Mechanism of Structure Variations at Rifted Margins in the Central Segment of South Atlantic:Insights from Numerical Modeling

Rifted margins in the central South Atlantic portray spatial variability in terms of preserved width and thickness,which relates to complex rift-related fault activities.However,there is still a lack of systematic and quantitative explanations for the causes of the variations that are observed along the paired rifts.To elucidate this issue,2D viscous-plastic thermomechanical numerical models are applied to capture the behavior of deformation,in which we investigate the effects of extensional rate,crustal strength and thickness on crust-mantle coupling,and timing of transition from rifting to breakup.Our numerical experiments demonstrate that crust-mantle decoupling accounts for crustal hyperextension,and that incorporating moderate-intensity rheology into lower crust may yield insights into the hyper-extended crust and asymmetric architecture observed in the central South Atlantic.The results also suggest that undulations in lithospheric basement cause asymmetric mantle upwelling.The lower crust of fold belts takes priority to be thermally weakened over craton and induces rift migration simultaneously.A new mechanism for the formation of failed rift is described,where the mechanical decoupling derived from thermally weakened lower crust gives access to dual rift migration.These results reinforce the interpretation on how crustal rheology shapes margins architectures and highlight the first-order effects of crust-mantle coupling.

Structural features and exploration targets of platform margins in Sinian Dengying Formation in Deyang-Anyue Rift, Sichuan Basin, SW China

Based on the seismic, logging, drilling and other data, the distribution, structural types and mound-shoal hydrocarbon accumulation characteristics of platform margins of the Sinian Dengying Formation in the Deyang-Anyue Rift and its periphery were analyzed. Four types of platform margins are developed in the Dengying Formation, i.e., single-stage fault-controlled platform margin, multi-stage fault-controlled platform margin, gentle slope platform margin, and overlapping platform margin. In the Gaoshiti West-Weiyuan East area, single-stage fault controlled platform margins are developed in the Deng 2 Member, which trend in nearly NEE direction and are shielded by faults and mudstones, forming fault-controlled–lithologic traps. In the Lezhi-Penglai area, independent and multi-stage fault controlled platform margins are developed in the Deng 2 Member, which trend in NE direction and are controlled by synsedimentary faults;the mound-shoal complexes are aggraded and built on the hanging walls of the faults, and they are shielded by tight intertidal belts and the Lower Cambrian source rocks in multiple directions, forming fault-controlled–lithologic and other composite traps. In the Weiyuan-Ziyang area, gentle slope platform margins are developed in the Deng 2 Member, which trend in NW direction;the mound-shoal complexes are mostly thin interbeds as continuous bands and shielded by tight intertidal belts in the updip direction, forming lithologic traps. In the Gaoshiti-Moxi-Yanting area, overlapping platform margins are developed in the Deng 2 and Deng 4 members;the mound-shoal complexes are aggraded and overlaid to create platform margin buildup with a huge thickness and sealed by tight intertidal belts and the Lower Cambrian mudstones in the updip direction, forming large-scale lithologic traps on the north slope of the Central Sichuan Paleouplift. To summarize, the mound-shoal complexes on the platform margins in the Dengying Formation in the Penglai-Zhongjiang area, Moxi North-Yanting area and Weiyuan-Ziyang area are large in scale, with estimated resources of 1.58×1012 m3, and they will be the key targets for the future exploration of the Dengying Formation in the Sichuan Basin.

Clinical outcomes for men with positive surgical margins after radical prostatectomy—results from the South Australian Prostate Cancer Clinical Outcomes Collaborative community-based registry

