Introduction To Diagnostic Imaging 2024 PDF

Foundations of Medicine 2024 INTRODUCTION TO DIAGNOSTIC IMAGING CRAIG BAILLIE MSPAS, PA-C ASSOCIATE PROFESSOR JWU CENTER FOR PHYSICIAN ASSISTANT STUDIES OBJECTIVES 1. Recognize the basic characteristics of the major imaging modalities used in medical evaluation and diagnosis. 2. Apply th...

Foundations of Medicine 2024 INTRODUCTION TO DIAGNOSTIC IMAGING CRAIG BAILLIE MSPAS, PA-C ASSOCIATE PROFESSOR JWU CENTER FOR PHYSICIAN ASSISTANT STUDIES OBJECTIVES 1. Recognize the basic characteristics of the major imaging modalities used in medical evaluation and diagnosis. 2. Apply the concepts and characteristics of imaging studies to reason the selection and value of type of study. 3. Identify & differentiate the indications, contraindications, limitations, advantages, disadvantages and cost for the following commonly used radiological imaging methods: Conventional radiology (plain films, x-rays) Computed topography (CT) with and without contrast Magnetic Resonance Imaging (MRI) Ultrasonography (US) Nuclear imaging 4. Recognize, discuss, and apply the use of the concepts, methods and/or techniques needed to effectively “read” the results of the imaging methods. 5. Utilize and/or demonstrate clinical reasoning and an evidence-based approach to the selection of commonly used radiological imaging for diseases and conditions presented. READING Chapter 1: Herring, W. Learning Radiology: Recognizing the Basics 2nd Ed. Philadelphia: 2007. Elsevier; 2012. http://www.learningradiology.com/index.htm Basic Radiology Introduction to Diagnostic Radiology OUTLINE 1. History 5. Imaging modalities & what 2. Physics & Radiation Safety they are good for X-ray 3. Imaging Concepts CT Density Ultrasound Object shape and projection MRI Contrast is essential! Nuclear imaging & PET scanning 4. Anatomic imaging planes HISTORY X-rays first documented in 1895 by German scientist Wilhelm Conrad Roentgen Won1st Nobel Prize in physics in1901 1st x-ray image was of his wife’s hand “X-rays” using x for unknown Conventional radiographic (CR) images HISTORY Used unidentified substance (ionizing radiation) striking a photosensitive surface (film). Latent image visible after processing. “Wet reading” = stat interpretation Limitations Processing time & chemicals Storage (space) Only in one place at a time PACS System – Picture Archiving Communication & Storage system Images from all modalities can be stored and retrieved from a server GENERAL PRINCIPLES Light is a form of electromagnetic radiation. Light vision limits us to surface evaluation. Physics of other types of waves provide ability to “see” deeper structures. Electromagnetic Radiation Periodic oscillations of charged particles. Magnetic & electrical fields. Does not require a medium. Travels at speed of light in a vacuum Gamma waves, X-rays, etc… Wavelength shorter than light. Allows deeper tissue penetration. IONIZING RADIATION Has sufficient energy to cause liberation of an electron! Can damage tissue (DNA)! THIS SLIDE IS ABOUT EFFECTS OF X-RAYS! IONIZING RADIATION SAFETY Conventional x-ray images are relatively low doses of ionizing radiation. Radiation has potential to cause cell mutations that could lead to cancer or other anomalies. Higher mitosis, higher risk, therefore younger > risk. Studies with x-rays should be avoided during potentially teratogenic times, such as pregnancy. Concept of ALARA (as low as reasonably achievable) in relationship to radiation dose – DO NO HARM. Only medically necessary diagnostic examinations should be performed. Risk < Benefit IONIZING RADIATION SAFETY PROTECT YOURSELF! 1. Time – limit your time length or frequency of exposure. 2. Distance – Further away from the x-ray source the better. 3. Shielding – stand outside a lead walled room, stand behind a shield, or wear a leaded apron when you may be exposed. Five X-ray Densities 1. Air Low density. Absorbs least x-rays therefore most X-rays penetrate (pass through) → black. 2. Fat 3. Soft tissue/fluid Soft tissue (muscle) and fluid (blood) have very similar density on conventional radiographs. 4. Bone Calcium is the densest, naturally occurring material. Absorbs most x-rays. 5. Metal High density, more absorption of X-rays → white (bullets, barium, pacemaker, some leads) contrast THICKNESS The thicker a structure is the more it will attenuate (absorb). metal bar getting thicker SHAPE Shape will affect radiographical appearance due to differences in thickness.  