Real-Time Megapixel Electro-Optical Imaging of THz Beams with Probe Power Normalization.

In this work, we present a simple method to improve the spatial uniformity of two-dimensional electro-optical imaging of terahertz (THz) beams. In this system, near-field THz images are captured by fully illuminating a sample using conventional optical microscope objectives. Unfortunately, due to the linear relationship between the optical probe power and the measured THz electric field, any spatial variation in probe intensity translates directly into a variation of the recorded THz electric field. Using a single normalized background frame information map as a calibration tool prior to recording a sequence of THz images, we show a full recovery of a two-dimensional flat field for various combinations of magnification factors. Our results suggest that the implementation of dynamic intensity profile correction is a promising avenue for real-time electro-optical imaging of THz beams.

Dual common bile duct examination with transcystic choledochoscopy and cholangiography in laparoscopic cholecystectomy for suspected choledocholithiasis: a prospective study.

BACKGROUND: Detection of common bile duct (CBD) stones is a major objective of intraoperative cholangiography (IOC) in laparoscopic cholecystectomy (LC). We evaluated the feasibility and safety of the routine use of transcystic choledochoscopy following IOC (dual common bile duct examination: DCBDE), which may improve the diagnostic accuracy of CBD stones and facilitate one-stage clearance, in LC for suspected choledocholithiasis. METHODS: Between May 2017 and November 2018, 38 patients with suspected choledocholithiasis were prospectively enrolled in this study, regardless of whether they underwent endoscopic sphincterotomy. Transcystic choledochoscopy was routinely attempted following IOC in LC. RESULTS: Five cases were excluded due to cholecystitis, bile duct anomaly, or liver cirrhosis. DCBDE was performed in the remaining 33 patients. The biliary tree was delineated by IOC in all patients. Subsequently, choledochosope was performed in 32 patients except for one who was found to have pancreaticobiliary malunion in IOC. The scope was successfully passed into the CBD in 25 (78.1%) patients. Choledochoscopy detected 3 (9.4%) cases of cystic duct stones and 4 (12.5%) cases of CBD stones which were not identified by IOC. All those stones were removed via cystic duct. There were no intra- and postoperative complications, except for two cases of wound infection and one case of a transient increase in serum amylase. CONCLUSIONS: DCBDE in LC is a safe and promising approach for intraoperative diagnosis and one-stage treatment of suspected choledocholithasis.

European Society for Clinical Nutrition and Metabolism (ESPEN) Malnutrition Criteria for Predicting Major Complications After Hepatectomy and Pancreatectomy.

BACKGROUND: Recently, diagnostic criteria for malnutrition have been proposed by the European Society for Clinical Nutrition and Metabolism (ESPEN). This study aimed to investigate the utility of the ESPEN malnutrition criteria as a predictor for major complications following hepatectomy and pancreatectomy. METHODS: Data were reviewed from 176 consecutive patients who underwent hepatectomy (n = 103) or pancreatectomy (n = 73) between November 2017 and December 2019. Patients were divided into two groups according to the ESPEN malnutrition criteria using a prospectively collected database. The clinical data and the surgical outcomes of patients in the malnourished and normal groups were retrospectively analyzed. RESULTS: Thirty-five (20%) patients were diagnosed with malnourishment according to ESPEN criteria. The malnourished group had a significantly low preoperative albumin concentration (p = 0.001). After hepatectomy, major complications (Clavien grade ≥ 3a) occurred significantly more frequently in the malnourished group than in the normal group (p = 0.013). Multivariate analysis indicated that operative duration ≥ 300 min (hazard ratio: 22.47, 95% CI: 2.17 to 232.73, p = 0.009) and malnourishment (hazard ratio: 14.56, 95% CI: 2.58 to 82.17, p = 0.002) were independently associated with major complications after hepatectomy. On the other hand, malnutrition was not associated with major complications after pancreatectomy. CONCLUSIONS: The ESPEN malnutrition criteria are a valuable predictor for major complications following hepatectomy.

Preoperative Controlling Nutritional Status plus Tumor Burden Score for the Assessment of Prognosis after Curative Liver Resection for Hepatocellular Carcinoma.