Objective Positive surgical margins(PSMs)after radical prostatectomy(RP)indicate failure of surgery to completely clear cancer.PSMs confer an increased risk of biochemical recurrence(BCR),but how more robust outcomes are affected is unclear.This study investigated factors associated with PSMs following RP and determined their impact on clinical outcomes(BCR,second treatment[radiotherapy and/or androgen deprivation therapy],and prostate cancer-specific mortality[PCSM]).Methods The study cohort included men diagnosed with prostate cancer(pT2-3b/N0/M0)between January 1998 and June 2016 who underwent RP from the South Australian Prostate Cancer Clinical Outcomes Collaborative database.Factors associated with risk of PSMs were identified using Poisson regression.The impact of PSMs on clinical outcomes(BCR,second treatment,and PCSM)was assessed using competing risk regression.Results Of the 2827 eligible participants,28%had PSMs—10%apical,6%bladder neck,17%posterolateral,and 5%at multiple locations.Median follow-up was 9.6 years with 81 deaths from prostate cancer recorded.Likelihood of PSM increased with higher pathological grade and pathological tumor stage,and greater tumour volume,but decreased with increasing surgeon volume(odds ratio[OR]:0.93;95%confidence interval[CI]:0.88-0.98,per 100 previous prostatectomies).PSMs were associated with increased risk of BCR(adjusted sub-distribution hazard ratio[sHR]2.5;95%CI 2.1-3.1)and second treatment(sHR 2.9;95%CI 2.4-3.5).Risk of BCR was increased similarly for each PSM location,but was higher for multiple margin sites.We found no association between PSMs and PCSM.Conclusion Our findings support previous research suggesting that PSMs are not independently associated with PCSM despite strong association with BCR.Reducing PSM rates remains an important objective,given the higher likelihood of secondary treatment with associated comorbidities.

Subducting passive continental margins with crustal (ultra)mafic intrusions: An underappreciated mechanism for recycling water back into the mantle

It is well known that outer rise bending-assisted oceanic plate hydration is an important mechanism for transporting substantial amounts of water into the mantle.A key question is:Are there other equally or more important water transport mechanisms?Here we propose,for the first time,that subducting passive continental margins,particularly those with crustal(ultra)mafic intrusions,play a critical role in recycling water back into the mantle.Evidence for this mechanism is the exceptionally high outer rise seismicity observed in a subducting passive continental margin(i.e.,the northeastern South China Sea continental margin)near the northern Manila trench,characterized by a high-velocity lower crust that has been attributed to(ultra)mafic intrusions.Our interpretation of this correlation between high outer rise seismicity and lower crust(ultra)mafic intrusions is that(ultra)mafic intrusions alter the crustal rheology and increase brittle deformation in the lower crust in this region,thereby promoting lithospheric fracturing and plate hydration,which is evidenced by increased outer rise seismicity.

A three-dimensional Moho depth model beneath the Yemeni highlands and rifted volcanic margins of the Red Sea and Gulf of Aden, Southwest Arabia

Knowing Moho discontinuity undulation is fundamental to understanding mechanisms of lithosphereasthenosphere interaction, extensional tectonism and crustal deformation in volcanic passive margins such as the study area, which is located in the southwestern corner of the Arabian Peninsula bounded by the Red Sea and the Gulf of Aden. In this work, a 3D Moho depth model of the study area is constructed for the first time by inverting gravity data from the Earth Gravitational Model(EGM2008) using the ParkerOldenburg algorithm. This model indicates the shallow zone is situated at depths of 20 km to 24 km beneath coastal plains, whereas the deep zone is located below the plateau at depths of 30 km to 35 km and its deepest part coincides mainly with the Dhamar-Rada ’a Quaternary volcanic field. The results also indicate two channels of hot magmatic materials joining both the Sana’a-Amran Quaternary volcanic field and the Late Miocene Jabal An Nar volcanic area with the Dhamar-Rada’a volcanic field. This conclusion is supported by the widespread geothermal activity(of mantle origin) distributed along these channels,isotopic data, and the upper mantle low velocity zones indicated by earlier studies.

