Modulators for Terahertz Communication: The Current State of the Art.

With the increase of communication frequency, terahertz (THz) communication technology has been an important research field; particularly the terahertz modulator is becoming one of the core devices in THz communication system. The modulation performance of a THz communication system depends on the characterization of THz modulator. THz modulators based on different principles and materials have been studied and developed. However, they are still on the way to practical application due to low modulation speed, narrow bandwidth, and insufficient modulation depth. Therefore, we review the research progress of THz modulator in recent years and evaluate devices critically and comprehensively. We focus on the working principles such as electric, optical, optoelectrical, thermal, magnetic, programmable metamaterials and nonlinear modulation methods for THz wave with semiconductors, metamaterials, and 2D materials (such as graphene, molybdenum disulfide, and tungsten disulfide). Furthermore, we propose a guiding rule to select appropriate materials and modulation methods for specific applications in THz communication.

Clinical evaluation of dual-energy bone removal in CT angiography of the head and neck: comparison with conventional bone-subtraction CT angiography.

AIM: To evaluate the bone-subtraction effect of dual-energy bone removal in computed tomography angiography (CTA) of the head and neck in comparison with conventional bone-subtraction CTA. MATERIAL AND METHODS: The study comprised 52 patients who were divided into two groups at random, and examined using dual-source CT for head and neck CTA. Dual-energy bone removal CTA and conventional bone-subtraction CTA were applied to each of the two groups, respectively. The bone subtraction was performed automatically in both methods. Vascular structures, as well as brain tissue remained visible. The subtracted images were further processed with maximum intensity projection (MIP) and volume-rendering technique (VRT) for image evaluation. Two experienced radiologists reviewed the resulting subtracted and non-subtracted volume data with respect to the delineation and detection of image quality and vascular pathology. RESULTS: The means of the weighted CT dose index (CTDIvol) for bone-removal dual-energy CTA and conventional bone-subtraction CTA were 20.56+/-0.01 mGy and 25.57+/-0.56 mGy, respectively. There was a significant difference between them. The percentage of carotid and vertebral arteries and all other vessels that could be successfully assessed with these two methods were 87.8, 68, and 83%, and 93.5, 91.8, and 92.6%, respectively. There were no significant differences in the visualization of the carotid arteries; however, there were significant differences in the visualization of the vertebral arteries. CONCLUSION: Compared with conventional bone-subtraction CTA, dual-energy bone-removal CTA had a lower radiation dose. It eliminated most bones in the head and neck successfully; however, the bone subtraction effect around the vertebral artery was unsatisfactory. Dual-energy bone-removal CTA provides a new method for detecting vascular diseases in routine clinical work.

Limb-salvage for osteosarcoma.

Limb-salvage surgery plays an important role in the treatment of osteosarcoma. Among 104 patients with osteosarcoma we managed from 1974 to 1993, 60 were treated with limb-salvage procedure. 44 patients with IIB tumor received adjuvant chemotherapy, and the five-year survival rate was 46.69%. The local recurrence rate of these 60 patients was 15%, the infection rate 11.7%, and the prosthetic mechanical complication was 13.3%. Our results suggest that limb-salvage procedures are not only possible but also can provide patients with better function.

[Bony changes at the femur side after hip joint replacement: radiologic analysis of 80 hip joints].

The authors, according to Amstutz, studied the roentgenographs of 80 postoperation cases of cemented hip joint replacement performed more than two years-ago. There were bone changes in 64 cases (80%), of them, sclerosis of bone in 32 cases (40%), atrophy of bone in 25 cases (31%), absorption of bone in 24 cases (30%), thickness of bone cortex in 18 cases (22%), enlargement of medullary cavity in 12 cases (15%), periosteum reaction in 8 cases (10%), and thinness of bone cortex in 1 case (1.3%). Most of them usually occurred in the sixth month to the second year post-operation and located mainly at the 1, 4, 5 and 7 regions. The authors think that the most important cause is the unbalance of biologic stress, and other factors are elasticity and hardness of prosthesis, frictional force, cemented of the stem, etc.

[Fast neutron treatment of osteosarcoma].

Twelve patients with advanced osteosarcoma were treated with fast neutron at the Neutron Therapy Facility, the Hight-Energy Physics Institute, Chinese Academy of Science. Of the 12 patients, 5 were operated after radiotherapy. Three of them received fast neutron alone, and the other 2 with added 60Co. The doses ranged from 660 NcGy to 2 168 NcGy. Pain was relieved and the tumor size decreased in all the treated patients. Only one case was found histologically free of viable tumor cells. Skin reaction was serious and the knee joint function was impaired in all patients.