OBJECTIVE: There are no previous studies analyzing the prognostic predictive value of adding the tumor factor (i.e., Tumor Burden (TB) score) to the Controlling Nutritional Status (CONUT) score for patients with hepatocellular carcinoma (HCC). This study aimed to investigate the value of the CONUT plus TB (CONUT-TB) score as a prognostic predictor in patients with HCC undergoing liver resection. METHODS: Between 2015 and 2018, 96 consecutive patients with HCC underwent liver resection at our institution. Patients undergoing repeated liver resection and combined resection of a metastatic lesion were excluded. Patients were divided into 2 groups according to their CONUT-TB scores according to a cutoff value. Clinicopathologic prognostic factors for survival were analyzed using a database containing the medical records. RESULTS: The optimal cutoff value of the CONUT-TB score determined by using a minimum p value approach was 13 points. Among the 81 patients included in the analytic cohort, 71 patients had low (<13) and 10 patients had high (>13) CONUT-TB scores. The overall 3-year survival rate of patients following liver resection for HCC in the high-CONUT-TB group was significantly worse than that of patients in the low-CONUT-TB group (62.5 vs. 89.3%, p = 0.003). Multivariate analysis indicated that a high CONUT-TB score was independently associated with overall survival after liver resection (p = 0.010). CONCLUSION: The CONUT-TB score is a valuable predictor of survival in patients with HCC after liver resection.

A novel classification of aberrant right hepatic ducts ensures a critical view of safety in laparoscopic cholecystectomy.

BACKGROUND: Based on the spatial relationship of an aberrant right hepatic duct (ARHD) with the cystic duct and gallbladder neck, we propose a practical classification to evaluate the specific form predisposing to injury in laparoscopic cholecystectomy (LC). METHODS: We retrospectively investigated the preoperative images (mostly magnetic resonance cholangiopancreatography) and clinical outcomes of 721 consecutive patients who underwent LC at our institute from 2015 to 2018. We defined the high-risk ARHD as follows: Type A: communicating with the cystic duct and Type B: running along the gallbladder neck or adjacent to the infundibulum (the minimal distance from the ARHD < 5 mm), regardless of the confluence pattern in the biliary tree. Other ARHDs were considered to be of low risk. RESULTS: A high-risk ARHD was identified in 16 cases (2.2%): four (0.6%) with Type A anatomy and 12 (1.7%) with Type B. The remaining ARHD cases (n = 34, 4.7%) were categorized as low risk. There were no significant differences in the operative outcomes (operative time, blood loss, hospital stay) between the high- and low- risk groups. Subtotal cholecystectomy was applied in four cases (25%) in the high-risk group, a significantly higher percentage than the low-risk group (n = 1, 2.9%). In all patients with high-risk ARHD, LC was completed safely without bile duct injury or conversion to laparotomy. CONCLUSIONS: Our simple classification of high-risk ARHD can highlight the variants located close to the dissecting site to achieve a critical view of safety and may contribute to avoiding inadvertent damage of an ARHD in LC.

Terahertz microscopy assisted by semiconductor nonlinearities.

Terahertz (THz) imaging is currently based on linear effects, but there is great interest on how nonlinear effects induced by terahertz radiation could be exploited to provide extra information that is unobtainable by conventional imaging schemes. In particular, at field strengths on the order of 100 kV cm-1 to 1 MV cm-1, transmission properties inside semiconductor materials are largely affected at the picosecond time-scale, which raise the prospect of interesting nonlinear imaging applications at THz frequencies. Here, we experimentally investigate a method to map the two-dimensional nonlinear near-field distribution of an intense THz pulse passing through a thin film-doped semiconductor. By inserting a metamaterial structure between the electro-optic sensor and the doped film, the nonlinear near-field dynamics shows a different and enhanced contrast of the sample when compared to its linear counterpart.

Reconsideration of the relaxational and vibrational line shapes of liquid water based on ultrabroadband dielectric spectroscopy.

The Debye relaxation function is widely used to describe the large dielectric dispersion of ambient water around 20 GHz. However, from a theoretical point of view, this function is supposed to give incorrect predictions at high frequencies owing to the inappropriate assumption that inertial effects and intermolecular interactions do not affect the relaxation dynamics. Our ultrabroadband spectroscopy investigation of liquid water ranging from 500 MHz to 400 THz did demonstrate that the Debye function is inaccurate far above the microwave region. As an alternative, we tried a stochastic frequency modulation (SFM) model assuming instantaneous modification of the line shapes by the correlation with the surrounding system. The SFM relaxation model reproduced the experimental dielectric spectra up to 400 THz, showing that the hydrogen-bond dynamics are associated with the inertial effect that causes the non-exponential relaxation behaviour in a very short time (typically 25 fs). Within the framework of this relaxation model, the hindered translation modes are able to be approximated as fast modulation (homogeneous) line shapes because the interaction time with frequency modulation is too short. Compared with them, the libation mode is found to have a relatively slow modulation (inhomogeneous) origin, where disturbance of water hydrogen bonds induced by the hindered translations leads to fluctuations in the libration frequency.

