Medical-imaging technology has surged ahead over the last several years, and new techniques can pin down practically any structure in the body, and also many important biological processes, like different rates of blood flow. The images are not only life-saving but also visually compelling, often pulling every crayon from the box.
One revealing new way to depict the brain is called diffusion tensor imaging (DTI). This image, created with DTI, was developed in a study on the brains of schizophrenics.
Diffusion tensor imaging is actually a specialized form of magnetic resonance imaging (MRI). While MRI traces the hydrogen atoms in water molecules, DTI builds a picture out of the direction in which those molecules are moving. Neuron fibers are long and skinny, and molecules tend to diffuse along them. Researchers can highlight spots where water molecules--and sets of neuron fibers--are headed in the same direction.
Diffusion tensor images like this one (rendered differently than the previous image) can reveal how a brain tumor has affected neuron connections or can help guide brain surgery. It can also reveal subtle abnormalities associated with stroke, multiple sclerosis, schizophrenia, and even dyslexia.
In MRI, a patient lies inside a cylindrical magnet and is exposed to a powerful magnetic field. Protons in water molecules line up when exposed to this field, then vibrate out of alignment when zapped with radio waves. As the protons realign, they produce a signal that can be picked up and processed into an image by a computer. Water-rich tissues send stronger signals and show up bright in the resulting images; bones appear relatively dark.
The technique is used here to depict arteries in the brain and neck. After an injection of contrast fluid, the scan is repeated as the dye moves through blood vessels, allowing a radiologist to see blockages that could cause a stroke, brain aneurysms, or even trauma injuries.
MRI is also frequently used in neuroimaging. The bright regions in the spinal canal and brain represent cerebrospinal fluid; the long string extending down the body is the spinal cord.
X-ray angiography can show even very small blood vessels in the hand. ("Angiography" means examination of the vessels.) The image quality provided by the latest digital detectors permits radiologists to see fine detail without resorting to high doses of radiation.
Here, the image shows the stark effects of hand trauma: no blood flows to the fourth finger, whereas small vessels are clearly visible in the other digits.
Creating a meaningful medical image involves two main tasks: collecting the data, and converting it into a picture that can be quickly and accurately interpreted. This image--produced by an advanced X-ray technique called computed tomography, or CT--show advances on both fronts.
Volume-rendering software was paired with CT angiography to discern an abnormal widening in the aorta (the large pink vessel running from the top of the image, surrounding the heart, to the lower parts of the body) close to the heart. Farther down, the liver (purple) and a kidney (bright red) can clearly be seen. Accurately gauging the diameter of the aorta is critical, since it tells a surgeon whether it's in danger of rupturing.
For CT angiography, used here for imaging the pelvis, a contrast agent is injected intravenously to make the blood vessels stand out against soft tissue. Software can further sharpen the distinction between bones and blood vessels to allow clearer and faster diagnosis.
CT generally uses a single X-ray source, but researchers are developing ways to combine two X-ray sources at different energies to better visualize soft tissue. Specific tissues--such as the tendons and ligaments featured in these hands--can be highlighted based on how they absorb the different energies.
To test the accuracy of the renderings, researchers scan cadavers and compare their virtual findings with the results of physical autopsies. The hands shown here are from a postmortem scan. The main aim of CT, of course, is to improve health, but there is also interest in the possibility of virtual autopsies. As part of a forensic exam, a CT scan like this one could reveal the path of an object like a knife.
Many medical imaging techniques focus on anatomical structures, but positron emission tomography (PET) is different: It produces pictures that highlight what cells are doing. A patient is injected with a radioactive tracer, and the cells that absorb it most readily glow bright.
Here the tracer is radioactive glucose. Because cancer cells grow and divide rapidly, they use a lot of energy, sucking up glucose and giving themselves away; the red coloring denotes disease in the patient's liver and shoulder area. The brain and heart (the C-shaped blotch is the heart's muscular wall, called the myocardium) are also big energy users, so they show up too. Combining PET scans with CT scans sharpens anatomy in the image. Image 1 shows PET alone; 2 shows CT alone; and 3 shows PET fused with CT, making it possible to see more exactly where the problem lies.
Like MRI equipment, PET instruments take data in multiple planes. Only one slice appears in the images here, but combining all the slices produces a 3-D picture.
Cancerous tissue identified by PET appears as a bright blue blob, and CT pinpoints its location in the colon. The structure of the kidneys (red), bones, and blood vessels--all from a CT scan--are clearly visible as well. PET is used most frequently in oncology exams but also has applications in cardiology and neurology.
GE Healthcare, the manufacturer of the instruments that produced this image, recently introduced two systems that will help researchers develop additional clinical applications. With its ability to monitor cell function, PET is the archetype of the new tools that can monitor our bodies at the cellular or even subcellular scale, says Bruce Hillman of the American College of Radiology Image Metrix.
This view of the heart is provided by big--or, more accurately, small--advances in cardiac ultrasound. Echocardiograms often use a sonar transmitter placed on the patient's chest to image the heart in a noninvasive manner, based on the ways high-frequency sound waves bounce off body parts. For some types of examination, though, other body parts make it difficult to get a clear view of the heart. The solution: Send a miniature probe down the esophagus.
This view of the mitral valve was taken using a transesophageal probe that can capture 3-D images in real time. By showing live, close-up video, the device is uniquely positioned to show how well the heart is functioning. In this case, the patient has had a ring placed in the mitral valve to repair it; the sutures appear as spots dotting the ring.
Heart ultrasounds are often needed at bedside, but transportable instruments have had limited performance. This new technology offers a solution.
This detailed ultrasound image of a heart was taken by an instrument the size of a laptop computer. Anatomy shows up in black and white. Activity (the direction and speed of blood flow), is in color. Red depicts blood flow toward the ultrasound transducer, and blue represents flow moving away from it.
Two valves, tricuspid (at left in the image) and mitral (right), control blood flow into the next chamber of the heart. In this patient, both are malfunctioning: Blood is flowing from the atria to the ventricles, as it should, but it is also leaking back the other way.
X-rays have been used to reveal living skeletons since the turn of the 20th century, but recent technological advances have substantially improved both the images and the potential for interpreting them.
Digital detectors can pick up soft tissue as well as bones; today's imaging software can show both components in a single picture. Since trauma to the neck sometimes damages more than just bones, combined images like this one allow a radiologist to look for soft tissue that might block the patient's airway.
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