Serial magnetic resonance imaging in patients following acute myocardial infarction.

The detection of serial changes in magnetic resonance (MR) signal intensity of the heart following acute myocardial infarction may provide a useful method of characterizing tissue healing. Fourteen patients with acute Q-wave infarction underwent T2-weighted, spin-echo cardiac imaging during hospitalization, followed by one or more additional MR studies (total 31) over a 6- to 27-wk period (mean: 3 mo). Visual assessment of the images demonstrated a gradual reduction in signal intensity and localization of the bright signal to the subendocardium of the infarction region over the three-mo study period. A quantitative measurement of signal intensity (infarction/normal myocardium) fell from 1.81 +/- 0.42 on the initial study to 1.34 +/- 0.37 (p less than 0.05) at a mean of 14 wk. Two patients had an increase in signal intensity on the follow-up study and both patients had been readmitted with acute coronary syndromes. In summary, characterization of changes in signal intensity may provide a useful method of assessing myocardial healing following acute myocardial infarction. Further studies are indicated to determine the prognostic significance of these parameters.     

Endoscopic microsuture repair of vocal fold defects

The presence of a nonvibratory segment of vocal folds after microlaryngeal surgery is often a cause of poor voice result. The etiology of a nonvibratory segment is due to full thickness epithelial defect followed by secondary wound closure and scar contracture. To reduce scar contracture and nonvibratory segment of the vocal folds, primary repair with a 6-0 chromic endo-knot suture technique was used to close defects and approximate microflaps of the vocal folds. This was done in 18 patients with epithelial defects after resection of benign vocal fold lesions. The pathologic findings included severe polypoid degeneration (n = 7), fusiform laryngeal polyps (n = 5), sulcus vocalis (n = 2), cyst (n = 2), and keratosis (n = 2). Voice was improved in all patients after surgery. Comparison of vocal fold vibration before and after surgery showed improvements in configuration, amplitude, and mucosal wave. Vocal folds that were sutured all had good vibratory characteristics; none had a nonvibrating segment at the site of suture placement. Voice and healing after microsuture technique were near normal by Day 10 and return of mucosal wave was often complete by Day 14. Endoscopic microsuture closure of microflaps of the vocal folds edge is safe and affords the surgeon an opportunity for primary repair with improved functional result.     

Evaluation of cartilage defect at medial femoral condyle in early osteoarthritis of the knee

OBJECTIVE: The purpose of this study was to evaluate cartilage defect at medial femoral condyle on MRI in early osteoarthritis and to compare with early osteoarthritis with meniscal tear without clear cartilage defect. MATERIALS AND METHODS: Twelve patients with medial pain of the knee and cartilage defect without meniscal tear by MRI were studied for cartilage defect. There were two males and 10 females with cartilage defect, and they were between 42 and 61 years of age (average, 51.6). Fifteen patients with medial pain of the knee and meniscal tear and without clear cartilage defect had been studied as meniscal tear cases. There were five males and 10 females with meniscal tear, and they were between 45 and 61 years of age (average 54.5). In both groups, knee injuries by trauma and Kellgren radiographic grade III and IV osteoarthritis were excluded. We compared cartilage defect cases and meniscal tear cases by gender, age, medial meniscus displacement ratio from the edge of the tibial medial joint surface, femorotibial angle (FTA) and Mikulicz line. We measured medial meniscus displacement ratio by the proportion of medial meniscus lesion protruding from the edge of tibial medial joint surface to all the medial meniscus width on MRI. For the evaluation of Mikulicz line, we measured the score by the length from tibial medial joint surface to Mikulicz line to tibial plateau width. chi(2) Test was used for gender, and Mann-Whitney U test was used for age, medial meniscus displacement ratio, FTA and Mikulicz line. RESULTS: Statistically significant difference was not observed between cartilage defect cases and meniscal tear cases for age and gender. Medial meniscus displacement ratio was 13+/-12.3% in cartilage defect cases and 50.4+/-20.1% in meniscal tear cases. Medial meniscus displacement ratio in cartilage defect cases was significantly smaller than in meniscal tear cases (P=.0001). FTA was 174.9+/-2.2 degrees in cartilage defect cases and 178.3+/-4.8 degrees in meniscal tear cases. FTA in cartilage defect cases was significantly smaller than in meniscal tear cases (P=.00390). The score by the length from tibial medial joint surface to Mikulicz line to tibial plateau width was 35.8+/-11.8% in cartilage defect cases and 21.7+/-15.8% in meniscal tear cases. Mikulicz line in cartilage defect cases passes more laterally than in meniscal tear cases significantly (P=.0264). CONCLUSION: In this study, we reported cartilage defect cases at medial femoral condyle in the early osteoarthritis of the knee. We think that these cases were different from early osteoarthritis with meniscal tear in alignment of lower limb and onset mechanism. It is necessary to evaluate meniscus and cartilage in MRI when we diagnose middle-aged patients with medial pain of the knee and without remarkable changes of X-ray.     

