Imaging Modalities

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.

RADIOLOGY

Branch of medical science that deals with the use of radiant energy in the diagnosis and treatment disease.

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.

Imaging Modalities

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

Imaging Modalities

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, relies on high frequence sound(ultrasonic) waves to create real-time images of the body's internal structures.

Ultrasound is the most common term used for this modality however occasionally ultrasonography (USG), or just sonography are used.

When abbreviated, USS, short for ultrasound scanning, may be used as an alternative.

Ultrasound images are produced by relying on properties of acoustic physics (reflection, refraction, absorption, and scattering).

Ultrasound machines Components

• An ultrasound machine includes the following major components:
• Display: A screen that shows images from the ultrasound scans.
• Keyboard: A key panel for data input and measurement display.

Central processing unit(CPU): A unit that processes signals from and to the transducer.

Pulse controls: Dials and controls that are used to change the amplitude, frequency, and duration of ultrasound pulses.

Transducer: Also known as a probe, generates ultrasound waves and detects reflected echoes. It contains piezoelectric materials, which vibrate due to echo pulses from the tissue. The transducer relies on the piezoelectric effect.

This piezoelectricity is amplified and transmitted to the display, where it is converted into an image form.

Types of ultrasound transducer

• Linear array transducer
• Convex array transducer
• Phased array transducer
• Endo cavitary transducers

3D/2D Transducer

Intraoperative transducer

Components cont………..

Amplifier: A unit that increases the size of the electrical pulses coming from the transducer after an echo is received. The amount of amplification is controlled by the gain control knob, which allows the user to adjust the gain to the required depth within the body.

• Storage device (not shown):A digital device that stores images for later use.

Printer: A unit that prints images from the displayed data.

Ultrasound gel

Ultrasound gel is a conductive medium that is applied to the skin before an ultrasound probe is used.

Its primary purpose is to facilitate the transmission of ultrasonic sound waves from the transducer into the body and back again.

Without the gel, air trapped between the transducer and the skin would interfere with the transmission of sound waves, leading to poor image quality.

ULTRASOUND IMAGES

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.

Imaging Modalities

• 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.

Imaging Modalities

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 low dose 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 ).

Characteristic X-ray produced by these target materials is used for breast imaging.

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

• compression paddle are positioned parallel to the table

Typical layout of Mammo room

Mammography vs mammogram

• Mammography refers to the process of using X-rays to create images of the breast tissue.

mammogram is the actual X-ray image produced during mammography Screening mammograms are used as a routine check for breast cancer in people without symptoms.

Diagnostic mammograms are performed when there are symptoms or abnormalities that need further evaluation

Mammograms

3D Mammography

A 3D mammography is an imaging test that combines multiple breast X-rays into a 3D picture of the breast. Another name for 3D mammogram is breast tomosynthesis.

A 3D mammogram can help find breast cancer in people who have no symptoms. It also can help find the cause of breast concerns, such as a breast mass, pain and nipple discharge.

3D Mammogram

Before the 3D mammogram became common, breast cancer screening mammograms used standard machines. Standard mammogram machines make 2D pictures of the breast. These 2D images still have some benefits.

So when it's used for breast cancer screening, a 3D mammogram machine makes both 3D and 2D images of the breast. Using these images together for breast cancer screening reduces the need for more imaging later. It also slightly increases the number of cancers found during screening.

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

COMPUTED TOMOGRAPHY (CT)

Computed tomography (CT), also known as computerized axial tomography (CAT), is an imaging modality that uses X-rays to build cross-sectional images ("slices") of the body.

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

CT Cont…….

A CT exam involves a higher radiation dose than conventional radiography because the CT image is reconstructed from many individual X-ray projections.

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 .

CT image formation

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.

During a CT scan, x-ray projections are taken from many angles around the patient.

The raw data from the X-ray projections is converted into a 3D image using a mathematical process(image reconstruction)the resulting 3D image shows the distribution of attenuation in the patient’s body.

The image reconstruction is done with different techniques the main being Back projection-Filtered back projection(FBP)

CT COMPONENT PARTS

CT MACHINES

CT IMAGES

Magnetic resonance imaging(MRI)

MRI is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body.

MRI scanners use strong magnetic fields, magnetic field gradients(coils) and radio waves to form images of the body’s organs.

MRI does not involve X-rays or ionizing radiation, distinguishing it from computed tomography (CT) and positron emission tomography (PET) scans.

MRI Cont…..

MRI is widely used in hospitals and clinics for medical diagnosis, staging and follow-up of disease.

Compared to CT, MRI provides better contrast in images of soft tissues, e.g. in the brain or abdomen An MRI system consists of four major components: A main magnet formed by superconducting coils, gradient coils, radiofrequency (RF) coils, and computer systems.

