Sung Kwan Shin

A Review of the Polarization-Nulling Technique for Monitoring Optical-Signal-to-Noise Ratio in Dynamic WDM Networks

The polarization-nulling technique utilizes the different properties of optical signal and amplified spontaneous emission (ASE) noise for accurate monitoring of the optical-signal-to-noise ratio (OSNR) in dynamic optical networks. However, the performance of this technique is bound to be deteriorated if the signal is depolarized by polarization-mode dispersion and/or nonlinear birefringence or the ASE noise is partially polarized due to polarization-dependent loss (PDL) in the transmission link. The authors analyze these effects on the performance of the polarization-nulling technique and introduce several techniques to overcome these problems. These improved versions of the polarization-nulling techniques could monitor the OSNR with accuracy of better than plusmn1 dB, even when the differential group delay is as large as 60 ps. These techniques could also negate the effect of the signal depolarization caused by nonlinear birefringence in a highly nonlinear transmission link. The effect of the partially polarized ASE noise due to PDL is found to be not severe in most cases, as long as the PDL/span is smaller than 0.2 dB. To verify the possibility of using the polarization-nulling technique in real systems, the OSNR of the wavelength-division-multiplexed (WDM) signals transmitted through a 120-km-long aerial fiber link is measured for one week. No significant degradation in the monitoring accuracy is observed during this long-term measurement. In addition, the performance of the polarization-nulling technique in an ultralong-haul transmission link is evaluated by using a 640-km-long recirculating loop. The results show that this technique could accurately measure the OSNR in the transmission link longer than 3200 km. From these results, the authors conclude that the polarization-nulling technique is well suited for monitoring the OSNR in dynamic WDM networks

Long-term outcome of early gastric cancer after endoscopic submucosal dissection: Expanded indication is comparable to absolute indication

BACKGROUND Endoscopic submucosal dissection has become widely used for early gastric cancer with an expanded indication, although there is no strong consensus. We aimed to compare the clinical and long-term oncological outcome after endoscopic submucosal dissection according to indication. METHODS Retrospective review of 1152 patients with 1175 lesions who had undergone endoscopic submucosal dissection for early gastric cancer at tertiary educational hospital in Korea, between March 2005 and November 2011. Of these, 366 and 565 lesions were included in the absolute and expanded indication groups, respectively. RESULTS En bloc resection rates were not significantly different between the absolute and expanded indication groups. The complete resection rate was higher in the absolute indication group versus the expanded indication group (94.8% vs. 89.9%, respectively; P=0.008). In the expanded indication group, complete resection rate was higher in the differentiated versus undifferentiated tumour subgroups (92.9% vs. 78.4%, respectively; P<0.001). Recurrence rates were 7.7% in the absolute indication group vs. 9.3% in the expanded indication group (P=0.524). Disease-free survival was not significantly different between the two indication groups (P=0.634). CONCLUSIONS Endoscopic submucosal dissection for early gastric cancer with expanded indication is a feasible approach to disease management. Periodic endoscopic follow-up is necessary to detect cancer recurrence.

High microsatellite instability predicts good prognosis in intestinal-type gastric cancers.

Background and Aim:  A subset of gastric cancers showed high microsatellite instability (MSI‐H). The reported clinicopathological features of MSI‐H gastric cancers are heterogeneous, and specific factors associated with prognosis have not been identified.

A Pilot Study of Sequential Capsule Endoscopy Using MiroCam and PillCam SB Devices with Different Transmission Technologies.

BACKGROUND/AIMS Studies have investigated the use of different types of radiofrequency capsules for comparison or sequential capsule endoscopy, but none have compared the MiroCam device - which utilizes a novel data transmission technology - with other capsules. This study compared the feasibility of sequential capsule endoscopy using the MiroCam and PillCam SB devices, which employ different transmission technologies. METHODS Patients with diseases requiring capsule endoscopy were enrolled. After a 12-hour fast, one randomly selected capsule was swallowed. The second capsule was swallowed once fluoroscopy had indicated that the first capsule had migrated below the gastric outlet. RESULTS The total operating time in 24 patients was 702+/-60 min (mean+/-SD) for the MiroCam and 446+/-28 min for the PillCam SB (p<0.0001). The rate of a complete examination to the cecum was 83.3% for the MiroCam and 58.3% for the PillCam SB (p=0.031). Diagnostic yields for the MiroCam, PillCam SB, and sequential capsule endoscopy were 45.8%, 41.7%, and 50.0%, respectively. The agreement rate between the two capsules was 87.5%, with a kappa value of 0.74. Electrical interference in data transmission between the two capsules was not observed, but temporary visual interferences were observed in seven patients (29.2%). CONCLUSIONS Sequential capsule endoscopy with the MiroCam and PillCam SB produced slight but nonsignificant increases in the diagnostic yield, and the two capsules did not exhibit electrical interference. A larger trial is necessary for elucidating the usefulness of sequential capsule endoscopy.

Thalidomide Suppresses the Interleukin 1β‐Induced NFκB Signaling Pathway in Colon Cancer Cells

Abstract: Thalidomide has been shown to have both antiinflammatory and antiangiogenic effects in several diseases. However, its cellular target and mechanism of action are poorly understood. We investigated the action mechanism of thalidomide through the NFκB pathway. Thalidomide inhibited interleukin (IL) 1β‐induced NFκB transcriptional activation and IL‐8 production in Caco‐2 colon cancer cells. In addition, thalidomide suppressed NFκB nuclear translocation, IκB degradation, and NFκB‐inducing kinase (NIK)‐induced NFκB transcriptional activation. These results suggest that the molecular target of the effects of thalidomide may be IκB phosphorylation by IκB kinase (IKK), whose activation follows NIK activation and precedes IκB degradation in the NFκB pathway.

