Study on Electrical and Mechanical Properties of Double-End Supported Elastic Substrate Prepared by Wet Etching Process.

Preparing elastic substrates as a carrier for dual-end supported nickel chromium thin film strain sensors is crucial. Wet etching is a vital microfabrication process widely used in producing microelectronic components for various applications. This article combines lithography and wet etching methods to microprocess the external dimensions and rectangular grooves of 304 stainless steel substrates. The single-factor variable method was used to explore the influence mechanism of FeCl3, HCl, HNO3, and temperature on the etching rate, etching factor, and etching surface roughness. The optimal etching parameter combination was summarized: an FeCl3 concentration of 350 g/L, HCl concentration of 150 mL/L, HNO3 concentration of 100 mL/L, and temperature of 40 °C. In addition, by comparing the surface morphology, microstructure, and chemical and mechanical properties of a 304 stainless steel substrate before and after etching treatment, it can be seen that the height difference of the substrate surface before and after etching is between 160 µm and -70 µm, which is basically consistent with the initial design of 0.2 mm. The results of an XPS analysis and Raman spectroscopy analysis both indicate that the surface C content increases after etching, and the corrosion resistance of the surface after etching decreases. The nano-hardness after etching increased by 26.4% compared to before, and the ζ value decreased by 7%. The combined XPS and Raman results indicate that the changes in surface mechanical properties of 304 stainless steel substrates after etching are mainly caused by the formation of micro-nanostructures, grain boundary density, and dislocations after wet etching. Compared with the initial rectangular substrate, the strain of the I-shaped substrate after wet etching increased by 3.5-4 times. The results of this study provide the preliminary process parameters for the wet etching of a 304 stainless steel substrate of a strain measuring force sensor and have certain guiding significance for the realization of simple steps and low cost of 304 stainless steel substrate micro-nano-processing.

Prognostic implications of left ventricular torsion measured by feature-tracking cardiac magnetic resonance in patients with ST-elevation myocardial infarction.

AIMS: The prognostic implication of left ventricular (LV) torsion on ST-elevation myocardial infarction (STEMI) is unclear. METHODS AND RESULTS: We analysed cardiovascular magnetic resonance (CMR) findings of 420 patients from a registry study (NCT03768453). These patients received CMR examination within 1 week after timely primary percutaneous coronary intervention. LV torsion and other CMR indexes were measured. Compared with healthy control subjects, STEMI significantly decreased patients' LV torsion (1.04 vs. 1.63°/cm, P < 0.001). During follow-up (median, 52 months), the reduction of LV torsion was greater in patients with than without composite major adverse cardiac and cerebrovascular events (MACCEs, 0.79 vs. 1.08°/cm, P < 0.001). The risk of MACCEs would increase to 1.125- or 1.092-fold, and the risk of 1-year LV remodelling would increase to 1.110- or 1.082-fold for every 0.1°/cm reduction in LV torsion after adjustment for clinical or CMR parameters respectively. When divided dichotomously, patients with LV torsion≤ 0.802°/cm had significantly higher risk of MACCEs (40.2 vs. 12.3%, P < 0.001) and more remarkable LV remodelling (46.1 vs. 11.9%, P < 0.001) than patients with better LV torsion. The addition of LV torsion to conventional prognostic factors such as the LV ejection fraction and infarction size led to a better risk classification model of patients for both MACCEs and LV remodelling. Finally, tobacco use, worse post-PCI flow, and greater microvascular obstruction size were presumptive risk factors for reduced LV torsion. CONCLUSION: LV torsion measured by CMR is closely associated with the prognosis of STEMI and would be a promising indicator to improve patients' risk stratification. CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov, NCT03768453.

