© Pol J Radiol, 2011; 76(1): 30-40 Aydin H et al – Is the quantitative diffusion-weighted MR Imaging… different b-factors in the diagnostics of meniscal tears of the knee in comparison to the routine MR imaging protocol. Material and Methods Our study included 74 consecutive patients referred to hos- pital due to pain and mechanical symptoms such as catching and locking, between May and November 2009. Thirty men and 44 women were analysed. Their age ranged from 24 to 63, and their mean age was 44. There were 37 left and 37 right knees with meniscal tears that were included in this study. Eleven of them were lateral meniscal tears, and 63 – medial meniscal tears. All of the tears originated from pos- terior horns. One tear, from medial meniscus, showed mac- eration as well. Twelve tears were also found in the anterior horns of the menisci: four of them in the lateral meniscus and 8 in the medial meniscus. Ten patients had both medial and lateral meniscal tears. All of them were included. Twenty patients underwent arthroscopic surgery followed by histo- pathological confirmation. The interval between MR imaging and arthroscopy of the meniscal tears in those 20 patients was about 15 days to 2 months. Other patients were were alive with meniscal tears. Each patient underwent a detailed history and physical examination at the time of initial evalu- ation. Informed consent was taken from all the patients prior to the section. Ethics committee approval from the hospital’s review board was also added. MR examinations were performed with Siemens Symphony Power 1.5 T mag- net (Siemens-Erlangen-Germany) with a maximum gradient strength of 30 mT/m, and a slew rate of 120 mlt per millisec- ond. A standard knee coil was used. A conventional knee MR protocol was as follows: T1W SE and T2W GE sagittal, T1W and PD-FS coronal, PD-FS axial planes; DWI was obtained by 3D-SE Echo-planar Imaging (EPI) in coronal and sagit- tal planes with TR 1900, TE 100, FOV 125*295 to 157*295 mm; ADC mapping was performed in coronal planes with b-factors of 50, 400, and 800 sec./mm2. Scanning time was about 0.15 min. T1W coronal and sagittal image parameters were as follows: TR/TE of 530/20, slice thickness of 4 mm, matrix of 256*512 and FOV of 240×160 mm, NEX 2, scan- ning time of about 45 seconds. T2W FS axial image param- eters: TR/TE of 2030/80, slice thickness of 4 mm, matrix of 152*480, and FOV of 250×150 mm, NEX 2, scanning time of about 57 seconds.T2W GE sagittal sequence parameters: TR/TE of 400/15, slice thickness of 4 mm, matrix of 256*256 and FOV of 250×150 mm, NEX 2, scanning time of about 2.15 minutes. PDW FS coronal sequence parameters: TR/TE of 2230/30, slice thickness of 4 mm, matrix of 244*400 and FOV of 240x160 mm, NEX 3, scanning time of about 1.17 min. Slice thickness of DWI sequence was 3 mm. Analysis of the data set obtained with all sequences was interpreted by a single radiologist with an 8-year experi- ence for musculoskeletal radiology who was blinded and unaware of the results of arthroscopy in 20 patients. In MR imaging: an increased meniscal signal was regarded as a meniscal tear when it could communicate with the infe- rior, superior or free edge of meniscal surface (or more than one of those) on two consecutive images and planes (sag- ittal and coronal) [5,7]. Tears were categorised as follows: Horizontal, a tear parallel to the tibial plateau separating the meniscus into the upper and the lower part; oblique, a tear extending obliquely to the main axis of the meniscus; longitudinal, a vertical tear perpendicular to the tibial pla- teau extending parallelly to the main axis of the meniscus; radial, a vertical tear that begins in the central free margin perpendicular both to the tibial plateau and the free edge of the meniscus; complex, multiple tears of more than one configuration and one cleavage orientation lacking conti- nuity; root, defined as a tear in the posterior or anterior meniscal attachments [2,7,8]. There were 2 radial tears, 7 complex and oblique tears, 2 root tears, 38 horizontal tears, and 18 longitudinal tears analysed in 74 patients. Lateral meniscal tears were of root, oblique and horizontal type, whereas medial meniscal tears included all types of tears. The criteria of meniscal tears in DWI and ADC mapping were the same as in routine MR imaging: an increased meniscal signal was regarded as a horizontal, oblique, lon- gitudinal, vertical, or complex meniscal tear if communi- cating with the inferior, superior or free edge of meniscal surface (or more than one of those) on sagittal and coronal images. All types of tears, either in the medial meniscus or the lateral meniscus, were termed meniscal tears and clas- sified as: medial meniscal tears and lateral meniscal tears. Tear involving either the posterior or anterior horns of menisci or both horns was also visualised. The absence or great damage to meniscus tissue due to the tear was record- ed as maceration and we had one such case in this paper. Tears remaining after arthroscopy and residual meniscal fragments after surgery were excluded from the study. The differentiation between the meniscal tears and meniscal degeneration was based on the following criteria in DWI and ADC mapping: A) increased meniscal signal, located in the meniscal bodies, without any relationship to the inferi- or, superior or free edges of meniscal surfaces, was regard- ed as degeneration. B) horizontal or triangular hyperinten- sity limited to meniscal bodies, was regarded as degener- ated meniscal fragments C) oblique or vertical signals in articular surfaces and increased meniscal signals in menis- cal attachment sites were never classified as degeneration. Statistical analysis Statistical analysis of DWI and ADC mapping with different b-factors was performed with the use of the Fisher’s test, Pearson chi square statistics and SPSS 11.5 software (SPSS-Inc, Chicago-IL). Sensitivity, specificity, positive pre- dictive value (PPV), and negative predictive value (NPV) were calculated with regard to routine knee MR imaging. P<0.05 was considered to be statistically significant. Results Table 1 summarises all datas of 74 patients with menis- cal tears, including age and gender, location of the menis- cal tear (in the right or in the left knee – in the medial or lateral meniscus and originating from anterior or posterior horns), MRI-DWI and ADC mapping findings, operational status and match or mismatch of MRI to DWI and ADC mapping for b-factors 50, 400, and 800 sec./mm2. When we compared the DWI results with the results of the routine MRI for both menisci and 74 tears, we found that DWI has 86% sensitivity and 100% specificity (p=0.149) with 31