Undifferentiated histology after endoscopic resection may predict synchronous and metachronous occurrence of early gastric cancer

Background: Endoscopic resection (endoscopic mucosal resection, EMR, and endoscopic submucosal dissection, ESD) has been accepted worldwide as a less invasive standard treatment for early gastric cancer (EGC). However, the risk of synchronous and metachronous gastric cancer developing in the post-endoscopic resection patient has become a major problem. We investigated the incidence and characteristics of synchronous and metachronous multiple gastric cancers in a retrospective study of patients with EGC after endoscopic resection. Patients and Methods: We studied the clinicopathological features of 235 patients with EGC who had undergone endoscopic resection and were periodically followed up using endoscopic examinations (181 with a single lesion, 34 synchronous multiple lesions, and 20 metachronous multiple lesions). Results: The overall incidence of synchronous and metachronous multiple gastric cancer was 14.5 and 8.5%, respectively, during a follow-up of 12–77 (median 26.5) months. Undifferentiated histology of the primary lesion was related to the occurrence of synchronous gastric cancer (p < 0.001). Undifferentiated histology and upper location of the primary lesion were correlated with the occurrence of metachronous gastric cancer (p = 0.002, 0.001). Most synchronous and metachronous lesions were well to moderately differentiated (82.4 and 80.0%); however, the proportion with undifferentiated histology (including poorly differentiated carcinoma and signet ring cell carcinoma) in synchronous and metachronous gastric cancer was significantly higher than in single gastric cancer (p = 0.008). Conclusions: Undifferentiated histology of EGC may predict the occurrence of synchronous and metachronous lesions after endoscopic resection.

Endoscopic management of anastomotic leakage after gastrectomy for gastric cancer: how efficacious is it?

Abstract Background. Anastomotic leak is a dreadful complication with a high mortality rate. The authors aimed to evaluate the efficacy of endoscopic closure of anastomotic dehiscence after gastrectomy in patients with gastric cancer. Methods. The authors retrospectively reviewed 33 patients with anastomotic leakage who had underdone endoscopic treatment among 5249 patients with gastric cancer who underwent radical total or subtotal gastrectomy. Methods of endoscopic closure included clipping with or without detachable snare, fibrosealant, Histoacryl® or stent insertion. Results of endoscopic treatment were categorized as complete, partial closure and failure. Results. The size of the tissue defect was the only factor that had statistically significant differences among the cases with complete closure, partial closure and failure (p = 0.005). For tissue defects smaller than 2 cm in size, complete closure was achieved in 19 (73.1%), partial closure in 5 patients (19.2%) and 2 failed (7.6%). For those larger than 2 cm in size, one (14.3%) was completely closed, four (57.1%) were partially closed and two (28.6%) failed. Conclusions. Endoscopic treatment for anastomotic dehiscence smaller than 2 cm in size had excellent success rate in this study.

Gastroduodenal Complications After Concurrent Chemoradiation Therapy in Patients With Hepatocellular Carcinoma: Endoscopic Findings and Risk Factors

PURPOSE Concurrent chemoradiation therapy (CCRT) is useful in advanced hepatocellular carcinoma (HCC), but little is known about radiation-induced gastroduodenal complications following therapy. To determine risk factors, we investigated the prevalence and patterns of gastroduodenal complications following CCRT using endoscopy. METHODS AND MATERIALS Enrolled in the study were 123 patients treated with CCRT for unresectable HCC between January 1998 and December 2005. Radiation-induced gastroduodenal complications were defined as radiation gastritis/duodenitis, radiation gastric/duodenal ulcer, or other gastroduodenal toxicity associated with radiation, based on Common Terminology Criteria for Adverse Events (CTCAE 3.0). Serious gastroduodenal complications were defined as events occurring within 12 months from completion of CCRT, those requiring prompt therapeutic intervention, or symptoms equivalent to Grade 3 or 4 radiation-related gastroduodenal toxicity, including nausea or vomiting, based on CTCAE 3.0. RESULTS A month after completion of CCRT, 65 (52.8%) patients displayed endoscopic evidence of radiation-induced gastroduodenal complications. Radiation gastric and duodenal ulcers were found in 32 (26.0%) and 20 (16.3%) patients, respectively; radiation gastritis and duodenitis were found in 50 (40.7%) and 42 (34.1%) patients, respectively. Radiation-related bleeding was observed in 13 patients (10.6%). Serious gastroduodenal complications occurred in 18 patients (14.6%) and were significantly more frequent in patients with liver cirrhosis than in those without cirrhosis (p=0.043). There were no radiation-related deaths. CONCLUSIONS Endoscopically detectable radiation-induced gastroduodenal complications were common in HCC following CCRT. Although serious complications were uncommon, the frequency was higher in patients with liver cirrhosis; thus, these patients should be closely monitored when receiving CCRT.

A multi-wavelength locker for WDM system

We demonstrate a simple technique to stabilize the wavelengths of WDM lasers using a synchronized etalon filter and a digital signal processing board. The results shows that the proposed technique could maintain the frequency stability of each WDM laser within 200 MHz.

Effects of stimulated Raman scattering on pilot-tone-based WDM supervisory technique

We report on the effects of stimulated Raman scattering (SRS) on the pilot-tone-based wavelength-division-multiplexing (WDM) monitoring technique. The SRS-induced ghost tones were measured after compensating the effects of erbium-doped fiber amplifiers (EDFAs) slow gain dynamics. Using these results, we estimated the maximum size of WDM network that the pilot-tone based monitoring technique could support.