Soft-tissue fat tumours: differentiating malignant from benign using proton density fat fraction quantification MRI.

AIM: To evaluate if quantifying proton density fat fraction (PDFF) would be useful in separating lipoma, atypical lipomatous tumour (ALT) and liposarcoma in the extremities and trunk. In addition, differentiating ALT versus non-classical lipomas using magnetic resonance imaging (MRI)-based fatty acid composition (FAC) and three-dimensional (3D) texture analysis was tested. MATERIAL AND METHODS: This prospective study (undertaken between 2014-2017; comprising 20 women, 21 men) was approved by the Regional Ethical Review Board and informed consent was obtained from all participants. For PDFF and FAC 3D spoiled gradient multi-echo images were acquired. PDFF was analysed in 16 lipomas (25-76 years), 14 ALTs (42-78 years) and 11 myxoid liposarcomas (31-68 years). The difference of mean PDFF was tested with one-way analysis of variance. A support vector machine algorithm was used to find the separating mean PDFF values. RESULTS: Mean PDFF for lipomas was 90% (range 76-98%), for ALT 83% (range 62-91%), and for liposarcoma 4% (range 0-21%). The difference of mean PDFF for liposarcomas versus ALT and lipoma was significant (p=0.0001, for both), and for ALT versus lipoma (p=0.021). The optimal threshold for separating liposarcoma from ALT and lipoma was 41.5%, and for ALT and lipoma 85%. Texture analysis could not separate ALT and non-classical lipomas, while the difference for FAC unsaturation degree was significant (p=0.013). CONCLUSION: Measuring PDFF is a promising complement to standard MRI, to separate liposarcomas from ALT and lipomas. Lipomas that are not solely composed of fat cannot confidently be separated from ALT using PDFF, FAC, or texture analysis.

Is CT indicated in diagnosing sacroiliac joint degeneration?

AIM: To assess the value of computed tomography (CT) in the diagnosis of symptomatic sacroiliac (SI) joint degeneration. MATERIALS AND METHODS: CT images from 123 patients with clinically diagnosed SI joint pain were compared to age- and gender-matched controls without chronic back pain or previous back surgery. Degeneration was graded assessing joint space narrowing, osteophytes, subchondral sclerosis, cysts, and vacuum phenomena. RESULTS: The mean total score for the patients was 9.6 and for the controls 9.7 (p=0.77). A subgroup analysis of the mean score for the SI joints that were subjected to surgery was 4.3, compared to 4.8 in the conservatively treated SI joints in the patient group (p=0.23) and 4.8 for all SI joints in the control group (p=0.25). For patients with unilateral left-sided pain (n=40), the mean score for the left side was 5.2 and for the right side 4.9 (p=0.49). For patients with right-sided pain (n=41), the mean score for the right side was 4.8 and the left side 4.7 (p=0.55). CONCLUSION: The prevalence of SI joint degeneration on CT is equal in symptomatic and non-symptomatic individuals. This study indicates that the value of CT is limited, but further studies are needed to establish if CT has a place in diagnosing SI joint degeneration.

Motion corrected DWI with integrated T2-mapping for simultaneous estimation of ADC, T2-relaxation and perfusion in prostate cancer.

OBJECTIVE: Multiparametric magnetic resonance imaging (MRI) and PI-RADS (Prostate Imaging - Reporting and Data System) has become the standard to determine a probability score for a lesion being a clinically significant prostate cancer. T2-weighted and diffusion-weighted imaging (DWI) are essential in PI-RADS, depending partly on visual assessment of signal intensity, while dynamic-contrast enhanced imaging is less important. To decrease inter-rater variability and further standardize image evaluation, complementary objective measures are in need. METHODS: We here demonstrate a sequence enabling simultaneous quantification of apparent diffusion coefficient (ADC) and T2-relaxation, as well as calculation of the perfusion fraction f from low b-value intravoxel incoherent motion data. Expandable wait pulses were added to a FOCUS DW SE-EPI sequence, allowing the effective echo time to change at run time. To calculate both ADC and f, b-values 200s/mm2 and 600s/mm2 were chosen, and for T2-estimation 6 echo times between 64.9ms and 114.9ms were used. RESULTS: Three patients with prostate cancer were examined and all had significantly decreased ADC and T2-values, while f was significantly increased in 2 of 3 tumors. T2 maps obtained in phantom measurements and in a healthy volunteer were compared to T2 maps from a SE sequence with consecutive scans, showing good agreement. In addition, a motion correction procedure was implemented to reduce the effects of prostate motion, which improved T2-estimation. CONCLUSIONS: This sequence could potentially enable more objective tumor grading, and decrease the inter-rater variability in the PI-RADS classification.

