In vivo MRI-based 3D Mechanical Stress–Strain Profiles of Carotid Plaques with Juxtaluminal Plaque Haemorrhage: An Exploratory Study for the Mechanism of Subsequent Cerebrovascular Events

Objectives

Atherosclerotic plaque features, such as fibrous cap erosion, ulceration and rupture and presence of haemorrhage in carotid plaque are two important characteristics associated with subsequent cerebrovascular events and juxtaluminal haemorrhage/thrombus (JLH/T) indicates these two high-risk characteristics. This study aims to investigate the association between JLH/T and subsequent events in patients suffering from transient ischaemic attack (TIA). Three-dimensional mechanical analysis was employed to represent the critical mechanical stress (P-CStress) and stretch (P-CStretch) within the plaque.

Methods

Fifty TIA patients with mild-to-moderate carotid stenosis (30–69%) underwent high-resolution magnetic resonance imaging (MRI) within 72 h of the acute event and eight were excluded from the analysis due to various reasons. A total of 21 patients were found to have JLH/T in the carotid plaque and 21 did not (N-JLH/T). During a 2-year follow-up period, 11 (52.4%) patients in the JLH/T group experienced recurrent events and none in the N-JLH/T group. Three-dimensional plaque structure was reconstructed based on the in vivo MRI for the mechanical analysis.

Results

P-CStress of both groups was comparable (N-JLH/T: 174.45 ± 63.96 kPa vs. JLH/T: 212.60 ± 89.54 kPa; p = 0.120), but P-CStretch of JLH/T was significantly bigger than that of N-JLH/T (N-JLH/T: 1.21 ± 0.08 vs. JLH/T: 2.10 ± 0.53; p < 0.0001). Moreover, there were much bigger variations in stress and stretch of the JLH/T group during one cardiac cycle than in those of N-JLH/T group.

Conclusions

In vivo MRI-depicted JLH/T might be a high risk factor initiating recurrent events, as big deformation appearing around the rupture site might prevent healing and tear the haemorrhage/thrombus away from the host structure and prompt further thrombo-embolic events.     

Impaired contractility and remodeling of the upper gastrointestinal tract in diabetes mellitus type-1

AIM To investigate that both the neuronal function of the contractile system and structural apparatus of the gastrointestinal tract are affected in patients with longstanding diabetes and auto mic neuropathy.METHODS The evoked esophageal and duodenal contractile activity to standardized bag distension was assessed using a specialized ultrasound-based probe. Twelve type-1 diabetic patients with autonomic neuropathy and severe gastrointestinal symptoms and 12 healthy controls were studied. The geometry and biomechanical parameters (strain, tension/stress, and stiffness) were assessed.RESULTS The diabetic patients had increased frequency of distension-induced contractions (6.0 ±0.6 vs 3.3 ± 0.5, P ＜ 0.001). This increased reactivity was correlated with the duration of the disease (P =0.009). Impaired coordination of the contractile activity in diabetic patients was demonstrated as imbalance between the time required to evoke the first contraction at the distension site and proximal to it (1.5 ± 0.6 vs 0.5± 0.1, P = 0.03). The esophageal wall and especially the mucosa-submucosa layer had increased thickness in the patients (P ＜ 0.001), and the longitudinal and radial compressive stretch was less in diabetics (P ＜0.001). The esophageal and duodenal wall stiffness and circumferential deformation induced by the distensions were not affected in the patients (all P ＞ 0.14).CONCLUSION The impaired contractile activity with an imbalance in the distension-induced contractions likely reflects neuronal abnormalities due to autonomic neuropathy. However, structural changes and remodeling of the gastrointestinal tract are also evident and may add to the neuronal changes. This may contribute to the pathophysiology of diabetic gut dysfunction and impact on future management of diabetic patients with gastrointestinal symptoms.     