Evaluation of hematoma by MRI in follow-up of aorto-femoral bypass

We selected a population of 20 patients with atherosclerotic disease, submitted to implantation of aorto-femoral bypass graft. These patients were studied by MRI with T1- and T2-weighted sequences (w.s.) using a 0.5 T superconductive magnet. Investigation was performed at 1 wk, 1, 3, and 6 mo after dacron implantation, to evaluate the normal evolution of hematoma and the potential development of complications. At the first week examination, hematoma presented medium signal intensity on T1 w.s. and high signal intensity on T2 w.s.; at 1 mo control the amount of hematoma was slightly reduced and we found persistence of high signal intensity on T2 w.s.; progressive reduction of size and signal intensity on T2 w.s. was noted at 3 mo control, in patients operated for peripheral vascular disease; on the other hand we found persistence of high signal intensity in T2 w.s. in patients treated for abdominal aortic aneurysms; only after 6 mo it was evident in all patients fibrotic evolution of the collection and low signal intensity in both T1 and T2 w.s. Thus, MRI study was useful in the evaluation of patency, morphology, and in detection of intraluminal thrombosis, but also in the characterization of periprosthetic hematoma.     

Ultra-low-field magnetic resonance imaging of acute cruciate ligament tears

Ultra-low-field (0.04 T) magnetic resonance imaging (MRI) was evaluated in 15 patients with acute trauma to the knee and clinically suspected injuries of the cruciate ligaments. Subsequent arthroscopy was performed within 14 days (mean: 3 days) in 14 patients and after 3 mo in one patient. At arthroscopy/arthrotomy tears of the anterior cruciate ligament (ACL) were verified in 13 patients (11 complete, 2 partial tears). An additional tear of the posterior cruciate ligament (PCL) was found in one patient. All the tears could be demonstrated by MRI. There was one false positive MR diagnosis of ACL tear. It is possible with low-field MRI to diagnose injuries of the cruciate ligaments with good accuracy.     

Relationship between the shape of tibial spurs on X-ray and meniscal changes on MRI in early osteoarthritis of the knee