Surgical outcome of laparoscopic hepatic resection for hepatocellular carcinoma: A matched case-control study with propensity score matching.

BACKGROUND: Although the number of reports on laparoscopic hepatic resection (LHR) has increased, studies of long-term outcomes regarding tumor recurrence and patient survival compared to the conventional open approach are limited. We evaluated the long-term survival and feasibility of LHR in patients with hepatocellular carcinoma (HCC). PATIENTS AND METHODS: A retrospective analysis was performed on the clinical data of patients who underwent hepatic resection for primary HCC between August 2000 and December 2013. The patients were divided into the LHR or open hepatic resection (OHR) groups. To control for selection bias in the two groups, propensity score matching was used at a 1:1 ratio based on the following covariates: Child-Pugh grade, tumour size, tumour number and tumour location. Following propensity score matching, thirty patients were included in the LHR group and thirty were included in the OHR group. RESULTS: The respective disease-free survival rates at 1 year, 3 years and 5 years were 78.4%, 61.1% and 38.9%, respectively, for the LHR group, and 89.3%, 57.5% and 47.9%, respectively, for the OHR group (P = 0.89). Also, the overall survival rates at 1 year, 3 years and 5 years were 96.4%, 68.2% and 62.5%, respectively, for the LHR group and 100.0%, 95.8% and 72.3%, respectively, for the OHR group (P = 0.44). CONCLUSIONS: According to our study, using propensity score matching, LHR for HCC is safe, feasible and comparative, with good oncologic results.

Focusing light with orbital angular momentum by circular array antenna.

We experimentally demonstrated focusing of light with orbital angular momentum (OAM) using an 8-element circular array of linear antennas. A spiral phase plate was used to generate a vortex beam with an OAM of h in the terahertz (THz) frequency region. We used THz near-field microscope to directly measure the phase vortex. A beam profile with a center dark spot and 2π phase rotation was observed in the small center gap region of the circular array antenna after the vortex beam excitation. The beam size is reduced by a factor of 3.4 ± 0.2. Half-wave resonance of the antenna element is responsible for the focusing function, indicating the scalability of this method to other frequency regions. This method will enable deep subwavelength focusing of light with OAM and eliminate the obstacle for the observation of the dipole forbidden transition with finite OAM of the vortex beam.

[A Case of Gastric Cancer Associated with Sjögren's Syndrome and Interstitial Pneumonia].

A 77-year-old man presented with poor appetite and dyspnea. A gastroendoscopy showed an advanced gastric cancer and a CT scan demonstrated diffuse interstitial infiltrative shadows in both lungs. Laboratory data showed high level of anti-SSA and anti-SSB antibodies, suggestive of interstitial pneumonia associated with Sjögren's syndrome. Although the levels of KL-6 and SP-D, markers of interstitial pneumonia, decreased after steroid and immunosuppressive therapy, the CT findings of interstitial pneumonia showed no remarkable change. Surgery was performed 2 months after the administration of prednisolone since the respiratory function had improved, allowing the administration of general anesthesia. A CT scan revealed remarkable improvement of the lung lesions after the surgery. Therefore, it is likely that Sjögren's syndrome and interstitial pneumonia manifested as paraneoplastic syndromes in the presented case.

[A Case of Bullous Pemphigoid Relieved after Sigmoid Colon Cancer Resection].

A 76-year-old man presented with many bullous lesions and erythema over his whole body in August 2014. Blood examination showed an elevation of the anti-BP180 antibody (658 U/mL) and a biopsied specimen of the skin lesions showed subepidermal bulla. A diagnosis of bullous pemphigoid was made based on the clinical and histological findings. Although 20 mg/day of prednisolone was administered, there was a poor response and consequently the dose of steroid was increased to 70 mg/day after 2 weeks. Bullous pemphigoid related to a malignant tumor was suspected. Colonic endoscopic examination revealed a sigmoid colon cancer and he underwent a sigmoidectomy with lymphodenectomy. The histopathological findings revealed a moderately-differentiated adenocarcinoma, pT1b, pN1, pStage Ⅲa, and he received adjuvant chemotherapy(UFT/ LV). The dermatological findings were rapidly relieved after tumor resection and anti-BP180 antibody was normalized. He has had no signs or symptoms of recurrence, both of the cancer and the bullous pemphigoid, for 9 months after the operation.