The trade margins of Chinese agricultural exports to ASEAN and their determinants

How do Chinese agricultural exports to ASEAN（Association of Southeast Asian Nations） evolve？ And what factors affected the evolution pattern？ This study measures the trade margins of Chinese agricultural exports to ASEAN by utilizing the 2000-2015 Harmonized System＇s six-digit agricultural trade data, and further analyzes their determinants by developing an augmented gravity model of international trade. The results indicate that, the main growth source of Chinese agricultural exports to ASEAN has shifted from the extensive margin before the formal establishment of CAFTA（China-ASEAN Free Trade Area） in 2010 to the intensive margin since the formal establishment of CAFTA, but changes in Chinese agricultural exports to ASEAN have always mainly depended on the intensive margin. Since the formal establishment of CAFTA, the evolution pattern of Chinese agricultural exports to ASEAN has shifted from ＂more varieties, low price, and small quantity＂ to ＂less varieties, high price, and large quantity＂. Relative economic scale, relative population scale, capacity of agricultural export, trade integration, global financial crisis, and common border significantly affect the trade margins of Chinese agricultural exports to ASEAN.

Positive Surgical Margins (PSM) after Open Retropubic Radical Prostatectomy: Evaluation of Patient Survival

Background: Many patients who have had radical prostatectomy for prostate cancer may present with microscopic extraprostatic extension of the disease. Positive surgical margins are a common pathological finding in this subgroup of patients. To report the epidemiological, clinical and therapeutic aspects of PSM after radical prostatectomy (RP) and to evaluate the follow-up of patients. Patients and methods: A single-center retrospective descriptive study of patients who underwent radical prostatectomy between June 1, 2004 and December 31, 2019 was conducted. Patients who had radical prostatectomy with PSM on pathology report were included. The parameters studied were age, initial prostate specific antigen (PSA), Gleason and International Society of Uropathology (ISUP) scores, cTNM and pTNM stages, operative technique, PSA levels after surgery, adjuvant treatment and patient survival. Results: Eighty-six (86) radical prostatectomies were performed. PSM was found in 23 patients (26.7%). The mean age of the patients was 63.7 ± 6.1 years. The mean preoperative total PSA was 31.5 ng/mL (6.31 - 146 ng/mL). Prostate biopsy showed only prostatic adenocarcinoma. Thoracic-abdominopelvic CT was performed in all patients. Prostate cancers were found at the localized stage in 12 patients and locally advanced in 11 patients. A classification adjustment was obtained after pathological examination of the surgical specimen. The ISUP score 3 and 1 on the surgical specimen were in the majority with 9 and 7 patients respectively. After the recurrence, all patients who consented received hormone therapy, which was either medical with Goserelin and Triptorelin (7 patients) or surgical with testicular pulpectomy (1 patient). PSA was undetectable (<0.1 mg/mL) in 4 patients. The mean overall survival (OS) time was 28.1 months. Biological recurrence-free survival in the series was 25.7 months. Conclusion: RP with PSM is a fairly common condition that varies from less than 10% to more than 40% depending on the stage of the disease and the operators, and for which the main mean of treatment in our practice setting is hormone therapy.

Excision margins in squamous cell carcinoma of the tongue: A retrospective audit and review of the literature

The incidence of close and involved tongue resection margins for squamous cell carcinoma (SCC) were reviewed with the aim to identify any possible need for change in the surgical approach to glossectomies. The histopathological reports of 101 partial glossectomies for SCC between 2006 and 2012 were retrospectively reviewed. Results: Overall 52 (51.5%) patients had one or more close or involved margin and 9 (8.9%) had both close and involved margins. 42 (41.5%) patients had close margins and 11 (10.9%) had involved margins. The inferior/lateral muscoal margin was most frequently close/involved (32%) followed by deep margin (27%). The anterior margin was least close/involved (5%). The posterior and superior/medical margins were close/involved in 12% and 11% of cases respectively. Conclusions: 52.5% of patients had close or involved margins following surgery, potentially requiring further treatment to avoid an increased risk of tumour recurrence and the associated increase in morbidity and mortality. The inferior/lateral and deep margins were most frequently involved possible due to the anatomical difficulties visualising and dissecting these margins. The potential explanations for these disparities and possible solutions are discussed.

