Native-lung complications following single-lung transplantation for interstitial lung disease: an in-depth analysis.

BACKGROUND: Interstitial lung disease (ILD) represents a heterogeneous group of lung disorders characterized by fibrotic lung tissue changes. In regions with severe donor shortages, single-lung transplantation (SLTx) is often preferred over bilateral lung transplantation for advanced ILD. However, temporal changes and complications in the retained native lung remain poorly understood. METHODS: A retrospective analysis of 149 recipients who had undergone SLTx was conducted, including 34 ILD SLTx recipients. Native-lung volume, radiological alterations, and perfusion were assessed at distinct post-SLTx time points. Statistical analyses compared ILD and non-ILD SLTx groups. RESULTS: Our study revealed a progressive reduction in native-lung volume over time, accompanied by radiographic deterioration and declining perfusion. Complications in the retained native lung were observed, such as pneumothorax (29.4%), pulmonary aspergillosis (11.8%), and acute exacerbation (8.9%). Long-term survival rates were similar between ILD and non-ILD SLTx recipients. CONCLUSIONS: This study illuminates the unique challenges and complications with respect to the native lung following SLTx for ILD. Ongoing monitoring and tailored management are essential. Despite limitations, this research contributes to our understanding of the temporal progression of native-lung complications post-SLTx for ILD, underscoring the need for further investigation.

Evolution of Pleural Solitary Fibrous Tumors Causing Severe Hypoglycemia after Exceptionally Long Asymptomatic Periods: Report of Two Surgical Cases.

Non-islet cell tumor hypoglycemia (NICTH) is one of the paraneoplastic syndromes manifesting severe hypoglycemia caused by aberrant production of high-molecular-weight insulin-like growth factor 2 (big-IGF2). Two surgical cases of extremely large thoracic solitary fibrous tumors (SFT) with unusual history of NICTH are presented. One case manifested severe hypoglycemia after four years of the first complete surgical resection of the tumor with potential malignant transformation, and the other case showed severe hypoglycemia after ten years of the first detection of the tumor. Meticulous laboratory testing, including serum endocrinological tests and western immunoblotting before and after surgery was performed, and both cases were diagnosed as NICTH. Both patients underwent open thoracic surgery. The patients showed normal glucose and hormone levels immediately after the resection of responsible tumors with elevated blood insulin concentration. SFTs are generally considered benign; however, life-threatening hypoglycemia can happen regardless of treatment. Careful follow-up of the tumor growth is warranted.

Morphological Predictors of Primary Lung Cancer among Part-Solid Ground-Grass Nodules on High-Resolution CT.

Recent advancements in computed tomography (CT) scanning have improved the detection rates of peripheral pulmonary nodules, including those with ground-glass opacities (GGOs). This study focuses on part-solid pure ground-glass nodules (GGNs) and aims to identify imaging predictors that can reliably differentiate primary lung cancer from nodules with other diagnoses among part-solid GGNs on high-resolution CT (HRCT). A retrospective study was conducted on 609 patients who underwent surgical treatment or observation for lung nodules. Radiological findings from pre-operative HRCT scans were reviewed and several CT imaging features of part-solid GGNs were examined for their positive predictive value to identify primary lung cancer. The proportions of the nodules with a final diagnosis of primary lung cancer were significantly higher in part-solid GGNs (91.9%) compared with solid nodules (70.3%) or pure GGNs (66.7%). Among CT imaging features of part-solid GGNs that were evaluated, consolidation-to-tumor ratio (CTR) < 0.5 (98.1%), pleural indentation (96.4%), and clear tumor border (96.7%) had high positive predictive value to identify primary lung cancer. When two imaging features were combined, the combination of CTR < 0.5 and a clear tumor border was identified to have 100% positive predictive values with a sensitivity of 40.8%. Thus we conclude that part-solid GGNs with a CTR < 0.5 accompanied by a clear tumor border evaluated by HRCT are very likely to be primary lung cancers with an acceptable sensitivity. Preoperative diagnostic procedures to obtain a pathological diagnosis may potentially be omitted in patients harboring such part-solid GGNs.

Prognostic value of perioperative changes in the prognostic nutritional index in patients with surgically resected non-small cell lung cancer.