[A Case of Local Recurrence and Lung Metastasis from a Rectal Cancer Treated with Systemic Chemotherapy and Cyberknife].

A 73-year-old man underwent abdominoperineal resection for a rectal cancer. He developed a hip pain 3 years and 6 months after the surgery. A CT scan revealed a local recurrence in the perineum and multiple lung metastases in the bilateral lung. He received systemic chemotherapy consisting of XELOX with bevacizumab. Thereafter, the hip pain was slightly relieved. The hip pain worsened 1 year and 6 months after the recurrence. The border between the perineal tumor and skin was very narrow, and conventional radiation therapy could cause a perineal skin necrosis and subsequent poor wound healing. Therefore, we selected a Cyberknife treatment. The hip pain was relieved and a CT scan showed a reduction of the perineal tumor's size after the Cyberknife treatment. A Cyberknife treatment may be effective and promising as palliation for patients with local recurrence of rectal cancer.

Superradiant decay of cyclotron resonance of two-dimensional electron gases.

We report on the observation of collective radiative decay, or superradiance, of cyclotron resonance (CR) in high-mobility two-dimensional electron gases in GaAs quantum wells using time-domain terahertz magnetospectroscopy. The decay rate of coherent CR oscillations increases linearly with the electron density in a wide range, which is a hallmark of superradiant damping. Our fully quantum mechanical theory provides a universal formula for the decay rate, which reproduces our experimental data without any adjustable parameter. These results firmly establish the many-body nature of CR decoherence in this system, despite the fact that the CR frequency is immune to electron-electron interactions due to Kohn's theorem.

[A case of colorectal cancer with pelvic recurrence treated by systemic chemotherapy and radiotherapy].

A 63-year-old man who had a history of rectal cancer and was treated with low anterior resection in February 2006, presented with liver metastases in September 2007 and underwent right anterior sectionectomy of the liver. He developed a pelvic wall recurrence with buttock pain in September 2009. This was treated with conventional radiation therapy and Cyber- Knife. The buttock pain was relieved after CyberKnife treatment and the patient received systemic chemotherapy in the outpatient clinic. Subsequently, he developed a left sacral recurrence with buttock pain and gait disturbance in August 2013. Since the tumor was located close to the field previously subjected to radiotherapy, we opted for CyberKnife treatment again. Although the pain subsided, our patient died of lymphangitic carcinomatosis in April 2014, 7 years and 2 months after the surgery. In this case, CyberKnife was effective in treating pelvic recurrence with pain, and thus, may have a significant role to play in the multidisciplinary treatment of metastatic colorectal cancer.

[Four cases of bevacizumab-related gastrointestinal perforation].

We report 4 cases of gastrointestinal perforation associated with systemic administration of bevacizumab. Case 1: A 51- year-old man with colorectal cancer (CRC) received mFOLFOX+bevacizumab (Bev). A small intestinal perforation occurred 7 days after Bev administration (Bev-a) and was successfully treated with omental packing. Case 2: A 50-year-old woman with CRC received capecitabine+Bev. A small intestinal perforation was detected 5 days after Bev-a, and was successfully treated with primary suture and an omental flap. Case 3: A 74-year-old man with CRC received CapeOX+Bev. A duodenal perforation occurred on the same day as Bev-a, but could be treated conservatively. Case 4: A 57-year-old man with lung cancer received DTX+Bev. A small intestinal perforation occurred 13 days after Bev-a, but this could be managed with primary suture and an omental flap. The gastrointestinal perforation presented with mild abdominal pain and was detected within 14 days after Bev-a in each of these 4 cases. Three patients were successfully treated with only minimal surgical procedures and 1 patient could be managed with conservative treatment for a perforated duodenal ulcer.

Phase-resolved measurement and control of ultrafast dynamics in terahertz electronic oscillators.

