Synopsis

Keywords: Image acquisition: Motion Correction, Image acquisition: Whole Body, Image acquisition: Artefacts

In Italy the Healthcare System is Public. The Population is 59,11 millions (2021), 39% are affected by a chronic disease and the main causes of death are due circulatory system 37.49%, and tumors 30.36%.
In Italy there are a total of 1572 MRI scanner. Accessibility to the MRI is guaranteed within 72 hours for urgent services, and within 90 days for programmable exams.
The main field of research for radiographer is on artifact reduction, like the post-processing software O.P.E.R.A. Orthogonal-Phase-Encoding-Reduction-Artifact. It works on DICOM images and doesn't need hardware modifications, hence it could be used on different MR scanner.

In Italy the Healthcare System is Public. The Population is 59,11 millions (2021), 39% are affected by a chronic disease and the main causes of death are due circulatory system 37.49%, and tumors 30.36%. In Italy there are a total of 1572 MRI scanner. Accessibility to the MRI is guaranteed within 72 hours for urgent services, and within 90 days for programmable exams. The main field of research for Italian radiographer is on improve the image quality and artifact reduction. Artifacts are an important problem leading to reduced image quality, loss of diagnostic information, and time consuming (1). These problems led to a degradation of the radiographer's work. Artifacts can be reduced by using several algorithms, most of them specific for a single anatomical region, working at K-Space reconstruction level, and often leading to prolongation of the scan time (2,3). The software OPERA: Orthogonal Phase Encoding Reduction of Artifact (4) is a post-process software for the automatic correction of artifacts generated by motion and wrap-around. It works on DICOM images and doesn't need hardware modifications, hence it could be used on different MR scanner.
Purpose This prospective study were tested the MR value of OPERA on the reduction of artifacts, the reduction of the number of re-scan sequences due to severe artifacts and the reduction of additional sequences required by radiologists.
Method In MRI the position of ghosts, motion and aliasing artifacts is predictable along columns or rows of pixels, by knowing the phase encoding direction. OPERA algorithm compares the intensity values of the pixels of two DICOM images acquired on the same anatomy by using the same parameters but with orthogonal phase-encoding directions. In order to avoid prolongation of the exam time, the Number of Signal Averages (NSA), (or similar) can be exploited by making an even NSA, with half of them being distributed along one phase encoding direction and the remaining half being distributed along the opposite one. This study was conducted in a medium-sized general public hospital by using an Espree Siemens 1.5T MR scanner by comparing 3 full calendar weeks (MR exams n=302: Group A) with the following 3 weeks where OPERA procedure was applied to all MR sequences imaging of non-moving organs (MR exams n=302; Group B). A total of 604 MR exams were acquired on 585 patients (54.8% females; mean age 52.7±17.2 years)]. Imaged anatomical regions were: brain, n=182; spine, n=138; shoulder, n=64; elbow, n= 26; pelvis, n=96; knee, n=68; ankle, n=30. During the first 3 weeks (Group A), the sequences were acquired with the Standard parameters required by good clinical practice. For the next 3 weeks (Group B),OPERA procedure was used. Each sequence was acquired with vertical phase encoding direction and with horizontal phase encoding direction and NSAOPERA=NSASTD/2. Both sequences were sent to the PACS and the pair was processed in a remote-server by OPERA algorithm to obtain a third sequence with artifact-reduced images that were returned to the PACS. For both A and B Groups, the radiographer noted the sequences with several motion artifacts that were been repeated, and the additional sequences, over the standard protocol, required by radiologists for the diagnosis. Radiographers and radiologists have a long-standing MRI expertise (>15 years.) The MedCalc 17.2 statistical software was used for statistical analysis.
Results Significant motion artifacts were identified on sequences in 18.42 % (n= 279) of Group A, and in 13.34% (n= 202) Group B ( Fig 1). Additional sequences were required by radiologist in 12.48 % (n= 189) of Group A, and in 9.7% (n= 147) of Group B. (Fig 2) Overall, as compared to the standard procedure, OPERA algorithm consistently reduced the percentages of repeated sequences of 5.9% (two tailed p value= 0.0639) while reducing the percentage of additional sequences of 2.17% (Hodges-Lehmann median difference 5,9200; 95% Confidence interval -1,2900 to 13,3700; Mann-Whitney U, 10,00; two tailed p value= 0.3379).
Conclusion The present study confirms the potential of OPERA algorithm in reducing both the need for MR sequence repetition due to severe artifacts and MR sequences addiction for better diagnosis. Even the software could be usable on uncooperative patient or patients with pathology which do not allow motionless posture during the MR examination. The method was demonstrated to be applicable to several sequences and anatomical regions. Elbow studies were characterized by severe motion artifacts due to the patient position and the extremely pain in post-traumatic cases. The remarkable number of sequences “not-repeat” could potentially have a positive side effect in saved time. The peculiarities of the present algorithm allows a wide applicability to different commercially available MRI machines. OPERA would simplify the radiographer work by eliminating the parameter “ phase encoding direction”, oversampling, or saturation regions.