RADIOGRAPHIC EVALUATION Radiodense/radiopaque structures are easy to evaluate. Bone Calcium Barium Metal Radiolucent also relatively easy. Air will not see Fat Intermediate density fluid and soft tissue are more difficult. Adjacent structures of differing densities like bone and fat can be distinguished more easily – contrast. Greatest contrast in areas of greatest difference in density of adjacent structures! 1. Air/Lung 2. Fat/Adipose 3. Soft tissue 4. Bones  IMAGE PROJECTION Radiographs represent 3D subject in 2D. All 3D structures are superimposed. Single view limits ability to infer 3D.  Square object is outside chest but appears to be inside on AP projection. Multiple views are needed!  IMAGE PROJECTION (A) Posteroanterior (PA) CXR obtained by placing x-ray source behind patient. (B) Anteroposterior projection (AP) results in apparent enlargement of the heart, a phenomenon known as magnification. (C) Lateral radiograph of the cervical spine is used to assess the alignment of the spine, thickness of the prevertebral soft tissues (between white arrows), and heights of the vertebral bodies (double black arrow) and lateral discs (double white arrow). In this patient, disc space narrowing is present at C5-C6 (black arrow). oblique (D) Oblique view of the cervical spine highlights bony contours of the neural foramina WHERE IS THE BULLET? HAVE YOU SEEN MY KEYS?  CONTRAST AGENTS Variety of substances are available to enhance contrast between different anatomical structures. Contrast media can be classified as positive or negative. Positive contrast agents result in increased attenuation and show up as white. Barium and iodinated agents are positive contrast agents. Negative contrast agents result in decreased attenuation and show up as black or gray. Air and carbon dioxide are negative agents. CONTRAST AGENTS ANATOMIC PLANES ANATOMIC IMAGING PLANES Three standard planes: 1. Transverse or axial plane 2. Coronal plane 3. Sagittal plane  TRANSVERSE OR AXIAL PLANE Viewed from below as looking towards head. Feet would come out of the screen. Patient lying supine in scanner. SAGITTAL PLANE Looking at a patient from the side. Plane x-ray often called lateral image.  CORONAL PLANE Front view, looking at patient from the front. Sternum would be in front of screen. Upper thoracic spine behind screen. CONVENTIONAL RADIOGRAPHY (CR) PLAIN FILMS X-RAYS  CONVENTIONAL RADIOLOGY (CR) PLAIN FILMS Images produced through ionizing Without added contrast material. radiation (x-rays). Inexpensive Can be obtained almost anywhere Major advantage Still most widely obtained imaging modality! Limited range of densities demonstrated. Major disadvantages Reliance on ionizing radiation.  CONVENTIONAL RADIOLOGY (CR) PLAIN FILMS Conventional radiographs require; Source to produce x-rays (x-ray machine) Recording method (film, cassette, or photosensitive plate) Processing (chemicals or digital reader)  X-RAYS High energy, have no electrical charge so easily penetrate materials. Can be absorbed or scattered. Effectively blocked by heavier atoms (Lead). In medical imaging x-rays can either: Pass through completely. Be absorbed (attenuated). Partially or completely Mosaic attenuation X-RAYS OVERVIEW Indications: Trauma, bone fractures, chest infections, foreign bodies, tube and line placement, fluid where it normally is not, evaluation of hyperdense and hypodense structures particularly with high contrast adjacent structures. Contraindications: Pregnancy: Relative contraindication due to potential radiation exposure to the fetus. Advantages: Availability: Widely available and quick to perform. Cost-effective: Generally cheaper than other imaging modalities. Simplicity: Easy to perform and interpret for many conditions. Disadvantages: Radiation exposure: Involves ionizing radiation, which carries a risk of cancer with repeated exposure. Limited soft tissue contrast: Not ideal for imaging soft tissues compared to CT or MRI. Cost Considerations: Low cost: Typically, less expensive than other modalities making it a first-line investigation for many conditions. FLUOROSCOPY FLUOROSCOPY Fluoroscopy (or “fluoro”) uses x-rays in performing real-time visualization of the body in a way that allows for evaluation of; The motion of body parts. Real-time positioning changes of bones and joints. The location and path of externally administered contrast agents through the GI, GU tract, blood vessels, tube placement, etc. Images can be viewed as they are acquired on video screens and captured as a series of static images or motion (video) images “Snapshots” during the procedure are called spot films usually obtained by the radiologist performing procedure.  