Clinical study of intercondylar fossa formation to prevent intercondylar fossa impingement after high tibia osteotomy / 中国骨伤

OBJECTIVE@#To observe the clinical efficacy of intercondylar fossa plasty in preventing intercondylar fossa impingement syndrome after high tibial osteotomy.@*METHODS@#From August 2018 to August 2020, 84 patients with inverted knee osteoarthritis were treated by arthroscopy combined with high tibial osteotomy, and were divided into two groups with 42 cases in each group according to different surgical methods. In the intercondylar fossa plasty group, there were 13 males and 29 females, age ranged from 52 to 67 years old with an average of(58.27±4.32) years old, and arthroscopic intercondylar fossa plasty was performed first, and then high tibial osteotomy. In the arthroscopic cleansing group, 16 males and 26 females, age ranged from 50 to 71 years old with an average of (59.02±5.14) years old, underwent arthroscopic cleansing and then high tibial osteotomy. Postoperative treatment was evaluated using visual analogue scale(VAS), hospital for special surgery (HSS) score for the knee, and the occurrence of intercondylar percussa impingement.@*RESULTS@#All 84 patients were followed up, the duration ranged from 12 to 18 months with an average of (14.1±1.6) months. The VAS and HSS score of knee joint at 6, 12 and 18 months after surgery were significantly improved compared with preoperative period, and there was no significant difference between the two groups (P>0.05), but the incidence of intercondylar fossa index and intercondylar fossa impact between the two groups was significantly compared 18 months after surgery (P<0.05).@*CONCLUSION@#Intercondylar fossa plasty can effectively prevent the incidence of intercondylar fossa impact after high tibial osteotomy, and has a more significant effect on postoperative knee pain and function improvement.

Analysis of the curative effect of triple surgery under endoscope in the treatment of intractable heel pain / 中国骨伤

OBJECTIVE@#To investigate the clinical effect the treatment of arthroscopy-assisted calcaneal spur resection combined with plantar fascia release and calcaneal decompression in the treatment of the patients with intractable calcaneal pain.@*METHODS@#The clinical data of 50 patients with intractable heel pain from January 2016 to January 2019 were retrospectively analyzed, including 20 males and 30 females;aged from 40 to 68 years old with an average of (50.12±7.35)years old, the medical history ranged from 1 to 4 years. All patients underwent arthroscopy-assisted calcaneal spur resection combined with plantar fascia release and calcaneal decompression, and were followed up, the duration ranged from 24 to 60 months with an average of(42.00±3.28) months. All patients had obvious heel pain before surgery, and X-ray examinations often showed the presence of calcaneal spurs. In addition to the routine foot examination, the changes in the height and angle of the arch of the foot were also measured pre and post-operatively by X-ray, for the evaluation of clinical effect. The VAS system was used to evaluate the degree of foot pain;the AOFAS scoring system was used to comprehensively evaluate the foot pain, voluntary movement, gait and stability.@*RESULTS@#The VAS decreased from (8.75±1.24) before surgery to (5.15±2.35) at 3 months after surgery, (4.07±2.53) at 6 months after surgery, and (3.95±2.44) at the last fllow-up(P<0.05). The AOFAS score increased from (53.46±4.17) before surgery to(92.46±2.53) at 3 months after surgery, (96.33±2.46) at 6 months after surgery, and (97.05±2.37) at the last follow-up(P<0.05). The arch height was (41.54±1.15) mm before operation and (41.49±1.09) mm after the operation, the difference was not statistically significant(P>0.05). The internal arch angle of the foot arch was (121±6)° before operation and (122±7)° after operation. The difference was not statistically significant(P>0.05).@*CONCLUSION@#Arthroscopy-assisted calcaneal bone spurs resection combined with plantar fascia release and calcaneal decompression exhibited great clinical effect for treating intractable heel.

Treatment Progress in Diminished Ovarian Reserve: Western and Chinese Medicine / 中国结合医学杂志

Diminished ovarian reserve (DOR), generally defined as a decreased number or quality of oocytes, has a significant impact on quality of life and fertility in women. In recent years, the incidence of DOR has been increasing and the ages of patients are younger. The search for an effective DOR treatment has emerged as one of the preeminent research topics in reproductive health. An effective DOR therapy would improve ovarian function, fertility, and quality of life in patients. In this review we evaluated DOR treatment progress both in Western medicine and Chinese medicine, and elucidated the characteristics of each treatment.

Study of the Pattern Preparation and Performance of the Resistance Grid of Thin-Film Strain Sensors.