The Effectiveness of Intraoperative Frozen Section Analysis of Safety Margins in Breast Conserving Surgery and the Role of Surgeon in Decreasing the Rate of Positive Margins

Introduction: Nowadays the more accepted surgical option for treating early breast cancer is breast conserving surgery. The main challenge in this type of surgery is to get free safety margins without need of second surgical operation, so many breast surgeons have started to depend on intraoperative frozen sections to ensure free safety margins. Aim of work: To assess our policy that we prefer to depend on intraoperative frozen section analysis to get free safety margin in breast conserving surgery from the 1st surgery, and its oncologic outcome. Patients and Methods: This is a retrospective study conducted in Oncology Center—Mansoura University (OCMU), where the data of 219 patients with breast cancer, who were managed by breast conserving surgery with intraoperative frozen section analysis of the safety margins, was analyzed. Results: The intraoperative frozen section analysis of safety margin was negative from the start in 183 (83.6%) patients, while it was positive in 36 patients (16.4%). Intraoperative decision of margin re-excision was applied for 29 patients (13.2%) in order to reach negative margin, modified radical mastectomy was offered for 4 patients (1.8%), while nipple sparing mastectomy with immediate breast reconstruction using latissimus dorsi flap was offered for 3 patients (1.4%). The postoperative paraffin results were typical with intraoperative frozen section analysis results in 216 patients (98.6%) and different results were obtained in only 3 patients (1.4%) who were managed by modified radical mastectomy in a second operation. Only 4 patients had local recurrence (1.8%) during the period of follow-up duration which was ranged from 1 to 86 months with mean ± SD (22.3 ± 14.1). Conclusion: The intraoperative frozen section analysis of safety margins in breast conserving surgery has very high-rate typical results with the paraffin section analysis and it is very helpful in decreasing the rate of second surgical operation in cases of infiltrated margins. It should be used routinely in all cases of breast conserving surgery.

Frozen Section Analysis of Breast Lumpectomy Margins

Objectives: To evaluate breast lumpectomy margins by frozen section in breast conservation surgery. Methods: A retrospective study of frozen section of lumpectomy margins of one hundred ten patients was done at King Abdulaziz University Hospital from June 2007 to June 2013. All patients underwent lumpectomy + Sentinel lymph node biopsy. Patient records were studied for location of mass in breast, size of mass, site of breast, pre or postmenopausal, frozen section margins, new frozen section margins, permanent margins, reoperation. Complications like skin necrosis, numbness, and wound infection were studied. Result: Majority were Saudis (64.5%). Left breast was involved in 60%. Upper outer quadrant was involved in majority (51.9%). Size of mass was less than 1 cm in 14.8% cases, 1 - 2.9 cm in 43.5%, 3 - 4 cm in 13%, more than 4 cm in 10.2%. Lumpectomy plus sentinel lymph node biopsy was done in 96.4% and lumpectomy and axillary lymph node dissection was done in 1.8% cases. Gross margins were positive in 17.3% and frozen margins were positive in 28.2%. New margin on frozen section were positive in 3.6% and negative in 79.1%. Permanent section histology showed positive margins in 5.5% and negative in 94.5% cases. Re-operation was done in 7.3%. Lympho-vascular margins were positive in 20.9%. Skin necrosis was found in 2.2%, numbness was found in 4.4%, wound infection was in 2.2%. Conclusion: Lumpectomy margins with frozen section reduce re-operation and recurrence.

Hydrothermal Mineralization on the Mesoproterozoic Passive Continental Margins of China: A Case Study of the Langshan-Zha'ertaishan Belt,Inner Mongolia, China

