Medical Imaging Modalities: USG, CT Scan, and MRI

Vocabulary flashcards covering definitions, principles, patient preparations, advantages, and limitations of USG, CT Scan, and MRI based on the lecture transcript.

USG (Ultrasonography)

An imaging test that uses high frequency sound waves to produce real time images of internal organs and structures of the body.

Principle of USG

Works on the principle of reflection of high frequency sound waves from tissues, which are received by the transducer and converted into images.

Patient Preparation for Abdominal USG

Requires 6 to 8 hours fasting before the procedure.

Patient Preparation for Pelvic USG

Requires the patient's bladder to be full.

Limitations of USG

Image quality depends on operator, not useful in obese patients or gas filled bowel, and cannot assess deep structures clearly.

CT Scan (Computed Tomography)

An imaging technique that uses X-rays and computer processing to produce cross sectional images of the body.

Principle of CT Scan

Works on the principle of X-ray attenuation, where multiple X-ray beams pass through the body from different angles and a computer reconstructs the images.

Patient Preparation for CT Scan with Contrast

Requires fasting 4-6 hours, removing metal objects, explaining allergy history for contrast, and adequate hydration after contrast.

Limitations and Contraindications of CT Scan

Exposure to ionizing radiation, risk of contrast allergy or nephrotoxicity, and relative contraindication in pregnancy.

MRI (Magnetic Resonance Imaging)

An imaging technique that uses strong magnetic field and radio waves to produce detailed images of internal body structures.

Principle of MRI

Based on the principle of nuclear magnetic resonance, where hydrogen protons align in a magnetic field and emit signals converted into images when disturbed by radio waves.

Advantages of MRI

No ionizing radiation, excellent soft tissue contrast, and multiplanar imaging.

Contraindications for MRI

Not suitable for patients with a pacemaker, metal implants, or claustrophobia.