Extended Abstract
1. Introduction
Two-dimensional spin-echo sequences are commonly used to study knee osteoarthritis. The Three-dimensional Double-echo Steady State (3D-DESS) imaging sequence is among the sequences of Siemens Magnetic Resonance Imaging (MRI) machine. This sequence helps to diagnose lesions in knee cartilage by increasing the contrast difference between synovial joint fluid and cartilage. No comprehensive comparison has been made between the DESS sequence and other routine sequences to demonstrate the effectiveness of this sequence.
Moriya et al. investigated the increase in flip angle from 10 to 90 degrees on Contrast-to-Noise Ratio (CNR). The CNR obtained for the 90-degree DESS sequence had the highest value [1].
Schaefer et al. compared the three DESS, PD FS FSE, and PD SPACE sequences in detecting cartilage anomalies on the human body patella. The DESS sequence provided better relative contrast values, compared to the other sequences [2].
In 1999, Mosher and Pruett conducted a comparative study between the FLASH and DESS sequences on patella cartilage phantom in an albumin solution to assess the diagnosis of cartilage lesions. The DESS sequence performed more effectively in assessing cartilage surface lesions.
We aimed to explore the effectiveness of the DESS sequence to better diagnose osteoarthritis-induced cartilage anomalies in the knee.
2. Materials and Methods
This study was performed on 15 patients suspected of having osteoarthritis at Shahid Kamyab and Imam Reza (AS) Hospitals of Mashhad University of Medical Sciences from April 2018 to March 2019.
 Considering s^2=30.25 and x ̅=18.2 according to the previous similar article of Han et al. [21]; d=.2 x ̅ and with the type I error of 0.05; the test power of 80%, and the 20% sample dropouts, the sample size was estimated to be 15 individuals.
A 1.5 T Siemens MRI machine (Avanto series, made in Germany) was used to obtain the required images. Quantitative image processing was performed using Radiant DICOM Viewer 4.6.9 software. Then, using SPSS, the obtained numerical values were compared. To perform statistical analysis, the Friedman test and Wilcoxon signed-rank test were employed. P<0.05 was considered statistically significant.
3. Results
The Friedman test data for the measured values of relative contrast in the weight-bearing area indicated a significant relationship between the investigated sequences. According to the statistical tests performed for the sequences as well as the measured values of relative contrast for all sequences, the DESS sequence with a flip angle of 90° and an average value of 77.2667 has the best numerical value of relative contrast among the sequences. Besides, the FLASH sequence has the lowest value in this regard.
4. Conclusion
Moria et al. qualitatively compared the DESS sequence at the flip angles of 90° and 40°. Accordingly, the DESS sequence with a flip angle of 90° (due to better contrast difference between liquid and cartilage) led to more effective diagnosis of the lesion, compared to the DESS sequence with a flip angle of 40°. The quantitative results obtained by measuring the relative contrast in the present study agree with their findings.
The DESS sequence has significant capabilities in imaging cartilaginous lesions; thus, it is recommended to use this imaging sequence as a complementary sequence along with other routine sequences in medical imaging centers.
5. Conclusion
Due to the cooperation of all medical departments, there were no restrictions for performing this study. The DESS sequence is highly efficient for imaging knee cartilage, as well as knee joint fluid. Furthermore, it could improve the contrast ratio of joint fluid to cartilage; thus, it could help to better diagnose knee cartilage lesions.

Ethical Considerations
Compliance with ethical guidelines
This research project obtained code of ethics with the ID of IR.MUMS.MEDICAL.REC.1397.215, which was approved on 23.05.2018.
Funding
The financial resources of this project have been provided by the Research Center of Mashhad University of Medical Sciences and have been registered in the Pajouhan system (Code: 961866).
Authors' contributions
Conceptualization: Alireza montazerabadi, Amir shahriyar ariamanesh; Methodology: Behzad Aminzade; Investigation : Hormoz Abed, & Sepehr Lotfi; writing _review and editing: Sepehr Lotfi; Analysis: Alireza Montazerabadi, Sepehr Lotfi.
Conflicts of interest
There is no conflict of interest to be declared by the authors.
Acknowledgements
We are very grateful to Mashhad University of Medical Sciences Research Center as the funding provider of this research; Mashhad Medical Physics Department, Medical Imaging Department of Shahid Kamyab Hospital of Mashhad University of Medical Sciences, Orthopedic Department of Imam Reza Hospital of Mashhad University of Medical Sciences, and the esteemed board that guided us in carrying out this research. Eventually, we would like to thank the esteemed officials of Ofogh-e-Danesh Scientific-Research Journal, who helped us in developing this article in the best possible manner by providing us their best guidance.