Deformation of the pelvic floor muscles during a vaginal delivery

Pelvic floor dysfunction is a hidden problem with a magnitude unknown to many. Statistics show that one in every ten women will have pelvic floor dysfunction so severe that it will require surgery. Several studies have shown that pelvic floor injuries during a vaginal delivery can be considered a significant factor in the development of urinary incontinence, fecal incontinence, and pelvic organ prolapse. The objective of the present work is to contribute to the clarification of the mechanisms behind pelvic floor disorders related to a vaginal delivery. For this purpose, a numerical simulation based on the finite element method was carried out. The finite element model intends to represent the effects that the passage of a fetal head can induce on the muscles of the pelvic floor, from a mechanical point of view. The model used for the simulation represents the pelvic bones, with the attached pelvic floor muscles and the fetus. In this work, we simulated the movements of the fetus during birth, in vertex position. We simulated the engagement, descent, flexion, internal rotation, and extension of the fetal head. Results for the pelvic floor stretch values obtained during the passage of the fetus head are presented; the deformation field is also shown. The results were obtained using the finite element method and a three-dimensional computer model of the pelvic floor and fetus. The maximum deformation obtained was 0.66 for a vertical displacement of the fetal head of approximately 60 mm.     

Evaluation of a new computerized analysis system developed for the processing of CT follow-up scans after EVR of infrarenal aneurysm

Purpose

The aim of this retrospective study was to present a new computerized analysis system developed for the evaluation of follow-up CT scans after endovascular repair (EVR) of infrarenal aneurysm and to compare it to the conventional evaluation method as regards preciseness and ease of application. The system is based on the extraction of the surface of the stent-graft (SG) and that of the spinal canal and the overlay of surfaces obtained at different points in time.

Materials and methods

A total of 116 CT follow-up data sets obtained from 49 patients after EVR of infrarenal aneurysm were evaluated using both, the conventional method and the new computerized system. Two parameters were analyzed: SG length and the distance between the most ventral point of the SG and the vertebral column. The correlation between the results of the two methods and the correlation between the results obtained by two independent observers (radiologist and lay person) using the new system were assessed by statistical analysis.

Results

Comparison of the two methods yielded a very high correlation for both parameters, (correlation coefficients of around 0.9 and p < 0.001). Comparison of the results obtained by the two observers yielded an equally high correlation (correlation coefficients of around 0.9 and p < 0.001).

Conclusion

Our results show that the new computerized system is as precise and reliable as the conventional method, but allows better visualization and quantification of SG changes by surface overlay. Moreover, it is easier to apply and less time-consuming and can be easily integrated into existing systems.     

MRI evaluation of the classification,frequency, and disc morphology of temporomandibular joint disc displacements: a multicenter retrospective study in a Turkish population

Objectives  Magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ) and temporomandibular disorders (TMDs) have been discussed in detail for various populations. As no such study has examined the Turkish population, we determined the frequency of TMDs in the Turkish population through a multicentric investigation using MRI. Methods  This retrospective study examined 504 TMJs of 252 symptomatic patients who had undergone bilateral MRI investigation in four different dental schools. The image analysis included the assessment of disc position and morphology, and recaptured the coronal and sagittal planes in the closed and open mouth positions. The TMJ disorders were classified using the Clinical Diagnostic Criteria for Temporomandibular Disorders (CDC/TMD). The correlations among the groups of TMJs and disc morphologies were analyzed statistically using the chi-square test (P ≤ 0.05). Results  Disc displacement and abnormal disc morphology were detected in 69.5% of the symptomatic TMJ patients. Of the joints examined using MRI, 154 were normal, 135 had anterior disc displacement with reduction (ADDwR), 145 had anterior disc displacement without reduction (ADDwoR), 30 had partial anterior disc displacement, and 18 had sideways disc displacements. Regarding disc morphology, enlargement in the posterior band was the most commonly encountered type and was observed in 152 TMJs. Overall, the average time for referral for treatment, which was defined as the time from symptom onset until the time of referral, was 1.5 years. Conclusions  The most common type of disc displacement found in the Turkish population studied was ADDwoR. In addition, patients did not perceive the symptoms of TMDs as a disease and did not seek help until the TMJ derangement caused a major complaint.     

