A modality is the method of which a diagnostic procedure is performed. The modalities are classified by source of energy. Sound, radio waves, visual light, radiation whether ionizing or not. In the world of medical imaging, some examples of modality are X-ray (DX), Computed Tomography (CT), Magnetic Resonance Imaging (MR), Ultrasound(US) or Nuclear Medicine(NM).
Watch the video on imaging modalities below:
Ionizing radiation where the source of radiation is a cathode ray tube
X-Ray Radiography
Source of Radiation: Ionizing radiation. X-Ray photon produced by a cathode ray tube.
Protocol: Single static image capture. Separate views may be captured.
Image Type: Static high resolution images in grayscale
Detector: Digital Radiography or Computed Radiography
DICOM Tag: DX or CR
Example: Chest X-RAY, X-Ray of the hand
Fluorography
Source of Radiation: Low dose Ionizing radiation. X-Ray photon produced by a cathode ray tube.
Protocol: Continuous sequence of images captured. Results in moving cine.
Image Type: Movie of lower resolution images in grayscale
Detector: X-ray image intensifier
DICOM Tag: RF
Example: Barium swallow study, Catheterization
Computed Tomography
Source of Radiation: Collimated X-Ray tube that rotates in a elliptical motion around the patient
Protocol: Continuous acquisition of imaging as patient is positioned in a gantry
Image Type: Thin transverse sections of images are reconstructed for multiplanar viewing
Detector: Solid state scintillators that rotate opposite to the cathode tube
DICOM Tag: CT
Example: Chest CT, CT of the head w/o contrast
Ionizing radiation where the source of radiation is the patient
Nuclear Medicine
Source of Radiation: Radioactive isotope that has been injected, inhaled or consumed by the patient
Protocol: Static View imaging or Single Photon Emission Computed Tomography
Detector: Sodium Iodide scintillation of gamma or beta rays
Image Type: Grayscale static images or reconstructed multiplanar images
DICOM Tag: NM
Example: Lung VQ Scan, Myocardial perfusion imaging
Positron Emission Tomography
Source of Radiation: Positron that has been injected, inhaled or consumed by the patient
Protocol: Continuous acquisition of imaging as patient is positioned in a gantry
Detector: Scintillation detector which is usually paired with a CT for fusion imaging
Image Type: Multiplanar images of physiology that can be fused with anatomical CT images
DICOM Tag: PT
Example: Whole Body PET Scan, Cardiac PET
Non-ionizing radiation
Magnetic Resonance Imaging
Source of Energy: Radiofrequency pulses by magnetic field.
Protocol: Continuous acquisition of imaging as patient is positioned in a gantry
Detector: Phased array receiver coils
Image Type: Grayscale multiplanar images
DICOM Tag: MR
Example: MR of the brain with contrast
Ultrasound
Source of Energy: Doppler ultrasound
Protocol: Transducer acquires sound waves and converts into static or dynamic images
Detector: Electric current transducer
Image Type: Static images or Multi-frame movie images
DICOM Tag: US
Example: Echocardiography, Venous doppler
Visible Light
Source of Energy: Visible light from photographic camera
Protocol: Static or video imaging
Detector: Camera lens
Image Type: Still image photograph or full spectrum video
DICOM Tag: VL
Example: Endoscopy, Dermatology image, Microscopy