPHIC AND IMAGE PROCESSING TECHNIQUES (UNIT II NOTES) X-RAY FILM: X-ray film is a specialized photographic film used for capturing images with X-rays. It is available in two types: double-coated and single-coated. Double-coated film has a radiation-sensitive emulsion on both sides of a transparent plastic base, which improves sensitivity and image quality. Single-coated film has the emulsion on just one side of the base and is commonly used in situations where reduced sensitivity is sufficient, such as in dental X-rays or certain types of radiographic imaging where less detail is required. X-ray film is composed of several distinct layers, each serving a specific purpose to ensure optimal image quality and functionality. SINGLE COATED FILM 1  DOUBLE COATED FILM 1. Super Coat Material and Function: Composition: The super coat is typically made of a thin layer of a hardening agent, often a type of plastic such as polyester or a similar polymer. Function: This layer protects the emulsion layers from physical damage and scratches during handling and processing. It also helps to prevent dust and other contaminants from affecting the film's surface. 2. Emulsion Layer Material and Function: Composition: The emulsion layer consists of a gelatin matrix embedded with silver halide crystals, primarily silver bromide, silver chloride, or a combination of these. This layer is known as the active layer of the film. Function: The emulsion is sensitive to X-ray radiation and, when exposed, the silver halide crystals undergo a chemical change that creates a latent image. During development, this latent image is converted into a visible image. The emulsion is essentially the heart of the X-ray film, responsible for capturing the image detail. 2  3. Adhesive Layer Material and Function: Composition: The adhesive layer is typically made of a type of synthetic adhesive or a similar bonding agent. Function: This layer bonds the emulsion to the base layer. It ensures that the emulsion remains securely attached to the base throughout the film's life, from handling to processing and imaging. 4. Base Layer Material and Function: Composition: The base layer is usually made from a flexible, transparent plastic material, commonly polyester (polyethylene terephthalate resin). Polyester is chosen for its durability and stability. Function: The base provides structural support to the film and maintains its flatness. It is designed to be robust enough to withstand various processing conditions without deforming or becoming brittle. 5. Antihalation Layer Material and Function: Composition: The antihalation layer is generally made from a layer of dye or pigment incorporated into a coating on the base layer. These dyes are often yellow or other colours. Function: This layer absorbs any stray light or X-rays that might scatter and reflect back onto the film. This reflection can cause unwanted light exposure, resulting in a halo effect around bright areas. By absorbing this scattered radiation, the antihalation layer helps to ensure sharp and clear images. 6. Anti-Curl Back Layer 3  Material and Function: Composition: The anti-curl back layer is usually made from a thin layer of a polymer or other stabilizing material. Function: This layer is applied to the opposite side of the base layer and serves to counteract the tendency of the film to curl or bend during processing and handling. It helps to keep the film flat, ensuring that it remains in contact with the imaging surfaces and does not become damaged or distorted. Note: In summary, X-ray film is a multi-layered construct designed to optimize image quality and durability: Super Coat: Protects the film from physical damage and contaminants. Emulsion Layer: Contains silver halide crystals sensitive to X-rays, responsible for image capture. Adhesive Layer: Bonds the emulsion to the base layer. Base Layer: Provides structural support and stability, made of flexible plastic like polyester. Antihalation Layer: Prevents unwanted reflections and halation by absorbing scattered radiation. Anti-Curl Back Layer: Maintains film flatness and prevents curling Standard X-ray Film: Double-Coated Film Structure and Function: 4  Emulsion Layers: Double-coated X-ray film has a radiation-sensitive emulsion coated on both sides of a transparent plastic base. Each side of the film contains its own layer of emulsion, which is sensitive to X-ray radiation. Sensitivity and Image Quality: The dual coating enhances the film's overall sensitivity to X-rays. This means it requires less radiation exposure to produce a clear image. The presence of emulsion on both sides increases the likelihood of capturing high-quality images even if the X-rays are not perfectly aligned or if there is some scatter. Applications: This type of film is typically used in general diagnostic radiography, including chest X-rays, abdominal imaging, and