Radiological Techniques: Introduction

Introduction to Basics of Radiological Techniques

• The lecture provides an introduction to basic radiological techniques
• Presented by Dr./ Nesreen Mohey for the medical diagnostic imaging course RMI113 in Spring 2025

Intended Learning Outcomes

• Identify different types of imaging modalities
• List imaging modalities using X-ray tubes
• Identify different parts of an X-ray tube
• List the uses of fluoroscopy
• Understand basic concepts of computed tomography

What is Radiology?

• Radiology is a medical specialty using imaging to diagnose and treat visualized diseases in the human body
• Radiologists use an array of imaging modalities
• Some modalities use X-ray machines or radiation devices
• Other modalities like MRI and ultrasound do not involve radiation

Types of Radiology

• Radiology has two sub-fields: Diagnostic and Therapeutic
• Diagnostic radiology uses imaging modalities to aid in diagnosing diseases
• Therapeutic radiology uses radiation to treat diseases like cancer, called radiation therapy

Imaging Modalities

• General Radiography (Conventional X-Ray)
• Fluoroscopy
• Mammography
• Computed Tomography (CT)
• Magnetic Resonance Imaging (MRI)
• Ultrasonography
• Angiography
• Nuclear medicine
• Position Emission Tomography (PET)

Conventional X-Rays

• Wilhelm Roentgen, a physics professor, discovered X-rays in 1895
• Roentgen's X-ray of his wife’s hand was the first ever taken, and he received the Nobel Prize in Physics in 1901
• Plain Radiographs, also known as X-rays, are a 2D representation of a 3D structure
• X-rays are a type of electromagnetic energy produced within an X-ray tube

Applications of X-Rays

• Used in medicine for diagnosis and therapy (e.g., detecting bone fractures and chest infections)
• Used to detect flaws, cracks, and air bubbles in finished goods like airplanes, cars, and trains
• Used to study the structure of crystals
• Used as metal detectors

X-Ray Modalities

• Many modalities in radiology use X-ray tubes
• This includes Radiography, Fluoroscopy, Mammography, and Computed Tomography

Conventional X-Ray Image Formation

• The difference in what is absorbed and what passes through is the main basis for forming an image
• X-rays can be absorbed, transmitted through the patient, or scattered

Fate of X-Ray beam

• Radio-opaque materials, like bone containing calcium, stop X-rays and form white shadows
• Radio-Lucent materials, like air in the lungs, allow X-rays to pass through easily, so images are dark

X-Ray Tube Components

• Cathode: Negatively charged, creates free electrons
• Anode: Positively charged, absorbs electrons, and creates X-rays
• Glass Envelop: Creates a vacuum around the cathode and anode to protect the tube
• Tube Housing: Absorbs X-ray photons except those aimed at the patient

Requirements of X-Ray Production

• A source of electrons via thermionic emission
• Acceleration of electrons through applied electrical voltage, kilovoltage peak, kVp, creating high kinetic energy
• Deceleration or de-energizing when electrons strike the anode in the x-ray tube, releasing heat and X-rays
• Only 1% of the electron energy converts to X-rays, with the other 99% becoming heat

Advantages and Disadvantages of X-Rays

• Advantages: Low cost, widely available, portable, short examination time
• Disadvantages: Ionizing radiation, non-availability of post-processing functions, relatively insensitive (2D image), requires patient cooperation

Fluoroscopy

• Fluoroscopy is a medical imaging technique displaying a real-time view of internal body structures using X-rays
• Generates a live X-ray video, rather than a static image
• Used for examination of moving (dynamic) internal structures and fluids
• It allows evaluation of anatomical structure location and system functions
• A contrast medium highlights the anatomy

Uses of Fluoroscopy

• Gastrointestinal tract (GIT) imaging (e.g., barium swallow, barium meal, barium enema)
• Genitourinary tract imaging (e.g., hysterosalpingography)
• Guiding catheters to blood vessels in angiography
• Placing devices intra-operatively such as stents and heart valves
• Foreign body removal
• Positioning orthopedic implants like artificial hips or knees

Mammography

• Mammography uses X-rays to image the breast, looking for breast cancer
• Types of Mammography:
• Screening Mammography: Performed every 1-2 years on all women after age 40 to identify breast cancer
• Diagnostic Mammography: Used when a patient has symptoms like a lump, pain, or nipple discharge

Computed Tomography (CT)

• A CT scan procedure involves aiming a rotating X-ray beam at the patient, with signals producing cross sectional images called “slices”
• Slices can create a 3D image of the patient, improving identification of structures
• Unlike conventional X-rays, which use a fixed X-ray tube, a CT scanner uses a motorized X-ray source rotating with a circular opening called a "gantry"

How CT scans operate

• A CT scan uses higher levels of ionizing radiation than radiographs
• Density of different tissues is measured by Hounsfield Units (HU), based on X-ray beam absorption and ranges from -1000 (Air) to +1000 (Bone)
• CT scans use window levels (e.g., lung, bone, soft tissue windows)
• CT images are processed into different planes, axial, sagittal and coronal
• CTs can be performed with and without contrast