PURPOSE: This single-institution retrospective cohort study was conducted to assess the prognostic significance of perioperative changes in the prognostic nutritional index (PNI) in patients who underwent surgery for non-small cell lung cancer (NSCLC). METHODS: Clinicopathological data were collected from 441 patients who underwent lobectomy for NSCLC between 2010 and 2016.The PNI ratio (postoperative PNI/preoperative PNI) was used as an indicator of perioperative PNI changes. Prognostic differences were investigated based on PNI ratios. RESULTS: The optimal cut-off value of the PNI ratio for overall survival (OS) was set at 0.88 using a receiver operating characteristic curve. The PNI ratio was inversely related to a high smoking index, interstitial lung disease, and postoperative pulmonary complications. The 5-year OS rates for the high vs. low PNI ratio groups were 88.2% vs. 68.5%, respectively (hazard ratio [HR]: 3.04, 95% confidence interval [CI]: 1.90-4.86). Multivariable analysis revealed that a low PNI ratio was significantly associated with poor prognosis (HR: 2.94, 95% CI: 1.77-4.87). The PNI ratio was a more sensitive indicator than postoperative PNI status alone for identifying patients at high risk of mortality, particularly those with non-lung cancer causes. CONCLUSION: The perioperative PNI change is a significant prognostic factor for patients with NSCLC.

The CONUT score is associated with the pathologic grade in non-small cell lung cancer.

PURPOSE: Nutritional scores have been reported to be useful prognostic factors for various cancers. This study evaluated the usefulness of the preoperative controlling nutritional status (CONUT) score as a predictor of recurrence of non-small cell lung cancer (NSCLC). METHODS: The present study included 422 patients with stage I-IIIA NSCLC who underwent complete resection at Tohoku University Hospital between January 2010 and December 2016. The patients were divided into the low-CONUT and high-CONUT groups based on their CONUT scores. Overall survival (OS), recurrence-free survival (RFS), and cumulative recurrence rates in the low- and high-CONUT groups were evaluated retrospectively. RESULTS: One hundred forty-seven patients (34.8%) were assigned to the high-CONUT group. The high-CONUT group had a significantly worse performance status, pleural invasion, vascular invasion, and lung metastasis. In the whole cohort, the low-CONUT group showed better overall survival, recurrence-free survival, and a low cumulative recurrence rate in comparison to the high-CONUT group. There was no significant difference in prognosis or recurrence between the low- and high-CONUT groups after propensity score matching. CONCLUSION: Patients with a high CONUT score may be at high risk of recurrence because of the high frequency of pleural invasion, vascular invasion, and lung metastasis.

Long-term survival and clinical outcomes of delayed chest closure following lung transplantation.

PURPOSES: Delayed chest closure (DCC) is a widely accepted procedure in the context of lung transplantation (LTx); yet there are few reports detailing its long-term survival and clinical outcomes. METHODS: We reviewed the medical records of recipients who underwent deceased-donor lung transplantation (LTx) at Tohoku University Hospital. Long-term survival, including overall survival, freedom from chronic lung allograft dysfunction (CLAD), and CLAD-free survival and the clinical outcomes of graft function and physical performance and constitution were reviewed in recipients with DCC. RESULTS: Between 2009 and 2022, 116 patients underwent LTx, 33 of whom (28.4%) required DCC. The intra-and post-operative courses of the recipients who required DCC were more complicated than those of the recipients who underwent primary chest closure (PCC), with frequent volume reduction surgery and longer periods of invasive mechanical ventilation. Pulmonary vascular disease was considered a risk factor for these complications and DCC. Nonetheless, long-term survival and graft functions were comparable between the DCC and PCC groups. The physical performance and constitution of recipients who required DCC continued to improve, and by 2 years after transplantation, exhibited almost no difference from those who underwent PCC. CONCLUSIONS: In view of the profoundly complicated intra- and post-operative courses, DCC should be performed cautiously and only when clinically indicated, despite which it can result in equivalent long-term survival and acceptable outcomes to PCC.

Diverse and divergent functions of IL-32ß and IL-32γ isoforms in the regulation of malignant pleural mesothelioma cell growth and the production of VEGF-A and CXCL8.

