T2W weighted images contain inherent T1W weighted contrast. Pseudo-STIR images are generated by a simple post processing technique of subtracting T1W images from the T2W images. In this study we probe the diagnostic value of Pseudo-STIR to identify hyperintense marrow lesions in comparison with T2 STIR sequences.
117 spine MR cases with sagittal T1FSE (n=85) or T1 FLAIR (n=32), T2W and STIR images from studies performed on 1.5T and 3.0T machines were extracted from PACS. The Pseudo-STIR images were created on an Osirix workstation by using the subtraction tool. The resulting 234 sets of STIR and Pseudo-STIR images were anonymized and blindly read by three independent Radiologists (R1, R2, R3 with 13 years, 16 years and 32 years of experience) with respect to the number of hyperintense lesions seen. The quality of study, and the confidence level of the observer in rating the lesions were also encoded. Accuracy for each Pseudo-STIR case was determined based on the observers\’ ability to match their independently reported count of the corresponding STIR Image.
The accuracy of the observers in reporting the count of hyper intense lesions in the Pseudo-STIR cases was reasonably good (R1: 69 %, R2: 78 %, R3: 64 %). The accuracy increased when the observers reported on cases where they assigned the highest image quality rating of three. All three reporters were more accurate while reporting cases that they gave the highest confidence rating of three (R1: 75 %, R2: 80 %, R3: 69%). It was observed that only two out of 117 cases (both T1 FLAIR derived Pseudo-STIR) were incorrectly marked by all three observers. Additionally, there was no significant bias in quality rating (at the highest rating of three) with respect to the Pseudo- STIR origin, with R1 (76% / 24 %), R2 (77 % / 23 %) and R3 (69 % / 31 %) scoring in line with the data distribution (73% / 27%). Finally, statistical testing for difference in accuracy based on Pseudo-STIR origin (T1FSE / T1 FLAIR), revealed no difference in each of the three observers.
These results point to the value offered by including STIR sequence in an MSK protocol. In the absence of a specific view plane, a Pseudo-STIR provides supporting evidence.
In this study, we demonstrate potential complimentary value offered by a simple post processing technique especially in situations where the STIR sequence is not obtained prospectively
