Question: Enumerate
the radiological modalities which have no radiation hazards. What are the
advantages of MRI?
Radiological modalities with no ionizing
radiation hazards
These imaging
techniques do not use ionizing radiation (unlike X-ray, CT, fluoroscopy,
nuclear medicine):
1. Ultrasound (USG): Uses high-frequency
sound waves.
2. Magnetic Resonance Imaging (MRI): Uses
magnetic fields and radiofrequency pulses.
3. Optical imaging (e.g., endoscopy, optical
coherence tomography)
—sometimes included
depending on curriculum; not traditionally considered “radiology,” but it has
no radiation.
Thus, the principal
radiological modalities free of radiation hazard are Ultrasound and MRI.
Advantages of MRI :MRI offers multiple benefits due to its
physics and high soft-tissue contrast:
1. No ionizing radiation
Safe for repeated
examinations.
Preferred in children,
pregnancy (after the first trimester), and follow-up imaging.
2. Superior soft-tissue contrast: Excellent
visualization of brain, spinal cord, muscles, ligaments, tendons, marrow,
pelvic organs.
3. Multiplanar imaging: True axial, sagittal, coronal, and oblique
planes without repositioning the patient.
4. Functional and advanced imaging
capabilities
DWI/ADC: stroke,
tumors, cellularity.
fMRI: brain activation
mapping.
MR angiography (MRA):
vascular imaging without radiation.
MR spectroscopy:
biochemical analysis.
Perfusion MRI:
tumor/ischemia assessment.
Cardiac MRI: anatomy,
viability, function.
5. Excellent for detection of lesions obscured
on CT: Brain tumors, multiple sclerosis plaques, ligament tears, marrow
pathology.
6. Contrast agents generally safer:
Gadolinium has fewer allergic reactions compared to iodinated contrast (though
nephrogenic systemic fibrosis is a concern in severe renal failure).
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