How can you choose the right bioimaging method for your application?

2 Electron microscopy

Electron microscopy uses a beam of electrons to scan the surface or the interior of a sample and create high-resolution images. Electron microscopy can achieve much higher resolution than optical microscopy, up to 0.1 nm, and reveal the ultrastructure and morphology of cells and molecules. Electron microscopy can be classified into two types: scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM produces images of the surface topography and composition of a sample, while TEM generates images of the cross-sections and internal structures of a sample. Electron microscopy is very powerful and informative, but it is also expensive, complex, and destructive. For instance, electron microscopy requires special sample preparation, such as fixation, dehydration, and coating, which can alter the natural state of the sample.

3 Magnetic resonance imaging

Magnetic resonance imaging (MRI) uses a strong magnetic field and radio waves to generate images of the internal structures and functions of the body. MRI can produce high-contrast images of soft tissues, such as the brain, heart, and muscles, and reveal the blood flow, metabolism, and oxygenation of different regions. MRI can also be combined with contrast agents, such as gadolinium or iron oxide nanoparticles, to enhance the signal and specificity of the imaging. MRI is non-invasive, safe, and versatile, but it is also costly, noisy, and time-consuming. Moreover, MRI has low spatial resolution, typically 1-5 mm, and is sensitive to motion artifacts and magnetic interference.

4 Ultrasound imaging

Ultrasound imaging uses high-frequency sound waves to create images of the internal organs and tissues of the body. Ultrasound imaging works by sending sound pulses into the body and detecting the echoes that bounce back from different interfaces. Ultrasound imaging can measure the size, shape, and movement of organs, such as the heart, liver, and kidneys, and detect abnormalities, such as tumors, cysts, and stones. Ultrasound imaging can also be used to monitor the development and health of fetuses during pregnancy. Ultrasound imaging is portable, inexpensive, and harmless, but it has low resolution, contrast, and penetration. For example, ultrasound imaging cannot image bones, lungs, or deep tissues.

5 Nuclear imaging

Nuclear imaging uses radioactive substances, called radiotracers, to visualize the distribution and activity of molecules in the body. Nuclear imaging involves injecting, inhaling, or swallowing a radiotracer that binds to a specific target, such as a receptor, enzyme, or gene, and then detecting the gamma rays emitted by the radiotracer using a special camera. Nuclear imaging can provide functional and molecular information about various diseases, such as cancer, cardiovascular disorders, and neurological disorders. Nuclear imaging can be performed using different modalities, such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Nuclear imaging is highly sensitive, specific, and quantitative, but it is also invasive, expensive, and risky. For instance, nuclear imaging exposes the patient and the environment to ionizing radiation, which can cause damage to the DNA and increase the risk of cancer.