LECTURE – 1 – RHPT – 485 READING IN MEDICAL IMAGING LEVEL - 8

X-RAY INTRODUCTION Discovered and named by Dr. W. C. Röentgen at University of Würzburg, 1895 Awarded first Nobel prize for physics, 1901

In 1895 Wilhelm Conrad Roentgen discovered X-rays, so paving the way for the development of a new branch of medicine called radiology. Initially, radiology was the science of 'X-rays', but today it involves a variety of imaging techniques to study and investigate patients so that a diagnosis can be achieved. In addition, therapeutic procedures are performed by radiologists under image guidance, a branch also known as interventional radiology.

FIRST X-RAY Roentgen’s wife's hand

What are the Different Imaging Modalities Radiography “plain films” Computed axial tomography “CT” Magnetic resonance imaging “MRI” Ultrasound “US” Interventional radiology “angio”

RADIOLOGY TOOLS X- RAY ULTRASOUND NUCLEAR MEDICINE MAGNETIC RESONANCE COMPUTED TOMOGRAPHY

HOW IS IMAGING DONE? IONIZING RADIATION X-ray, CT, Nuclear Medicine SOUND WAVES Ultrasound MAGNETIC FIELDS / RADIO WAVES Magnetic Resonance To image the patient a energy source is directed into a volume of tissue and an image is created of the tissue interaction.

How to Approach Reading any Image Identify the patient When was the image taken Are these the proper images The five densities Are the images technically adequate

Radiography – X - Ray Also called “plain films” or “standard films” Image formed using broad beam ionizing radiation The image formed is related to the subjects density May involve the use of contrast agents Iodinated Barium Air

X-RAY High Energy Photon --Kilo Electron Volts Ionizing Radiation Exposes Film / Detector Projection Data X-RAY X-ray beam detector X-rays are short-wave electromagnetic radiation produced by accelerating electrons across an evacuated tube onto a tungsten anode using a high voltage.

An X-ray tube is similar to a light bulb with a filament and a current to heat the filament. There is also a high voltage to accelerate the electrons from the filament at a target. This collision releases the x-ray radiation that is used to image the patient.

X-RAYS PLAIN FILM RADIOGRAPHY - Clinical uses Chest Bones Spine / Extremities / Skull Soft tissue Mammography / Abdomen These are typical body regions that plain x-ray is used to evaluate.

X - RAY --- FIVE BASIC DENSITIES Air / Gas Soft Tissue / Fluid filled space Bone Fat Metal

The x-rays can traverse tissue to create the image. We can only separate the 5 basic densities noted. Air / Gas, Soft tissue / Fluid filled space, Bone, Fat & Metal. Here we see the Air in the lungs, the soft tissue of the heart and the bone density of the ribs. Water will appear of the same density as soft tissue and cannot be separated. Fat is difficult to see on the chest and better noted on abdominal x-rays

Plain film projections There are a number of projections or views commonly used when taking plain films. If a beam passes through the patient's ventral (anterior) surface first then through the dorsal (posterior) surface to reach the film, it is called an anteroposterior projection. Similarly, if the beam passes from dorsal to ventral through the body then a posteroanterior view is obtained.

Advantages cheap good first line imaging test readily available low radiation dose non-invasive standardized techniques

Disadvantages two-dimensional imaging no cross section imaging poor soft tissue contrast poor for individual organs

CONTRAST RADIOGRAPHY Injection, ingestion, or other placement of opaque material within the body. Improves visualization and tissue separation. Can demonstrate functional anatomy and pathology.

Administering a contrast agent modifies the image to give more information. Clinical uses :- Typical ones are barium, an inert particulate contrast used in GI tract evaluation. Iodine, a water soluble agent which can be injected into the vascular tree.(ANGIOGRAPHY) + intravenous agents to visualize the renal tract (intravenous pyelogram - IVP) Interventional procedures

ARTERIOGRAM UPPER GI--(GASTRO INTESTINAL) ORAL BARIUM CONTRAST ARTERIOGRAM INTRAARTERIAL IODINE CONTRAST

The contrast agent -Barium- will outline the GI tract, determine size and show patency or obstruction. The contrast agent-Iodine can be injected and is water soluble. In the blood stream, it will outline the vessel and demonstrate anatomy. Iodine is also filtered by the kidney and can show information about tissue function.

Reactions and side effects slight nausea or sensation of heat, to anaphylactoid shock and death. The mechanism of idiosyncratic reactions, such as urticaria, angioneurotic oedema, bronchospasm, vasomotor collapse and respiratory arrest, is poorly understood.

Risk factors asthma, allergies, renal or cardiac impairment, diabetes and myeloma.

Contrast agent administration Intra-arterial and intravenous contrast agents These water soluble non-ionic contrast agents. used for evaluation of the venous and arterial systems. Injected either directly into the veins (eg for intravenous pyelography, venography, or CT) or intra-arterially (eg for evaluation of carotid, renal, coronary, abdominal and limb arteries) Their excretion is via the renal tract.

Intrathecal (water soluble) contrast agents Water soluble intrathecal contrast agents are used for evaluation of the cervical, thoracic and lumbar subarachnoid space. Oral and rectal contrast Barium sulphate is the agent used for the detailed evaluation of the gastrointestinal tract. It is derived from mineral barites. Barium sulphate preparations are not water soluble and are rarely associated with any contrast reactions.