The team behind MBR Health were asked an interesting question recently by a couple who had completed our Executive Package at Whole Body MRI™. After comparing their imaging reports, they noticed that one examination contained more image series and a greater number of images than the other.
“We had exactly the same scan, so why does my partner’s scan have more series or more images? Has something been missed?”
The short answer is no. In most cases, nothing has been missed. Although two people may undergo the same imaging protocol on the same scanner, it is entirely normal for the resulting studies to differ in both the number of image series and the total number of images. These differences are expected and, in almost all cases, do not indicate that diagnostic images are missing.
Understanding MRI Series
Most all diagnostic imaging is organised into series. Generally, each series is a collection of related images acquired for a particular purpose. For example, different series may image the body using different MRI sequences (e.g. DWI, T1-Weighted), orientations or reconstruction techniques.
Modern imaging systems may also generate additional series that are not new scans, or images, of the patient. These can include:
- reconstructed images generated after the scan
- presentation states, which store display settings such as windowing, annotations or measurements
- segmentation or post-processing data
- technical information produced by the MRI scanner
- equipment-generated information sent to the Picture Archiving and Communication System (PACS)
Depending on the scanner, software version and workflow, one examination may include additional non-diagnostic series compared with another person’s study. This is a normal variation in how imaging data is stored and managed.
Why Are There Different Numbers of Images?
Individuals are often surprised that two scans performed using the same protocol (at the same provider) can contain different numbers of images.
Cross-sectional imaging, such as CT and MRI, acquires the body as a series of thin slices. The number of slices required depends on the anatomical coverage of the area being examined. In the case of whole-body MRI, someone who is taller, has a longer torso, or simply has different body proportions will naturally require more slices to cover the same anatomical regions.
Small differences can also occur because of:
- normal variation in patient positioning
- slight differences in where a scan begins or ends
- automatic scanner optimisation
- image reconstruction methods
Ultimately, these variations can account for differences in number of image count, even when the examination is the same protocol, performed on the same machine, by the same provider.
Does This Mean Images Are Missing?
In almost every case, no. Differences in image or series counts should not be interpreted as evidence that part of the examination was omitted. Radiologists assess whether all required diagnostic sequences have been acquired, not whether two different patients have identical numbers of images.
Importantly, the presence of additional presentation states, technical series or reconstructed images does not change the diagnostic completeness of the examination.
Comparing MRI Studies
It is natural for couples to compare their imaging numbers, particularly when they undergo screening together through our Executive Package. However, MRI studies are individual examinations, reflecting each person’s anatomy and the way their images are processed and stored.
It’s also important to remember that image and series counts cannot be directly compared between different imaging providers. Every whole-body MRI provider develops its own imaging protocols, including the sequences acquired, slice thickness, anatomical coverage, reconstruction techniques and post-processing workflows. These protocol differences can result in substantial variation in the number of series and images produced, even when the clinical examination being performed is considered to be the “same”.
For comprehensive screening programs such as those offered by Whole Body MRI™ and MBR Health, small differences in image and series numbers are an expected part of modern medical imaging and are not, on their own, a cause for concern.
Additional Information
If you have any questions or would like to book a scan, please Contact Us.
Frequently Asked Questions
Below are some commonly asked questions about MRI scan metrics. For a full list of frequently asked questions, please see our FAQ page.
Why do two people having the same MRI have different image counts?
Image counts are influenced by individual anatomy. For example, a taller person or someone with a longer torso will usually require more image slices to cover the same anatomical region. Small differences in positioning and scanner optimisation can also affect the final image count.
Does a different number of series mean images are missing?
Not usually. Differences in series counts commonly reflect additional reconstructed images, presentation states, technical information or post-processing performed by the imaging system. These differences do not generally indicate that diagnostic images are missing.
Does a higher number of images mean a better MRI?
Sometimes; however, the number of images is not a reliable measure of MRI quality.
Image count is influenced by many factors, including the imaging protocol, slice thickness, anatomical coverage, and the number of MRI sequences (or tissue weightings) acquired. A scan with thinner slices or additional sequences may naturally produce more images, but this does not necessarily make it a higher-quality examination. The diagnostic quality of an MRI depends on much more than the number of images. Factors such as signal-to-noise ratio (SNR), image resolution, contrast, freedom from motion and other artefacts, distortion correction, and adherence to an appropriate imaging protocol all contribute to producing images that can be interpreted accurately by a radiologist.
Can I compare my MRI with one performed at another imaging provider?
Not directly. Different radiology providers use different MRI protocols, including variations in imaging sequences, slice thickness, anatomical coverage, reconstruction methods and post-processing. As a result, the number of images or series may differ considerably between providers, even when performing the same type of examination.
Related Articles
- Precision Matters: The Critical Standards Full-Body MRI Providers Must Uphold
- Whole-body MRI: Is Faster Better?
- The Importance of Diffusion Weighted Imaging (DWI)
Author: A Forbes, PhD.