Most ore-forming characteristics of the Langshan-Zha'ertaishan hydrothermal exhalation belt, which consists of the Dongshengmiao, Huogeqi, Tanyaokou and Jiashengpan large-superlarge Zn-Pb-Cu-Fe sulfide deposits, are most similar to those of Mesoproterozoic SEDEX-type provinces of the world. The characteristics include: (1) All deposits of this type in the belt occur in third-order fault-basins in the Langshan-Zha'ertaishan aulacogen along the northern margin of the North China Platform; (2) these deposits with all their orebodies hosted in the Mesoproterozoic impure dolomite-marble and carbonaceous phyllite (or schists) have an apparent stratabound nature; ores display laminated and banded structures, showing clear depositional features; (3) there is some evidence of syn-sedimentary faulting, which to a certain extent accounts for the temporal and spatial distribution and the size of the orebodies in all deposits and the formation of intrabed conglomerates and breccias; (4) they show lateral and vertical zonation of sulfides; (5) The Cu/(Pb+Zn+Cu) ratio of the large and thick Pb+Zn+Cu orebodies gradually decreases from bottom to top; and (6) barite is interbedded with pyrites and sometimes with sphalerite. However, some characteristics such as the Co/Ni radio of the pyrites, the volcanism, for example, of the Langshan-Zha'ertaishan metallogenic belt, are different from those of the typical SEDEX deposits of the world. The meta-basic volcanic rock in Huogeqi, the sodic bimodal volcanic rocks in the Dongshengmiao and potassic bimodal-volcanic rocks with blastoporphyritic and blasto-glomeroporphyritic texture as well as blasto-amygdaloidal structure in the Tanyaokou deposits have been discovered in the only ore-bearing second formation of the Langshan Group in the past 10 years. The metallogeny of some deposits hosted in the Langshan Group is closely related to syn-sedimentary volcanism based on the following facts: most of the lead isotopes in sphalerite, galena, pyrite, pyrrhotite and chalcopyrite plot on both sides of the line for the mantle or between the lines for the mantle and lower crust in the lead isotope composition diagram; cobalt content of some pyrites samples is much higher than the nickel content (Co/Ni=11.91-12.19). Some volcanic blocks and debris have been picked out from some pyritic and pyrrhotitic ores. All Zn-Pb-Cu-Fe sulfide orebodies in these deposits occur in the strata overlying metamorphic volcanic rocks in the only ore-bearing second formation. In the Jiashengpan deposit that lacks syn-sedimentary volcanic rocks in the host succession only Pb and Zn ores occur without Cu ore, but in the Dongshengmiao, Tanyaokou and Huogeqi deposits with syn-sedimentary volcanic rocks in the host succession Cu ores occur. This indicates a relatively higher ore-forming temperature. The process of syn-sedimentary volcanic eruption directly supplied some ore-forming elements, and resulted in secular geothermal anomaly favorable for the circulation of a submarine convective hydrothermal system, which accounts for the precipitation of deep mineralizing fluids exhaling into anoxidic basins along the syn-sedimentary fault system in the Langshan-Zha'ertai rift. The Dongshengmiao, Tanyaokou, and Huogeqi deposits hosted in the Langshan Group appear to be a transitional type of mineral deposit between SEDEX and VMS-types but with a bias towards SEDEX, while the Jiashengpan deposit hosted in the Zha'ertai Group is of a characteristic SEDEX type. This evidence, together with other new discoveries of Mesoproterozoic volcanic rocks and the features of lithogeny and metallogeny of the Bayun Obo deposit in the neighborhood emphasize the diversity, complexity and uniqueness of the Mesoproterozoic Langshan-Zha'ertai-Bayun Obo ore belt.

Tectonic Setting and Metallogenic System of North China Block Margins

The paleocontinental margins have frequent and intensive tectonic movement and various ore forming processes. According to their tectono dynamic characteristics, the paleocontinental margins can be classified into three types: the divergent, the convergent and the transformational. Each type has its specific geological geochemical processes and metallogenic system. The paper discusses the tectonic evolution and ore forming features of the North China block margins, puts forward conceptions such as complexity, variety and multi stage development of metallogenic evolution in the paleocontinental margins, and expounds five factors controlling the formation of large superlarge ore deposits in the paleocontinental margins: (1) channelway, (2) rendezvous of fluids, (3) abundance of ore source, (4) thermo dynamic anomaly, (5) long duration of structural activities.

