Radiography Imaging Techniques

Unit 7: Radiation Characteristics and Radiation Protection

• Ionization: Electrons remain stable in orbits around the nucleus until x-ray photons collide. Photons are bundles of pure energy with no weight or mass. Ions are atoms that have gained or lost an electron, becoming electrically unbalanced. X-rays have enough energy to push an electron out of its orbit, creating an ion in a process called ionization.

Review: Properties of X-Rays

• X-rays are a form of energy that penetrates matter. Like visible light, radar, radio, and television waves, they are part of electromagnetic radiation. Electromagnetic radiation is made up of photons that travel at the speed of light in a straight line with a wave-like motion. The shorter the wavelength of an x-ray, the greater its energy.

Types of Radiation

• Primary radiation: X-rays originating from the x-ray tube target (useful beam).
• Secondary radiation: X-radiation created when the primary beam interacts with matter.
• Scatter radiation: A form of secondary radiation resulting from the deflection of the x-ray beam from its path by interaction with matter.

Radiation Effects

• All ionizing radiation is harmful, producing biological changes in living tissue. The amount of x-radiation used in dental radiography is small, but biological changes still occur. Dental assistants must understand how radiation's harmful effects occur and how to discuss risks with patients. The entire x-ray area is considered a radiation hazard area.

Biological Effects of Radiation

• Exposure to radiation can cause changes in body chemicals, cells, tissues, and organs. These effects may not be evident for years after exposure. This time lag is the latent period.

Cumulative Effects

• Exposure to radiation has a cumulative effect over a lifetime. When exposed to x-rays, some tissue damage occurs. Tissues can repair some damage, but do not return to their original state. The cumulative effect of radiation exposure is comparable to the cumulative effect of years of sun exposure.

Disorders of Critical Organs

• Exposure to radiation can cause disorders in critical organs. This table lists some examples of these.
• Lens of the eye: Cataracts
• Bone marrow: Leukemia
• Salivary gland: Cancer
• Thyroid gland: Cancer
• Skin: Cancer
• Gonads: Genetic abnormalities

Genetic and Somatic Effects

• X-rays affect both genetic and somatic cells. Genetic cells are reproductive cells (sperm and ova). Damage to them is passed on to future generations. All other body cells are somatic cells; x-rays can damage them, but the damage is not passed on to future generations.

Radiation Measurement

• Radiation is measured similarly to time, distance, and weight. Two systems are used:
• Traditional: Roentgen (R), radiation absorbed dose (rad), Roentgen equivalent man (rem)
• SI: Coulombs per kilogram (C/kg), Gray (Gy), Sievert (Sv)

Maximum Permissible Dose

• The maximum permissible dose (MPD) for occupationally exposed individuals is 5000 mrem (5.0 rem) per year, or 100 mrem per week. For non-occupationally exposed individuals, the current MPD is 500 mrem (5 mSv) per year.
• Dental personnel should strive for an occupational dose of 0.

Responsibilities of the Dentists

• Prescribe only necessary images.
• Maintain radiographic equipment safely.
• Ensure appropriate shielding for staff and patients.
• Train personnel involved in image acquisition.
• Use only necessary techniques for diagnostic images.
• Adhere to regulatory requirements.
• Obtain informed consent from patients and families.
• Review patient records for prior imaging.

Protective Devices

• Dental tubeheads must have components like aluminum filters and lead collimators.
• Periodically check equipment using provincial or federal regulations.
• Repair any faulty equipment immediately.

Patient Protection

• Lead aprons and thyroid collars must be used on all patients for all exposures, regardless of age, sex or number of images.
• Aprons should cover patients' necks to laps, to protect reproductive and blood-forming tissues from scatter radiation.

Fast-Speed Film

• Film speed in film-based x-rays refers to the radiation needed to create an image. Film speed is primarily determined by the size of the silver bromide crystals. Larger crystals mean faster speed. Faster film requires less exposure to create a quality radiograph. Fast film is used for intraoral and extraoral radiography.

Image Receptor-Holding Devices

• These devices keep patients' hands from x-ray exposure, keep the film stable and allow the operator to position the film/sensor and PID properly.

Proper Technique

• Proper technique is essential for diagnostic quality images. Ensure minimal patient exposure. Retakes should be avoided because they increase radiation exposure to patients.

X-Rays During Pregnancy

• Guidelines state that dental radiographic procedures don't need to be altered due to pregnancy.
• Using a lead apron during procedures minimizes radiation to the pelvic region and is close to zero.
• This protection minimizes detectable exposure to the embryo or fetus.

Radiation Monitoring

• Film badges, pocket dosimeters (pen style), and thermoluminescent dosimeters (TLDs) are used to determine radiation exposure to personnel.

Equipment Monitoring

• Dental x-ray machines must be monitored for radiation leakage. Faulty tubehead seals can cause leakage and need repair. Monitoring is done with calibration devices provided by the manufacturer or state health department.

Patient Questions

• Provide explanations of procedures using clear, patient-friendly language.
• Emphasize that the office takes necessary safety precautions.
• Explain the use of lead aprons and thyroid collars.
• Explain the use of high-speed film or sensor to reduce radiation exposure.

Patient Issues: Informed Consent and Confidentiality

• Informed consent: The operator must obtain and document informed consent from each patient before taking images.
• Patient must receive an explanation in lay terms about procedure risks. A signed consent form provides documentation.
• Confidentiality: Patient images are part of the patient record. Clinicians are obligated to ensure privacy in line with HIPAA and state/federal laws. Patients have the right to have copies of their records transmitted to other providers in keeping with professional courtesy.