other standard radiographic procedures. The increased sensitivity and improved image quality make it suitable for capturing detailed anatomical structures and diagnosing various conditions. Advantages: Improved Image Resolution: The dual emulsion layers help in capturing finer details, which is crucial for accurate diagnosis. Reduced Radiation Dose: Higher sensitivity means less radiation is needed to produce a diagnostic-quality image, reducing patient exposure to X-rays. Single-Coated Film Structure and Function: Emulsion Layer: Single-coated X-ray film has the radiation-sensitive emulsion applied to just one side of the transparent plastic base. The other side is left uncoated. Sensitivity and Image Quality: This film type is less sensitive compared to double- coated film due to the presence of emulsion on only one side. It requires a higher dose of radiation to achieve a similar image quality, which may be acceptable in certain diagnostic contexts. 5  Applications: Single-coated films are often used in specific applications where high sensitivity is not as critical. Common uses include dental radiography, where detailed images of teeth and surrounding areas are needed but with less overall sensitivity. It is also used in some specialized radiographic examinations where image quality demands are lower. Advantages: Cost-Effective: Single-coated films are generally less expensive than double-coated films, making them a cost-effective choice for certain applications. Simplicity: Suitable for situations where detailed image quality is not as critical, or where lower radiation doses are acceptable. Note: - Double-Coated Film is preferred for general diagnostic purposes where higher sensitivity and image quality are essential. Its dual emulsion layers enhance detail and reduce the required radiation dose. Single-Coated Film is used for more specific or less critical imaging needs where reduced sensitivity is acceptable, such as in dental X-rays. It is a cost-effective choice for applications where less detailed images are sufficient. Dental X-ray Films: Dental X-ray films are specialized films designed to meet the unique imaging needs of dental diagnostics. They come in two main types: intraoral and extraoral films. Each type is tailored to capture detailed images of the teeth, jaw, and surrounding structures from different perspectives. Intraoral Film Description and Features: 6  Size and Shape: Intraoral films are smaller and typically rectangular or square, designed to fit comfortably inside the mouth. They come in various sizes to accommodate different areas of the mouth, such as the anterior or posterior regions. Sensitivity: These films are highly sensitive to X-rays to ensure that detailed images of small structures, like individual teeth and the surrounding bone, can be captured with minimal radiation. Applications: o Bitewing X-rays: Used to detect interproximal caries (cavities between teeth) and assess the health of the bone around the teeth. o Periapical X-rays: Capture the entire tooth structure, including the root and surrounding bone, which is essential for diagnosing issues like root infections or bone loss. o Occlusal X-rays: Provide a view of the entire arch of teeth in a single image, often used to assess the development of teeth and detect abnormalities. Advantages: Detailed Imaging: The small size and high sensitivity of intraoral films allow for detailed imaging of individual teeth and adjacent structures, which is crucial for precise diagnosis and treatment planning. Reduced Radiation: High sensitivity enables the use of lower radiation doses, making it safer for patients. Extraoral Film Description and Features: Size and Shape: Extraoral films are larger and are used outside the mouth to capture broader views of the dental structures. They come in various sizes, with common formats including panoramic and cephalometric. 7  Sensitivity: While these films are less sensitive compared to intraoral films, they are designed to capture comprehensive images of larger areas, including the entire mouth and jaw. Applications: o Panoramic X-rays: Capture a wide, single image of the entire mouth, including all teeth, the upper and lower jaws, and surrounding structures. They are useful for assessing the overall dental structure, planning orthodontic treatment, and detecting issues like impacted teeth or jaw disorders. o Cephalometric X-rays: Provide a side view of the head, including the jaw and dental structures. These images are often used in orthodontics to analyze tooth and jaw relationships and to plan orthodontic treatments. Advantages: Comprehensive View: Extraoral films provide a broad view of dental structures, which is essential for comprehensive diagnostics, treatment planning, and evaluating conditions that affect multiple teeth or the entire jaw. Convenience: They can capture a large area in a single image, which is particularly useful for orthodontic assessments and planning. Specialty X-ray Film: 1. Screen-Film Combinations Description and Function: Screen-Film Technology: This involves using X-ray films in conjunction with fluorescent screens. The screens, often made of materials like rare earth phosphors (e.g., gadolinium oxysulphide or lanthanum oxybromide), absorb X-rays and emit visible light. This light then exposes the X-ray film, which is coated with a light-sensitive emulsion. 