Effect of disease progression on liver apparent diffusion coefficient and T2 values in a murine model of hepatic fibrosis at 11.7 Tesla MRI

Purpose:

To evaluate the effects of hepatic fibrosis on ADC and T₂ values of ex vivo murine liver specimens imaged using 11.7 Tesla (T) MRI.

Materials and Methods:

This animal study was IACUC approved. Seventeen male, C57BL/6 mice were divided into control (n = 2) and experimental groups (n = 15), the latter fed a 3, 5‐dicarbethoxy‐1, 4‐dihydrocollidine (DDC) supplemented diet, inducing hepatic fibrosis. Ex vivo liver specimens were imaged using an 11.7T MRI scanner. Spin‐echo pulsed field gradient and multi‐echo spin‐echo acquisitions were used to generate parametric ADC and T₂ maps, respectively. Degrees of fibrosis were determined by the evaluation of a pathologist as well as digital image analysis. Scatterplot graphs comparing ADC and T₂ to degrees of fibrosis were generated and correlation coefficients were calculated.

Results:

Strong correlation was found between degrees of hepatic fibrosis and ADC with higher degrees of fibrosis associated with lower hepatic ADC values. Moderate correlation between hepatic fibrosis and T₂ values was seen with higher degrees of fibrosis associated with lower T₂ values.

Conclusion:

Inverse relationships between degrees of fibrosis and both ADC and T₂ are seen, highlighting the utility of these parameters in the ongoing development of an MRI methodology to quantify hepatic fibrosis. J. Magn. Reson. Imaging 2012;35:140‐146. © 2011 Wiley Periodicals, Inc.     

Insomnia symptoms influence CPAP compliance

Purpose

The aim of this study is to determine parameters which influence 6-month compliance of continuous positive airway pressure therapy (CPAP) in patients with obstructive sleep apnea syndrome (OSAS).

Methods

This prospective study investigated 73 patients (24 females) with OSAS and medical indication for CPAP therapy: age 55.1?±?11.5 years, body mass index (BMI) 30.8?±?5.0 kg/m2, Apnea–Hypopnea Index (AHI) 39.2?±?26.7/h, Oxygen Desaturation Index (ODI) 33.2?±?25.4/h, minimum O₂ saturation 78.9?±?7.6%. The influence of baseline parameters (demographic and polysomnographic data, sleeping medication intakes, BMI, psychometrics [Epworth Sleepiness Scale, Regensburg Insomnia Scale, Vigilance test and Beck Depression Inventory]) on 6-month compliance was evaluated with a correlation and a linear regression analysis.

Results

The baseline value of the Regensburg Insomnia Scale (RIS) predicts 6-month CPAP compliance (r?=??0.376, R ²?=?0.14, p?<?0.001), although no other baseline parameter correlates. Patients with a compliance of <4 h/night show higher RIS scores, i.e., more insomnia symptoms (17.6?±?8.8) compared to those with ≥4 h/night (12.6?±?6.9; p?<?0.05).

Conclusions

Insomnia symptoms prior to the beginning of CPAP treatment show a negative influence on CPAP compliance. Further studies should clarify, if a treatment of insomnia symptoms leads to a benefit in compliance.     

High-resolution variable flip angle 3D MR imaging of trabecular microstructure in vivo

Two conceptually related variable-flip-angle 3D spin-echo pulse sequences were designed for imaging at voxel sizes of 2–5 × 10^?3 mm³ corresponding to pixel areas of less than 100 × 100 μm² and section thicknesses on the order of 300–400 μm on a conventional 1.5 T MR imaging system equipped with 1 G/cm imaging field gradients, providing 12 sections in 10 min imaging time. The pulse sequences make use of the concept of restoring longitudinal magnetization inverted by the 180° phase reversal pulse and are derivatives of pulse sequences previously dubbed “FATE” and “RASEE.” It is shown that even in the small-voxel regime (< 10^?2 mm³ voxel size) and at echo times on the order of 10 ms, gradient echo images are sensitive to intrinsic fields causing artifactual boundary effects, including signal loss from intravoxel phase scrambling and spatial mismapping. At this resolution the variable flipangle spin-echo pulse sequences are demonstrated to be better suited for imaging magnetically heterogeneous systems such as trabecular bone microstructure in vivo. These pulse sequences are found to be substantially less sensitive to distortions from magnetic dipole fields occurring at the boundaries of two phases of different magnetic permeability.     

