Magnetic Resonance Imaging: Interpretive Errors & Diagnostic Limitations

Magnetic Resonance Imaging (MRI) is a powerful diagnostic tool that uses a magnetic field and radio waves to produce high-resolution images of bones, joints, and soft tissues.¹ MRI is widely used by many physicians and surgeons to aid in the diagnosis of musculoskeletal conditions and has advantages over X-ray in terms of visualizing soft tissue.² Although MRI is considered the ‘gold standard’, MRI findings can still lead to incorrect diagnoses, unnecessary surgeries, inappropriate interventional procedures and poor outcomes for patients.²

RELIABITLIY AND VALIDITY OF MRI FINDINGS

The reliability of MRI findings refers to the consistency of the results when used repeatedly on the same patient or on different patients.³ The accuracy of MRI findings refers to the ability of the imaging test to correctly diagnose or rule out a particular condition.⁴ MRI is frequently used in the evaluation of degenerative conditions in the lumbar spine.^5-7 During a routine lumbar spine MRI, seventy-five subjects were assessed for 10 different lumbar degenerative findings at individual lumbar levels using a standardized criterion. The absolute interrater agreement had a narrow range, from 74.5% to 91.5%.⁵ When stratified by condition, absolute interrater agreement ranged from 65.1% to 92.0% with disc hydration, disc space height, and bone marrow changes exhibiting the lowest absolute interrater agreements.⁵ Kappa coefficients ranged from fair-to-substantial agreement (0.28-0.61).⁵

Another study reported 49 distinct ‘findings’, 16 unique findings, and only 1 consistent finding in 9 of 10 scans in one patient collected at ten different MRI centers over a 3-week period.⁶ The authors concluded that the MRI center location and radiologist available to interpret the examination has a direct impact on the diagnosis, subsequent choice of treatment, and clinical outcome.⁶ 

MRI is often perceived as a commodity service where there are no meaningful differences in quality and patients can be advised to select a provider based on price and convenience alone. If this prevailing view is correct, then a patient should expect to receive the same radiological diagnosis regardless of which imaging center he or she visits, or which radiologist reviews the examination. However, it appears that this assumption is not correct; that is, the specific imaging center and the individual radiologist used can negatively impact patient care, outcomes, and costs.⁷

MRI findings in patients with suspected medial meniscus tears were inaccurate in 25% of cases and patients with suspected anterior cruciate ligament tears were inaccurate in 22% of cases, after arthroscopy revealed no tears. ⁸

QUALITY OF MRI IMAGING

Poor MRI image quality due to motion artifacts, patient obesity, and/or metal can cause blurring and ghosting of the images, making it difficult to accurately identify certain pathologies.⁹ More specifically, patient obesity can result in reduced image quality due to increased tissue thickness and metal artifacts (such as joint replacements) can interfere with the MRI signal.⁹

INTERPRETIVE ERRORS OF RADIOLOGISTS 

Musculoskeletal radiology experience, training, and specialization can impact the accuracy of MRI image interpretation of scans for knee osteoarthritis and shoulder instability.^10-11 An error rate of 33% was found between radiologists interpretation of positive films (films that contain an abnormality) when measured against the consensus of a group of experts.¹² In a typical clinical practice (comprised of both normal and abnormal studies), the diagnostic error rate is approximately 4%, which translates into approximately 40 million interpretive errors per year worldwide.^13-14

PATIENT POSITIONS

MRI image interpretation can also differ depending on the position (sitting, standing, or supine) of the patient during the scan.^15-16 Conventional MRI “does not truly reflect the physiological forces experienced by the disco-ligamentous structures during normal upright posture and ambulation.”¹⁷ Supine position MRIs can cause changes in the position of certain structures leading to changes in image results.^15-16 