8  Components: o Fluorescent Screens: These screens are placed inside the X-ray cassette and are responsible for converting X-ray radiation into visible light. o X-ray Film: The film is placed in close contact with the screen, so the light emitted by the screen exposes the film rather than direct X-ray radiation. Applications: Screen-film combinations are used in various radiographic procedures, including chest X-rays, abdominal imaging, and some specialized diagnostic procedures. This technology helps improve image quality and reduce patient radiation dose. Advantages: Reduced Radiation Dose: Since the film is exposed to light rather than direct X-rays, less radiation is needed to produce a high-quality image, reducing patient exposure. Improved Image Quality: The use of fluorescent screens allows for enhanced contrast and detail in the images. 2. High-Speed Film Description and Function: Sensitivity: High-speed X-ray films are designed to be highly sensitive to X-ray radiation. They contain larger or more efficiently sensitive silver halide crystals in the emulsion layer, which allows the film to capture images with less exposure. Applications: o Emergency Situations: Ideal for scenarios where rapid imaging is necessary, such as in emergency medicine or trauma cases. o Patient Movement: Useful when dealing with patients who have difficulty remaining still, as the film requires a shorter exposure time to capture a clear image. 9  Advantages: Reduced Exposure Time: High-speed films reduce the amount of time required for exposure, which is beneficial for quick imaging and minimizing patient discomfort. Lower Radiation Dose: Shorter exposure times result in less overall radiation dose to the patient. 3. Low-Speed Film Description and Function: Sensitivity: Low-speed X-ray films are less sensitive to X-ray radiation compared to high-speed films. They use smaller silver halide crystals in the emulsion layer, which results in finer image detail but requires longer exposure times. Applications: o Detailed Imaging: Used when high image resolution is crucial, such as in mammography or detailed orthopedic imaging. o Specialized Diagnostics: Useful in situations where the quality of image detail is more critical than the speed of imaging. Advantages: High Resolution: Provides greater image detail and resolution, making it suitable for diagnostic situations where precise information is needed. Enhanced Contrast: Offers better contrast in the images, which is useful for detecting subtle differences in tissue densities. Note: Screen-Film Combinations: 10  Technology: Uses fluorescent screens to convert X-rays into visible light, which then exposes the film. Applications: Commonly used in various radiographic procedures. Benefits: Reduces radiation dose and improves image quality. High-Speed Film: Sensitivity: Highly sensitive to X-rays, requiring less exposure time. Applications: Suitable for rapid imaging and scenarios involving patient movement. Benefits: Reduces exposure time and radiation dose. Low-Speed Film: Sensitivity: Less sensitive to X-rays, requiring longer exposure times. Applications: Ideal for detailed imaging where high resolution is essential. Benefits: Provides finer detail and enhanced image contrast. In the context of digital radiography, traditional X-ray film is replaced by advanced digital imaging technologies that offer significant improvements in efficiency and diagnostic capabilities. The two primary types of digital X-ray systems are Computed Radiography (CR) and Direct Digital Radiography (DR). Here’s a detailed explanation of each: Digital X-ray Film (in the context of digital radiography): 1. Computed Radiography (CR) Plates Description and Function: Photostimulable Phosphor Plates: CR systems use imaging plates coated with photostimulable phosphors, typically composed of materials like barium fluorohalide or a similar compound. These phosphors capture X-ray energy and store it as a latent image. 