Spontaneous Degeneration of Porcine Bioprosthetic Valves

From October, 1971, to October, 1979, 490 patients with 560 porcine bioprosthetic valves were discharged from the hospital. During these 8 years, 23 valves were removed because of failure due to spontaneous degeneration. Bioprosthetic valve survival without degeneration was at 4 years, 98.9% ± 0.6 (standard error); at 5 years, 96.4% ± 1.3; at 6 years, 90.8% ± 2.4; and at 7 years, 84.2% ± 3.7. There was no difference in degeneration observed with regard to sex, valve position, or whether the valves were rinsed with antibiotics prior to implantation. There was an increase in degeneration in patients 35 years old and younger compared with those more than 35 years old (p = 0.0001). Valve failure was gradual, and valve changes were noted by echocardiogram and phonocardiogram prior to actual failure. Specific factors leading to degeneration require further investigation.     

Effect of endothelin receptor antagonist on parathyroid gland growth, PTH values and cell proliferation in azotemic rats.

BACKGROUND: A variety of stimuli are involved in the pathogenesis of parathyroid gland hyperplasia in renal failure. Recently, it was shown that blocking the signal from the endothelin-1 (ET-1) receptor (ET(A)R/ET(B)R) by a non-selective receptor antagonist, bosentan, reduced parathyroid cell proliferation, parathyroid gland hyperplasia and parathyroid hormone (PTH) levels in normal rats on a calcium deficient diet. Our goal was to determine whether in 5/6 nephrectomized (NPX) rats with developing or established hyperparathyroidism, the endothelin receptor blocker, bosentan, reduced the increase in parathyroid cell proliferation, parathyroid gland hyperplasia and PTH values. METHODS: High (HPD, 1.2%) or normal phosphorus diets (PD) (NPD, 0.6%) were given to 5/6 NPX rats for 15 days (NPX(15)). In each dietary group, one-half the rats were given bosentan (B) i.p. 100 mg/kg/day. The four groups of rats were: (1) NPX(15)-1.2% P; (2) NPX(15)-1.2% P+B; (3) NPX(15)-0.6% P; and (4) NPX(15)-0.6% P+B. In a second study in which hyperparathyroidism was already established in 5/6 NPX rats fed a HPD for 15 days, rats were divided into two groups in which one group was maintained on a HPD and the other group was changed to very low PD (VLPD, <0.05%) for an additional 15 days. In each dietary group, one-half the rats were given bosentan i.p. 100 mg/kg-day. The four groups of rats were: (1) NPX(30)-1.2% P; (2) NPX(30)-1.2% P+B; (3) NPX(30)-0.05% P and (4) NPX(30)-0.05% P+B. Parathyroid cell proliferation was measured by proliferating cell nuclear antigen (PCNA) staining and ET-1 expression by immunohistochemical techniques. RESULTS: In the study of developing hyperparathyroidism, bosentan reduced ET-1 expression in the parathyroid glands of rats on the NPD and HPD (P<0.05). But only in rats on the NPD did bosentan result in a reduced increase in parathyroid gland weight (P<0.05). In the study of established hyperparathyroidism, in which 5/6 NPX rats were given a HPD for 15 days, bosentan started on day 15 reduced (P<0.05) ET-1 expression in rats maintained for 15 additional days on the HPD or the VLPD. On the VLPD, parathyroid gland weight was less (P<0.05) than that in rats on the HPD sacrificed at 15 or 30 days. Bosentan did not reduce parathyroid cell proliferation or parathyroid gland weight in rats maintained on the HPD or further reduce these parameters beyond that obtained with dietary phosphorus restriction. PTH values were lowest in the VLPD group, intermediate in the NPD group, and highest in the HPD group, but in none of the three groups did bosentan decrease PTH values. CONCLUSIONS: In azotemic rats with developing hyperparathyroidism, bosentan resulted in a reduced increase in parathyroid gland weight when dietary phosphorus content was normal. Despite a reduction in ET-1 expression in rats on a HPD with developing or established hyperparathyroidism, bosentan did not reduce the increase in parathyroid cell proliferation, parathyroid gland growth or PTH values. Thus, ET-1 blockade with bosentan did not prevent parathyroid gland growth in the azotemic rat.