Many transforaminal imaging findings, such as intervertebral disc herniations and exit foraminal stenosis, can be dissected on weight-bearing MRI (pMRI), but may not be visible in supine or non-weight bearing MRI.¹⁶ pMRI and dynamic-kinetic MRI (kMRI) can provide greater imaging benefits over recumbent MRI (rMRI) when determining spinal diseases associated with true axial loading.¹⁸ Notably, rMRI underestimated the presence and maximum degree of gravity-dependent spinal pathology and missed pathology of a dynamic nature, factors that are optimally revealed with p/kMRI.¹⁸  Degenerative spondylolisthesis is routinely missed in one third of supine MRI cases.¹⁹

The position of the spinal cord and nerve roots may also be altered, leading to changes in the apparent size and severity of a compression or impingement.^20-21 More specifically, increases in dural sac cross-sectional areas were noted in standing positions when compared to supine.²² In addition, upright imaging of the spine demonstrated symptomatic patients had 48% larger disc bulging in the lumbar spine when compared to asymptomatic volunteers.²³ Therefore, for some cases, it may be necessary to acquire images in various positions to help optimize MRI interpretation. 

CONCLUSION

While MRI is a valuable tool in the diagnosis of many neuromusculoskeletal conditions, discrepancies in the interpretation of MRI findings do frequently occur. Musculoskeletal radiology experience, training, and specialization can impact the accuracy of MRI image interpretation. In addition, the specific imaging center and the individual radiologist used can impact the accuracy and quality of the MRI findings. These discrepancies can lead to incorrect diagnoses, unnecessary surgeries, inappropriate interventional procedures and poor outcomes for patients.

AUTHORS

Manya Saxena, PT, Cert. DN.
Clinical director, Theramedic Rehab physical therapy, Houston, TX
Fellow-in-Training, AAMT Fellowship in Orthopaedic Manual Physical Therapy

Casey Charlebois, PhD(c), DPT, MSc, FAAOMPT, Dip. Osteopractic
Director of Clinical Research, AAMT Fellowship in Orthopaedic Manual Physical Therapy
PhD Candidate, Nova Southeastern University, Fort Lauderdale, FL

James Dunning, PhD, DPT, MSc, FAAOMPT, Dip. Osteopractic
Director, AAMT Fellowship in Orthopaedic Manual Physical Therapy
Montgomery Osteopractic Physical Therapy & Acupuncture, Montgomery, AL

Paul Bliton PT, DPT, OCS, SCS, FAAOMPT, Dip. Osteopractic
Associate Director, AAMT Fellowship in Orthopaedic Manual Physical Therapy
William S. Middleton Veterans Hospital, Madison, WI

Patrick Gorby, DPT, MPH, FAAOMPT, Dip. Osteopractic
Assistant Director, AAMT Fellowship in Orthopaedic Manual Physical Therapy
Gorby Osteopractic Physiotherapy & Wellness, Colorado Springs, CO

