MPI is an acronym with several widely used meanings depending on the field. The two you’re most likely searching for are myocardial perfusion imaging, a common heart scan used to check blood flow to your heart muscle, and the Multidimensional Poverty Index, a global measure of poverty published by the United Nations. MPI also refers to the Master Patient Index in healthcare IT and Magnetic Particle Imaging in biomedical research. Here’s what each one means and why it matters.
Myocardial Perfusion Imaging: The Heart Scan
Myocardial perfusion imaging is a noninvasive test that shows how well blood flows through your heart muscle. It’s one of the most common ways doctors evaluate chest pain, check for coronary artery disease, and determine whether previous treatments like stents or bypass surgery are working. The scan can also reveal whether parts of the heart muscle have been permanently scarred or still have enough blood supply to recover.
The test works by injecting a small amount of a radioactive tracer into your bloodstream. The tracer travels with your blood and settles into heart muscle cells in proportion to how much blood flow they’re receiving. A specialized camera then captures images showing which areas of your heart are getting adequate blood and which are not. Three tracers are commonly used: thallium-201, which is actively pulled into heart cells, and two technetium-based tracers (sestamibi and tetrofosmin), which spread passively with blood flow. The technetium tracers have a half-life of about 6 hours, meaning they leave your body relatively quickly. Thallium sticks around longer, with a half-life of roughly 73 hours.
You’ll typically have images taken twice: once while your heart is stressed (either through exercise on a treadmill or with a medication that mimics the effect of exercise) and once while you’re resting. Comparing the two sets of images tells your doctor whether reduced blood flow only shows up under stress, which suggests a blockage that could benefit from treatment, or whether it’s present even at rest, which may indicate permanent damage.
How Accurate Is It?
For detecting significant blockages in the coronary arteries, the standard version of this scan (called SPECT) picks up disease correctly about 87% to 89% of the time, with a specificity around 73% to 75%. That means it’s quite good at catching real problems but occasionally flags something that turns out to be fine. The newer PET version of the scan is more accurate, with sensitivity around 92% and specificity near 85%. In one head-to-head comparison, PET achieved 91% overall diagnostic accuracy compared to 76% for SPECT, with PET reaching 100% specificity.
Perhaps most reassuring: if your scan comes back normal, the chance of a major cardiac event in the following two years is very low. A large analysis of over 39,000 patients found that the annual event rate after a negative scan was just 0.6%.
Multidimensional Poverty Index: Measuring Global Poverty
The Multidimensional Poverty Index is a measure developed by the Oxford Poverty and Human Development Initiative and used by the United Nations Development Programme. Unlike traditional poverty measures that look only at income, the MPI captures whether people are deprived across three core dimensions of life: health, education, and living standards.
Each dimension carries equal weight (one-third of the total score) and is measured through specific indicators:
- Health looks at nutrition (whether anyone in the household is undernourished) and child mortality (whether a child under 18 has died in the household within the past five years).
- Education checks whether any household member has completed at least six years of schooling and whether all school-aged children are currently attending school.
- Living standards covers six indicators: cooking fuel (whether the household relies on dung, wood, charcoal, or coal), sanitation, access to safe drinking water within a 30-minute round trip, electricity, adequate housing materials for floors, walls, and roof, and ownership of basic assets like a phone, radio, TV, bicycle, or refrigerator.
A person is considered multidimensionally poor if they are deprived in at least one-third of these weighted indicators. This approach reveals poverty that income alone would miss. A family might earn above a dollar-a-day threshold but still lack clean water, sanitation, and schooling for their children. The MPI captures that reality, and it’s now used to track poverty reduction in over 100 countries.
Master Patient Index: Linking Health Records
In healthcare information technology, an MPI is a database that assigns each patient a single unique identifier and uses it to connect all of that person’s records across different electronic systems. If you’ve visited a hospital, a specialist, and a primary care office that all use different software, an MPI is what ties those separate records together so that any provider can see your complete medical history.
The system works through patient matching algorithms that compare details like your name, date of birth, and gender to determine whether records in different databases belong to the same person. When a match is confirmed, a unique patient identifier is assigned and linked to all of those records going forward. Larger health networks use what’s called an Enterprise Master Patient Index, which extends this matching across multiple hospitals and clinics within a system.
Getting this right is harder than it sounds. The average healthcare organization has a duplicate record rate of 8% to 12%, and large health systems can see rates as high as 15% to 16%. A study analyzing nearly 400,000 confirmed duplicate records found that 95% of them had discrepancies in key identifying fields like name, date of birth, or address. These errors matter: duplicate or mismatched records can lead to missing medical history, repeated tests, or even treatment decisions based on the wrong patient’s information.
Magnetic Particle Imaging: A Newer Technology
Magnetic Particle Imaging is a relatively new biomedical imaging technique that directly detects superparamagnetic iron oxide nanoparticles injected as a tracer. Unlike MRI, which images the body’s own water molecules and then struggles to distinguish contrast agents from surrounding tissue, MPI picks up only the tracer itself. This means zero background signal from bones, organs, or other tissue, producing very clean images with high sensitivity.
The technique involves no radiation, offers unlimited tissue penetration, and provides a signal that scales linearly with the amount of tracer present, making it possible to precisely quantify how much tracer is in a given location. Current research applications include tracking cells as they move through the body, imaging blood flow, visualizing tumors, and guiding magnetic hyperthermia (a cancer treatment that heats nanoparticles to destroy tumor cells). MPI remains primarily a research tool but is advancing toward clinical use.
Multidimensional Prognostic Index: Geriatric Risk
One less common but clinically important MPI is the Multidimensional Prognostic Index used in geriatric medicine. This tool estimates the short and long-term mortality risk for hospitalized older adults by scoring eight domains: daily functioning, independence in tasks like cooking and managing finances, cognitive status, number and severity of existing illnesses, nutritional status, risk of pressure sores, number of medications, and social support. The final score ranges from 0 (low risk) to 1 (high risk) and is split into three risk groups. It gained wider attention during COVID-19, when it was used to help predict outcomes for older patients admitted to the hospital.