Metallogenic‘factories’and resultant highly anomalous mineral endowment on the craton margins of China

The current margins of the North China and Yangtze Cratons provide arguably the best examples globally of anomalously high mineral endowment within a 100 km buffer zone,hosting 66 diverse world-class to giant ore systems that help explain China’s premier position as a producer of multiple metal and mineral commodities.After the cratonization of these crustal blocks during the Neoarchean-Paleoproterozoic,with incorporation of iron ores on assembled micro-block margins,the margins of the cratons experienced multiple convergence and rifting events leading to metasomatism and fertilization of their underlying sub-continental lithospheric mantle.The rifted margins with trans-lithosphere faults provided pathways for Cu-Au(Mo-W-Sn)-bearing felsic to Ni-Cu-bearing ultrabasic intrusions and REE-rich carbonatite magmas,and for the development of marginal sedimentary basins with both Cu-Pb-Zn-rich source units and reactive carbonate or carbonaceous host rocks.There was diachronous formation of hydrothermal orogenic gold,antimony,and bismuth systems in the narrow orogenic belts between the cratons.Complexity in the Mesozoic Paleo-Pacific subduction systems resulted in asthenosphere upwelling and lithosphere extension and thinning in the North China Craton,leading to anomalous heat flow and formation of orogenic gold deposits,including those of the giant Jiaodong gold province on its north-eastern margin.These gold deposits,many of which formed from fluids liberated by devolatilization of previously metasomatized sub-continental lithospheric mantle,helped propel China to be the premier gold producer globally.The thick sub-continental lithospheric mantle of the cold buoyant cratons helped the preservation of some of the world’s oldest porphyry-skarn and epithermal mineral systems.Although craton margins globally control the formation and preservation of a diverse range of mineral deposits,China represents the premier example in terms of metal endowment due to the anomalous length of its craton margins combined with their abnormally complex tectonic history.

Tectonic Development of the Proterozoic Continental Margins in East Qinling and Adjacent Regions

The East Qinling and adjacent cratonic regions belong to two geotectonic units, the Sinokorean Subdomain including the Sinokorean Platform and its southern continental margin the North Qinling Belt, and the Yangtzean Subdomain comprising the Yangtze Platform and its northern continental margin the South Qinling Belt .The Qinling region may thus be subdivided into two continental margin belts separated from each other by the Proterozoic Qinling marine realm , which did not disappear until Late Triassic . The convergent crustal consumption zone ,the megasuture between the two belts ,lies between the Fengxian Shangnan line in the north and the Shanyang Xijia line in the south and was much deformed and displaced through Mesozoic intracratonic collision and compression.In the northern subdomain the Lower Proterozoic is represented by protoaulacogen volcano-sediments , the inner Tiedonggou Group and the outer marginal Qinling Group , which were folded and metamorphosed in the Luliangian orogeny ,a general process of aggregation and stabilization of the Early Proterozoic mobile belts between and around the Archaean nuclei. Genuine aulacogen occurred in the Middle Proterozoic and was represented by the Xionger rift volcanics . The Middle and Upper Proterozoic comprise the inner Guandaokou shelf sediments and the outer extensional' back- arc' Kuanping Group behind the Qinling island chain . Oceanic subduction from the south of the Qinling arc representing the Jinningian orogeny caused the folding of the Mid dle and Upper Proterozoic and emplacement of island arc-continent collision type of granite . After the Jinningian orogeny Late Sinian glacigene deposits formed the platform cover and the Erlangping back arc basin began to develop on the northern slope of the Qinling arc .In South Qinling the Lower Proterozoic Tongbe Group was probably an original marginal part of the Yangtze Platform . The passive margin began rifting in Middle Proterozoic with the formation of the inner Shennongjia aulacogen and the outer marginal Wudang aulacogen. Deformation of the Wudang and Douling groups indicating Jinningian Movement seemed to have been caused by a southward compression of the Tongbe Massif. Resumed rifting in the Sinian evidenced by the sedimentary facies pattern caused the northward separation of the Douling Massif, which formed part of the Fuping-Zhenan island chain , the northern boundary of the South Qinling Belt. In the western part of South Qinling , in the Hanzhong region , the Middle and Upper Proterozoic are represented by the Huodiya shelf sediments and the Xixiang marginal volcano sedimentaries , The Jinningian orogeny is well represented by the deformed Xixiang Group and the subduction pattern of magmatism from north to south in the Beiba area . It seems that the genuine arc-basin system in the continental margin and the aulacogen in the inner part of the platform began in the Middle Proterozoic (1800 Ma), which marks the beginning of a new tectonic megastage in lithosphere evolution.

