Computed Tomography (CT) Basics

Study Notes

CT uses X-rays to create images of the body
A heated cathode releases high-energy electrons, converting to X-ray radiation
X-rays pass through tissues, hitting a detector on the opposite side
Denser tissues absorb more X-rays
CT excels at differentiating subtle density variations
Modern CT employs 'Spiral CT' with a single radiation source and multiple detectors rotating around the patient

Gantry: The large circular part of the CT machine where the patient lies
Table: The motorized table that moves the patient in and out of the gantry
Computer System: Processes data from the detectors, reconstructing it into images

X-ray source and detectors rotate around the patient
Detectors capture X-rays after passing through the body
Computer processes the data to form 2D cross-sectional images (slices) of the body
These slices can be combined to create a 3D image for a comprehensive view of internal structures

Diagnosis: Diagnosing conditions affecting bones, organs, soft tissues, blood vessels (tumors, fractures, infections, internal bleeding)
Guided Procedures: Guiding biopsy procedures and surgical planning
Monitoring: Monitoring diseases like cancer and the effectiveness of treatment

Standard CT: Uses a rotating X-ray beam to capture images of the body
Spiral (or Helical) CT: The scanner rotates continuously as the patient moves through the gantry, resulting in higher-resolution images
CT Angiography: Provides visualization of blood vessels after contrast material injection

CT provides much more detail than standard X-rays
CT scans are much faster, often taking only a few minutes
CT exposes patients to more radiation than standard X-rays, but is generally considered safe when used appropriately

Iodine-based IV contrast is frequently used in most CT scans
Oral Contrast: Liquid contrast (often barium) is administered prior to scans of the abdomen or pelvis to highlight the gastrointestinal tract.
Intravenous (IV) Contrast: Contrast is injected into a vein to enhance blood vessels, organs, or tissues. This aids in better distinguishing between normal and abnormal structures.
Exceptions: Contrast is usually not used for CT KUBs (Kidney, Ureter, Bladder scan), head CT unless a mass is suspected, or patients with poor kidney function

Technique: Non-contrast CT typically the first step for evaluating the brain, particularly in emergencies like trauma or suspected stroke. A contrast-enhanced CT scan may be necessary in specific cases.
Non-contrast Applications: Detecting hemorrhage, fractures, ischemic strokes, and brain edema
Contrast-enhanced Applications: Visualizing tumors, infections (such as abscesses), and blood vessel abnormalities
Preparation: Typically no special preparation is required; fasting may be necessary with IV contrast use

Provided detailed insights into the CT protocols, procedures, and techniques utilized for evaluating various body regions.

CT Chest: Examinations with or without contrast to evaluate blood vessels, lung structures, and mediastinal anatomy, including pulmonary embolism and lung diseases.
CT Abdomen and Pelvis: Scans utilize oral and/or IV contrast to visualize the gastrointestinal tract, liver, pancreas, kidneys, and other organs, assessing liver masses, cirrhosis, lesions (e.g., hepatocellular carcinoma), kidney stones, tumors, inflammation (e.g., pancreatitis), and appendicitis.
CT Spine: Evaluating bony structures such as vertebrae, assessing soft tissue, diagnosing spinal fractures, degenerative changes, disc herniation, and postoperative spine evaluation.
CT Musculoskeletal System: Detecting bone fractures, assessing complex joint structures, identifying bone tumors, metastases, infections (osteomyelitis), and evaluating arthritis.
CT Shoulder CT , Knee CT, Foot CT, Hand CT
CT Angiography (CTA): Assessing coronary artery disease (blockages, stenosis), aortic aneurysms, Peripheral Arteries (PAD), cerebral vascular abnormalities, etc.