11  Imaging Process: o Exposure: The CR plate is exposed to X-rays, which causes the phosphor crystals to store energy proportional to the X-ray exposure. o Scanning: After exposure, the CR plate is inserted into a scanner called a CR reader. The scanner uses a laser to stimulate the phosphors, causing them to release the stored energy as visible light. o Digital Conversion: The emitted light is captured by a photodetector and converted into an electrical signal, which is then processed by a computer to produce a digital image. Advantages: Flexibility: CR plates can be reused multiple times, as they can be erased and re-exposed. This makes them versatile for different imaging needs. Cost-Effective: While initial setup costs can be significant, the reuse of CR plates can make this a more economical option over time compared to film-based systems. Compatibility: CR systems can often be integrated into existing X-ray equipment, providing a pathway to digital imaging without completely replacing older systems. Applications: CR is used in various medical and veterinary fields for general radiography, including chest X-rays, musculoskeletal imaging, and more. It is suitable for environments where flexibility and cost efficiency are prioritized. 2. Direct Digital Radiography (DR) Plates Description and Function: Digital Sensors: DR systems use digital detectors or sensors that directly capture X-ray images and convert them into digital data. There are two main types of DR detectors: 12 o Direct Conversion: These detectors use a layer of material like amorphous selenium (a- Se) that directly converts X-ray photons into electrical charges. These charges are then read by a thin-film transistor (TFT) array to produce the digital image. o Indirect Conversion: These detectors use a scintillator material, such as cesium iodide (CsI) or gadolinium oxysulphide (GOS), to convert X-rays into visible light. The light is then detected by a photodiode array and converted into an electrical signal, which is processed into a digital image. Advantages: Immediate Processing: DR systems provide real-time image processing, allowing for immediate review and diagnosis. This speeds up patient care and workflow efficiency. High Image Quality: DR plates offer superior image resolution and contrast compared to traditional film, which enhances diagnostic accuracy. Lower Radiation Dose: DR systems often require less radiation exposure to achieve high-quality images due to their sensitivity and efficiency in capturing X-rays. Reduced Handling: DR eliminates the need for film processing, chemicals, and physical storage, streamlining the imaging workflow. Applications: DR is widely used in hospitals and specialized clinics for a range of diagnostic imaging, including emergency radiology, orthopedics, and advanced imaging procedures. Its immediate processing and high-quality output make it ideal for environments where rapid and precise imaging is critical. Note:- Computed Radiography (CR) Plates: 13  Technology: Uses photostimulable phosphor plates to capture and store X-ray energy, which is later read and converted into digital images by a scanner. Advantages: Flexibility, cost-effectiveness, compatibility with existing equipment. Applications: General radiography, suitable for a wide range of imaging needs. Direct Digital Radiography (DR) Plates: Technology: Employs digital detectors that directly convert X-ray images into digital format using either direct or indirect conversion methods. Advantages: Immediate image processing, high image quality, lower radiation dose, reduced handling. Applications: Emergency radiology, specialized imaging, and advanced diagnostic procedures. General Radiography Film Sizes: 8 x 10 inches (20 x 25 cm): Commonly used for chest X-rays and some body imaging, providing a wide view of the thoracic cavity. 10 x 12 inches (25 x 30 cm): Often used for larger body parts or specific studies, offering a larger imaging area. 14 x 17 inches (35 x 43 cm): Frequently used for full-body imaging, including abdominal and pelvic studies, where a larger area is needed. Handling Tips: Size Management: Ensure the correct size film is used for the specific body part or diagnostic requirement to avoid compromised image quality. 14  Film Placement: For larger films, make sure they are properly aligned in the X-ray cassette to ensure complete and accurate imaging. 2. Mammography Film Sizes: 18 x 24 cm (7 x 10 inches): Standard size for mammography films, used to capture detailed images of breast tissue. 24 x 30 cm (10 x 12 inches): Occasionally used in mammography, especially in cases where a larger view is needed. Handling Tips: Special Care: Handle mammography films with extreme care due to their detailed nature and the sensitivity required in breast imaging. Darkroom Procedures: Ensure that mammography films are processed in a light-tight environment to prevent fogging and preserve image quality. 3. Dental Radiography Film Sizes: Size 0: Smallest size, used for very young children or for capturing images of small areas, such as anterior teeth. Size 1: Slightly larger than Size 0, often used for capturing images of the anterior teeth in older children and adults. Size 2: The most commonly used size for standard adult dental imaging, suitable for capturing the entire arch of teeth. Size 4: Extra-large size, used for occlusal radiographs to capture a broader view of the dental arches and related structures. 