OBJECTIVE: The purpose of this study was to evaluate the relationship between the shape of tibial spurs on plain X-rays and the meniscal changes on magnetic resonance imaging (MRI) in early osteoarthritis of the knee. MATERIALS AND METHODS: Sixty-three patients (age range, 40 to 59 years; average, 51.8) underwent X-ray and MRI examinations of their knees. Ligament injuries caused by trauma and Kellgren Radiographic Grades III and IV on X-ray were excluded. The shapes of the medial and lateral tibial spurs on X-ray were classified into four types: (a) normal type; (b) horizontal type, in which the spur protruded horizontally; (c) upward type, in which the spur protruded upward; and (d) downward type, in which the spur protruded downward. The femorotibial angle (FTA) on the X-rays was also measured. The medial and lateral meniscal displacement rates on MRI were measured by the proportion by which the meniscal lesion protruded from the edge of the tibial joint surface to the overall meniscal width. The medial and lateral meniscal signal changes on MRI were classified into three types: (a) normal type; (b) intrameniscal type, which showed a high signal within the meniscus; and (c) tear type, which showed a high signal extending to the tibial joint surface. The relationships between the shape of the medial and lateral tibial spur classification on X-ray, the medial and lateral meniscal displacement rates on MRI, the medial and lateral meniscal signal changes on MRI and the FTA were evaluated statistically. RESULTS: Statistically significant correlations were observed between the medial tibial spur classification on X-ray, the medial meniscal displacement rate on MRI and the medial meniscal signal change classification on MRI. In the downward type of medial tibial spur, the medial meniscal displacement rate (50.46+/-17.95%) and the percentage (8 out of 8 cases; 100%) involving the tear type of medial meniscus were greater than the other types. Statistical significance was not observed among the lateral tibial spur classification on X-ray, the lateral meniscal displacement rate on MRI and the lateral meniscal signal change classification on MRI. However, in the horizontal type of lateral tibial spur, the percentage (7 out of 10 cases; 70%) involving the tear type of lateral meniscus was greater than the other types. Correlations tended to be observed between the medial meniscal displacement rate on MRI and the FTA. CONCLUSIONS: In this study, there was a relationship between the shape of the tibial spur on X-ray and the meniscal changes on MRI in early osteoarthritis of the knee. The shape of the medial tibial spur on X-ray can be a useful indicator for predicting the progression of osteoarthritis of the knee. A downward type of medial tibial spur classification on X-ray may be a risk factor for developing severe osteoarthritis of the knee.     

Effects of radiation therapy on the human normal brain (white matter) visualized by MR imaging

Sequential MR imaging could provide information related to the pathological changes due to the application of external cytotoxic agents such as radiotherapy on the central nervous system. This paper describes the results of our attempt to demonstrate short-term changes associated with normal brain during and immediately following radiotherapy when the whole brain is irradiated for malignant conditions. No observable changes were found in the normal brain parenchyma in any of the patients (n = 8) in T₁-, T₂-, and proton-density-weighted images in the sequential scans in the first and second weeks and immediately following radiotherapy. Also, no changes were observed in the normal brain appearance at 2 mo (n = 6), up to 6 mo (n = 1), and up to 15 mo (n = 1) after completion of radiotherapy.     

Osteogenic differentiation of rat bone marrow stromal cells by various intensities of low-intensity pulsed ultrasound

Bone growth and repair are under the control of biochemical and mechanical signals. Low-intensity pulsed ultrasound (LIPUS) stimulation at 30 mW/cm² is an established, widely used and FDA approved intervention for accelerating bone healing in fractures and non-unions. Although this LIPUS signal accelerates mineralization and bone regeneration, the actual intensity experienced by the cells at the target site might be lower, due to the possible attenuation caused by the overlying soft tissue. The aim of this study was to investigate whether LIPUS intensities below 30 mW/cm² are able to provoke phenotypic responses in bone cells. Rat bone marrow stromal cells were cultured under defined conditions and the effect of 2, 15, 30 mW/cm² and sham treatments were studied at early (cell activation), middle (differentiation into osteogenic cells) and late (biological mineralization) stages of osteogenic differentiation. We observed that not only 30 mW/cm² but also 2 and 15 mW/cm², modulated ERK1/2 and p38 intracellular signaling pathways as compared to the sham treatment. After 5 days with daily treatments of 2, 15 and 30 mW/cm², alkaline phosphatase activity, an early indicator of osteoblast differentiation, increased by 79%, 147% and 209%, respectively, compared to sham, indicating that various intensities of LIPUS were able to initiate osteogenic differentiation. While all LIPUS treatments showed higher mineralization, interestingly, the highest increase of 225% was observed in cells treated with 2 mW/cm². As the intensity increased to 15 and 30 mW/cm², the increase in the level of mineralization dropped to 120% and 82%. Our data show that LIPUS intensities lower than the current clinical standard have a positive effect on osteogenic differentiation of rat bone marrow stromal cells. Although Exogen™ at 30 mW/cm² continues to be effective and should be used as a clinical therapy for fracture healing, if confirmed in vivo, the increased mineralization at lower intensities might be the first step towards redefining the most effective LIPUS intensity for clinical use.     