In this study, we sought to elucidate the roles of the interleukin (IL)-32ß and IL-32γ in mesothelioma cell growth, and vascular endothelial growth factor (VEGF)-A and C-X-C motif chemokine ligand 8 (CXCL8) expression. IL-32 elicited a growth-promoting effect against one of the six mesotheliomas lines and exerted diverse regulatory functions in VEGF-A and CXCL8 secretion from mesotheliomas stimulated with or without IL-17A. Retroviral-mediated transduction of mesothelioma lines with IL-32γ resulted in enhanced IL-32ß expression, which facilitated or suppressed the in vitro growth, and VEGF-A and CXCL8 expression. Overexpressed IL-32ß-augmented growth and VEGF-A and CXCL8 production were mainly mediated through the phosphatidylinositol-3 kinase (PI3K) signaling pathway. On the other hand, overexpressed IL-32ß-deceased growth was mediated through mitogen-activated protein kinase (MAPK) pathway. NCI-H2373IL-32γ tumors grew faster than NCI-H2373Neo tumors in a xenograft model, which was associated with increased vascularity. These findings indicate that IL-32 are involved in the regulation of growth and angiogenic factor production in mesotheliomas.

Metabolic and Epigenetic Regulation of SMAD7 by STC1 Ameliorates Lung Fibrosis.

As shown in our previous studies, the intratracheal-administration of STC1 (stanniocalcin-1) ameliorates pulmonary fibrosis by reducing oxidative and endoplasmic reticulum stress through the uncoupling of respiration in a bleomycin-treated mouse model. However, the overall effect of STC1 on metabolism was not examined. Therefore, we first conducted a comprehensive metabolomics analysis to screen the overall metabolic changes induced by STC1 in an alveolar epithelial cell line using capillary electrophoresis time-of-flight mass spectrometry. The results were subsequently validated in multiple alveolar epithelial and fibroblast cell lines by performing precise analyses of each substance. STC1 stimulated glycolysis, acetyl-CoA synthesis, and the methionine and cysteine-glutathione pathways, which are closely related to the uncoupling of respiration, modulation of epigenetics, and reduction in oxidative stress. These results are consistent with our previous study. Subsequently, we focused on the inhibitory factor SMAD7, which exerts an antifibrotic effect and is susceptible to epigenetic regulation. STC1 upregulates SMAD7 in an uncoupling protein 2-dependent manner, induces demethylation of the SMAD7 promoter region and acetylation of the SMAD7 protein in human alveolar epithelial and fibroblast cell lines and a bleomycin-treated mouse model, and subsequently attenuates fibrosis. The antifibrotic effects of STC1 may partially depend on the regulation of SMAD7. In the evaluation using lung tissue from patients with idiopathic pulmonary fibrosis, SMAD7 expression and acetylation were high in the alveolar structure-preserving region and low in the fibrotic region. The intratracheal administration of STC1 may prevent the development of pulmonary fibrosis by regulating the metabolism-mediated epigenetic modification of SMAD7 in patients.

Outcome and prognostic factors after lung transplantation for bronchiectasis other than cystic fibrosis.

BACKGROUND: While lung transplant (LTX) can be an effective therapy to provide the survival benefit in selected populations, post-transplant outcome in LTX recipients with bronchiectasis other than cystic fibrosis (CF) has been less studied. Pseudomonas aeruginosa, often associated with exacerbations in bronchiectasis, is the most common micro-organism isolated from LTX recipients. We aimed to see the outcomes of patients with bronchiectasis other than CF after LTX and seek the risk factors associated with pre- and post-transplant Pseudomonas status. METHODS: Patients who underwent LTX at Tohoku University Hospital between January 2000 and December 2020 were consecutively included into the retrospective cohort study. Pre- and post-transplant prevalence of Pseudomonas colonization between bronchiectasis and other diseases was reviewed. Post-transplant outcomes (mortality and the development of chronic lung allograft dysfunction (CLAD)) were assessed using a Cox proportional hazards and time-to-event outcomes were estimated using the Kaplan-Meier method. RESULTS: LTX recipients with bronchiectasis experienced a high rate of pre- and post-transplant Pseudomonas colonization compared to other diseases with statistical significance (p < 0.001 and p < 0.001, respectively). Nevertheless, long-term survival in bronchiectasis was as great as non-bronchiectasis (Log-rank p = 0.522), and the bronchiectasis was not a trigger for death (HR 1.62, 95% CI 0.63-4.19). On the other hand, the chance of CLAD onset in bronchiectasis was comparable to non-bronchiectasis (Log-rank p = 0.221), and bronchiectasis was not a predictor of the development of CLAD (HR 1.88, 95% CI 0.65-5.40). CONCLUSIONS: Despite high prevalence of pre- and post-transplant Pseudomonas colonization, the outcome in LTX recipients with bronchiectasis other than CF was comparable to those without bronchiectasis.