Evaluation of the margins of differentiated early gastric cancer by using conventional endoscopy

AIM: To evaluate the determination of the margin of differentiated-type early gastric cancers by using conventional endoscopy.METHODS: We retrospectively evaluated 364 differentiated early gastric cancers that were endoscopically resected as en-bloc specimens and diagnosed pathologically in detail between November 2007 and October 2008. All procedures were done with conventional endoscopes and all endoscopic samples, before and after indigo carmine dye, were re-evaluated using a digital filing system by one endoscopist. We analyzed the incidence of lesions with unclear margins and the relationship between unclear margins and relevant clinicopathological findings. RESULTS: The rate of lesions with unclear margins was 20.6%(75/364). Multivariate regression analysis suggested that the factors that make the determination of the margin difficult were normal color, presence of components of flat area(0-IIb), a diameter ≥ 21 mm, ulceration, and components of poorly differentiated adenocarcinoma in the mucosal surface.CONCLUSION: As many as 20% of differentiated early gastric cancers show unclear margins. Consideration of the factors associated with unclear margins may help endoscopists to accurately determine the margins of the lesion.

Multicomponent Assessment of the Geometrical Uncertainty and Consequent Margins in Prostate Cancer Radiotherapy Treatment Using Fiducial Markers

The aim is to compute all sources of geometrical uncertainty in prostate radiotherapy using fiducial markers and determine the safety treatment margins. Based on the markers position, correlations between prostate rotation/deformation and rectal and bladder fillings as well as changes in prostate volume during the treatment course are analyzed. The study includes 375 pre-treatment CBCT images from 15 prostate cancer patients treated with hypofractionated radiotherapy. The position coordinates of the markers were obtained from each image acquisition. In addition, rectum and bladder were outlined on CBCTs. The intrafractional error was estimated by an additional post-treatment CBCT acquired on alternate days. Tau-Kendall analysis was performed to correlate organ fillings with prostate rotation/deformation. Delineation uncertainty was assessed from contours of 10 patients performed by two radiation oncologists and repeated twice. The CT contouring was assisted by a multiparametric MR approach combining a T2-weighted with diffusion-weighted imaging, and a gradient recalled echo for fiducial marker identification. Uncertainty associated to treatment unit was estimated from phantom measurements. The obtained clinical margins were 4.4, 7.3, 5.1 mm in the Left-Right, Superior-Inferior, and Anterior-Posterior directions, respectively, being the contouring the most important contribution. The mechanical limitations of the beam delivery system and the associated imaging device entailed errors of the same order as prostate motion, rotation or deformation. Weak correlations between variation of the rectal volume and the presence of rotations/deformations were found (correlation coefficient 0.182, p = 0.001 for rotations around lateral axis;correlation coefficients 0.1, p < 0.05 for deformations). The distance between markers decreased with session number, becoming more pronounced from fraction 13 and reaching 1 - 1.8 mm at the end of the treatment. In summary we have determined the optimal treatment margins based on geometrical uncertainty assessment using van Herk formalism. An appropriate preparation of rectum and bladder involves minimizing the effect of prostate rotations/deformations. The prostate tends to decrease in size during the treatment which could influence treatment re-planning strategies.

Feasibility of CT-CT fusion imaging for evaluation of the cryoablation margins in visible hepatocellular carcinoma on unenhanced CT images:Initial experience

Objective:To demonstrate the feasibility of CT-CT fusion imaging for assessment of the cryoablation margins in visible hepatocellular carcinoma(HCC)on unenhanced CT images.Methods:This retrospective study analyzed 14 patients with 14 HCC lesions treated with CT-guided cryoablation.Nine lesions in nine patients who developed local tumor progression(LTP)during the follow-up period of at least8 months were reviewed.The unenhanced CT data were used to retrospectively create fusion images of the intraoperative CT images on a workstation.The minimal ablative margin(MAM)was assessed on the fusion images.The concordance between the site of LTP and the MAM area was also assessed.Results:Eight of the nine lesions with LTP were in the subcapsular region of the liver.Seven of the nine cases were treated by cryoablation combined with transcatheter arterial chemoembolization.The median time required to fuse the images for the nine lesions was 5:17 min(range,5:04-7:37 min).The site of LTP relative to the HCC lesion was craniocaudal in nine,dorsoventral in six,and lateral in seven lesions.In all lesions,the site of LTP was congruent with the MAM area.Conclusions:CT-CT fusion imaging enables a real-time intraoperative treatment evaluation for HCC lesions visible on unenhanced CT images.Fused imaging evaluation has proved to be an accurate and useful tool for assessment of the cryoablation margins.

