Imaging Advances of the Cardiopulmonary System

Abstract

A technological explosion has been revolutionizing imaging technology of the heart and lungs over the last decade. These advances have been transforming the health care industry, both preventative and acute care medicine. Ultrasound, nuclear medicine, computed tomography (CT), and magnetic resonance imaging (MRI) are examples of radiological techniques which have allowed for more accurate diagnosis and staging (determination of severity of disease). The most notable advances have occurred in CT and MRI. Most medical subspecialties rely on CT and MRI as the dominant diagnostic tools an exception being cardiology. CT and MRI are able to provide a detailed image of any organ or tissue in the body without the necessity of invasive or painful procedures. Virtually any individual could be tested as long as they are able to remain immobile for the duration of the study. Image generation traditionally has been limited by the perpetual motion of the human body. For example, the human heart is continually contracting and relaxing without a stationary moment during which an image could be obtained. Lung imaging has been more successful than cardiac imaging, but studies were limited to the length of time an ill person is able to hold his or her breath. Historically, imaging technology was limited by inability to take a picture fast enough of a moving object while maintaining a clinically useful level of resolution. Recent technologic innovation, resulting in high speed electrocardiogram- gated CT and MRI imaging, now allows the use of these imaging modalities for evaluation of the heart and lungs. These novel innovations provide clinicians with new tools for diagnosis and treatment of disease, but there are still unresolved issues, most notably radiation exposure. Ultrasound and MRI studies are the safest of the imaging modalities and subjects receive no radiation exposure. Nuclear studies give an approximate radiation dose of 10mSv and as high as 27mSv (Conti, 2005). In CT imaging, radiation dose can vary depending on the organ system being imaged and the type of scanner being used. The average radiation dose for pulmonary studies is 4.2mSv (Conti, 2005). The use of multi-detector CT (MDCT) to evaluate the heart can range from 6.7—13mSv. To put it into perspective, according to the National Institute of Health, an average individual will receive a radiation dose of 360mSv per year from the ambient environment. It is unlikely that the radiation doses received in routine imaging techniques will lead to adverse reactions such as cancer, but patients should be informed of the risks and benefits of each procedure so that they can make informed decisions. It is especially important that patients be informed when radioactive material is to be injected into their bodies. The reasons for this will be discussed later on in the chapter.