Visualization of calcium phosphate cement in teeth by zero echo time 1H MRI at high field

¹H magnetic resonance imaging (MRI) by a zero echo time (ZTE) sequence is an excellent method to image teeth. Calcium phosphate cement (CPC) materials are applied in the restoration of tooth lesions, but it has not yet been investigated whether they can be detected by computed tomography (CT) or MRI. The aim of this study was to optimize high‐field ZTE imaging to enable the visualization of a new CPC formulation implanted in teeth and to apply this in the assessment of its decomposition in vivo. CPC was implanted in three human and three goat teeth ex vivo and in three goat teeth in vivo. An ultrashort echo time (UTE) sequence with multiple flip angles and echo times was applied at 11.7 T to measure T₁ and T₂* values of CPC, enamel and dentin. Teeth with CPC were imaged with an optimized ZTE sequence. Goat teeth implanted with CPC in vivo were imaged after 7 weeks ex vivo. T₂* relaxation of implanted CPC, dentin and enamel was better fitted by a model assuming a Gaussian rather than a Lorentzian distribution. For CPC and human enamel and dentin, the average T₂* values were 273 ± 19, 562 ± 221 and 476 ± 147 μs, respectively, the average T₂ values were 1234 ± 27, 963 ± 151 and 577 ± 41 μs, respectively, and the average T₁ values were 1065 ± 45, 972 ± 40 and 903 ± 7 ms, respectively. In ZTE images, CPC had a higher signal‐to‐noise‐ratio than dentin and enamel because of the higher water content. Seven weeks after in vivo implantation, the CPC‐filled lesions showed less homogeneous structures, a lower T₁ value and T₂* separated into two components. MRI by ZTE provides excellent contrast for CPC in teeth and allows its decomposition to be followed.     

In vivo MR guided boiling histotripsy in a mouse tumor model evaluated by MRI and histopathology

Boiling histotripsy (BH) is a new high intensity focused ultrasound (HIFU) ablation technique to mechanically fragmentize soft tissue into submicrometer fragments. So far, ultrasound has been used for BH treatment guidance and evaluation. The in vivo histopathological effects of this treatment are largely unknown. Here, we report on an MR guided BH method to treat subcutaneous tumors in a mouse model. The treatment effects of BH were evaluated one hour and four days later with MRI and histopathology, and compared with the effects of thermal HIFU (T‐HIFU). The lesions caused by BH were easily detected with T₂w imaging as a hyper‐intense signal area with a hypo‐intense rim. Histopathological evaluation showed that the targeted tissue was completely disintegrated and that a narrow transition zone (<200 µm) containing many apoptotic cells was present between disintegrated and vital tumor tissue. A high level of agreement was found between T₂w imaging and H&E stained sections, making T₂w imaging a suitable method for treatment evaluation during or directly after BH. After T‐HIFU, contrast enhanced imaging was required for adequate detection of the ablation zone. On histopathology, an ablation zone with concentric layers was seen after T‐HIFU. In line with histopathology, contrast enhanced MRI revealed that after BH or T‐HIFU perfusion within the lesion was absent, while after BH in the transition zone some micro‐hemorrhaging appeared. Four days after BH, the transition zone with apoptotic cells was histologically no longer detectable, corresponding to the absence of a hypo‐intense rim around the lesion in T₂w images. This study demonstrates the first results of in vivo BH on mouse tumor using MRI for treatment guidance and evaluation and opens the way for more detailed investigation of the in vivo effects of BH. Copyright © 2016 John Wiley & Sons, Ltd.     

PET and MRI for the evaluation of regional myocardial perfusion and wall thickening after myocardial infarction

Background

Deterioration of left ventricular (LV) function after myocardial infarction (MI) is a major cause of heart failure. Myocardial perfusion performance may play an important role in deterioration or improvement in LV function after MI. The aim of this study was to evaluate the myocardial perfusion reserve (MPR) and stress perfusion in deteriorating and non-deteriorating LV segments in patients after MI by PET and MRI, respectively.

Methods

Regional wall thickening of 352 segments in 22 patients was assessed at 4 and 24?months after MI by cardiac MRI. PET was performed to evaluate MPR and adenosine stress ¹³N-ammonia perfusion 24?months after MI. Segments were divided into four groups according to deterioration or improvement in wall thickening.

Results

Normal functional segments at 4?months after MI that remained stable had a significantly higher mean MPR and mean stress perfusion PET value than deteriorated segments (p?p?Conclusion This study demonstrated the additional value of myocardial perfusion assessment in relation to the functional integrity of the injured myocardium. Segmental functional LV improvement after MI was associated with better regional myocardial perfusion characteristics. Furthermore, the amount of wall thickening reduction was associated with regional myocardial perfusion abnormalities in patients after MI.     

123I-Labelled metaiodobenzylguanidine for the evaluation of cardiac sympathetic denervation in early stage amyloidosis

Purpose

Cardiac amyloidosis is a rare disorder, but it may lead to potentially life-threatening restrictive cardiomyopathy. Cardiac manifestations frequently occur in primary amyloidosis (AL) and familial amyloidosis (ATTR), but are uncommon in secondary amyloidosis (AA). Echocardiography is the method of choice for assessing cardiac amyloidosis. Amyloid deposits impair the function of sympathetic nerve endings. Disturbance of myocardial sympathetic innervations may play an important role in the remodelling process. ¹²³I-MIBG can detect these innervation changes.

