Low back imaging: All-in-one MR makes strong showing vs. added CT
Two emerging MRI techniques show promise as all-in-one imaging tests for patients with pain in and below the lower back due to changes in the sacroiliac joint.
If supported by additional research, the techniques stand to uncover both early changes such as bone edema and chronic changes such as subchondral sclerosis.
What’s more, MRI as a standalone modality in these cases would preclude the need for CT, sparing patients radiation exposure while shortening radiologists’ time to diagnosis and recommendation.
The study behind the potential shift was conducted at Zurich University Hospital in Switzerland and published online June 30 in Skeletal Radiology [1].
Corresponding author Tim Finkenstaedt, MD, and colleagues looked at zero echo time MRI and black bone MRI as compared with CT as the reference standard.
Zero echo time (ZTE) is one in a number of novel 3D MRI pulse sequences that use an ultrashort echo time, one millisecond or less, the authors point out. The technique supplies a “contrast mechanism that affords visualization of the cortical bone of the sacroiliac joint,” they explain.
Meanwhile, established but overlooked black bone (BB) sequences offer sharp contrast between bone and non-bone tissues while reducing contrast between individual soft tissues. The effect is to allow the “black bone” to stand out for fast identification and evaluation.
A Nonradiative but No Less Illuminating Option to CT
To test these sequences against CT, Finkenstaedt and fellow researchers prospectively sent 79 patients for clinically appropriate ZTE and BB scans with a 3T MRI unit. All patients were imaged with CT within 12 months of the MRI exam.
The team had two blinded readers assess the bone tissue by grading each side of each sacroiliac joint using a 4-point scale on seven features (osteophytes, subchondral sclerosis, erosions, ankylosis, joint irregularity, joint widening and gas in the sacroiliac joint).
Comparing grades between all three modalities, they found overall good interreader agreement and the following particulars:
- Except for the feature “gas in sacroiliac joint”—where ZTE exhibited significantly lower scores than CT—ZTE and BB showed similar performance relative to CT for all other features. Inter-modality agreement was “substantial to almost perfect.”
- When combining the data from all features except for gas in the sacroiliac joint and when binarizing grading scores, combined sensitivity/specificity was 76.7%/98.6% for ZTE and 80.8%/99.1% for BB, respectively, compared to CT.
Commenting on the comparable performance of the ZTE and BB sequences with the CT imaging for bone assessment of the SI joint, the authors suggest the sequences might offer a nonradiative but no less illuminating option to CT.
Cutting Time to Treatment for Patients With Inflammatory Low-Back Pain
“Some of the different sacroiliac joint pathologies arise from etiologies (e.g., traumatic and rheumatic) which are present in younger patients where ionizing radiation is a particular concern,” Finkenstaedt et al. write. “Especially, since radiosensitive organs, like the ovaries and testes, are located in close proximity to the sacroiliac joints, the substitution of a CT scan by ionizing radiation-free ZTE or BB MRI sequences would remedy this concern.”
More:
Adding a ZTE or BB sequence to the regular sacroiliac joints MRI protocol would allow for the simultaneous detection of both osseous and non-osseous (e.g., cartilage abnormalities and enthesitis) changes in the sacroiliac joints with only one single MRI scan. The results show the value of ZTE and BB MRI sequences in displaying precise osseous morphology and offering detail beyond what traditional MR sequences can provide. Streamlining the diagnostic process can improve time to treatment, especially critical in inflammatory etiologies.”
The study is available in full for free.
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Reference:
- Lucas Wolharn, Tim Finkenstaedt, et al., “Detailed bone assessment of the sacroiliac joint in a prospective imaging study: comparison between computed tomography, zero echo time, and black bone magnetic resonance imaging.” Skeletal Radiology, June 30, 2022. DOI: https://doi.org/10.1007/s00256-022-04097-3
Dave P. has worked in journalism, marketing and public relations for more than 30 years, frequently concentrating on hospitals, healthcare technology and Catholic communications. He has also specialized in fundraising communications, ghostwriting for CEOs of local, national and global charities, nonprofits and foundations.