S-Scan vs. O-Scan: Is An Open MRI or Extremity MRI Right for You?
If your doctor has ordered an MRI for joint pain, an injury or another musculoskeletal concern, you may assume that every MRI machine is basically the same. As a radiologic technologist, I can tell you that the type of scanner used can make a noticeable difference in both the exam itself and your overall experience.
At Extremity & Open MRI, we use specialized MRI technology designed specifically with musculoskeletal imaging and patient comfort in mind. Two of these systems are the Esaote S-scan and Esaote O-scan.
Both provide detailed MRI imaging without ionizing radiation, and both offer a more open experience than many people associate with traditional MRI machines. However, they are designed for different types of exams.
So, what is the difference between the S-scan and O-scan, and which one might be used for your MRI? Before we answer that we must discuss Tesla and MRI coils. Here's what you should know.
What Does Tesla Mean in MRI?
Patients sometimes see numbers such as 0.25T, 0.31T, 1.5T or 3T and assume the largest number automatically means the "best" MRI.
That's not quite how it works.
Tesla, abbreviated T, is the unit used to measure the strength of an MRI system's magnetic field. The S-scan operates at 0.25T, while the O-scan operates at 0.31T.
Traditional hospital MRI scanners commonly use higher field strengths, but field strength is only one part of MRI imaging. The scanner's design, software, imaging sequences, dedicated coils (as explained above), anatomy being examined and proper patient positioning all contribute to the images produced.
The S-scan and O-scan are low-field systems specifically optimized for musculoskeletal applications.
In other words, comparing one of these scanners with a traditional 1.5T or 3T whole-body scanner based on Tesla alone doesn't tell the whole story. These systems have been designed for a different purpose.
What Are MRI Coils?
Think of the coil like an antenna. The MRI scanner creates the magnetic environment, while the coil is positioned close to the body part being examined so it can pick up a strong, clear signal.
Specialized coils can significantly improve image quality, allowing lower-field MRI systems such as the S-Scan to produce highly detailed images that can compete with higher-field systems in certain applications.
Ultimately, image quality is not determined by field strength alone. What matters is achieving a strong signal-to-noise ratio (SNR) and capturing enough high-quality signal to produce clear, diagnostic images.
What Is the S-Scan MRI?
The S-scan is a 0.25 Tesla open MRI system designed specifically for musculoskeletal imaging. Unlike a traditional closed MRI scanner where a patient may be positioned inside a long cylindrical bore, the S-scan uses dedicated transmit/receive coils that improve image quality in an open permanent magnet and a wide, rotating patient table.
It is designed to image musculoskeletal anatomy from the foot through the shoulder, including important cervical and lumbar spine.
What Body Parts Can the S-Scan Image?
Depending on the exam ordered and the available coil, the S-scan can be used for areas including:
Foot and ankle
Tibia/Fibula
Knee
Thigh/Femur
Hip
Hand and wrist
Forearm
Elbow
Humerus
Shoulder
Cervical spine, or neck
Thoracic spine, or midback
Lumbar spine, or lower back
The system has multiple dedicated MRI coils designed for specific anatomy, including coils for the hand and wrist, knee, ankle and foot, shoulder, cervical spine and lumbar spine. That versatility makes the S-scan especially useful when we need to examine an area closer to the center of the body, such as the shoulder, hip or spine, rather than only the extremities (arms or legs).
Is the S-Scan an Open MRI?
Yes. The S-scan uses an open magnet design rather than the long, enclosed tunnel many patients picture when they hear the word "MRI."
From a technologist's perspective, this design can make positioning easier while creating a more comfortable experience for patients who are nervous about MRI. If you've previously struggled with claustrophobia during a traditional MRI, an open MRI system may feel significantly less confining.
The S-scan also uses a wide, asymmetric rotating table. This allows us to position the body part being examined carefully while keeping the patient as stable and comfortable as possible. Proper positioning is important because reducing movement helps us obtain clearer images.
What Is the O-Scan MRI?
The O-scan is a 0.31 Tesla MRI system dedicated specifically to extremity imaging. Unlike the S-scan, which can accommodate areas such as the shoulder and spine, the O-scan focuses on the arms and legs.
Think of it as an MRI designed around your extremities rather than requiring your entire body to enter a scanner.
For many exams, the patient sits comfortably while the specific arm or leg being examined is positioned inside the magnet. The rest of the body remains outside. That makes the O-scan particularly appealing to patients who are anxious about enclosed spaces.
What Body Parts Can the O-Scan Image?
The O-scan is designed for areas such as:
Hand
Wrist
Forearm
Elbow
Foot
Ankle
Calf
Knee
If your doctor orders an MRI of your ankle after a sports injury, for example, we are able to position only your lower leg inside the scanner rather than placing your entire body inside a traditional MRI bore.