The thin-film strain sensor is a cutting-force sensor that can be integrated with cutting tools. The quality of the alloy film strain layer resistance grid plays an important role in the performance of the sensor. In this paper, the two film patterning processes of photolithography magnetron sputtering and photolithography ion beam etching are compared, and the effects of the geometric size of the thin-film resistance grid on the resistance value and resistance strain coefficient of the thin film are compared and analyzed. Through orthogonal experiments of incident angle, argon flow rate, and substrate negative bias in the ion beam etching process parameters, the effects of the process parameters on photoresist stripping quality, etching rate, surface roughness, and resistivity are discussed. The effects of process parameters on etching rate, surface roughness, and resistivity are analyzed by the range method. The effect of substrate temperature on the preparation of Ni Cr alloy films is observed by scanning electron microscope. The surface morphology of the films before and after ion beam etching is observed by atomic force microscope. The influence of the lithography process on the surface quality of the film is discussed, and the etching process parameters are optimized.

Fabrication, Performance, Characterization and Experimental Calibration of Embedded Thin-Film Sensor for Tool Cutting Force Measurement.

Thin-film strain sensors are widely used because of their small volume, fast strain response and high measurement accuracy. Among them, the thin-film material and preparation process of thin-film strain sensors for force measurement are important aspects. In this paper, the preparation process parameters of the transition layer, insulating layer and Ni-Cr alloy layer in a thin-film strain sensor are analyzed and optimized, and the influence of each process parameter on the properties of the thin film are discussed. The surface microstructure of the insulating layer with Al2O3 or Si3N4 transition layers and the film without transition layer were observed by atomic force microscopy. It is analyzed that adding a transition layer between the stainless steel substrate and insulation layer can improve the adhesion and flatness of the insulation layer. The effects of process parameters on elastic modulus, nanohardness and strain sensitivity coefficient of the Ni-Cr resistance layer are discussed, and electrical parameters such as the resistance strain coefficient are analyzed and characterized. The static calibration of the thin-film strain sensor is carried out, and the relationship between the strain value and the output voltage is obtained. The results show that the thin-film strain sensor can obtain the strain generated by the cutting tool and transform it into an electrical signal with good linearity through the bridge, accurately measuring the cutting force.

Impact of Concomitant Impairments of the Left and Right Ventricular Myocardial Strain on the Prognoses of Patients With ST-Elevation Myocardial Infarction.

Background: The impact of concomitant impairments of left and right ventricular (LV and RV) strain on the long-term prognosis of acute ST-elevation myocardial infarction (STEMI) is not clear. Methods: We analyzed CMR images and followed up 420 first STEMI patients from the EARLY Assessment of MYOcardial Tissue Characteristics by CMR in STEMI (EARLY-MYO-CMR) registry (NCT03768453). These patients received timely primary percutaneous coronary intervention (PCI) within 12 h and CMR examination within 1 week (median, 5 days; range, 2-7 days) after infarction. Global longitudinal strain (GLS), global radial strain (GRS), and global circumferential strain (GCS) of both ventricles were measured based on CMR cine images. Conventional CMR indexes were also assessed. Primary clinical outcome was composite major adverse cardiac and cerebrovascular events (MACCEs) including cardiovascular death, re-infarction, re-hospitalization for heart failure and stroke. In addition, CMR data from 40 people without apparent heart disease were used as control group. Results: Compared to controls, both LV and RV strains were remarkably reduced in STEMI patients. During follow-up (median: 52 months, interquartile range: 29-68 months), 80 patients experienced major adverse cardiac and cerebrovascular events (MACCEs) including cardiovascular death, re-infarction, heart failure, and stroke. LV-GCS > -11.20% was an independent predictor of MACCEs (P < 0.001). RV-GRS was the only RV strain index that could effectively predict the risk of MACCEs (AUC = 0.604, 95% CI [0.533, 0.674], P = 0.004). Patient with RV-GRS ≤ 38.79% experienced more MACCEs than those with preserved RV-GRS (log rank P < 0.001). Moreover, patients with the concomitant decrease of LV-GCS and RV-GRS were more likely to experience MACCEs than patients with decreased LV-GCS alone (log rank P = 0.010). RV-GRS was incremental to LV-GCS for the predictive power of MACCEs (continuous NRI: 0.327; 95% CI: 0.095-0.558; P = 0.006). Finally, tobacco use (P = 0.003), right coronary artery involvement (P = 0.002), and LV-GCS > -11.20% (P = 0.012) was correlated with lower RV-GRS. Conclusions: The concomitant decrease of LV and RV strain is associated with a worse long-term prognosis than impaired LV strain alone. Combination assessment of both LV and RV strain indexes could improve risk stratification of patients with STEMI. Trial Registration: ClinicalTrials.gov, NCT03768453. Registered 7 December 2018 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03768453.