Methods

Patients with biopsy-proven amyloidosis underwent general work-up, echocardiography and ¹²³I-MIBG scintigraphy. Left ventricular internal dimensions and wall thickness were measured, and highly refractile cardiac echoes (sparkling) were analysed. Early (15?min) and late (4?h) heart-to-mediastinum ratio (HMR) and wash-out rate were determined after administration of MIBG.

Results

Included in the study were 61 patients (30 women and 31 men; mean age 62?years; 39 AL, 11 AA, 11 ATTR). Echocardiographic parameters were not significantly different between the groups. Sparkling was present in 72?% of ATTR patients, in 54?% of AL patients and in 45?% of AA patients. Mean late HMR in all patients was 2.3?±?0.75, and the mean wash-out rate was 8.6?±?14?% (the latter not significantly different between the patient groups). Late HMR was significantly lower in patients with echocardiographic signs of amyloidosis than in patients without (2.0?±?0.70 versus 2.8?±?0.58, p?<?0.001). Wash-out rates were significantly higher in these patients (?3.3?±?9.9?% vs. 17?±?10?%, p?<?0.001). In ATTR patients without echocardiographic signs of amyloidosis, HMR was lower than in patients with the other types (2.0?±?0.59 vs. 2.9?±?0.50, p?=?0.007).

Conclusion

MIBG HMR is lower and wash-out rate is higher in patients with echocardiographic signs of amyloidosis. Also, ¹²³I-MIBG scintigraphy can detect cardiac denervation in ATTR patients before signs of amyloidosis are evident on echocardiography.     

Kinetics and 28-day test–retest repeatability and reproducibility of [11C]UCB-J PET brain imaging

[¹¹C]UCB-J is a novel radioligand that binds to synaptic vesicle glycoprotein 2A (SV2A). The main objective of this study was to determine the 28-day test–retest repeatability (TRT) of quantitative [¹¹C]UCB-J brain positron emission tomography (PET) imaging in Alzheimer’s disease (AD) patients and healthy controls (HCs). Nine HCs and eight AD patients underwent two 60 min dynamic [¹¹C]UCB-J PET scans with arterial sampling with an interval of 28 days. The optimal tracer kinetic model was assessed using the Akaike criteria (AIC). Micro-/macro-parameters such as tracer delivery (K₁) and volume of distribution (V_T) were estimated using the optimal model. Data were also analysed for simplified reference tissue model (SRTM) with centrum semi-ovale (white matter) as reference region. Based on AIC, both 1T2k_V_B and 2T4k_V_B described the [¹¹C]UCB-J kinetics equally well. Analysis showed that whole-brain grey matter TRT for V_T, DVR and SRTM BP_ND were –2.2% ± 8.5, 0.4% ± 12.0 and –8.0% ± 10.2, averaged over all subjects. [¹¹C]UCB-J kinetics can be well described by a 1T2k_V_B model, and a 60 min scan duration was sufficient to obtain reliable estimates for both plasma input and reference tissue models. TRT for V_T, DVR and BP_ND was <15% (1SD) averaged over all subjects and indicates adequate quantitative repeatability of [¹¹C]UCB-J PET.     

Novel coronavirus epidemic in the Hungarian population,a cross-sectional nationwide survey to support the exit policy in Hungary

GeroScience - After months of restrictive containment efforts to fight the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) epidemic, European countries are planning to reopen. To...     

Genetic polymorphisms altering microRNA activity in psoriasis – a key to solve the puzzle of missing heritability?

Psoriasis is a chronic immune‐mediated skin disease in which the balance in the interplay of immune cells and keratinocytes is disturbed. MicroRNAs (miRNAs) are endogenous small regulatory RNAs that stabilize cellular phenotypes and fine‐tune signal transduction feedback loops through the regulation of gene networks. Through the regulation of their multiple target genes, miRNAs regulate the development of inflammatory cell subsets and have a significant impact on the magnitude of inflammatory responses. Since the discovery of deregulated miRNA expression in psoriasis, we have learned that they can regulate differentiation, proliferation and cytokine response of keratinocytes, activation and survival of T cells and the crosstalk between immunocytes and keratinocytes through the regulation of chemokine production. In recent years, it became apparent that genetic polymorphisms in miRNA genes and/or in miRNA binding sites of target genes can affect miRNA activity and contribute to disease susceptibility. Psoriasis has a strong genetic background; however, the contribution of genetic variants involving miRNAs is largely unexplored in psoriasis. We propose that changes in miRNA‐mediated gene regulation may be a major contributor to the disturbed balance in immune regulation that results in chronic skin inflammation. In this viewpoint essay, we focus on the emerging new aspects of the role of miRNAs in psoriasis and propose that genetic polymorphisms that affect miRNA activity might be important in the pathogenesis of psoriasis.