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• Best test for diagnosing PEBSI.
  Irina Obedkova
  Published on: 5 April 2021

• Published on: 5 April 2021

  Best test for diagnosing PEBSI.

  • Irina Obedkova, Nuclear Medicine Medical Resident Puerta de Hierro University Hospital , Madrid

  Dear colleagues, I have read with a great interest this systematic review “Esh R, Grødahl LHJ, Kerslake R, et al. Diagnostic accuracy of MRI for identifying posterior element bone stress injury in athletes with low back pain: a systematic review and narrative synthesis”[1] and would like to make some comments. Further research, as authors concluded, are always desired and I wish there are appropriate studies in the next future to decide if MRI could be a modality of choice for diagnosing PEBSI and not SPECT/CT as it is by now. But the referred articles from this review do not support this assertion for the following reasons.
  First, there are just 2 articles from 4 included in this review compared MRI and SPECT/CT and just in 1 of them (Juvenil spondilolysis: a comparative analysis of CT, SPECT and MRI) the results of both techniques were concordant, although the main causes of discrepancy were between MRI and SPECT/CT for diagnoses of stress reaction in absence of overt fracture and distinguishing incomplete fracture from intact pars of complete defects (22 patients and 40 pars defect) [2].
  Second, in the 2nd article the authors mention that sensitivity and specificity of MRI was 80 and 100% respectively skipping the SPECT/CT results and author’s conclusion that in the original article was following: “These results suggest that there is a high rate of active spondylolysis in active athletes with low back pain. MRI is inferior to bone scintigraphy (with SPECT)/c...

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  Dear colleagues, I have read with a great interest this systematic review “Esh R, Grødahl LHJ, Kerslake R, et al. Diagnostic accuracy of MRI for identifying posterior element bone stress injury in athletes with low back pain: a systematic review and narrative synthesis”[1] and would like to make some comments. Further research, as authors concluded, are always desired and I wish there are appropriate studies in the next future to decide if MRI could be a modality of choice for diagnosing PEBSI and not SPECT/CT as it is by now. But the referred articles from this review do not support this assertion for the following reasons.
  First, there are just 2 articles from 4 included in this review compared MRI and SPECT/CT and just in 1 of them (Juvenil spondilolysis: a comparative analysis of CT, SPECT and MRI) the results of both techniques were concordant, although the main causes of discrepancy were between MRI and SPECT/CT for diagnoses of stress reaction in absence of overt fracture and distinguishing incomplete fracture from intact pars of complete defects (22 patients and 40 pars defect) [2].
  Second, in the 2nd article the authors mention that sensitivity and specificity of MRI was 80 and 100% respectively skipping the SPECT/CT results and author’s conclusion that in the original article was following: “These results suggest that there is a high rate of active spondylolysis in active athletes with low back pain. MRI is inferior to bone scintigraphy (with SPECT)/computed tomography. Bone scintigraphy (with SPECT) should remain the first-line investigation of active athletes with low back pain followed by limited computed tomography if bone scintigraphy is positive” [3], 39 subjects and 50 pars interarticularis were included. The authors of the review make the opposite conclusion, that there were no false negative results of MRI, but false positive results of SPECT/CT due to SPECT´s high sensitivity of ongoing bone turnover activity and lacked classification system for SPECT.
  Regarding to metabolic bone turnover activity I would like kindly remind a metabolism of 99mTc-diphosphonates, which is used for scintigraphy. The incorporation of diphosphonates is carried out in the hydroxyapatite crystals, in such a way that the degree of uptake will be proportional to the presence of those crystals, which, will be proportional to the osteoblastic activity and, therefore, to the metabolic turnover bone activity. The metabolism cannot be deceived, if it is increased focally or diffusely, there are more crystals that will bind with more diphosphonates in the exact localization [4].
  Third, the authors mention that there is no established grading system defining SPECT abnormality in lumbar spine. System which normally used in Nuclear Medicine for defining an uptake in scintigraphy with/without SPECT is a semi-quantitative scale or a color scale of ROI (region of interest) lesion. Also nowadays quantitative SPECT has been commercially available for several years [5].
  Forth, the authors mention possible false positive results of SPECT/TC, saying that scintigraphy uptake occurs frequently in athletes (34-45.2%) in non-painful sites, making a conclusion that such false positive cases are commonly regarded as adaptive changes and are perceived normal, giving as a link an article “Assessment o a clinical significance of asymptomatic lower extremity uptake abnormality in Young Athletes” [6]. Skipping the fact that in this study was used planar scintigraphy of lower extremities and not SPECT/CT of spine, there is a huge difference between false positive and asymptomatic abnormality, which can be translate into some irrelevant for treatment or following but present detection, and this is really frequent in athletes, that’s why it is not recommended to make scintigraphy in the absence of pain [6]. As you can check the images of this article, there are uptakes which are not considered as false positives, the authors are discussing its origin and relevance, but not calling in question the fact of the uptakes.
  And the last, the risk of cancer development using nuclear medicine techniques is very low, even if the authors mention that “The effective dose from a single course of X-ray and SPECT-CT scans is 10X more, than what UK dwellings get in a year from natural background radiation exposure”. I can suppose that the authors took an effective dose of ionizing radiation 1mSv per year for UK dwelling and compared with approximately 10mSv received from SPECT/CT. There are epidemiological studies on populations exposed to radiation, such as atomic bomb survivors or radiotherapy patients, showed a significant increase of cancer risk at doses above 100 mSv [7] and despite intensive study, evidence to prove an increased cancer risk associated with radiation doses below ~100 mSv is lacking; however, concerns about ionizing radiation in medical imaging remain and can affect patient care [8]. Also nowadays it is used a lower dose CT protocols when performing SPECT-CT, permitting a reduction in the mean effective dose to 1.8 mSv from 4.0 mSv without a loss of CT image quality [9]. As an effective dose of an adult bone scintigraphy is between 2.9-4mSv [10], so the final effective dose of SPECT/CT is much lower than considered as risky for human health.
  As a conclusion, with the analysed studies of this systematic review we can make a conclusion, that SPECT/CT has better sensitivity (100%), than MRI (80%) in 1 study [3], which means a loss of the fifth part of pathology, not detected by MRI and concordant results in the other article [2]. The SPECT/CT is still a technique of choice in patients with PEBSI without neurological symptoms. In the absence of risk, it would be preferably to use more sensible technique, although further research is desired to find out the best test for diagnosing PEBSI.