Is polycystic ovary syndrome appropriately diagnosed by obstetricians and gynaecologists across China: a nationwide survey.

BACKGROUND: To describe the diagnostic criteria used and their application accuracy in the practice of polycystic ovary syndrome (PCOS) caring among obstetricians and gynaecologists across China. METHODS: This was an Online cross-sectional survey of Obstetricians and gynecologists involved in PCOS caring conducted via the largest continuing education platform of obstetrics and gynecology across China from September 2019 to November 2019. RESULTS: A total of 2,328 respondents were eligible for the final analysis. Of these, 94.5 % were general obstetricians and gynaecologists (Ge-ObGyn), and 5.5 % were reproductive endocrinologists (Re-ObGyn). Overall, the most frequently used criteria were the Androgen Excess and Polycystic Ovary Syndrome Society (AE-PCOS) criteria (48.2 %), followed by the Rotterdam criteria (35.7 %) and NIH criteria (12.1 %). Of the respondents, 31.3 % used their diagnostic criteria in their clinical practice. More respondents who chose the Rotterdam criteria could accurately apply the diagnostic criteria than those who chose the AE-PCOS criteria (41.2 % vs. 32.1 %, P < 0.001). Compared with Ge-ObGyn, Re-ObGyn were less likely to use the AE-PCOS criteria (adjusted odds ratio, 0.513; 95 % CI, 0.328-0.802; P < 0.05) and 1.492 times more likely to accurately use their criteria (95 % CI, 1.014-2.196; P < 0.05). CONCLUSIONS: Less than one-third of obstetricians and gynaecologists across China could accurately use the diagnostic criteria they choose to diagnose PCOS. There is an urgent need to train obstetricians and gynaecologists on PCOS diagnosis in an effort to improve the medical care quality of patients with PCOS.

Short-term combined treatment with exenatide and metformin for overweight/obese women with polycystic ovary syndrome / 中华医学杂志(英文版)

BACKGROUND@#Obesity and insulin resistance (IR) are common features of polycystic ovary syndrome (PCOS). Metformin (MET) increases insulin sensitivity, but it is associated with unsatisfactory weight loss. The glucagon-like peptide-1 receptor agonist exenatide has been shown to reduce weight and IR in patients with diabetes. This study aimed to explore the therapeutic effects of exenatide once-weekly (QW) combined with MET on body weight, as well as metabolic and endocrinological parameters in overweight/obese women with PCOS.@*METHODS@#Fifty overweight/obese women with PCOS diagnosed via the Rotterdam criteria were randomized to one of two treatment groups: MET (500 mg three times a day [TID]) or combination treatment (COM) (MET 500 mg TID, exenatide 2 mg QW) for 12 weeks. The primary outcomes were anthropometric changes associated with obesity, and the secondary outcomes included changes in reproductive hormone levels, glucose and lipid metabolism, and C-reactive protein.@*RESULTS@#Forty (80%) patients completed the study. COM therapy was superior to MET monotherapy in reducing weight (P = 0.045), body mass index (BMI) (P = 0.041), and waist circumference (P = 0.023). Patients in the COM group on an average lost 3.8 ± 2.4 kg compared with 2.1 ± 3.0 kg in the MET group. In the COM group, BMI and waist circumference decreased by 1.4 ± 0.87 kg/m2 and 4.63 ± 4.42 cm compared with 0.77 ± 1.17 kg/m2 and 1.72 ± 3.07 cm in the MET group, respectively. Moreover, levels of fasting glucose, oral glucose tolerance test (OGTT) 2-h glucose, and OGTT 2-h insulin were significantly lower with COM therapy than with MET (P < 0.050). Mild and moderate gastrointestinal reactions were the most common adverse events in both groups.@*CONCLUSIONS@#COM therapy was more effective than MET alone in reducing body weight, BMI, and waist circumference, and improving insulin sensitivity in overweight/obese women with PCOS, with acceptable short-term side effects.@*TRIAL REGISTRATION@#ClinicalTrials.gov, NCT04029272. https://clinicaltrials.gov/ct2/show/NCT04029272.

