Angle‐sensitive MRI for quantitative analysis of fiber‐network deformations in compressed cartilage

Purpose

To demonstrate the feasibility of a novel experimental method to quantitatively analyze fiber‐network deformation in compressed cartilage by angle‐sensitive magnetic resonance imaging (MRI) of cartilage.

Methods

Three knee cartilage samples of an adult sheep were imaged in a high‐resolution MRI scanner at 7 T. Main fiber orientation and its “offset” from the direction perpendicular to the bone‐cartilage boundary were derived from MR images taken at different orientations with respect to B₀. Bending of the collagen fibers was determined from weight‐bearing MRI with the load (up to 1.0 MPa) applied over the whole sample surface. A “fascicle” model of the cartilage ultrastructure was assumed to analyze characteristic intensity variations in T₂‐weighted images under load.

Results

T₂‐weighted MR images showed a strong variation of the signal intensities with sample orientation. In the T₂‐weighted weight‐bearing series, regions of high signal intensity underwent shifts from the lateral to the central parts in all three cartilage samples. The bending of the collagen fibers was determined to be 27.2°, 35.4°, and 40.0° per MPa, respectively.

Conclusion

Assuming a “fascicle” model, the presented MRI method provides quantitative measures of structural adjustments in compressed cartilage. Our preliminary analysis suggests that cartilage fiber deformation includes both bending and crimping.     

Neointimal Hyperplasia after Silverhawk Atherectomy versus Percutaneous Transluminal Angioplasty (PTA) in Femoropopliteal Stent Reobstructions: A Controlled, Randomized Pilot Trial

Background

Due to intimal hyperplasia instent reobstruction in the femoropopliteal arterial segment is still an unsolved problem. Different techniques have been discussed in case of reintervention to guarantee longlasting patency rate.

Methods

We conducted a randomized, controlled, pilot trial comparing Silverhawk atherectomy with percutaneous transluminal angioplasty (PTA) in patients with a first instent reobstruction in the femoropopliteal arterial segment, to evaluate intima media thickness (IMT) within the treated segment, as a parameter of recurrence of intimal hyperplasia.

Results

In a total 19 patients were included: 9 patients in the atherectomy device and 10 patients in the PTA arm. IMT within the treated segment was statistically significantly elevated in all patients treated with the Silverhawk device versus the patients treated with PTA. The obvious differentiation in elevation of IMT in nonfavor for patients treated with the Silverhawk device started at month 2 (max IMT SH 0.178 mm vs. IMT PTA 0.1 mm, p = 0.001) with a spike at month 5 (max IMT SH 0.206 mm vs. IMT PTA 0.145 mm, p = 0.003) and a decline once again at month 6 (max IMT SH 0.177 mm vs. IMT PTA 0.121 mm, p = 0.02). The values for mean IMT performed the same way.

Conclusions

Although Silverhawk atherectomy provides good results at first sight, in the midterm follow-up of treatment of first instent restenosis it did not perform better than PTA as it showed elevated reoccurrence of intimal media hyperplasia.     

Dynamic hysteresis between gradient echo and spin echo attenuations in dynamic susceptibility contrast imaging

Perfusion measurements using dynamic susceptibility contrast imaging provide additional information about the mean vessel size of microvasculature when supplemented with a dual gradient echo (GE) – spin echo (SE) contrast. Dynamic increase in the corresponding transverse relaxation rate constant changes, ΔR_2GE and ΔR_2SE, forms a loop on the (Δ, ΔR_2GE) plane, rather than a reversible line. The shape of the loop and the direction of its passage differentiate between healthy brain and pathological tissue, such as tumour and ischemic tissue. By considering a tree model of microvasculature, the direction of the loop is found to be influenced mainly by the relative arterial and venous blood volume, as well as the tracer bolus dispersion. A parameter Λ is proposed to characterize the direction and shape of the loop, which might be considered as a novel imaging marker for describing the pathology of cerebrovascular network. Magn Reson Med 69:981–991, 2013. © 2012 Wiley Periodicals, Inc.     