  1) Esh R, Grødahl LHJ, Kerslake R, et al. Diagnostic accuracy of MRI for identifying posterior element bone stress injury in athletes with low back pain: a systematic review and narrative synthesis. BMJ Open Sport & Exercise Medicine 2020;0:e000764. doi:10.1136/ bmjsem-2020-000764
  2) Campbell et al. Juvenil spondilolysis: a comparative analysis of CT, SPECT and MRI. Skeletal Radiology volume 34, pages63–73(2005) https://link.springer.com/article/10.1007/s00256-004-0878-3
  3) Masci et al. 2005. Use of the one-legged hyperextension test and magnetic resonance imaging in the diagnosis of active spondylolysis. Br J Sports Med 2006; 40:940–946. doi: 10.1136/bjsm.2006.030023 https://www.researchgate.net/publication/6812831_Use_of_the_one-legged_h...
  4) Yuda, H., Wakao, H. 99mTc-MDP accumulation mechanisms in bone: Basic study on the adsorption onto hydroxyapatite. Oral Radiol. 12, 27–32 (1996) https://link.springer.com/article/10.1007/BF02351579
  5) Kangasmaa, T.S., Constable, C. & Sohlberg, A.O. Quantitative bone SPECT/CT reconstruction utilizing anatomical information. EJNMMI Phys 8, 2 (2021). https://doi.org/10.1186/s40658-020-00348-1
  6) Laura A. Drubach, Leonard P. Connolly, Pierre A. D’Hemecourt and S. Ted Treves. Assessment of the Clinical Significance of Asymptomatic Lower Extremity Uptake Abnormality in Young Athletes Journal of Nuclear Medicine February 2001, 42 (2) 209-212. https://jnm.snmjournals.org/content/42/2/209
  7) https://www.who.int/news-room/fact-sheets/detail/ionizing-radiation-heal...
  8) Ferrero A. et al. Understanding, justifying, and optimizing radiation exposure for CT imaging in nephrourology. Nature reviews. Urology, 01 Apr 2019, 16(4):231-244 https://scite.ai/reports/10.1038/s41585-019-0148-8
  9) Sandeep Kumar Gupta et al. Radionuclide bone scan SPECT-CT: lowering the dose of CT significantly reduces radiation dose without impacting CT image quality. Am J Nucl Med Mol Imaging 2017;7(2):63-73 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5435612/pdf/ajnmmi0007-0063...
  10) The EANM practice guidelines for bone scintigraphy. T. Van den Wyngaert, K. Strobel, W. U. Kampen, T. Kuwert, W. van der Bruggen, H. K. Mohan, G. Gnanasegaran, R. Delgado-Bolton, W. A. Weber, M. Beheshti, W. Langsteger, F. Giammarile, F. M. Mottaghy, F. Paycha, On behalf of the EANM Bone & Joint Committee and the Oncology Committee. Eur J Nucl Med Mol Imaging. 2016; 43: 1723–1738. Published online 2016 Jun 4. doi: 10.1007/s00259-016-3415-4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4932135/pdf/259_2016_Articl...

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  Conflict of Interest:
  None declared.

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