Author Correction: Identifying long-term stable refugia for relict plant species in East Asia.

In the original version of this Article, an incorrect sample size was provided for the number of relict species (443 instead of 442) and the number of relict forests (423 instead of 422). These errors have been corrected in both the PDF and HTML versions of the Article.

Identifying long-term stable refugia for relict plant species in East Asia.

Today East Asia harbors many "relict" plant species whose ranges were much larger during the Paleogene-Neogene and earlier. The ecological and climatic conditions suitable for these relict species have not been identified. Here, we map the abundance and distribution patterns of relict species, showing high abundance in the humid subtropical/warm-temperate forest regions. We further use Ecological Niche Modeling to show that these patterns align with maps of climate refugia, and we predict species' chances of persistence given the future climatic changes expected for East Asia. By 2070, potentially suitable areas with high richness of relict species will decrease, although the areas as a whole will probably expand. We identify areas in southwestern China and northern Vietnam as long-term climatically stable refugia likely to preserve ancient lineages, highlighting areas that could be prioritized for conservation of such species.

Absorption-enhancing mechanisms and advances of polymer-based supersaturated drug delivery system / 药学学报

Supersaturated drug delivery systems (SDDS) are defined as systems that are able to generate and maintain a sustained drug supersaturation in the gastrointestinal tract, facilitating the oral absorption of drugs with poor water solubility. Supersaturated drug solution is generated from a higher energy form of the drug or rapid dissolution through various formulation options. However, supersaturated solution is a thermodynamically unstable system that can easily lead to drug precipitation, missing the aim of improving the absorption. Therefore, maintenance of the supersaturated state is essential for the development of SDDS. Polymer-based SDDS take polymers as the precipitation inhibitor,which can effectively prevent the precipitation of drugs, generating an excellent effect on maintenance of the stability of supersaturated solution. However, different polymers have distinct anti-precipitation ability, and the mechanisms of such activity supported by the polymer remain unrevealed. In this review, we summarize the research advances in the absorption-enhancing mechanisms and in vitro evaluations of polymers-based SDDS. This review provides a reference for the design of rational SDDS.

Traditional Chinese Medicine data management policy in big data environment / 中国中药杂志

As traditional data management model cannot effectively manage the massive data in traditional Chinese medicine(TCM) due to the uncertainty of data object attributes as well as the diversity and abstraction of data representation, a management strategy for TCM data based on big data technology is proposed. Based on true characteristics of TCM data, this strategy could solve the problems of the uncertainty of data object attributes in TCM information and the non-uniformity of the data representation by using modeless properties of stored objects in big data technology. Hybrid indexing mode was also used to solve the conflicts brought by different storage modes in indexing process, with powerful capabilities in query processing of massive data through efficient parallel MapReduce process. The theoretical analysis provided the management framework and its key technology, while its performance was tested on Hadoop by using several common traditional Chinese medicines and prescriptions from practical TCM data source. Result showed that this strategy can effectively solve the storage problem of TCM information, with good performance in query efficiency, completeness and robustness.