利用连通器原理设计体内加压及眼球体积监测装置观测兔眼球蠕变特性

利用连通器原理，自行设计加压装置，对兔眼前房施加4.9 kPa高压；加压过程中，通过读取生理盐水与水银界面的刻度，确定特定时刻体内兔眼眼球整体体积的变化，进而得出4.9 kPa高压作用下，眼球体积随时间的变化情况。实验得出了4例样本眼球体积变化随加压时间变化的趋势。结果表明，在此高压作用下，体内兔眼眼球整体体积变化范围为843~1063 μL，当加压时间持续308~463 min后，眼球体积基本不发生变化。实验结果对急性高眼压模型造模时间标准等相关研究起到了提示作用。     

The tableting properties of melibiose monohydrate

In this research, the tableting properties of α-melibiose monohydrate were studied. Melibiose is a disaccharide which bears structural resemblance to lactose, because they both consist of galactose and glucose monosaccharide subunits. Compactibility and deformation behavior of two melibiose batches from different suppliers were studied and compared with α-lactose monohydrate and some other typical tableting excipients. Differences in the deformation behavior were determined comparing the shape of the Heckel plots, the yield pressure values and the strain rate sensitivity (SRS) indexes. In addition, the effect of moisture on the tabletability was studied. According to the yield pressures and SRS indexes melibiose was concluded to be fragmenting, even at higher degree than lactose monohydrate. However, the overall deformation behavior of melibiose was found to be similar to that of lactose monohydrate. Increase in moisture content resulted in higher tensile strengths of tablets for both melibiose batches, but it seemed to have more effect on compactibility of the other batch. In conclusion, melibiose has potential to be used as an excipient in tablet formulations.     

X-Strain技术评价低钙透析液对血液透析患者颈动脉弹性的影响

目的 应用速度矢量成像技术（X-Strain）检测低钙透析液对维持性血液透析（MHD）患者颈动脉形变能力及弹性的早期影响.方法 应用X-Strain技术检测30例未发生形态学颈动脉粥样硬化的MHD患者使用低钙透析液前后颈动脉形变能力及弹性的变化.结果 ①使用低钙透析液后MHD患者血钙、血磷、钙磷乘积均降低,甲状旁腺素升高,差异有统计学意义;②使用低钙透析液后,入组前未发生形态学颈动脉粥样硬化的MHD患者颈动脉IMT、RI降低,EDV升高,差异有统计学意义;③使用低钙透析液后,入组前未发生形态学颈动脉粥样硬化的MHD患者颈动脉X-Strain参数,S1、S2、S3、S4、S6、Sr1、Sr2、Sr3、Sr4、Sr5、Sr6、CS、CSr均升高,差异有统计学意义;④CS、CSr与血钙、钙磷乘积、IMT、RI有明显相关性;⑤一元线性回归分析示,血钙、钙磷乘积、IMT、RI对CS、CSr有显著影响,其中血钙对CS及CSr的独立影响力最大.结论 应用X-Strain技术能检测出低钙透析液对未发生形态学颈动脉粥样硬化的MHD患者颈动脉形变能力及弹性的影响,为预防血管异位钙化问题提供新的治疗佐证.     

An adaptive radiotherapy planning strategy for bladder cancer using deformation vector fields

Purpose

Adaptive radiotherapy (ART) has considerable potential in treatment of bladder cancer due to large inter-fractional changes in shape and size of the target. The aim of this study was to compare our clinically applied method for plan library creation that involves manual bladder delineations (Clin-ART) with a method using the deformation vector fields (DVFs) resulting from intensity-based deformable image registrations (DVF-based ART).

Materials and methods

The study included thirteen patients with urinary bladder cancer who had daily cone beam CTs (CBCTs) acquired for set-up. In both ART strategies investigated, three plan selection volumes were generated using the CBCTs from the first four fractions; in Clin-ART boolean combinations of delineated bladders were used, while the DVF-based strategy applied combinations of the mean and standard deviation of patient-specific DVFs. The volume ratios (VRs) of the course-averaged PTV for the two ART strategies relative the non-adaptive PTV were calculated.

Results

Both Clin-ART and DVF-based ART considerably reduced the course-averaged PTV, compared to non-adaptive RT. The VR for DVF-based ART was lower than for Clin-ART (0.65 vs. 0.73; p < 0.01).

Conclusions

DVF-based ART for bladder irradiation has a considerable normal tissue sparing potential surpassing our already highly conformal clinically applied ART strategy.