FLUOROSCOPY Requires special x-ray unit for controlled motion of; X-ray tube Imaging sensor And the patient To find the best projection to evaluate the body part being studied Contrast is injected into vessels, tubes, or ducts that can be imaged to demonstrate; Anatomy Pathology Position of catheters or other devices FLUOROSCOPY OVERVIEW Indications: GI disorders: Evaluating motility, structure, and obstructions in the GI tract. Musculoskeletal injuries: Assisting in joint injections, fracture reduction, and arthrography. Cardiovascular diseases: Diagnosing and treating blood vessel abnormalities, such as blockages, aneurysms, assessing coronary arteries and guiding cardiac device placements. Urological diseases: Evaluating bladder function and detecting obstructions in the urinary tract. Interventional procedures: Guiding biopsies, catheter placements, and endoscopic instruments Contraindications: Pregnancy: Relative contraindication due to potential radiation exposure to the fetus. Allergic reactions: Patients with known allergies to contrast agents. Severe renal impairment: The use of contrast can worsen kidney function in patients with existing renal impairment. Advantages: Availability: Widely available and quick to perform. Familiarity: Generally easy to perform and interpret for many conditions. Disadvantages: Radiation exposure: Involves ionizing radiation, which carries a risk of cancer with repeated exposure. Need specific machine and table. Need skilled knowledgeable operator.  Interventional Radiology (IR) is a medical specialty that uses minimally invasive image-guided procedures to diagnose and treat diseases in almost every organ system. Use multiple modalities for procedures including X-ray, fluoroscopy, CT, US. Interventional Radiologist – Sub-specialty within Radiology. PAs do practice in this area of medicine performing procedures that they are trained to conduct. COMPUTED TOMOGRAPHY (CT)  COMPUTED TOMOGRAPHY (CT) First introduced in the 1970’s Quantum leap in medical imaging Uses a gantry with a rotating x-ray beam and multiple detectors in various arrays CT scanner connected to a computer which generates composite tomographic “slices” based on many data points Multi-detector array allows many images to be obtained simultaneously  COMPUTED TOMOGRAPHY (CT) Most commonly viewed in axial plane. View images as if standing at foot of bed. Can view images in any plane from single scan due to computer ability to “reformat”  COMPUTED TOMOGRAPHY (CT) Denser substances absorb more x-rays are said to demonstrate increased attenuation and are seen as whiter densities on CT images. Less-dense substances absorb fewer x-rays are said to demonstrate decreased attenuation and are displayed as blacker densities on CT images.  CT CONTRAST Oral contrast: defines bowel IV contrast: defines vessels or blood flow. A. Oral contrast B. IV contrast Kidneys Vessels Pancreas Descriptive terms refer to density: Hyperdense (brighter) – Increased attenuation Hypodense (less bright) – Decreased attenuation CT OVERVIEW Indications: Emergency settings: Rapid assessment of trauma patients and acute conditions such as stroke or abdominal pain. Cancer initial identification, staging, and follow-up: Detailed imaging for detecting and monitoring cancer. Complex anatomical evaluations: Excellent for visualizing complex structures in the head, chest, abdomen, and pelvis including evaluations of vascular structures with IV contrast and GI/GU structures with contrast. Cardiovascular assessments: Non-invasive imaging of the heart and blood vessels. Infectious diseases: Identifying abscesses, infections, and their extent. Contraindications: Pregnancy: Relative contraindication due to potential radiation exposure to the fetus. Allergic reactions: Patients with known allergies to contrast agents. Severe renal impairment: The use of contrast can worsen kidney function in patients with existing renal impairment. CT OVERVIEW Advantages: CT scans are the cornerstone of cross-sectional imaging and are widely available. Speed: Head to toe in 5 basic densities via CR. Post processing: Ability to review in multiple planes and advanced 3D can reduce need for more invasive procedures. Disadvantages: Radiation exposure: Higher dose of ionizing radiation compared to conventional X-rays. ~70x x-ray Contrast reactions: Risk of allergic reactions to iodinated contrast agents and potential nephrotoxicity. Scatter with significant foreign bodies or implanted devices containing metal. Availability and cost: Cost of machine. Need an operator. More expensive and not as widely available as conventional X-rays. ULTRASOUND ULTRASOUND Uses acoustic energy above audible frequency – Non-Ionizing! Human ear 20 – 20,000 Hz Ultrasound >20,000 Hz Usually 2-17 MHz Widely used in medical imaging First choice in many studies including imaging the female pelvis, pediatric, noninvasive vascular, pregnancy, real time image guided biopsies  ULTRASOUND PRINCIPLES Transducer used to send & “listen“. Ultrasonic wave sent out via transducer. Wave bounces off anatomic structure. Wave returns to transducer. Onboard computer reconstructs image by: Strength of returning signal. Time to return. Echos occur when there is a change in density. Stored as static images or in form of a movie. Descriptive terms refer to echogenicity: Hyperechoic – brighter Hypoechoic – darker  ULTRASOUND MODES A-mode (amplitude) Shows strength of return signal as amplitude B-mode (brightness) Shows strength of return signal as brightness M-mode (motion) Shows motion of return signal over time Can see difference with reflector that is moving TRANSDUCER FREQUENCY High → Good resolution, poor penetration Low → Resolution less good, better (deeper) penetration Air “blocks” ultrasound (e.g., bowel)  US ARTIFACT (A) Increased through-transmission (arrow) is seen deep to cyst. (B) Shadowing (black arrows) is seen deep to two ribs (white arrows) (C) Comet tail artifacts (arrow) (D) Ring down artifact (arrow) from gas in bowel.  US STRENGTHS VS. WEAKNESS STRENGTHS WEAKNESSES NO IONIZING RADIATION! Excellent safety Inherent dependence on operator skill, can range profile. from excellent to abysmal. Wide availability, relatively low cost of the equipment. Limited evaluation of deep structures. Portability allows for bedside exam & guidance. Bone and intracranial assessments. Hands-on, allows for positive patient-provider Limited in patients with large body habitus. interaction. Inability to evaluate structures deep to gas Real-time imaging: evaluation of moving structures. collections. Generally good resolution, allows for eval of soft Lower spatial resolution compared to CT and MRI. tissue structures. Uncooperative patients. Allows evaluation of blood flow. Evaluating over/under open wounds.  US BEST INDICATIONS BEST INDICATIONS: Solid organ and fluid filled structures such as vessels. Pregnancy-related conditions: Routine monitoring and diagnosis of complications. Abdominal conditions: Gallstones, liver disease, kidney stones, and appendicitis. Cardiovascular assessment: Heart function, vascular diseases, and DVT. Emergency medicine, trauma, critical care, procedural guidance. Intrabdominal bleeding, cardiac arrest, etc. Breast and thyroid evaluation: Masses, nodules, and cancer screening. Pediatric conditions: Abdominal assessments in children to reduce radiation.  MAGNETIC RESONANCE IMAGING (MRI) MRI uses potential energy stored in the body’s hydrogen atoms. Protons (H+) in atoms have various “spins”. Powerful magnet can align the spin of the protons. Magnetic field is released, protons return to their original spin, and energy is released, generating radio waves. Frequency of the radio waves used to reconstruct image (“hydrogen maps”).  