Exposure and Technique Errors

• There are several reasons why images can appear unexposed, overexposed, under-exposed, be absent of apical structures, have improperly placed receptors, be affected by overlapping contacts, be foreshortened or elongated, have cone-cut artifacts, or exhibit bending or creasing. Consult image examples for visualization of these image quality problems.

Unit 8: Quality Assurance, Legal Considerations, Digital Radiography

Digital Radiography

• Digital images are used instead of traditional x-rays or films.
• Digital images are electronic signals that are captured by sensors and displayed on a computer.
• These are instant and can be e-mailed.
• Hard copies can be printed on image quality paper.

Digital Radiography (Cont.)

• Traditional x-ray machines are still needed to expose the images.
• Strict infection control is needed when reusing sensors and phosphor storage plates.
• FDA-cleared disposable barriers must be used with digital image sensors and phosphor plates.

Types of Digital Imaging Systems

• Two basic methods exist:
• Direct imaging
• Indirect imaging

Direct Digital Imaging

• A solid-state sensor (silicon chip with an embedded electronic circuit) is the image receptor.
• The charge-coupled device (CCD) sensor is commonly used as a direct digital receptor.
• Some CCDs are wireless, while others have direct connections to a computer, similar to telephones.

Indirect Digital Imaging

• Phosphor storage plates (PSPs) are a common indirect digital imaging receptor.
• A thin flexible plate, similar to film, is coated with phosphor crystals and used to store x-ray energy.
• A scanner, using a laser beam, releases the energy to produce a digital image.

Phosphor Storage Imaging

• After scanning, the plates are exposed to bright light to erase energy and are ready for reuse.
• Infection control is crucial, using specially designed barrier envelopes for each plate.
• The plates must not be autoclaved. Handling of the plates must be careful to avoid scratching.

Digitizing Film-Based Radiographs

• Film-based radiographs can be digitized for computer viewing.
• Digital scanners capture and digitize the light signal of the film as with other documents.
• This process is akin to placing film on a duplicator lightbox for copy. This produces a less detailed image than direct digital imaging.

Digital Imaging Software Programs

• Most digital imaging software offers image enhancement via contrast, brightness, zoom/sharpness, reversal, and pseudocolor adjustments.

Federal Regulations

• Federal and provincial regulations govern dental x-ray equipment manufactured or sold in the U.S. after 1974. These include safety standards concerning filtration, accuracy of milliamperage-time and kilovoltage settings. Equipment is also subject to regional or provincial radiation health codes.

Provincial/Federal Requirements

• The Healing Arts Radiation Protection Act necessitates proper training and certification for individuals performing dental radiographs.
• Each province determines its policy for qualifying individuals to expose radiographs.
• Specific approval from the province's HARP (Healing Arts Radiation Protection) approved educational institution might be required.

Risk Management

• The dental practice utilizes risk management policies to reduce the likelihood of malpractice lawsuits.
• Dental assistants play a crucial role in managing risk. They must be careful to avoid saying anything negative about the x-ray equipment or its operation. Statements made without careful consideration can put the office at risk.

Informed Consent

• It's the dentist's responsibility to explain the need for radiographs in a comprehensible way.
• The dental assistant may provide support.
• Patients should give informed consent, as required for dental procedures.

For Valid Informed Consent

• Patients need to receive information in plain language about the risks and benefits of radiographic procedures.
• The specific person exposing the images, the number of images and their type, the consequences of not having images, and any alternative diagnostic methods should be explained.

Ownership of Dental Radiographs

• Dental images belong to the dentist, not the patient or insurance provider. This applies even if they paid for the images.
• Patients, however, can request copies of their images.

Quality Assurance

• Quality assurance in dental offices is a method of ensuring high-quality diagnostic images. Specific quality control steps are needed involving equipment, supplies, image processing, and administrative processes. These include keeping records of maintenance and operations.

Types of Quality Control Tests

• Regular testing of x-ray equipment (output, focal spot, tubehead stability, timer accuracy, milliamperage, and kilovoltage). 
• Film and PSP testing including examining film in boxes, unprocessed film quality, process results, and safelighting in the x-ray workroom.

X-Ray Machine Quality Control Steps

• Routine testing of x-ray machine output, focal spot size, tubehead stability, timer accuracy, milliamperage, and kilovoltage.

Dental X-Ray Film: Traditional Film Plates

• Film quality is checked initially and during processing. This checks for proper storage, handling, and processing. 

View Boxes

• View boxes should be routinely inspected for dirt and discoloration, and any damaged parts (bulbs) should be replaced.

Darkroom Lighting

• Regular darkroom checks (e.g., every six months) should be done to detect any light leaks.

Processing Solutions

• Processing solutions must be replenished daily and changed regularly to maintain quality. Testing the developer and fixer solutions can be used in place of calendar-based checks. Daily checks of the solution are important.

Stepwedge Radiograph

• A stepwedge is a device with layered aluminum steps used to expose different densities of radiation on film. This is a quality control test that produces varying densities.

Test your knowledge on radiography imaging concepts and techniques. This quiz covers topics such as receptor bending, motion unsharpness, and sensor maintenance. Perfect for students studying dental or medical imaging.