Waiting time and mortality rate on lung transplant candidates in Japan: a single-center retrospective cohort study.

BACKGROUND: As lung transplantation (LTX) is a valuable treatment procedure for end-stage pulmonary disease, delayed referral to a transplant center should be avoided. We aimed to conduct a single-center analysis of the survival time after listing for LTX and waitlist mortality in each disease category in a Japanese population. METHODS: We included patients listed for LTX at Tohoku University Hospital from January 2007 to December 2020 who were followed up until March 2021. Pulmonary disease was categorized into the Obstructive, Vascular, Suppurative, Fibrosis, and Allogeneic groups. Risk factors for waitlist mortality were assessed using a Cox proportional hazards model. The Kaplan-Meier method was used to model time to death. RESULTS: We included 269 LTX candidates. Of those, 100, 72, and 97 patients were transplanted, waiting, and dead, respectively. The median time to LTX and time to death were 796 days (interquartile range [IQR] 579-1056) and 323 days (IQR 129-528), respectively. The Fibrosis group showed the highest mortality (50.9%; p < .001), followed by the Allogeneic (35.0%), Suppurative (33.3%), Vascular (32.1%), and Obstructive (13.1%) groups. The Fibrosis group showed a remarkable risk for waitlist mortality (hazard ratio 3.32, 95% CI 2.11-4.85). CONCLUSIONS: In Japan, the waiting time is extremely long and candidates with Fibrosis have high mortality. There is a need to document outcomes based on the underlying disease for listed LTX candidates to help determine the optimal timing for listing patients based on the estimated local waiting time.

[Anterior Mediastinal Cholesterin Granuloma Associated with Bilateral Pleurisy and Pericarditis].

The patient was a 41-year-old man. He was diagnosed with pleurisy and came to our hospital. The pleural effusion and pleurisy remained even after administration of sufficient doses of antibiotics. A thorough examination revealed an anterior mediastinal tumor. Six months later, pericarditis also developed. Autoimmune diseases, infections, and malignant diseases were suspected, but a definitive diagnosis could not be made. In order to confirm the diagnosis, anterior mediastinal tumor resection and pleural biopsy were performed. The anterior mediastinal tumor was diagnosed as cholesterin granuloma pathollogically. Cholesterin granuloma is a granuloma formed by deposition of cholesterin crystals and cholesterin granuloma occurring in the mediastinum is extremely rare.

[Assessment of Computed Tomography Sagittal Images for Early Diagnosis of Pulmonary Torsion after Lung Resection].

The incidence of postoperative pulmonary torsion is not frequent but it has a high mortality rate once it occurs, and prompt diagnosis and treatment are required. From past reports, it is considered effective to point out disruption of pulmonary blood flow by contrast-enhanced computed tomography (CT) examination for diagnosis. However, the comparison of pre- and post-operative plain CT images is considered to be useful in diagnosing lung torsion, and postoperative CT lung window setting sagittal images were examined in three cases of postoperative lung torsion. Results indicate that pulmonary torsion of the middle lobe after right lower lobectomy and the middle lobe after right upper lobectomy can be diagnosed by the present method.

[Ingenuity for Completion of Thoracoscopic Pulmonary Resection after Esophageal Cancer Treatment].

In recent years, with the improvement of diagnostic techniques and treatment outcomes, the number of lung cancer cases after esophageal cancer treatment has been increasing. In general, severe adhesions are expected in the right lung, during lung resection after esophageal cancer surgery. In this study, we reviewed intraoperative findings of lung resection with respect to the influence of different treatment methods for esophageal cancer, the site of adhesion formation for each lobe, and the techniques and precautions for lung resection. There were no difficulty in the left upper major segmentectomy. During the left lower lobectomy, the inflammation around the inferior pulmonary vein was noted. The adhesions between the reconstructed gastric tube and the inferior pulmonary vein were found during the right lower lobectomy. During the right upper lobectomy, severe adhesions between the lung and the superior vena cava as well as the gastric tube in the posterior mediastinum were observed, which should be paid much attention.

