Radiology Equipment: Operating Principles

RADIOLOGY AND IMAGING EQUIPMENT

OBJECTIVES

• Expected learning outcomes:
• At the end of the course/module students will be able to:
• Identify different radiology and imaging modalities.
• Component of convectional x ray and their functions

Describe component and functions of dental equipment

Determine care of different radiology and imaging equipment.

• Identify accessories for radiological investigations
• To understand operation of x ray machine to examine patients

To understand operation of dental x ray machine to examine patient.

Understand operation of fluoroscopic machine to examine patient.

• Understand conducting quality control procedures for x ray machine.
• Understand conducting of basic quality control procedures for dental x ray machine.

To maintain record events of all equipment for maintenance and servicing.

INTRODUCTION

Medical imaging plays a crucial role in diagnosing and monitoring a wide range of medical conditions. Among the most common imaging techniques are X-ray, ultrasound, CT scan MRI, and radionuclide scan X ray modality can be classified into Dental x ray

• Mammography

Fluoroscopy x ray machine

X RAY IMAGING

• X-ray imaging, uses ionizing radiation to produce detailed images of the body's interior.

X-ray Machine: A machine emits a controlled amount of X-ray radiation through the body.

Absorption: Dense structures, like bones and tumors, absorb more X-rays, resulting in white areas on the X-ray image.

Image Capture: X-rays that pass through the body are captured on a detector, creating an image.

Radiology Equipment: Operating Principles

Medical imaging of the human body requires some form of energy (radiation). In imaging techniques used in radiology, the energy used to produce the image must be capable of penetrating tissues.

In diagnostic X-ray imaging, images are formed by the interaction of the X-ray beam with the patient.

As the X-ray beam passes through the patient, the photons interact with the body tissues and are absorbed/scattered by the patient. The degree of absorption is related to the density of the material that is in the beam’s path.

Dense objects (such as bone and metal) have a high degree of photon absorption, while less dense objects (such as fat and water) absorbs less photons.

The differential absorption of photons by different materials in the photons' path results in the beam exiting the patient with different intensities. This is known as transmitted beam.

A detector is used to measure the intensity variation, thus providing information on the different densities in the beam’s path.

Origin of X-ray Source remains same for all x-ray imaging devices

• i.e X-ray tube
• Evacuated glass tube
• Target

Filament

Radiology Equipment: Operating Principles

Radiography X-ray equipment has an x-ray tube on one side and an x-ray detector on the other side of the patient. A short duration pulse of x-rays is emitted by the x-ray tube, a large fraction of the x- rays interacts in the patient, some of the x-rays pass through the patient (transmitted x-rays) and reach the detector. These transmitted x-rays form the radiographic image on the film/detector.

In radiography, the image is formed with screen-film system, CR cassette or with digital detectors.

In screen-film radiography, areas of high intensity (thus low material absorption) within transmitted beam result in more blackening of the film, while areas of low intensity (thus high material absorption) will result in less blackening of the film. The film will remain white in areas with no photons.

Human body is made up of tissues with varying densities, in the film black corresponds to tissues with little attenuation (such as air) and white corresponds to tissue with a high degree of attenuation (such as bone).

Bone

• Air
• Soft tissue
• X
• Primary collimation
• Film, fluorescent screen or image intensifier
• Beam intensity at
• detector level
• « Latent » radiological Image formed

Antiscatter Grid

• Scattered radiation

X-ray Image Formation

APPLICATION OF X RAY

Orthopedics: X-rays are commonly used to detect fractures, bone diseases, and joint problems.

• Dental: Dental X-rays are essential for diagnosing oral health issues.
• Chest Imaging: It helps diagnose lung conditions like pneumonia and lung cancer.

Mammography: X-ray mammography is used for breast cancer screening.

Advantage of x ray imaging

• noninvasively and painlessly help to diagnose disease and monitor therapy;

support medical and surgical treatment planning; and Guide medical personnel as they insert catheters, stents, or other devices inside the body, treat tumors, or remove blood clots or other blockages

ULTRASOUND IMAGING

Ultrasound imaging, also known as sonography, relies on sound waves to create real-time images of the body's internal structures.

IMAGE FORMATION IN ULTRASOUND

Sound Waves: A small handheld device called a transducer emits high-frequency sound waves into the body.

Reflection: When these sound waves encounter different tissues and organs, they bounce back (reflect) at varying speeds depending on the density of the tissues.

Image Formation: The transducer collects the reflected waves and sends them to a computer, which processes the data to create dynamic images on a screen

APPLICATION OF ULTRASOUND

Obstetrics: Ultrasound is commonly used during pregnancy to monitor fetal development.

Abdominal Imaging: It helps diagnose conditions in the liver, gallbladder, pancreas, and other abdominal organs.

• Cardiac Imaging: Echocardiograms use ultrasound to assess heart function.
• Musculoskeletal Imaging: It aids in diagnosing soft tissue injuries and joint conditions.
• Small parts imaging: it helps diagnose conditions of the breast, scrotum, neck and eye

Vascular imaging: helps in diagnose condition of blood vessels

Advantage of ultrasound

• SAFETY

No Ionizing Radiation: The main benefit of ultrasound imaging is that it uses ultrasonic sound waves to create images.

Ultrasound techniques differ from other imaging procedures, as no radiation is used.

As a result, any adverse patient response usually caused by radiation exposure is avoided.

Radiology Equipment: Operating Principles

• Other imaging tests often need substances known as contrast agents. These contrast agents help to emphasize specific areas in the body with issues during diagnostic imaging. Patients are usually administered the agents by oral medications or injection in blood circulation pathways.
• Many people suffer allergic reactions to these substances. Similar contrast agents for ultrasound imaging are not required in most cases, thus ensuring patient safety.

