Proper comparison is key when considering supine vs. upright imagingPosted on: 01.19.17 by Digirad
Cardiologists and their patients are learning more than ever about the benefits and limitations of supine vs. upright positioning for nuclear diagnostic imaging. While horizontal, face-up scans taken while patients are lying flat is the traditional method, upright imaging is a well-established method that has gained popularity, most likely due to the comfort and ease of use it offers to both the patient and the technologist.
Proper comparison is the key
Although both approaches have pros and cons, the key to proper image analysis is the comparison with a system-matched, multi-site, low-likelihood normals database. Due to the differences in anatomic distribution of potential sources of artifacts, quantification of the two methods will vary by gender, and by imaging convention (upright or supine). There may also be differences in system resolution, collimation, acquisition, and processing protocols including reconstruction algorithms, as well as filtering approaches and choices required for imaging. When using a normals database for comparisons, one must be certain to use a database of true comparables with regards to these variables. The normals database should include separate images for male and female anatomies.
A matter of patient comfort
Clinically, choosing one position over the other does not impact the imaging results. Physicians are finding confidence with both methods. There are some distinct differences, however. When in the supine position, patients are instructed to lie completely still with their arms above their head. Unfortunately, some patients, particularly those with shoulder or arm impediments, find this especially uncomfortable and a difficult position to hold. Also, it’s necessary for the scanners to be close to the patient’s head and face, which may bring on the feeling of claustrophobia.
In contrast, in the upright position, patients are seated with their arms rested on the device’s armrest, which is a much more natural and comfortable position. The camera’s detectors are much less imposing, providing significant improvement in comfort, and may help lower the patient’s anxiety level. These comfort-centric advantages often improve patient compliance, leading to minimal patient movement, which reduces motion artifacts in the final images.
Position change leads to reading ease
In the supine position, where the patient is lying down, versus the upright position, where the patient is sitting in a chair, the patient’s organs will settle differently. For example, when a patient’s arms are raised in the supine position it can cause a shift in the diaphragm, which, in some cases, may obstruct a clear view of the heart. In this instance, upright imaging offers the benefit of allowing the technologist to center the heart in the field-of-view, without extending the torso, thus keeping the diaphragm lower, and reducing the potential for diaphragmatic artifacts.
Therefore, parallel comparison is key: Supine patient studies should be scored against a normals database created with studies acquired on a supine system; upright patient studies should be compared to a normals database created with studies from an upright system.
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