Prognosis and Determinants of Outcome Following Locoregional or Distant Recurrence in Patients with Cutaneous Melanoma

Objective Information on prognosis for patients with cutaneous melanoma after locoregional or distant recurrence is sparse and controversial. The aim of this study was to analyze factors influencing outcome after the development of a first relapse. Methods Information was extracted from the Sydney Melanoma Unit database for 873 melanoma patients with American Joint Committee on Cancer (AJCC) Stage I and II disease treated between 1960 and 2002 who relapsed following treatment of their primary melanoma. Clinical and pathologic factors predicting survival were analyzed using the Cox proportional hazards regression model. Results Initial presentation of recurrence was local: 95 patients (10.9%), in transit: 86 patients (9.9%), regional lymph node: 300 patients (34.4%), and distant: 392 patients (44.9%). Independent prognostic factors for survival of the 481 patients with only locoregional recurrence were type of recurrence, primary tumor ulceration, and patient age. Predictors for longer survival in the 392 patients with distant metastasis at the time of first presentation with recurrence were lung vs other sites and diagnosis of relapse after 1990 compared with diagnosis before 1980. Conclusions The type of recurrence is the most important prognostic factor in melanoma patients who relapse. Primary tumor ulceration is the most important pathologic predictor. The results of this study suggest that management of distant metastases may have improved over the last 25 years, but many confounders and improved staging techniques make assessment of this unreliable.     

S-Classification of Sentinel Lymph Node Predicts Axillary Nonsentinel Lymph Node Status in Patients with Breast Cancer

Background One-half of breast cancer patients with positive sentinel lymph node (SN) have no further metastases in the axillary lymph node basin. The aim of the present study was to identify patients with positive SN who are unlikely to have further metastases in the axillary lymph node basin, using a new classification of SN, namely the S-classification. Methods Specimens of positive SN were subjected to a pathological review according to the previously published S-classification. S-stages of positive SN were correlated with the status of further metastases in the axillary lymph node basin after axillary lymph node dissection (ALND). Results Of 117 patients who underwent sentinel lymph node biopsy, 36 (30.8%) had a positive SN and were subjected to level I and II ALND. The occurrence of positive nonsentinel nodes was significantly related to the S-stage of SN. No patient with stage SI had additional metastases in the nonsentinel lymph nodes, while 14.3% of patients with SII stage disease and 60.9 % of patients with SIII disease had other non-SN that were metastatic. Conclusion S-stages of positive SN are highly predictive for axillary nonsentinel node status. Especially patients with SI sentinel node metastases appear to be at low risk for further nonsentinel node metastases.     

Prospective study of transitional cell carcinoma in the prostatic urethra and prostate in the cystoprostatectomy specimen. Incidence, characteristics and preoperative detection

OBJECTIVES: To prospectively evaluate the incidence of transitional cell carcinoma (TCC) in the prostatic urethra and prostate in the cystoprostatectomy specimen, investigate characteristics of bladder tumours in relation to the risk of involvement of the prostatic urethra and prostate and examine the sensitivity of preoperative loop biopsies from the prostatic urethra. MATERIAL AND METHODS: Preoperatively, patients were investigated with cold cup biopsies from the bladder and transurethral loop biopsies from the bladder neck to the verumontanum. The prostate and bladder neck were submitted to sagittal whole-mount pathological analysis. RESULTS: The incidence of TCC in the prostatic urethra and prostate in the cystoprostatectomy specimen was 29% (50/175 patients). Age, previous bacillus Calmette-Guérin treatment, carcinoma in situ (Cis) in the cold cup mapping biopsies and tumour grade were not associated with the risk of TCC in the prostatic urethra/prostate. Cis, multifocal Cis (> or = 2 locations) and tumour location in the trigone were significantly more common in cystectomy specimens with TCC in the prostatic urethra and prostate: 21/50 (42%) vs 32/125 (26%), p=0.045; 20/50 (40%) vs 27/125 (22%), p=0.023; and 20/50 (40%) vs 26/125 (21%), p=0.01, respectively. Preoperative resectional biopsies from the prostatic urethra in the 154 patients analysed identified 31/47 (66%) of patients with TCC in the prostatic urethra/prostate, with a specificity of 89%. The detection of stromal-invasive and non-stromal involvement was similar: 66% and 65%, respectively. CONCLUSIONS: The incidence of TCC in the prostatic urethra and prostate was 29% (50/175) in the cystoprostatectomy specimen. Preoperative biopsies from the prostatic urethra identified 66% of patients with such tumour growth. Our findings suggest that preoperative cold cup mapping biopsies of the bladder for detection of Cis add little extra information with regard to the risk of TCC in the prostatic urethra and prostate.     

Amnesic Concentrations of the Nonimmobilizer 1,2-Dichlorohexafluorocyclobutane (F6, 2N) and Isoflurane Alter Hippocampal θ Oscillations In Vivo

Background: Drug-induced temporary amnesia is one of the principal goals of general anesthesia. The nonimmobilizer 1,2-dichlorohexafluorocyclobutane (F6, also termed 2N) impairs hippocampus-dependent learning at relative, i.e., lipophilicity-corrected, concentrations similar to isoflurane. Hippocampal [theta] oscillations facilitate mnemonic processes in vivo and synaptic plasticity (a cellular model of memory) in vitro and are thought to represent a circuit level phenomenon that supports memory encoding. Therefore, the authors investigated the effects of F6 and isoflurane on [theta] oscillations (4-12 Hz).

