Magnetic Particle Imaging

MPI was first presented during 2005 and began to come into its own by 2012. So far, only a handful of prototype small-animal MPI scanners have been constructed worldwide. It has the potential to revolutionize the biomedical imaging field. The new tracer imaging modality is gaining significant interest from NMR and MRI researchers. MPI employs the same superparamagnetic iron oxide (SPIO) contrast agents that are sometimes used for MR angiography and are often used for MRI cell tracking studies.

These SPIOs are much safer for humans than iodine or gadolinium. SPIOs in MPI generate positive, bright blood contrast. With this ideal contrast, even prototype MPI scanners can already achieve fast, high-sensitivity, and high-contrast angiograms with millimeter-scale resolutions.

While the physics of MPI differ substantially from MRI, it employs hardware and imaging concepts that are familiar to MRI researchers, such as magnetic excitation and detection, pulse sequences, and relaxation effects.

MPI shows great potential for an exciting array of applications, including stem cell tracking and inflammation imaging in vivo, first-pass contrast studies to diagnose or stage cancer.

CT, MRI, PET and SPECT Scans

Had a chance to sample some of this technology recently and realized many folks are not aware of what the terms actually mean. Each requires a distinct type of radiology equipment used to perform mostly medical procedures. Each piece of equipment costs millions of dollars and data shows that more machines cause more tests to be performed. Various pieces of equipment may look different than the pictures below, due to company design and age of the equipment.

A CT (computed axial tomography) scan uses X-rays, an MRI (Magnetic resonance imaging) scan uses magnetic and radio waves, a PET (Positron emission tomography) scan uses a radioactive substance injected in the body and gamma rays, and SPECT (Single photon emission computed tomography) scan uses a radioactive substance injected into the body and a gamma camera. Tomography is a technique for displaying a representation of a cross section through a human body or other solid object using a penetrating wave.

CT Scanner

A CT scan is better suited to cancer, pneumonia, abnormal chest x-rays, and bleeding in the brain, especially after an injury. A CT scan shows organ tear and organ injury more quickly, so is more suitable for trauma cases. Broken bones and vertebrae are more clearly visible on a CT scan. CT scans provide a better image of the lungs and organs in the chest cavity between the lungs.

MRI Scanner

An MRI is better for examining the spinal cord. An MRI show a more visible brain tumor.

A CT scan does not show tendons and ligaments, but an MRI does.

A CT or MRI scan can assess the size and shape of body organs and tissue, but they cannot assess how these work.

PET Scanner

The PET system detects pairs of rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body. Three-dimensional images of tracer concentration within the body are then constructed by computer analysis. A PET scan can show how an organ works, and is often used with a CT or MRI scan. PET scans are used to diagnose a condition or to track how it is developing. PET scans are used to investigate epilepsy, Alzheimer's disease, cancer, and heart disease.

The SPECT system works like a PET, but uses gamma rays to show a tracer dose of radioactive material injected into the body. The material moves to areas of bone and elsewhere highlighting healing or cancer progression as it is usually lit up on SPECT scans.

I Know What You Are Thinking

Intel Corp. has introduced software that analyzes functional MRI scans to determine what parts of a person's brain are being activated as he or she thinks. it has 90 percent accuracy in guesses about which of two words a person was thinking about. Eventually, the technology could help the severely physically disabled to communicate.

The system works best when a person is first scanned while thinking of dozens of different concrete nouns - words like "bear" or "hammer." When test subjects are then asked to pick one of two new terms and think about it, the software uses the earlier results as a baseline to determine what the person is thinking. Very cool stuff.