He离子辐照6H-SiC引入缺陷的光谱研究

实验采用300 keV的He²⁺辐照6H-SiC,辐照温度分别为室温,450,600和750 ℃,辐照剂量范围为1×10¹⁵–1×10¹⁷ cm^-2,辐照完成后对样品进行拉曼散射和紫外可见透射光谱测试与研究. 这两种分析方法的实验结果表明,He离子辐照产生的缺陷以及缺陷的恢复与辐照剂量和辐照温度有着直接关系. 室温下辐照会使晶体出现非晶化,体现在拉曼特征峰消失,相对拉曼强度达到饱和(同时出现了较强的Si-Si峰);高温下辐照伴随着晶体缺陷的恢复过程,当氦泡未存在时,高温辐照很容易导致Frenkel对、缺陷团簇等缺陷恢复,当氦泡存在时,氦泡会抑制缺陷恢复,体现在相对拉曼强度和相对吸收系数曲线斜率的变化趋势上. 本文重点讨论了高温辐照情况下氦泡对缺陷聚集与恢复的影响,并与高温下硅离子辐照碳化硅结果进行了对比. 关键词： 6H-SiC 氦泡 拉曼散射光谱 紫外可见透射光谱     

Low intensity pulsed ultrasound for fracture healing: a review of the clinical evidence and the associated biological mechanism of action

Low intensity pulsed ultrasound is used in the clinical treatment of fractures and other osseous defects. Level I clinical studies demonstrate the ability of a specific ultrasound signal (1.5 MHz ultrasound pulsed at 1 kHz, 20% duty cycle, 30 mW/cm² intensity (SATA)) to accelerate the healing time in fresh tibia, radius and scaphoid fractures by up to 40%. Additionally, the same ultrasound signal has been shown to be effective at resolving all types of nonunions of all ages, following a wide range of fracture types and primary fracture management techniques.Recently, significant efforts have resulted in a more comprehensive understanding of the biological mechanism of action that produces the documented clinical outcomes. Low intensity pulsed ultrasound has been demonstrated to accelerate in vivo all stages of the fracture repair process (inflammation, soft callus formation, hard callus formation). In particular, accelerated mineralisation has been demonstrated in vitro with increases in osteocalcin, alkaline phosphatase, VEGF and MMP-13 expression. Integrins, a family of mechanoreceptors present on a wide range of cells involved in the fracture healing process, have been shown to be activated by the ultrasound signal. Downstream of the integrin activation, focal adhesions occur on the surface of cells with the activation of multiple signalling pathways, including the ERK, NF-κβ, and PI3 kinase pathways. These pathways have been directly linked to the production of COX-2 and prostaglandin, which are key to the processes of mineralisation and endochondral ossification in fracture healing.     

Septal repair implants: evaluation of magnetic resonance imaging safety at 3 T

Specialized implants are used for transcatheter closure of septal defects, including atrial and ventricular septal defects, and patent foramen ovale. These metallic devices may pose a risk to patients undergoing magnetic resonance imaging (MRI) procedures especially if performed at 3 T. Therefore, this investigation evaluated MRI safety at 3 T for septal repair implants (CardioSEAL Septal Repair Implant and STARFlex Septal Repair Implant, NMT Medical, Boston, MA, USA) by characterizing magnetic field interactions, heating and artifacts. These implants exhibited minor magnetic field interactions; heating was not excessive (+0.5°C); and artifacts will only create a problem if the area of interest is in the same area as or near these devices. Thus, the findings indicated that it would be safe for a patient with these implants to undergo MRI at 3 T or lower. Importantly, because of the minor magnetic field interactions, MRI may be performed immediately after implantation.     