2. Non-invasive Approach

Ultrasound exams do not require invasive procedures.

Technicians only need to place the appropriate acoustic transducers in direct contact with the skin over the specific areas that require visualization.

Radiology Equipment: Operating Principles

For example, to check a patient’s thyroid gland, the probe is placed on the patient’s neck. For pregnant women, it is placed on the belly.

In some cases, radiologists often place the ultrasonic probe inside the body cavities to produce images of specific organs. This does not require invasive procedures (i.e., breaking the skin). For this reason, patients do not suffer postoperative pain and scarring associated with many medical procedures.

3. PAINLESS

Diagnostic ultrasound methods are generally painless. After all, they do not need injections, incisions, or needles. As a result, patients avoid postoperative chronic pain or operative complications.

For example, simply placing a probe on a pregnant woman’s belly produces a clear image of her unborn baby. Very easy and painless. This makes an ultrasonography examination appropriate for various applications.

4. NO RECOVERY TIME

Usually, non-invasive methods require no recovery period.

Since there is no recovery period, patients can undergo ultrasonography at any time and easily fit the sessions into their schedules.

5. COST

Since ultrasound techniques are also relatively inexpensive compared to other diagnostic imaging tests – it is affordable for many patients

SOFT TISSUE DETAILS

Unlike other imaging methods like X-rays used for examining hard tissue, such as bones, ultrasonography is ideal for visualizing soft tissues

DIFFERENCE BETWEEN X RAY AND ULTRASOUND

Radiation Exposure: Ultrasound does not use ionizing radiation, making it safer for pregnant women and children. X-rays, on the other hand, expose patients to a small dose of ionizing radiation.

Image Clarity: X-rays provide detailed images of bones and dense tissues, making them suitable for orthopedics and dentistry. Ultrasound excels in visualizing soft tissues, such as organs and muscles.

Real-Time Imaging: Ultrasound offers real-time imaging, making it ideal for monitoring moving structures, like a beating heart or a developing fetus. X-rays typically produce static images.

Portability: Ultrasound machines are often portable, allowing for use in various healthcare settings, including remote areas. X-ray machines are bulkier and less portable.

Cost: Ultrasound is generally more cost-effective than X-ray imaging.

FLUOROSCOPY X RAY MACHINE

Fluoroscopy – a continuous X-ray image is displayed on a monitor, allowing for real-time monitoring of a procedure or passage of a contrast agent ("dye") through the body. Fluoroscopy can result in relatively high radiation doses, especially for complex interventional procedures (such as placing stents or other devices inside the body) which require fluoroscopy be administered for a long period of time

Fluoroscopy

Fluoroscopy refers to the continuous acquisition of a sequence of x-ray images over time, essentially a real-time x-ray movie of the patient. It is called dynamic imaging.

Most general-purpose fluoroscopy systems use television technology, which provides images at the rate of 30 frames per second.

Newer fluoroscopy systems allow the acquisition of a real- time digital sequence of images (digital video), that can be played back as a movie loop.

Fluoroscopy is used for positioning catheters in arteries, for visualizing contrast agents in the gastrointestinal (GI) tract, and for other medical applications such as invasive therapeutic procedures where real-time image feedback is necessary.

Mammography

• X-ray mammography is the most reliable method of detecting breast cancer.

It is employed both as a screening tool and for diagnosis.

Mammography also uses x-rays for breast imaging; however, there are fundamental differences between a mammography system and a diagnostic x-ray system. Due to the tissue characteristics of the breast and pathology of interest, mammography systems utilize lower tube potential (15-35 kVp ).

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In addition, two compression plates are used to decrease breast thickness and minimize motion, thus resulting in the less scatter radiation and better overall image quality.

Typical layout of Mammo room

A) Dental (Intra-oral x-ray examination)

• Dedicated equipment used for radiography of tooth with low power stationary anode tube
• Tube is deployed on an extendable arm for easier positioning
• Tube potential : 60-70 kVp

• Exposure is varied by altering the exposure time
• Exposure time varies from 30 ms to 2.5 s
• Focus-skin distance, 10 cm for 60 Kv and 20cm for 60-75 kVp
• 10 cm for 60 kV,

20 cm for 60-75 kVp

Diameter of lead cone (collimator) diameter shall be less than 7.5 cm at the end of cone.

• It uses x-ray film (without film) or sensor for imaging purpose as detector.

Dental Radiography

CT SCAN

CT – many X-ray images are recorded as the detector moves around the patient's body. A computer reconstructs all the individual images into cross-sectional images or "slices" of internal organs and tissues. A CT exam involves a higher radiation dose than conventional radiography because the CT image is reconstructed from many individual X-ray projections.

Radiology Equipment: Operating Principles

Computed Tomography (CT) images are produced by passing x-rays through the body, at a large number of angles, by rotating the x-ray tube around the body.

Multiple linear array detectors, opposite the x-ray source, collect the transmission projection data. The numerous data points collected in this manner are synthesized by a computer into a tomographic image of the patient.

The term tomography refers to a picture (graph) of a slice (tomo).

CT is transmission technique that results in images of individual slices of tissue in the patient.

The advantage of a tomographic image over projection image is its ability to display the anatomy in a slice of tissue in the absence of over or underlying structures .

• Typical layout of CT room

Computed Tomography

Bone Mineral Densitometry Equipment

• Bone density or bone mineral density (BMD) is the amount of bone mineral in bone tissue.
• Bone density scanning, also called dual-energy x-ray

absorptiometry (DEXA) or bone densitometry.

Two x-ray beams with different energies are aimed at the patient’s bones. When soft tissue absorption is subtracted out, the BMD can be determined.

Bone density testing is used to assess the strength of the bones and the probability of fracture in persons at risk for osteoporosis.