The effect of tin prefiltration on extremity cone-beam CT imaging with a twin robotic X-ray system.

INTRODUCTION: While tin prefiltration is established in various CT applications, its value in extremity cone-beam CT relative to optimized spectra has not been thoroughly assessed thus far. This study aims to investigate the effect of tin filters in extremity cone-beam CT with a twin-robotic X-ray system. METHODS: Wrist, elbow and ankle joints of two cadaveric specimens were examined in a laboratory setup with different combinations of prefiltration (copper, tin), tube voltage and current-time product. Image quality was assessed subjectively by five radiologists with Fleiss' kappa being computed to measure interrater agreement. To provide a semiquantitative criterion for image quality, contrast-to-noise ratios (CNR) were compared for standardized regions of interest. Volume CT dose indices were calculated for a 16 cm polymethylmethacrylate phantom. RESULTS: Radiation dose ranged from 17.4 mGy in the clinical standard protocol without tin filter to as low as 0.7 mGy with tin prefiltration. Image quality ratings and CNR for tin-filtered scans with 100 kV were lower than for 80 kV studies with copper prefiltration despite higher dose (11.2 and 5.6 vs. 4.5 mGy; p < 0.001). No difference was ascertained between 100 kV scans with tin filtration and 60 kV copper-filtered scans with 75% dose reduction (subjective: p = 0.101; CNR: p = 0.706). Fleiss' kappa of 0.597 (95% confidence interval 0.567-0.626; p < 0.001) indicated moderate interrater agreement. CONCLUSION: Considerable dose reduction is feasible with tin prefiltration, however, the twin-robotic X-ray system's low-dose potential for extremity 3D imaging is maximized with a dedicated low-kilovolt scan protocol in situations without extensive beam-hardening artifacts. IMPLICATIONS FOR PRACTICE: Low-kilovolt imaging with copper prefiltration provides a superior trade-off between dose reduction and image quality compared to tin-filtered cone-beam CT scan protocols with higher tube voltage.

Myocardial lipid content in Fabry disease: a combined 1H-MR spectroscopy and MR imaging study at 3 Tesla.

BACKGROUND: Fabry disease is characterized by a progressive deposition of sphingolipids in different organ systems, whereby cardiac involvement leads to death. We hypothesize that lysosomal storage of sphingolipids in the heart as occurring in Fabry disease does not reflect in higher cardiac lipid concentrations detectable by 1H magnetic resonance spectroscopy (MRS) at 3 Tesla. METHODS: Myocardial lipid content was quantified in vivo by 1H-MRS in 30 patients (12 male, 18 female; 18 patients treated with enzyme replacement therapy) with genetically proven Fabry disease and in 30 healthy controls. The study protocol combined 1H-MRS with cardiac cine imaging and LGE MRI in a single examination. RESULTS: Myocardial lipid content was not significantly elevated in Fabry disease (p = 0.225). Left ventricular (LV) mass was significantly higher in patients suffering from Fabry disease compared to controls (p = 0.019). Comparison of patients without signs of myocardial fibrosis in MRI (LGE negative; n = 12) to patients with signs of fibrosis (LGE positive; n = 18) revealed similar myocardial lipid content in both groups (p > 0.05), while the latter showed a trend towards elevated LV mass (p = 0.076). CONCLUSIONS: This study demonstrates the potential of lipid metabolic investigation embedded in a comprehensive examination of cardiac morphology and function in Fabry disease. There was no evidence that lysosomal storage of sphingolipids influences cardiac lipid content as measured by 1H-MRS. Finally, the authors share the opinion that a comprehensive cardiac examination including three subsections (LGE; 1H-MRS; T1 mapping), could hold the highest potential for the final assessment of early and late myocardial changes in Fabry disease.

Age Dependency of Myocardial Triglyceride Content: A 3T High-Field 1H-MR Spectroscopy Study.

PURPOSE: The role of myocardial triglyceride (mTG) content in the aging human heart is not entirely understood. The aim of this study was to measure concentrations of mTG content from healthy volunteers and to determine the association between age, mTG content and systolic heart function. Furthermore, the technical stability of the (1)H-magnetic resonance spectroscopy ((1)H-MRS) and the reliability of peak evaluation at 3 T were evaluated. MATERIALS AND METHODS: The total study population of 47 healthy volunteers was divided into 4 age classes, according to the age of the subjects (1(st) cohort 20 - 29 years (yrs.), n = 20; 2(nd) cohort 30 - 39 yrs., n = 10; 3(rd) cohort 40 - 49 yrs., n = 9; 4(th) cohort 50 - 60 yrs., n = 8). Cardiac MRI and double triggered (1)H-MRS of the myocardium were consecutively performed using a 3 T scanner. Each participant underwent spectroscopic measurements twice in the same investigation. RESULTS: mTG content increases with age. The correlation of age and mTG is minimal (r = 0.48; p < 0.001). The following age-averaged mTG content values expressed as % of mTG signal compared to the water signal were determined for each cohort: 1(st) cohort 0.25 % (±â€Š0.17); 2(nd) cohort 0.48 % (±â€Š0.30); 3(rd) cohort 0.48 % (±â€Š0.18); 4(th) cohort 0.77 % (±â€Š0.70). There was no significant correlation (r = 0.04; p = n.s.) between LV mass and mTG content in healthy volunteers. Within our cohorts, no effects of age or mTG content on systolic heart function were seen (r = - 0.01; p = n.s.). The intraclass correlation coefficient of spectroscopic measurements was high (r = 0.965; p < 0.001). CONCLUSION: Myocardial TG content increases with age. The normal age-dependent concentration ranges of myocardial lipid metabolites reported in this study may be helpful for the correction of acquired (1)H-MRS data in patients when evaluating metabolic and cardiovascular diseases in future magnetic resonance spectroscopy studies.