MRI TECHNIQUES Computers generate images using various algorithms, which emphasize different types of tissue. “T1” images: Fat = white CSF = black “T2” images: Fat = dark, CSF = white Contrast agent used to differentiate vessels from other tissue. MRI STRENGTHS Strengths: Not ionizing radiation! Superior soft-tissue contrast. Neurological disorders: High-resolution imaging of the brain and spinal cord. Best study to evaluate complex neurological conditions! Musculoskeletal injuries: Superior imaging of subtle bone injuries, infections, and injuries of the spinal column. Soft tissues such as ligaments, tendons, bone marrow, and cartilage. Cardiovascular diseases: Non-invasive assessment of heart and vascular structures. Abdominal and pelvic diseases: Detailed imaging of organs and tissues in the abdomen and pelvis. Breast cancer: High sensitivity in detecting and staging breast cancer. Vascular abnormalities: Detailed imaging of blood vessels with contrast or without the need for contrast in some cases. Functional brain mapping: Assessing brain activity and planning for surgical interventions. MRI WEAKNESSES Weaknesses: Relatively high cost of study and machine. High on-going operating cost. Not as widely available. Long scan times (30-60 minutes). Inability to be still for long periods may require sedation. Inability to maintain positioning due to pain or otherwise. Claustrophobia is a problem. Diameter or lumen of tube is too small for some Ferrous METAL! Certain devices (pacemakers), foreign bodies, projectiles, etc Possible RF side effects and contrast NUCLEAR MEDICINE  NUCLEAR IMAGING Use a radioactive isotope (radioisotope) which is an unstable form of an element that emits radiation from its nucleus as it decays. Humans artificially make them for most imaging. Referred to as radionuclides, radiotracers, or sometimes simply tracers. Radiopharmaceuticals are combinations of radioisotopes attached to a pharmaceutical that has binding properties that allow it to concentrate in certain body tissues. Typically administered via bloodstream, some eaten. Gamma camera detects radiation emitted by patient.  NUCLEAR IMAGING Single photon emission computed tomography (SPECT) Many 2D images from multiple angles, reconstructed by computer into a 3D data set Can be manipulated to demonstrate thin slices in any projection Gamma camera rotates around patient Positron emission tomography (PET) 3D images that depict the body’s biochemical and metabolic processes Performed with a positron (positive electron) producing radioisotope Most often used in the diagnosis and treatment follow-up of cancer Used to locate hidden metastases from a known tumor or to detect recurrence Oncologic PET scans make up about 90% of the clinical use of PET  NUCLEAR IMAGING Bone scan: Bone scan: Normal Metastasis PET SCAN Brain PET scan: Listening to Last lecture of music the day Resting  PET SCAN PET scans often combined with CT: Bronchogenic carcinoma with right supraclavicular lymph node metastasis  NUCLEAR MEDICINE STRENGTHS VS. WEAKNESS STRENGTHS WEAKNESSES Cancer diagnosis and management: Detecting, staging, and Radiation exposure: Involves exposure to monitoring various types of cancer. radioactive materials, although the dose is Cardiac evaluation: Assessing coronary artery disease, generally low. myocardial viability, and overall cardiac function. Availability and cost: Specialized equipment and Neurological disorders: Evaluating brain metabolism and radiopharmaceuticals can make these tests function in epilepsy, dementia, and neurodegenerative expensive and less widely available. diseases. Preparation and time: May require specific Endocrine disorders: Diagnosing and evaluating thyroid and preparation, and imaging can take a significant parathyroid conditions. amount of time. Bone pathology: Detecting bone metastasis and infections. Resolution: Generally lower spatial resolution GI issues: Localizing GI bleeding and assessing gastric compared to CT and MRI. emptying. Renal function: Evaluating kidney perfusion.  DIAGNOSTIC IMAGING COST $$$$$ RADIOGRAPHY COST Progressive reliance on diagnostic radiology as an integral part of evaluation has resulted in marked growth in number of studies. Due to enormous variability in reimbursement rates, impossible to provide absolute cost for each modality and type of exam. Imaging Modality Relative Cost Bar (Scale 1-10) Conventional Radiology (X-rays) ████ (1) Ultrasonography (US) █████ (2) Computed Tomography (CT) ███████████ (5) Magnetic Resonance Imaging (MRI) ███████████████████ (8) Nuclear Imaging █████████████████████████████ (10)  Equivalent in Cups Approximate Imaging Modality of Starbucks Cost Coffee Conventional Radiology (X-rays) $50 10 cups Ultrasonography (US) $100 20 cups Computed Tomography (CT) $500 100 cups Magnetic Resonance Imaging (MRI) $1,000 200 cups Nuclear Imaging $2,500 500 cups RADIOGRAPHY COST WHEN RADIOLOGISTS TAKE A SELFIE QUESTIONS?