Matrix-based autologous chondrocyte implantation for cartilage repair: noninvasive monitoring by high-resolution magnetic resonance imaging

OBJECTIVE: Monitoring of articular cartilage repair after matrix-associated autologous chondrocyte implantation (MACI) by a new grading and point-scale system based on noninvasive cartilage-specific magnetic resonance imaging (MRI) protocol. PATIENTS AND METHODS: In 20 patients, postoperative high-resolution MRI follow-up examinations at 4, 12, 24 and 52 weeks after matrix-based ACI for cartilage repair were initiated. The repair tissue was described with separate variables: degree of defect repair in width and length, surface, structure and signal intensity of the repair tissue, and status of the subchondral lamina and bone. For these variables, a grading system with point-scale evaluation was applied, and the mean average values were calculated for every follow-up MR exam of each patient. RESULTS: In 10 patients, an incomplete filling of the defect improved to complete filling (6 patients) or less incomplete (4 patients) filling of the defect. Three cases of implant hypertrophy returned to normal within 1 year. Complete filling of the defect by repair tissue was found in 2 patients from the beginning. Integration was complete in 10 cases. Improvement of incomplete to complete integration was found in 3 patients. The signal intensity of the implant developed to native cartilage signal in 13 patients. The mean average values increased from the 4th to the 52 nd week in 17 of 20 patients and decreased in 3 of 20 patients. CONCLUSION: High-resolution MRI provides a noninvasive tool for monitoring the development of cartilage repair tissue in MACI over time and helps to differentiate abnormal repair tissue from a normal maturation process.     

Development and evaluation of an optical fibre-based helium-neon laser irradiation system for tissue regeneration: A pilot study

Low level laser therapy is being extensively used to treat various medical ailments including wound healing. In the present study, an optical fibre-based helium-neon (He-Ne) laser irradiation system was designed, developed and evaluated for optimum tissue repair on mice excision wounds. Circular wounds of 15 mm diameter were created on the dorsum of animals and single exposure of uniformly distributed laser beam was administered at 1, 2 and 3 J/cm² to the respective test groups with suitable controls. Progression of healing was monitored by measuring wound contraction and mean healing time. Significant reduction in wound size and mean healing time (p <0.001) were observed in the test groups for the laser dose of 2 J/cm² compared to the unilluminated controls, suggesting the suitability of this dose.     

五磷酸镧钕激光晶体发光的温度效应

研究了低温下Nd0.9 La0.1 P5O14晶体中,Nd3+离子在0.9,1.05,以及1.35μm附近发光光谱的精细结构及相应的跃迁过程,并与Nd:YAG晶体中Nd3+离子发光光谱及相应的跃迁作了比较。在77K-500K的温度变化范围内,研究了Nd3+在两种晶体中最强的发光线的温度依赖关系,发现相反的变化规律,指出这是与两种晶体的结构及跃迁过程有关。     

Ultrasound therapy modulates osteocalcin expression during bone repair in rats

The aim of this study was to measure the temporal pattern of the protein expression of RUNX2, RANKL, OPG, and osteocalcin after ultrasound therapy during the process of bone healing by immunohistochemistry. The animals were randomly distributed into two groups: control or ultrasound-treated group. A non-critical size bone defects were surgically created at the upper third of the tibia. The treatments started 24 h post-surgery, and they are performed for 3, 6, and 12 sessions, with an interval of 48 h. A low-intensity pulsed ultrasound (1.5 MHz, 1:4 duty cycle, intensity SATA 30 mW/cm², 20 min/session, stationary mode application) was used. On days 7, 13, and 25 post-injury, rats were killed individually by carbon dioxide asphyxia. The tibias were removed for analysis. The histopathological analysis pointed out no remarkable differences between groups for all periods evaluated. However, immunohistochemical data revealed that ultrasound therapy produced an up-regulation of osteocalcin at day 7th and 13th post-surgery. Taken together, our results indicate that ultrasound therapy modulates osteocalcin expression during bone repair in rats as depicted by differential immunopression at the initial and intermediate stages of recovery.     

MR knee imaging: axial 3DFT GRASS pulse sequence versus spin-echo imaging for detecting meniscal tears.