Calculation of compact amplitude-integrated EEG tracing and upper and lower margins using raw EEG data

Amplitude-integrated EEG (aEEG) is a popular method for monitoring cerebral function. Although various commercial aEEG recorders have been produced, a detailed aEEG algorithm currently is not available. The upper and lower margins in the aEEG tracing are the discriminating features for data inspection and tracing classification. However, most aEEG devices require that these margins be measured semi-subjectively. This paper proposes a step-by-step signal-processing method to calculate a compact aEEG tracing and the upper/lower margin using raw EEG data. The high accuracy of the algorithm was verified by comparison with a recognized commercial aEEG device based on a representative testing dataset composed of 72 aEEG data. The introduced digital algorithm achieved compact aEEG tracing with a small data size. Moreover, the algorithm precisely represented the upper and lower margins in the tracing for objective data interpretation. The described method should facilitate aEEG signal processing and further establish the clinical and experimental application of aEEG methods.

Asymmetric Atlantic continental margins

We analyze the gross crustal structure of the Atlantic Ocean passive continental margins from north to the south,comparing eleven sections of the conjugate margins.As a general result,the western margins show a sharper continental-ocean transition with respect to the eastern margins that rather show a wider stretched and thinner margin.The Moho is in average about 5.7±1dipping toward the interior of the continent on the western side,whereas it is about 2.7±1in the eastern margins.Moreover,the stretched continental crust is on average 244 km wide on the western side,whereas it is up to about 439 km on the eastern side of the Atlantic.This systematic asymmetry reflects the early stages of the diachronous Mesozoic to Cenozoic continental rifting,which is inferred as the result of a polarized westward motion of both western and eastern plates,being Greenland,Northern and Southern Americas plates moving westward faster with respect to Scandinavia,Europe and Africa,relative to the underlying mantle.

Current strategies to diagnose and manage positive surgical margins and local recurrence after partial nephrectomy

Objective:No standard strategy for diagnosis and management of positive surgical margin(PSM)and local recurrence after partial nephrectomy(PN)are reported in literature.This review aims to provide an overview of the current strategies and further perspectives on this patient setting.Methods:A non-systematic review of the literature was completed.The research included the most updated articles(about the last 10 years).Results:Techniques for diagnosing PSMs during PN include intraoperative frozen section,imprinting cytology,and other specific tools.No clear evidence is reported about these methods.Regarding PSM management,active surveillance with a combination of imaging and laboratory evaluation is the first option line followed by surgery.Regarding local recurrence management,surgery is the primary curative approach when possible but it may be technically difficult due to anatomy resultant from previous PN.In this scenario,thermal ablation(TA)may have the potential to circumvent these limitations representing a less invasive alternative.Salvage surgery represents a valid option;six studies analyzed the outcomes of nephrectomy on local recurrence after PN with three of these focused on robotic approach.Overall,complication rates of salvage surgery are higher compared to TA but ablation presents a higher recurrence rate up to 25%of cases that can often be managed with repeat ablation.Conclusion:Controversy still exists surrounding the best strategy for management and diagnosis of patients with PSMs or local recurrence after PN.Active surveillance is likely to be the optimal first-line management option for most patients with PSMs.Ablation and salvage surgery both represent valid options in patients with local recurrence after PN.Conversely,salvage PN and radical nephrectomy have fewer recurrences but are associated with a higher complication rate compared to TA.In this scenario,robotic surgery plays an important role in improving salvage PN and radical nephrectomy outcomes.