Assessment of wear and periacetabular osteolysis using dual energy computed tomography on a pig cadaver to identify the lowest acceptable radiation dose.

OBJECTIVES: Computed tomography (CT) plays an important role in evaluating wear and periacetabular osteolysis (PAO) in total hip replacements. One concern with CT is the high radiation exposure since standard pelvic CT provides approximately 3.5 millisieverts (mSv) of radiation exposure, whereas a planar radiographic examination with three projections totals approximately 0.5 mSv. The objective of this study was to evaluate the lowest acceptable radiation dose for dual-energy CT (DECT) images when measuring wear and periacetabular osteolysis in uncemented metal components. MATERIALS AND METHODS: A porcine pelvis with bilateral uncemented hip prostheses and with known linear wear and acetabular bone defects was examined in a third-generation multidetector DECT scanner. The examinations were performed with four different radiation levels both with and without iterative reconstruction techniques. From the high and low peak kilo voltage acquisitions, polychrmoatic images were created together with virtual monochromatic images of energies 100 kiloelectron volts (keV) and 150 keV. RESULTS: We could assess wear and PAO while substantially lowering the effective radiation dose to 0.7 mSv for a total pelvic view with an accuracy of around 0.5 mm for linear wear and 2 mm to 3 mm for PAO. CONCLUSION: CT for detection of prosthetic wear and PAO could be used with clinically acceptable accuracy at a radiation exposure level equal to plain radiographic exposures.Cite this article: B. Sandgren, M. Skorpil, P. Nowik, H. Olivecrona, J. Crafoord, L. Weidenhielm, A. Persson. Assessment of wear and periacetabular osteolysis using dual energy computed tomography on a pig cadaver to identify the lowest acceptable radiation dose. Bone Joint Res 2016;5:307-313. DOI: 10.1302/2046-3758.57.2000566.

Intra-Articular Synovial Sarcomas: Incidence and Differentiating Features from Localized Pigmented Villonodular Synovitis.

Purpose. To determine the incidence of intra-articular synovial sarcomas and investigate if any radiological variables can differentiate them from localized (unifocal) pigmented villonodular synovitis (PVNS) and if multivariate data analysis could be used as a complementary clinical tool. Methods. Magnetic resonance images and radiographs of 7 cases of intra-articular synovial sarcomas and 14 cases of localized PVNS were blindedly reviewed. Variables analyzed were size, extra-articular growth, tumor border, blooming, calcification, contrast media enhancement, effusion, bowl of grapes sign, triple signal intensity sign, synovial low signal intensity, synovitis, age, and gender. Univariate and multivariate data analysis, the method of partial least squares-discriminant analysis (PLS-DA), were used. Register data on all synovial sarcomas were extracted for comparison. Results. The incidence of intra-articular synovial sarcomas was 3%. PLS-DA showed that age, effusion, size, and gender were the most important factors for discrimination between sarcomas and localized PVNS. No sarcomas were misclassified as PVNS with PLS-DA, while some PVNS were misclassified as sarcomas. Conclusions. The most important variables in differentiating intra-articular sarcomas from localized PVNS were age, effusion, size, and gender. Multivariate data analysis can be helpful as additive information to avoid a biopsy, if the tumor is classified as most likely being PVNS.

Presacral myelolipoma in a patient with rectal cancer: diagnosis by magnetic resonance imaging and aspiration cytology.

State-of-the-art magnetic resonance imaging (MRI) protocol for the evaluation of rectal cancer suggests only T2-weighted fast spin-echo sequences. We present a case of rectal cancer with a simultaneous presacral myelolipoma that could have been misdiagnosed on MRI as a metastasis if a T1-weighted sequence had not also been used in the evaluation.