Effects of three preparation technologies on the oral bioavailability of berberine α-hydroxy β-decanoylethyl sulfonate / 中成药

AIM To compare the effects of three preparation technologies on the oral bioavailability of HB (berberine α-hydroxy β-decanoylethyl sulfonate,houttuyn berberine).METHODS Solid dispersions,HP-β-CD inclusion complexes and nanosuspension freeze-dried powders were prepared.The suspensions of crude drug and these three preparations were intragastrically administered to SD rats,respectively.HPLC-MS/MS was adopted in the content determination of HB in plasma.then pharmacokinetics parameters were calculated.RESULTS Compared with the crude drug,three preparation technologies could significantly increase the Cmax value of this component (P ＜ 0.05),especially for HP-β-CD inclusion complexes (P ＜ 0.01).And HP-β-CD inclusion complexes demonstrated much higher AUC0-6h than the crude drug and the other two preparation technologies (P ＜ 0.05).CONCLUSION HP-β-CD inclusion complexes can effectively increase the oral bioavailability of HB.

Status and Expectations in Study on Quantization of Prescription Properties / 中国中医药信息杂志

Due to abstract and intricate theories of TCM theories, its essential characteristics are difficult to master, so the mechanism can be better explored through study on quantification of prescription properties. At present, quantification research by many scholars mainly adopts isolated research model limited to one or several kinds of TCM properties, which is difficult to reveal treatment mechanism of prescriptions. The development of big data and cloud computing technology provides a new way for the deep analysis of massive and complex TCM information. Based on syndrome differentiation, it is trending in prescription quantification to employ a comprehensive analysis by using "four properties - five flavors - channel tropism - ascending and descending, floating and sinking - toxicity -efficacy" overall on macroscopic level to analyze and quantify the characteristics of TCM prescriptions and their relationships among each other. This article reviewed recent research progress in the quantification of prescription properties and provided references for the modernization and specification of quantification of prescription properties.

The Bidirectional Effects of Arsenic on miRNA-21: A Systematic Review and Meta-analysis / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>Arsenic is a metalloid environmental carcinogen involved in the occurrence and development of many cancers. miRNA-21 plays a crucial role in arsenic-induced carcinogenesis. We aimed to elucidate the mechanism by which miRNA-21 influences arsenic-induced cancer.</p><p><b>METHODS</b>We used meta-analysis of published studies to determine how arsenic induces cancerous cells through miRNA-21.</p><p><b>RESULTS</b>Low-dose arsenic exposure (⪕ 5 μmol/L) can increase miRNA-21 and phosphorylated signal transducter and activator of transcription 3 (pSTAT3) expression, and decrease programmed cell death protein 4 (PDCD4) and protein sprouty homolog 1 (Spry1) expression. High-dose arsenic exposure (> 5 μmol/L), can increase miRNA-21 expression, and decrease Spry1 and E-cadherin expression. Short-term arsenic exposure (⪕ 24 h) can increase miRNA-21 and pSTAT3 expression, and decrease PDCD4 expression. Moreover, long-term arsenic exposure (> 24 h) can increase the miRNA-21, STAT3, and pSTAT3 expression, and decrease PDCD4 expression. We found that activation of miRNA-21 and pSTAT3 were most pronounced following long-term arsenic exposure at low doses, and the effects on PDCD4 expression were most pronounced following short-term arsenic exposure at low doses. miRNA-21 inhibitors increased the expression of tumor suppressor genes PDCD4, PTEN, and Spry1 and miRNA-21-mimics suppressed the expression of these tumor suppressor genes.</p><p><b>CONCLUSION</b>Arsenic can cause cancer by activating miRNA-21 and inhibiting the expression of PDCD4, PTEN, and Spry1.</p>

The application of poly (2-ethyl-2-oxazoline) in drug delivery system / 药学学报

Poly(2-ethyl-2-oxazoline) (PEOz), a hydrophilic long-chain polymer synthesized by living cationic ring-opening isomerization polymerization of 2-ethyl-2-oxazoline, has the characteristics of low toxicity, biocompatibility, flexible chain, and modified expediently. PEOz is a potential substitute of polyethylene glycol (PEG) to render the ability of long-circulation, enhance cellular uptake and endosomal escape behaviors to PEOz modified drug delivery system. In this review, we summarized recent literature for the research progress of physicochemical properties, synthetic methods and the application of PEOz in drug delivery system.