Methods: Thirteen adult rats were implanted with multichannel depth electrodes to measure the microelectroencephalogram and were exposed to a range of concentrations of isoflurane and F6 spanning the concentrations that produce amnesia. Five of these animals also underwent control experiments without drug injection. The authors recorded the behavioral state and hippocampal field potentials. They confirmed the electrode location postmortem by histology.

Results: The tested concentrations for isoflurane and F6 ranged from 0.035% to 0.77% and from 0.5% to 3.6%, respectively. Isoflurane increased the fraction of time that the animals remained immobile, consistent with sedation, whereas F6 had the opposite effect. Electroencephalographic power in the [theta] band was less when the animals were immobile than when they explored their environment. F6 suppressed the power of oscillations in the [theta] band. Isoflurane slowed [theta] oscillations without reducing total power in the [theta] band.     

Amnesic concentrations of the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (F6, 2N) and isoflurane alter hippocampal theta oscillations in vivo

BACKGROUND: Drug-induced temporary amnesia is one of the principal goals of general anesthesia. The nonimmobilizer 1,2-dichlorohexafluorocyclobutane (F6, also termed 2N) impairs hippocampus-dependent learning at relative, i.e., lipophilicity-corrected, concentrations similar to isoflurane. Hippocampal theta oscillations facilitate mnemonic processes in vivo and synaptic plasticity (a cellular model of memory) in vitro and are thought to represent a circuit level phenomenon that supports memory encoding. Therefore, the authors investigated the effects of F6 and isoflurane on theta oscillations (4-12 Hz). METHODS: Thirteen adult rats were implanted with multichannel depth electrodes to measure the microelectroencephalogram and were exposed to a range of concentrations of isoflurane and F6 spanning the concentrations that produce amnesia. Five of these animals also underwent control experiments without drug injection. The authors recorded the behavioral state and hippocampal field potentials. They confirmed the electrode location postmortem by histology. RESULTS: The tested concentrations for isoflurane and F6 ranged from 0.035% to 0.77% and from 0.5% to 3.6%, respectively. Isoflurane increased the fraction of time that the animals remained immobile, consistent with sedation, whereas F6 had the opposite effect. Electroencephalographic power in the theta band was less when the animals were immobile than when they explored their environment. F6 suppressed the power of oscillations in the theta band. Isoflurane slowed theta oscillations without reducing total power in the theta band. CONCLUSIONS: Drug-induced changes in theta oscillations may be a common basis for amnesia produced by F6 and isoflurane. The different patterns suggest that these drugs alter network activity by acting on different molecular and/or cellular targets.     

Haplotypes of transcription factor 7-like 2 (TCF7L2) gene and its upstream region are associated with type 2 diabetes and age of onset in Mexican Americans

TCF7L2 acts as both a repressor and transactivator of genes, as directed by the Wnt signaling pathway. Recently, several highly correlated sequence variants located within a haplotype block of the TCF7L2 gene were observed to associate with type 2 diabetes in three Caucasian cohorts. We previously reported linkage of type 2 diabetes in the San Antonio Family Diabetes Study (SAFADS) cohort consisting of extended pedigrees of Mexican Americans to the region of chromosome 10q harboring TCF7L2. We therefore genotyped 11 single nucleotide polymorphisms (SNPs) from nine haplotype blocks across the gene in 545 SAFADS subjects (178 diabetic) to investigate their role in diabetes pathogenesis. We observed nominal association between four SNPs (rs10885390, rs7903146, rs12255372, and rs3814573) in three haplotype blocks and type 2 diabetes, age at diagnosis, and 2-h glucose levels (P = 0.001-0.055). Furthermore, we identified a common protective haplotype defined by these four SNPs that was significantly associated with type 2 diabetes and age at diagnosis (P = 4.2 x 10(-5), relative risk [RR] 0.69; P = 6.7 x 10(-6), respectively) and a haplotype that confers diabetes risk that contains the rare alleles at SNPs rs10885390 and rs12255372 (P = 0.02, RR 1.64). These data provide evidence that variation in the TCF7L2 genomic region may affect risk for type 2 diabetes in Mexican Americans, but the attributable risk may be lower than in Caucasian populations.