The knees of 17 patients (34 menisci) referred for magnetic resonance (MR) imaging to evaluate knee pain were examined using thin axial three-dimensional Fourier transform (3DFT) gradient-refocused acquisition in a steady state (GRASS) images through the menisci, to determine if this method is sensitive and specific for detecting meniscal tears. Results were compared with spin-echo images with long TR and double-echo TE in both coronal and sagittal planes. Arthroscopy results, available in each case, were used as the "gold standard." Twelve meniscal tears were identified at arthroscopy. Axial 3DFT GRASS technique detected 10 of the 12 meniscal tears compared to 9 or 12 using spin-echo technique. With axial 3DFT GRASS technique one false-positive meniscal tear was reported, compared with two false-positive tears on spin-echo images. Axial 3DFT GRASS images were very useful in detecting peripheral tears, showing displaced meniscal fragments, and evaluating complex tears. In this small study, thin axial 3DFT GRASS images were comparable to spin-echo images for detecting meniscal tears, and were helpful in complicated cases in which they provided complementary information to that obtained from spin-echo images.     

Differences in Cartilage Repair between Loading and Unloading Environments in the Rat Knee

We investigated the histopathological and immunohistochemical effects of loading on cartilage repair in rat full-thickness articular cartilage defects. A total of 40 male 9-week-old Wistar rats were studied. Full-thickness articular cartilage defects were created over the capsule at the loading portion in the medial condyle of the femur. Twenty rats were randomly allocated into each of the 2 groups: a loading group and a unloading group. Twenty rats from these 2 groups were later randomly allocated to each of the 2 groups for evaluation at 1 and 2 weeks after surgery. At the end of each period, knee joints were examined histopathologically and immunohistochemically. In both groups at 1 and 2 weeks, the defects were filled with a mixture of granulation tissue and some remnants of hyaline cartilage. The repair tissue was not stained with toluidine blue in both groups. Strong staining of type I collagen was observed in the repair tissue of both groups. The area stained with type I collagen was smaller in the unloading group than in the loading groups, and the stained area was smaller at 2 weeks than at 1 week. In the staining for type II collagen, apparent staining of type II collagen was observed in the repair tissue of both groups at 1 week. At 2 weeks, there was a tendency toward a higher degree of apparent staining in the loading group than in the unloading group. Accordingly, these results indicated that loading and unloading in the early phase of cartilage repair have both merits and demerits.     

VO2薄膜表面氧缺陷的修复:F4TCNQ分子吸附反应

VO₂表面氧缺陷的存在对VO₂材料具有显著的电子掺杂效应, 极大地影响材料的本征电子结构和相变性质. 通过2, 3, 5, 6-四氟-7, 7', 8, 8'-四氰二甲基对苯醌(F₄TCNQ)分子表面吸附反应, 可以有效消除表面氧缺陷及其电子掺杂效应. 利用同步辐射光电子能谱和X射线吸收谱原位研究了修复过程中电子结构的变化以及界面的化学反应, 发现这种方式使得VO₂薄膜样品氩刻后得到的V³⁺失去电子成功地被氧化成原先的V⁴⁺, 同时F₄TCNQ分子吸附引起电子由衬底向分子层转移, 界面形成带负电荷的分子离子物种. 受电化学性质的制约, F₄TCNQ分子吸附反应修复氧缺陷较氧气氛退火更安全有效, 不会引起表面过度氧化形成V₂O₅.     

Modulated amplitude waves and defect formation in the one-dimensional complex Ginzburg–Landau equation

The transition from phase chaos to defect chaos in the complex Ginzburg–Landau equation (CGLE) is related to saddle-node bifurcations of modulated amplitude waves (MAWs). First, the spatial period P of MAWs is shown to be limited by a maximum P_SN which depends on the CGLE coefficients; MAW-like structures with period larger than P_SN evolve to defects. Second, slowly evolving near-MAWs with average phase gradients ν≈0 and various periods occur naturally in phase chaotic states of the CGLE. As a measure for these periods, we study the distributions of spacings p between neighbouring peaks of the phase gradient. A systematic comparison of p and P_SN as a function of coefficients of the CGLE shows that defects are generated at locations where p becomes larger than P_SN. In other words, MAWs with period P_SN represent “critical nuclei” for the formation of defects in phase chaos and may trigger the transition to defect chaos. Since rare events where p becomes sufficiently large to lead to defect formation may only occur after a long transient, the coefficients where the transition to defect chaos seems to occur depend on system size and integration time. We conjecture that in the regime where the maximum period P_SN has diverged, phase chaos persists in the thermodynamic limit.