15  Handling Tips: Specific Size Use: Choose the appropriate size film based on the patient’s age and the type of dental examination to ensure the best possible image quality. Gentle Handling: Given the small size and delicate nature of dental films, handle them with clean, dry hands or gloves to prevent contamination and physical damage. Film Handling and Care Temperature and Humidity Control: Store films at a stable, cool temperature (15°C to 25°C or 59°F to 77°F) and relative humidity between 30% and 60%. Light Protection: Keep films in dark environments until they are processed to avoid exposure to light that can fog the film. Physical Protection: Use clean, dry hands or gloves when handling films to avoid leaving fingerprints or causing scratches. Store films in protective containers to prevent physical damage. Chemical Safety: Keep films away from chemicals and ensure proper ventilation in storage areas to avoid chemical contamination. Organization and Labeling: Clearly label and organize films for easy retrieval and ensure accurate identification. Maintain a system for tracking and managing film usage and storage. Monitoring: 16  Regularly check storage conditions and film quality to ensure they remain within recommended parameters. Implement backup systems to manage any fluctuations in temperature or humidity. Training: Ensure that all personnel involved in handling and processing films are properly trained to minimize errors and damage. Film Contrast in Radiography Definition and Importance: Film contrast refers to the difference in density between various areas of an X-ray film, which determines how well different structures and tissues are distinguished from each other. It is a crucial factor in radiographic imaging as it affects the diagnostic quality of the image. Proper contrast ensures that subtle differences in tissue density are visible, aiding in accurate diagnosis and interpretation. Components Influencing Film Contrast: 1. Film Emulsion: o Sensitivity: The type of emulsion and the size of silver halide crystals in the film's emulsion layer impact how the film responds to X-ray exposure. Films with larger crystals generally exhibit higher speed and contrast, while finer crystals offer more detailed contrast but require longer exposure. o Characteristic Curve: Each film type has a characteristic curve that defines its response to different exposure levels. The shape of this curve affects the film's contrast, with steeper curves indicating higher contrast and flatter curves indicating lower contrast. 2. Exposure Factors: o X-ray Dose: The amount of X-ray exposure impacts the film’s contrast. Overexposure can lead to reduced contrast, with images appearing washed out, while underexposure can result in high contrast with potentially missing details in darker areas. 17 o Technique Factors: Proper adjustment of exposure settings (kVp and mAs) is essential to achieve optimal contrast. The kilovolt peak (kVp) controls the penetration power of the X-rays and influences contrast, while milliampere-seconds (mAs) affects the overall exposure. 3. Film Processing: o Developer Chemistry: The chemicals used in the development process affect film contrast. The developer's composition, temperature, and time can alter the contrast by affecting the development of the silver halide crystals. o Processing Conditions: Consistent and accurate processing conditions are crucial for maintaining desired film contrast. Variations in temperature, agitation, and time can lead to inconsistent contrast levels. 4. Film Type and Speed: o High-Speed Films: Generally provide lower contrast but require shorter exposure times. These films are useful in situations requiring quick imaging but may lack the fine detail needed for detailed analysis. o Low-Speed Films: Offer higher contrast and finer detail but require longer exposure times. They are preferred when detailed imaging is necessary, such as in mammography or high-resolution studies. 