This observational analytic prospective study was conducted from February 2019 through December 2019 after being ethically approved by the institution committee.
Study participants
This study included forty two (twenty males and twenty-two females) patients known to have SCD. All patients were complaining of bone pain when they were referred from the emergency room and/or orthopedic department to the MRI unit. They underwent chemical shift imaging (T1-weighted dual gradient-echo in-phase and out-of-phase sequence) which was included within the routine MRI study on the symptomatic anatomic part of the skeleton. All the patients underwent complete clinical examination, CBC, differential white blood cell count, inflammatory markers, serum ferritin, and renal function tests. Informed written consent was obtained from all patients prior to study.
Inclusion criteria
In patients diagnosed with SCD, the inclusion criteria were based acute bone pain and chronic persistent bone pain with a clinical concern of osteomyelitis.
Exclusion criteria
Skeletal trauma and musculoskeletal pathologies other than SCD were the exclusion criteria.
CSI and MRI techniques
All MRI studies were performed on a 1.5-T Achieva; Philips (Netherlands) closed MRI machine and using appropriate surface receiver coils.
At least, the following sequences were performed in all studies:
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1-
Fat-suppressed fluid-sensitive sequence using either short tau inversion recovery STIR (TR/TE 6580/102, TI 130) or TSE T2-fs (TR/TE 4200/92 frequency selective fat saturation) or TSE PD-fs (TR/TE 7650/34 frequency selective fat saturation).
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2-
Pre-contrast T1-fs sequence (TR/TE 883/23, frequency selective fat saturation).
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3-
T1-weighted dual gradient-echo in-phase and out-of-phase sequence in axial and/or coronal planes (TR/TEs, 7/4.8 and 2.4).
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4-
Post-contrast T1-fs sequence (TR/TE 883/23), in more than one plane, in case of absence of T1 hyperintensity on pre-contrast images and after ensuring that the renal function is normal. 0.2 ml/kg body weight Magnevist (Schering, Germany) was used.
Image analysis
Three observers with 13, 6, and 5 years of experience interpreted the images independently. For diffuse marrow signal alteration, the IP and OP images were simultaneously analyzed for signal intensity; equal-sized region of interest (ROI) with equal number of pixels were placed over the same area of normal-appearing bone marrow (i.e., lacking any focal lesions) on the IP and the corresponding OP images. In order to perform an accurate measurement, the entire sequences were carefully scrutinized to avoid placement of the ROI cursors over any focal marrow abnormality, and the selected position for ROI placement was targeted on an area that did not attain any hyperintensity on STIR and/or T1WI. Computation of the percentage of signal loss on CSI was then obtained from IP-OP/IP formula; the result was considered abnormal when the value was < 20%, absent, or shows negative value.
For focal bone marrow lesions whether osteonecrosis or osteomyelitis, the STIR sequence together with the pre- and post-contrast-enhanced T1-fs and CSI images were scrutinized for number, location, and signal characteristics of signal abnormality areas within the bone marrow and/or the overlying soft tissues.
The frequency of detection of marrow focal lesions was recorded across different study sequences in order to assess the value of IP and OP images in focal marrow abnormality detection.
Statistical analysis
Results of CSI were recorded and tabulated. The statistical analysis was done using SPSS-16, and the descriptive data were represented as number and percent. Comparison between serum ferritin levels across different patterns of diffuse bone marrow signal changes was done by ANOVA test. Correlation between serum ferritin level and the percentage of bone marrow signal loss on CSI was done and represented as a scatterplot. Inter-rater agreement was assessed for focal bone marrow abnormalities.