Is the O-Scan an Open MRI?
The O-scan is best described as a miniature closed-tunnel MRI. It is a dedicated extremity MRI with an open, non-claustrophobic design.
Because only the extremity being examined needs to be positioned within the scanner, your head and most of your body generally remain outside the magnet. For patients with significant claustrophobia, this can make a major difference in how they feel about having an MRI.
It can also make the process easier for someone who has previously delayed or avoided an MRI because of anxiety about being enclosed.
S-Scan vs. O-Scan: What's the Difference?
The easiest way to understand the difference is to look at what each scanner was built to do.
Both scanners are designed around musculoskeletal imaging, but the biggest distinction is how much anatomy each system can accommodate.
The O-scan is highly specialized for extremities. The S-scan provides a wider range of musculoskeletal imaging options, including areas closer to the center of the body.
Why Use a Dedicated Extremity MRI?
If we're only imaging your knee or wrist, you may wonder why your entire body needs to go inside a large MRI scanner.
Well the good news is that with a dedicated extremity MRI, it doesn't have to!
For an appropriate exam, systems such as the O-scan allow us to focus the scanner on the anatomy we actually need to evaluate.
This approach may offer several advantages for patients, including a less enclosed experience, easier positioning and a quieter environment. Esaote reports an acoustic noise level of approximately 59.7 dB for the O-scan.
For someone who already has pain from an orthopedic injury, finding a comfortable position and remaining still can be challenging. Dedicated musculoskeletal equipment gives the technologist more options for positioning the area being examined.
What Can an Extremity or Musculoskeletal MRI Look For?
MRI is particularly valuable because it can provide detailed images of many soft-tissue structures surrounding a joint.
Depending on your symptoms and the exam your health care provider orders, musculoskeletal MRI may be used to evaluate structures such as:
Muscles
Tendons
Ligaments
Cartilage
Menisci
Bone and bone marrow
Joint structures
Soft tissues surrounding a joint
For example, a knee MRI may be ordered to investigate a suspected meniscus or ligament injury or tear, while a shoulder MRI may be used to evaluate the rotator cuff and other soft-tissue structures.
The radiologist ultimately interprets the images and sends the findings to your referring health care provider for review.
Which MRI Machine Will I Use?
You generally don't need to decide between an S-scan and O-scan yourself.
Before your appointment, our team reviews the MRI order and the anatomy your provider needs evaluated. We can then determine which scanner is appropriate for the requested examination.
As a simple rule of thumb:
If we're imaging an extremity such as your hand, wrist, elbow, knee, ankle or foot, the O-scan is the appropriate option.
If we're imaging an area such as your shoulder, hip or spine, the S-scan is the more appropriate option.
Some areas can be imaged on either system. In those situations, the best choice depends on the specific exam, patient anatomy, clinical question and imaging protocol.
Our goal isn't simply to put every patient into the same machine. It's to match the patient and the exam with the appropriate technology.
What If I'm Claustrophobic?
Please tell us.
MRI anxiety is extremely common, and it's something radiologic technologists work with regularly. We work hard to make your experience more comfortable with blankets, pillows, and music.
One of the advantages of both the S-scan and O-scan is that they provide a spacious and less restrictive environment. If you've had difficulty completing a traditional MRI because of claustrophobia, don't assume that your next MRI experience has to be the same. Talk with our staff when scheduling your appointment so we can discuss the type of exam ordered and the scanner that may be appropriate for you.
S-Scan vs. O-Scan: The Bottom Line
Both the S-scan and O-scan provide specialized alternatives to traditional MRI for appropriate musculoskeletal examinations.
The O-scan is a 0.31T dedicated extremity MRI designed for areas of the arms and legs, such as the hand, wrist, elbow, knee, ankle and foot. Because only the extremity needs to be positioned in the scanner, it offers a particularly open experience.
The S-scan is a 0.25T open musculoskeletal MRI that expands imaging capabilities to areas including the shoulder, hip and important portions of the spine, in addition to many of the extremities.
Neither machine is simply "better" than the other. They serve different purposes. As technologists, our job is to use the equipment and imaging protocol that best matches the exam your health care provider has ordered while helping you remain as comfortable and still as possible.
Need an MRI?
If your health care provider has ordered a musculoskeletal or extremity MRI, at Extremity & Open MRI we offer specialized MRI technology designed with both diagnostic imaging and patient comfort in mind.
Whether you're dealing with a knee injury, shoulder pain, wrist problem, ankle injury or ongoing neck or lower back symptoms, our team can help determine which MRI system is appropriate for your exam.
Contact us today to schedule your MRI or learn more about our open and extremity MRI options. We accept most insurance plans or self-pay.
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