5. Image Receptor Characteristics: o Screen-Film Combinations: The type of fluorescent screen used in conjunction with the film affects contrast. Screens with higher conversion efficiency can enhance image contrast by converting X-ray energy into visible light more effectively. o Digital Systems: In digital radiography, contrast is controlled through software adjustments. Digital systems can offer greater flexibility in modifying contrast levels post-processing compared to traditional film. 18  Best Practices for Optimal Film Contrast: Proper Calibration: Regularly calibrate and maintain X-ray equipment and processing systems to ensure consistent exposure and processing parameters. Accurate Exposure Settings: Use appropriate exposure settings based on the type of film and the diagnostic requirement to achieve optimal contrast. Adjust kVp and mAs settings as needed for different imaging scenarios. Consistent Processing: Follow standardized processing protocols for developing films to ensure consistent contrast. Monitor and control processing conditions such as temperature, time, and chemical composition. Film Selection: Choose the appropriate film type based on the diagnostic needs. Use high-speed films for general purposes where high contrast is not as critical, and low-speed films for detailed imaging where high contrast is required. Characteristic Curve: The characteristic curve (also known as the D-log E curve) is a graphical representation of how an X-ray film responds to different levels of X-ray exposure. This curve is fundamental for understanding and optimizing the performance of radiographic films. It provides insights into several key characteristics of the film, including speed, base + fog, gamma, and latitude. detailed look at each characteristic: 1. Speed Definition: Film speed, or sensitivity, refers to how quickly the film responds to X-ray exposure. Higher speed films require less exposure to produce an acceptable image. Characteristic Curve Representation: Speed Index: On the characteristic curve, speed is typically indicated by the point where the curve starts to rise significantly from the base level. This point represents the film’s sensitivity to X-rays. 19  High-Speed Films: These films have larger silver halide crystals and exhibit a steeper slope at the lower end of the curve, indicating that they respond quickly to X-ray exposure and require less dose to achieve a usable image. Low-Speed Films: These have smaller crystals and a gentler slope, indicating that they require more exposure to achieve the same density compared to high-speed films. 2. Base + Fog Definition: Base + fog refers to the inherent density of the film without exposure to X- rays (base density) plus any additional fog density from processing or handling. Characteristic Curve Representation: Base Line: On the characteristic curve, base + fog is represented by the density of the film before any exposure, where the curve begins. It indicates the film's density due to the base material and any fogging effects. Minimizing Fog: Lower base + fog is desirable as it allows for better differentiation between the film’s darkest and lightest areas. High base + fog reduces the effective range of densities that can be represented on the film. 3. Gamma Definition: Gamma (γ) is the slope of the characteristic curve in the region where the curve rises most steeply. It represents the film’s contrast and indicates how well it differentiates between different levels of X-ray exposure. Characteristic Curve Representation: Steepness of the Curve: The gamma value is calculated by measuring the slope of the curve in the mid-density region, where the film's response to varying exposure levels is most linear. A steeper slope indicates higher contrast. 20  High Gamma: Films with a high gamma value exhibit high contrast, meaning they can show a large difference between light and dark areas. This is useful for detailed imaging where contrast between different tissues is crucial. Low Gamma: Films with a lower gamma value have lower contrast and show less differentiation between densities. This can be useful in situations where a wider range of densities needs to be captured. 4. Latitude Definition: Latitude (or exposure latitude) refers to the range of exposures over which the film produces a usable image. It indicates how forgiving the film is to variations in exposure. Characteristic Curve Representation: Width of the Curve: Latitude is reflected in the width of the curve’s steep portion. A broader curve indicates a wider latitude, meaning the film can produce good images over a range of exposure levels. Wide Latitude: Films with wide latitude are less sensitive to slight changes in exposure and can still produce a diagnostic image. This is beneficial for general radiography where exact exposure control might be challenging. 21  Narrow Latitude: Films with narrow latitude are more sensitive to exposure variations and require precise exposure settings to avoid underexposure or overexposure. Summary of Characteristics Speed: Indicates how quickly the film responds to X-ray exposure. Faster films require less exposure to achieve an acceptable image. Base + Fog: Represents the film's inherent density plus any additional fog from processing. Lower base + fog results in better image quality. Gamma: The slope of the characteristic curve in the steep region, representing contrast. Higher gamma values indicate higher contrast. Latitude: The range of exposure levels over which the film can produce a usable image. Wider latitude provides more flexibility in exposure settings. 22