Positron emission tomography/computed tomography as a clinical diagnostic tool for anterior mediastinal tumors.

PURPOSE: The purpose of this study was to assess the usefulness of positron emission tomography/computed tomography (PET/CT) in the differential diagnosis of anterior mediastinal tumors. METHODS: A total of 94 patients with anterior mediastinal masses or nodules (male, n = 41; female, n = 53; age, 17-84 years) were retrospectively evaluated. All patients were evaluated by PET/CT and the masses or nodules were histologically diagnosed in our institution. RESULTS: Anterior mediastinal masses and nodules were classified into two disease categories: Low (thymic hyperplasia, thymoma, mature teratoma, and MALT lymphoma) and High (thymic carcinoid, thymic cancer, diffuse large B-cell lymphoma, T-cell lymphoblastic lymphoma, Hodgkin's lymphoma, and malignant germ cell tumors) groups. The sensitivity and specificity of maximum standardized uptake value (SUVmax) 7.5 for the detection of High group were 77% and 100%, respectively. The SUVmax distributions of the WHO histological thymoma types and Masaoka stage thymomas extensively overlapped. Masaoka stage III thymomas had significantly higher SUVmax than Masaoka stage I thymomas. Regarding the TNM classification, the SUVmax of T3 and T1b thymomas was higher than T1a thymoma. CONCLUSION: Although the SUVmax of each disease overlapped, PET/CT findings provided useful information for the differential diagnosis of anterior mediastinal masses.

[Successful Multidisciplinary Treatment Accomplished by Collaboration of Multiple Clinical Departments for Synchronous Quadruple Cancer].

A 60-year-old man consulted a clinic complains of sore throat. Squamous cell carcinoma of the hypopharynx and adenocarcinoma of the stomach were pointed out and he was refered to our hospital. As a result of detailed systemic examination, squamous cell carcinoma of the esophagus and squamous cell carcinoma of the right lung were also pointed out, which led to a diagnosis of synchronous quadruple cancer. On the basis of discussions among multiple clinical departments, systemic chemotherapy with cisplatin(CDDP), fluorouracil (5-FU) and docetaxel(DTX) was preceded locolegional therapies. After that, complete thoracoscopic right lower lobectomy and then a laparoscopic distal gastrectomy was performed. Radiation therapy was applied for hypopharyngeal cancer. Finally, endoscopic submucosal dissection for esophageal cancer was performed. Twenty months have passed since the last treatment, the patient is alive with a relapse-free condition.

Bone marrow mesenchymal stromal cells protect allograft lung transplants from acute rejection via the PD-L1/IL-17A axis.

PURPOSE: Using a rat model of allograft lung transplantation, we investigated the effectiveness of mesenchymal stromal cells (MSCs) as prophylactic and therapeutic agents against the acute rejection of lung grafts. METHODS: Lung grafts were harvested from donor rats and transplanted orthotopically into major histocompatibility complex-mismatched rats. MSCs were administered to the recipients once (on day 0) or twice (on days 0 and 3) after transplantation. The grade of acute rejection was evaluated both macroscopically and microscopically 6 days after transplantation. To elucidate the related mechanism, mRNA levels of inflammatory cytokines and immunomodulatory receptors in the transplanted grafts were measured using quantitative RT-PCR. RESULTS: The lung graft tissue from the rats that received MSCs post-surgically was protected from acute rejection significantly better than that from the untreated controls. Notably, the rats administered MSCs twice after surgery exhibited the least signs of rejection, with a markedly upregulated mRNA level of PD-L1 and a downregulated mRNA level of IL-17A. CONCLUSION: This study assessed MSC protection of lung allografts from acute rejection by modulating T cell activity via enforced expression of PD-L1 in transplants and downregulation of IL-17A.

Mesenchymal stem cells attenuate ischemia-reperfusion injury after prolonged cold ischemia in a mouse model of lung transplantation: a preliminary study.