Simplified working principle of MRI

Unlike an X-ray or a computed tomography (CT) scan, an MRI does not rely on radiation. Instead, the technique uses very powerful magnetic fields to image water molecules in the body’s tissues.

A significant part of the human body is made up of water, and each water molecule is composed of two hydrogen atoms attached to one oxygen atom – H2O.

Imaging Modalities

Simplistically, MRIs work by using powerful magnetic fields to temporarily alter the orientation of subatomic particles (protons in hydrogen atoms) within water molecules inside the body.

Then, radio waves are used to force these particles out of this orientation and return them to their original alignment.

As they realign, the protons release resonance signals that are transmitted to a computer, which ultimately uses the signals to construct an image

MRI Cont……

MRI scanners rely on powerful magnets. Generally, the more powerful the magnet, the better the resolution of the image produced by the MRI scan.

The strength of MRI magnets is measured by a unit called Tesla (T). One Tesla is equal to roughly 20,000 times the strength of the Earth’s magnetic field at its surface.

Most MRI scanners used in clinics have magnets of 1.5 or 3 T, though more powerful magnets – 7 T, or even more than 10 T- are being explored in research.

MRI components

MRI

MRI IMAGES

Differences between MRI and CT Scan

MRI vs CT SCAN

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.

INTRODUCTION

Medical imaging plays a crucial role in diagnosing and monitoring a wide range of medical conditions. Among the most common imaging techniques/equipment 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

Imaging Modalities

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.

Imaging Modalities

Dense objects (such as bone and metal) have a high degree of photon absorption, while less dense objects (such as fat and water) absorb 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 the transmitted beam.

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

ULTRASOUND MACHINE

ULTRASOUND IMAGING

Ultrasound imaging, relies on high frequence sound(ultrasonic) waves to create real-time images of the body's internal structures.

Ultrasound is the most common term used for this modality however occasionally ultrasonography (USG), or just sonography are used.

When abbreviated, USS, short for ultrasound scanning, may be used as an alternative.

Frequency: The sound waves used in an ultrasound machine are typically in the range of 2 to 18 megahertz (MHz), which is far beyond the normal human hearing range (typically 20 Hz to 20 kHz)

Echography is a rare synonym but is seen especially concerning the ultrasound of the eye.

For historical reasons, ultrasound of the heart tends to be called echocardiography, or often just echo.

Imaging Modalities

Pulse controls: Dials and controls that are used to change the amplitude, frequency, and duration of ultrasound pulses to optimize image quality and penetration. .

involves adjusting parameters like pulse repetition frequency (PRF), amplitude, and duration to optimize image quality and penetration.

These controls determine the rate of pulses, their strength, and how long the transducer "listens" for echoes, impacting factors like image resolution, depth, and speed.

Imaging Modalities

Transducer: Also known as a probe, generates ultrasound waves and detects reflected echoes. It contains piezoelectric materials, which vibrate due to echo pulses from the tissue.

The transducer relies on the piezoelectric effect.

This piezoelectricity is amplified and transmitted to the display, where it is converted into an image form.

the transducer is a device that acts as both a transmitter and receiver of sound waves, using the piezoelectric effect to convert electrical energy into high-frequency sound and vice versa.

How it works

Emission: When an electrical current is applied, the piezoelectric crystals inside the transducer vibrate, producing high-frequency sound waves that are sent into the body. You cannot hear these sounds.

Reception: These sound waves travel into the body and bounce back as echoes when they hit different tissues, organs, or boundaries.

Conversion: The transducer then receives these returning echoes. The impact of the echoes generates an electrical signal in the piezoelectric crystals, which is sent to the ultrasound machine.

Imaging: The ultrasound machine processes these electrical signals, using the time it takes for the echoes to return to calculate the distance to the tissues. It then uses this information to construct a real-time 2D image of the internal structures.

Types of ultrasound transducer

• Linear array transducer
• Convex array transducer
• Phased array transducer
• Endo cavitary transducer

3D/2D Transducer

Intraoperative transducer

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.

How it works

Emission: When an electrical current is applied, the piezoelectric crystals inside the transducer vibrate, producing high-frequency sound waves that are sent into the body. You cannot hear these sounds.

Reception: These sound waves travel into the body and bounce back as echoes when they hit different tissues, organs, or boundaries.

Conversion: The transducer then receives these returning echoes. The impact of the echoes generates an electrical signal in the piezoelectric crystals, which is sent to the ultrasound machine.

Imaging: The ultrasound machine processes these electrical signals, using the time it takes for the echoes to return to calculate the distance to the tissues. It then uses this information to construct a real-time 2D image of the internal structures.

6. 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.