As a key component for next-generation wireless communications (6 G and beyond), terahertz (THz) electronic oscillators are being actively developed. Precise and dynamic phase control of ultrafast THz waveforms is essential for high-speed beam steering and high-capacity data transmission. However, measurement and control of such ultrafast dynamic process is beyond the scope of electronics due to the limited bandwidth of the electronic equipment. Here we surpass this limit by applying photonic technology. Using a femtosecond laser, we generate offset-free THz pulses to phase-lock the electronic oscillators based on resonant tunneling diode. This enables us to perform phase-resolved measurement of the emitted THz electric field waveform in time-domain with sub-cycle time resolution. Ultrafast dynamic response such as anti-phase locking behaviour is observed, which is distinct from in-phase stimulated emission observed in laser oscillators. We also show that the dynamics follows the universal synchronization theory for limit cycle oscillators. This provides a basic guideline for dynamic phase control of THz electronic oscillators, enabling many key performance indicators to be achieved in the new era of 6 G and beyond.

Broadband terahertz polarizers with ideal performance based on aligned carbon nanotube stacks.

We demonstrate a terahertz polarizer built with stacks of aligned single-walled carbon nanotubes (SWCNTs) exhibiting ideal broadband terahertz properties: 99.9% degree of polarization and extinction ratios of 10(-3) (or 30 dB) from ~0.4 to 2.2 THz. Compared to structurally tuned and fragile wire-grid systems, the performance in these polarizers is driven by the inherent anistropic absorption of SWCNTs that enables a physically robust structure. Supported by a scalable dry contact-transfer approach, these SWCNT-based polarizers are ideal for emerging terahertz applications.

Giant tunable Faraday effect in a semiconductor magneto-plasma for broadband terahertz polarization optics.

We report on a giant Faraday effect in an electron plasma in n-InSb probed via polarization-resolved terahertz (THz) time-domain spectroscopy. Polarization rotation angles and ellipticities reach as large as π/2 and 1, respectively, over a wide frequency range (0.3-2.5 THz) at magnetic fields of a few Tesla. The experimental results together with theoretical simulations show its promising ability to construct broadband and tunable THz polarization optics, such as a circular polarizer, half-wave plate, and polarization modulators.

Laparoscopic surgery in the management of hypersplenism and esophagogastric varices: our initial experiences.

BACKGROUND: Owing to recent advances in laparoscopic surgery, devascularization of the upper stomach with splenectomy (Spx) or Hassab's procedure (Has) as well as Spx for patients with portal hypertension have been attempted laparoscopically in some facilities, the results of which have been reported. This article describes the authors' surgical techniques and their results. METHODS: Between August 1999 and August 2010, the authors treated 110 cases of portal hypertension with Spx or Has. Among these patients, 56 who simultaneously underwent additional major operations were eliminated from the study, leaving 54 patients eligible. They included 38 with open surgeries and 16 with laparoscopic surgeries, which consisted of 10 splenectomies and 6 Has operations. The perioperative data for the 2 groups were compared. RESULTS: Purely laparoscopic Spx (L-Spx) was completed for 9 patients. Conversion from laparoscopic to hand-assisted laparoscopic surgery (HALS) was necessary for 1 patient because of poor visualization. Operative time was significantly longer in L-Spx than in the open method. Postoperative hospital stays were shorter for L-Spx. HALS was used for all 6 laparoscopic Has patients. There was no conversion from the laparoscopic to the open method. Operative time was significantly longer for laparoscopic Has than for open Has. Postoperative complication rates were significantly reduced, and postoperative hospital stays were significantly shorter for laparoscopic Has. CONCLUSIONS: Although the data are still preliminary, laparoscopic surgery for patients with portal hypertension may prove to be a successful strategy.

Passive mode-locking and terahertz frequency comb generation in resonant-tunneling-diode oscillator.

Optical frequency combs in the terahertz frequency range are long-awaited frequency standards for spectroscopy of molecules and high-speed wireless communications. However, a terahertz frequency comb based on a low-cost, energy-efficient, and room-temperature-operating device remains unavailable especially in the frequency range of 0.1 to 3 THz. In this paper, we show that the resonant-tunneling-diode (RTD) oscillator can be passively mode-locked by optical feedback and generate a terahertz frequency comb. The standard deviation of the spacing between the comb lines, i.e., the repetition frequency, is reduced to less than 420 mHz by applying external bias modulation. A simulation model successfully reproduces the mode-locking behavior by including the nonlinear capacitance of RTD and multiple optical feedback. Since the mode-locked RTD oscillator is a simple semiconductor device that operates at room temperature and covers the frequency range of 0.1 to 2 THz (potentially up to 3 THz), it can be used as a frequency standard for future terahertz sensing and wireless communications.