Here we continue the introduction to medical imaging and the modalities description for healthcare IT personnel.
After reviewing the ionizing radiation modalities during their development and the ultrasound usage, we should meet the other non ionizing radiological medical imaging modalities.
A brief overview of medical imaging modalities, part II
Magnetic resonance imaging (MRI):
The MR imaging is an advanced technology using a powerful magnetic field to align the hydrogen atoms throughout the human body into single orientation, then by radio frequency pulses the atoms would alter their orientations and such changes are received by antennas then computer processed to create images. The MR imaging technology enhanced the created images into superior soft tissue differentiation over the CT modalities especially among the musculoskeletal medical examinations.
The modality is safe with no hazard of ionizing radiation, still expensive and consumes large spaces. The MR imaging is contra-indicated to patients with metallic prosthesis and pacemakers as no metallic instruments are allowed in the range of the strong magnetic field.
The claustrophobia or fear of closed spaces inspired the scientist to invent the open MR machines which have wider space and provide more comfort for the patients of course on expense of the imaging quality.
The MR could create vascular imaging with no need to contrast injection, so the contrast media is limited to neoplastic processes and the continuous development of powerful magnets that even exceeded the 3 tesla has markedly improved the medical images quality and enabled viewing of further smaller details in clear way. MR images are created in multi-planner forms which are the axial, coronal and sagittal with no need for reconstruction. CT is still superior to MR in bone imaging, as mature cortical bones have no mobile atoms for imaging.
It’s an x-ray medical imaging technique that measures the bone mineral content and is usually dedicated to assess cases of osteoporosis. The imaging is directed to vertebra, wrists and femoral heads helping early detection of pathological conditions. Images are printed on ordinary papers in colors with measurement values.
It’s a huge branch of medical imagine that concerns both diagnostic and therapeutic purposes. The main concept is measuring of emitted particles from radioactive materials; besides medical imaging we can gain physiological data as well and on the contrary of the other medical imaging modalities, the human body is the source of radioactivity.
The most common forms of nuclear imaging are scintigraphy and PET.
It’s a form of medical imaging in which radio active isotopes are introduced in to the human body and the emitted radiation is captured by the gamma camera. Radio active isotopes differs according to the system under examination. It’s invasive technique and carries the hazards of radio active exposures. Patients had to keep away from pregnant women and children for variable periods according to the isotopes half life time.
Examples for scintigraphy include bone, thyroid, renal and cardiac scans. The imaging is limited to the system under investigation and provides medical data about diseases region and metastasis presence.
Positron emission tomography (PET):
It’s a more advanced medical imaging form of scintigraphy utilizing short life isotopes that is integrated with glucose and injected intravenous. The injected material is distributed throughout the body and accumulates at areas of rapidly growing tissue like tumors, metastasis and infection. The PET imaging is not restricted to certain single system as scintigraphy, but its value extends to cover the whole body. The high expenses limited its propagation till the moment.
Integration of two imaging modalities in one machine gave the advantage of medical pathological and anatomical definition, beside the ability of multi-planner images and 3D reconstruction.
Dr. Mohamed El-Refaey, MSc