Protective mechanisms of L-glutamate in gastrointestinal and drug development / 药学学报

L-Glutamate is an important amino acid in protein. It has many physiological functions, such as nutrient metabolism, energy supply, immune response, oxidative stress, and signaling pathways regulation. Recent studies have found that glutamate prevents gastrointestinal damage induced by non-steroidal anti-inflammatory drugs (NSAIDs) and promotes the healing of the lesions. It can inhibit colonization of Helicobacter pylori and cell apoptosis caused by NH3. Hence, it has a potential value in protection of gastrointestinal from damage caused by NSAIDs and Helicobacter pylori. This article provides a review of the metabolism and physiological function of glutamate and its protective mechanisms of gastrointestinal injury caused by NSAIDs and Helicobacter pylori, which may serve as a reference in the study of glutamate in drug development.

Preoperative Computed Tomography Angiography for Evaluation of Feasibility of Free Flaps in Difficult Reconstruction of Head and Neck.

BACKGROUND: Free tissue transfer has been advocated for anatomic and functional reconstruction of soft tissue defects after surgical removal of an extensive recurrent tumor and/or arising from previous irradiation in the head and neck. We report a case series of difficult reconstruction in the head and neck in which preoperative computed tomography (CT) angiography was utilized to evaluate the feasibility of free flap reconstruction. The preoperative radiological evaluation was performed to determine the availability of reliable vessels for anastomosis in free flap reconstruction. If none was found, regional pedicle flap or palliative treatment was applied instead. The use of CT angiography allows the clinical surgeon to perform precise surgical planning with greater confidence. This may improve surgical results, thereby potentially reducing perioperative morbidity. METHODS: Twenty CT angiograms were obtained from 20 patients. All patients were men with a mean age of 57.2 years (range, 42-72 years) and were scheduled to undergo difficult reconstruction in the head and neck. All patients (20/20 [100%]) suffered from oral squamous cell carcinoma. They had all received extensive operations and radiation therapy. Eighteen patients (18/20 [90%]) had completed a course of perioperative irradiation. The CT angiography reports were used to perform detailed preoperative surgical planning accordingly. The findings of CT angiography were classified into 3 groups: group I: normal CT angiography (patent recipient arteries) (Fig. 3); group II: abnormal CT angiography (recipient vessels were present but stenosis or atherosclerotic lesions were noted) (Fig. 4); group III: abnormal CT angiography with no patent recipient arteries in bilateral sides of the neck (Fig. 5); CT angiography results were correlated to the operative findings. RESULTS: The patients were classified into 3 groups based on the angiographic findings. Six patients (6/20 [30%]) were assigned to group I, 8 patients (8/20 [40%]) to group II, and 6 patients (6/20 [30%]) to group III. In groups I and III, all patients (12/12 [100%]) underwent the treatment according to the original preoperative detailed planning. No flap failure was noted in these 2 groups. In group II, 4 patients' recipient vessels (4/8 [50%]) possessed adequate blood flow intraoperatively; hence, microvascular free flaps were transplanted. Venous congestion in 1 case (1/4 [25%]) was noted. The remaining patients in this group (4/8 [50%]) underwent reconstruction with pedicle flaps rather than free flaps because of the lack of suitable target vessels intraoperatively. All flaps (4/4 [100%]) survived. Among the patients who were treated surgically, intraoperative findings were in accordance with those predicted by CT angiography. The total abnormality rate of CT angiography was 70%. Vascular abnormalities detected as a result of preoperative CT angiography led to changes in the operative plan in 50% (10/20) of the patients. CONCLUSIONS: The use of CT angiography should be considered for difficult microsurgical reconstructions in the head and neck. When an abnormality in vascular anatomy is detected by CT angiography, the surgeon is advised to consider altering the operative plan accordingly. This allows precise operation, thereby maximizing the possibility of an optimal outcome. Changing the operative plan based on results of CT angiography may also help to avoid the difficult situation in which the surgeon finds that there are no suitable recipient vessels for free flap reconstruction during the operation. In addition, CT angiography enables surgeons to conduct the preoperative surgical planning with greater confidence, thereby potentially enhancing the success rate of difficult reconstructions in the head and neck, which in turn would tend to improve the perioperative course for the patient and consequently to improve results by decreasing vascular complication rates.