REFERENCES

1. Expert Panel on MR Safety:, et al. “ACR guidance document on MR safe practices: 2013.” Journal of Magnetic Resonance Imaging 37.3 (2013): 501-530.
2. Strudwick, Mark W., et al. “The pearls and pitfalls of magnetic resonance imaging of the upper extremity.” journal of orthopaedic & sports physical therapy 41.11 (2011): 861-872. Nepple, Jeffrey J., et al. “Clinical and radiographic predictors of intra-articular hip disease in arthroscopy.” The American journal of sports medicine 39.2 (2011): 296-303.
3. Bartsch, A J., et al. “Intra-individual repeatability and inter-individual variability of magnetic resonance imaging-based structural brain connectivity.” Brain Connectivity (2016):784-795.
4. Tawfik, Nermeen A., et al. “Diagnostic value of spinal ultrasound compared to MRI for diagnosis of spinal anomalies in pediatrics.” Egyptian Journal of Radiology and Nuclear Medicine 51.1 (2020): 1-11. 
5. Fu, Michael C., et al. “Interrater and intrarater agreements of magnetic resonance imaging findings in the lumbar spine: significant variability across degenerative conditions.” The Spine Journal 14.10 (2014): 2442-2448.
6. Herzog, Richard, et al. “Variability in diagnostic error rates of 10 MRI centers performing lumbar spine MRI examinations on the same patient within a 3-week period.” The Spine Journal17.4 (2017): 554-561.
7. Hancock, Mark J., et al. “Reliability and validity of subjective radiologist reporting of temporal changes in lumbar spine MRI findings.” PM&R 14.11 (2022): 1325-1332.
8. Smith, Christian, et al. “Diagnostic efficacy of 3-T MRI for knee injuries using arthroscopy as a reference standard: a meta-analysis.” American Journal of Roentgenology 207.2 (2016): 369-377.
9. Singh, Dinesh R., Michael SM Chin, and Wilfred CG Peh. “Artifacts in musculoskeletal MR imaging.” Seminars in musculoskeletal radiology. Vol. 18. No. 01. Thieme Medical Publishers, 2014.
10. Harish, Srinivasan, et al. “Imaging findings in posterior instability of the shoulder.” Skeletal radiology 37 (2008): 693-707.
11. Hunter, D. J., et al. “Responsiveness and reliability of MRI in knee osteoarthritis: a meta-analysis of published evidence.” Osteoarthritis and cartilage 19.5 (2011): 589-605.
12. Garland, L. Henry. “On the scientific evaluation of diagnostic procedures: Presidential address thirty-fourth annual meeting of the Radiological Society of North America.” Radiology 52.3 (1949): 309-328.
13. Waite, Stephen, et al. “Analysis of perceptual expertise in radiology–Current knowledge and a new perspective.” Frontiers in human neuroscience 13 (2019): 213.
14. Bruno, Michael A., Eric A. Walker, and Hani H. Abujudeh. “Understanding and confronting our mistakes: the epidemiology of error in radiology and strategies for error reduction.” Radiographics 35.6 (2015): 1668-1676. 
15. Madsen, Rasmus, et al. “The effect of body position and axial load on spinal canal morphology: an MRI study of central spinal stenosis.” Spine 33.1 (2008): 61-67.
16. Fiani, Brian, et al. “Weight-bearing magnetic resonance imaging as a diagnostic tool that generates biomechanical changes in spine anatomy.” Cureus 12.12 (2020).
17. Botchu, R., et al. “Current concept in upright spinal MRI.” European Spine Journal 27 (2018): 987-993.
18. Jinkins, J. Randy, Jay S. Dworkin, and Raymond V. Damadian. “Upright, weight-bearing, dynamic–kinetic MRI of the spine: initial results.” European radiology 15 (2005): 1815-1825.
19. Davis, Rick. “ROUTINE DYNAMIC IMAGING FOR EVALUATING DEGENERATIVE LUMBAR STENOSIS: INCIDENCE OF DEGENERATIVE SPONDYLOLISTHESIS MISSED ON SUPINE MRI.” Spine Journal Meeting Abstracts. LWW, 2008.
20. Vroomen, Patrick CAJ, Marc CTFM de Krom, and J. André Knottnerus. “Consistency of history taking and physical examination in patients with suspected lumbar nerve root involvement.” Spine 25.1 (2000): 91.
21. Weishaupt, Dominik, et al. “Positional MR imaging of the lumbar spine: does it demonstrate nerve root compromise not visible at conventional MR imaging?.” radiology 215.1 (2000): 247-253.
22. Hirasawa, Yoichiro, et al. “Postural changes of the Dural sac in the lumbar spines of asymptomatic individuals using positional stand-up magnetic resonance imaging.” Spine 32.4 (2007): E136-E140.
23. Nguyen, Ha Son, et al. “Upright magnetic resonance imaging of the lumbar spine: Back pain and radiculopathy.” Journal of craniovertebral junction & spine 7.1 (2016): 31.