PURPOSE: Mesenchymal stem cells (MSCs) suppress inflammation and immune responses. We conducted this study to find out if MSCs attenuate ischemia-reperfusion injury in a mouse model of lung transplantation. METHODS: C57BL/6J mouse lungs perfused with low-potassium dextran glucose solution were preserved at 4 °C for 18 h. Human MSCs were slowly injected into the left pulmonary artery of the lung grafts, and orthotopic left lung transplantation was then performed. The lung isografts were reperfused for 6 h, and bronchoalveolar lavage fluid (BALF) from the left lung graft was collected. We measured the protein concentration, cell count, and proinflammatory cytokine concentrations in the BALF. RESULTS: The protein concentration and cell count in the BALF were significantly lower in the MSC-administered grafts than in the PBS-administered controls. Concentrations of proinflammatory cytokines, including IL-1ß, IL-17A, and TNF-α, in BALF tended to be lower in the MSC-administered grafts than in the controls, but the difference was not significant. CONCLUSION: The pre-transplant administration of MSCs via the pulmonary artery of the lung graft attenuated ischemia-reperfusion injury after prolonged cold ischemia in this mouse model of lung transplantation.

[Current Status of Preoperative Professional Oral Care by Dentists for Elderly Patients Undergoing Lung Resection and Occurrence of Postoperative Pneumonia].

Pneumonia in elderly people is mainly caused by silent aspiration due to an age-related impairment of cough and swallowing reflexes. Because most of the patients with lung cancer are elderly people, we hypothesized that the age-related impairment of these protective reflexes might exist or occur in patients undergoing lung surgery, and cause postoperative pneumonia. We revealed that many elderly patients showed depressed swallowing reflex even before surgery and transient attenuation of cough reflex after surgery, and that postoperative pneumonia occurred only in the patients whose cough and/or swallowing reflex was abnormal postoperatively. Then, we prospectively showed that 30 elderly patients who received perioperative intensive oral care, including professional assessment of oral status, dental cleaning, and patient education for self-oral care by dentists, followed by intensive oral care by intensive care unit nurses, and encouragement of self-oral care by floor nurses, did not develop pneumonia after lung resection. In this study, we retrospectively reviewed the execution status of professional oral care by dentists and the occurrence of postoperative pneumonia in 159 consecutive patients aged 65 or older undergoing lung resection from 2013 to 2014. Thoracic surgeons in our institute asked dentists to provide professional oral care before lung resection only in 30.3% of the subjects in 2013, and 45.8% in 2014. Postoperative pneumonia occurred in 3 out of 76 subjects(3.9%)in 2013, and 1 out of 83(1.2%) in 2014. In 2013, 1 patient who did not receive preoperative professional oral care developed aspiration pneumonia postoperatively followed by acute exacerbation of idiopathic pulmonary fibrosis and in-hospital death. We need to make an effective system to provide preoperative professional oral care by dentists especially for elderly patients and high-risk patients before lung resection.

Preoperative saline-filled computed tomography thoracography for awake video-assisted thoracic surgery: report of three cases.

Awake video-assisted thoracic surgery (VATS) is a therapeutic option for patients with intractable secondary spontaneous pneumothorax (SSP) complicated by impaired pulmonary function. The preoperative identification of air leak points is one of the keys to the success of this procedure. We describe how we performed saline-filled computed tomography (CT) thoracography to detect pleural fistulae in three patients with intractable SSP. Saline-filled CT thoracography showed bubble signs in two patients and an air-water level in bulla in one patient. The preoperative identification of air leak points resulted in successful awake VATS for all three patients. Our experience demonstrates that saline-filled CT thoracography is a useful diagnostic tool for SSP, especially when used in preparation for awake VATS when minimally invasive procedures are desirable.

[Effectiveness of a Simulation of the Donor Surgery with Other Extraction Teams to Improve Various Problems in Pulmonary Extraction from a Brain-dead Donor].

The pulmonary extraction from a brain-dead donor is one of the important elements for the success of lung transplantation, but the current scarcity of practical training opportunities is a major problem. We performed a simulation of the donor surgery of multiple organs using a pig with other extraction teams to provide more training opportunities. The effectiveness of this simulation lies in its potential to improve the surgical procedure;furthermore, it may solve problems associated with communicating with other extraction teams. However, it is difficult to judge whether the donor lung is suitable for transplantation, as it would be inappropriate to use such a lung for simulation in training. Since this simulation system is considered to be effective to solve various problems in the current donor surgery, it should be available more frequently to improve a technical level of the donor surgery and to aid surgeons in the rapid implementation of next-generation techniques.