Journal articles on the topic 'High definition color aerial photography'

The threatened malleefowl (Leipoa ocellata) constructs a large (often >3 m) incubator mound (nest) that is considered a useful proxy for surveying its presence and abundance in the context of an environmental impact assessment. Here we report on the effectiveness and relative cost of using high-definition aerial photography to search in 3D for malleefowl mounds by comparing results to those of earlier ground-based searches. High-definition colour aerial photography was taken of an area of ~7014 ha and searched in 3D for malleefowl mounds. All 24 active (i.e. in use) malleefowl mounds known before the examination of aerial photography were detected using the new assessment technique. Of the 108 total mounds (active and inactive) known from earlier on-ground surveys, 94 (87%) were recorded using the new technique. Mounds not detected were all old and weathered, many barely above ground level and some with vegetation growing in the crater. Approximately 6.3% of the identifications considered ‘confident’ and ~35.0% considered ‘potential’ based on the aerial photography proved to be false positives. The cost of detecting malleefowl mounds using the interpretation of high-definition 3D colour aerial photography and then subsequently examining these areas on the ground is appreciably cheaper than on-ground grid searches.

Abstract. The quality of cartographic products, obtained on base of aerial images, depends on their quality. The image‘s quality can be defined in terms of measurement characteristics and in it’s visual properties. The object of the paper is an aerial image’s quality, concerning its visual perception. The process of topographic aerial images quality assessing is currently not regulated, therefore, this problem becomes particularly relevant today. The article is devoted to development the quality criteria system for aerial images, obtained for mapping purposes, and definition the requirements for them. The analysis of factors affecting the quality of aerial images is carried out, they include natural conditions, technical and technological parameters of aerial surveying and images post-processing. The main imperfections of image quality, appearing as a result of these factors influence are determined – blurring, high level of random image noise, haze, color imbalance, loss of information in shadows and illumination. Methods of identifying these imperfections and assessing their influence on aerial images quality are shown.

Mangrove migration, or transgression in response to global climatic changes or sea-level rise, is a slow process; to capture it, understanding both the present distribution of mangroves at individual patch (single- or clumped trees) scale, and their rates of change are essential. In this study, a new method was developed to delineate individual patches and to estimate mangrove cover from very high-resolution (0.08 m spatial resolution) true color (Red (R), Green (G), and Blue (B) spectral channels) aerial photography. The method utilizes marker-based watershed segmentation, where markers are detected using a vegetation index and Otsu’s automatic thresholding. Fourteen commonly used vegetation indices were tested, and shadows were removed from the segmented images to determine their effect on the accuracy of tree detection, cover estimation, and patch delineation. According to point-based accuracy analysis, we obtained adjusted overall accuracies >90% in tree detection using seven vegetation indices. Likewise, using an object-based approach, the highest overlap accuracy between predicted and reference data was 95%. The vegetation index Excess Green (ExG) without shadow removal produced the most accurate mangrove maps by separating tree patches from shadows and background marsh vegetation and detecting more individual trees. The method provides high precision delineation of mangrove trees and patches, and the opportunity to analyze mangrove migration patterns at the scale of isolated individuals and patches.

ABSTRACT The January 2007 release of over 8,000 barrels of a condensate crude oil from a damaged well in Bayou Perot, Louisiana resulted in intermittent oiling of remote mud flats and salt marshes over a 30 square mile area. NOAA'S National Geodetic Survey collected aerial vertical digital photography 17 days after the spill to assist in locating and quantifying areas of oiling. The effective pixel size was 34 centimeters, however, the data were processed to 40 centimeter resolution. Useful products were posted to the web within two days after acquisition. Standard supervised and unsupervised image processing techniques were used in conjunction with oblique photography and field knowledge to define the oiling signatures. Time constraints required that the classification be conducted on mosaiced, non-color balanced images (ideally each image would be classified independently to account for differences in illumination and/or processing). However, the strong visible signature of the oiled areas and ground-truth data from field surveys resulted in high confidence levels for several oil types which in turn were used to enhance the identification of the remaining classes. Five oil types were identified: Black (218,000 ft2), Red (81,000 ft2), Orange (154,000 ft2), Yellow (38,000 ft2), and Light Yellow (349,000 ft2) corresponding to the color and attributes of the oil. The total conservative estimate of oiled area was 840,000 ft2 or nearly 20 acres. Based on estimated thicknesses of the different oils, the total volume of oil present at the time of imagery acquisition was 3,330 barrels. This value was close to the actual amount of oil recovered over the time period between the date of imagery acquisition and the end of cleanup.

This contribution promotes 3D photography as an important tool to obtain objective object information. Keeping mainly in mind World Heritage documentation as well as Heritage protection, it is another intention of this paper, to stimulate the interest in applications of 3D photography for professionals as well as for amateurs. In addition this is also an activity report of the international CIPA task group 3. The main part of this paper starts with “Digging the treasure of existing international 3D photography”. This does not only belong to tangible but also to intangible Cultural Heritage. 3D photography clearly supports the recording, the visualization, the preservation and the restoration of architectural and archaeological objects. Therefore the use of 3D photography in C.H. should increase on an international level. The presented samples in 3D represent a voluminous, almost partly “forgotten treasure” of international archives for 3D photography. <br><br> The next chapter is on “Promoting new 3D photography in Cultural Heritage”. Though 3D photographs are a well-established basic photographic and photogrammetric tool, even suited to provide “near real” documentation, they are still a matter of research and improvement. Beside the use of 3D cameras even single lenses cameras are very much suited for photographic 3D documentation purposes in Cultural Heritage. <br><br> Currently at the Faculty of Civil Engineering of the University of Applied Sciences Magdeburg-Stendal, low altitude aerial photography is exposed from a maximum height of 13m, using a hand hold carbon telescope rod. The use of this “huge selfie stick” is also an (international) recommendation, to expose high resolution 3D photography of monuments under expedition conditions. In addition to the carbon rod recently a captive balloon and a hexacopter UAV- platform is in use, mainly to take better synoptically (extremely low altitude, ground truth) aerial photography. Additional experiments with respect to “easy geometry” and to multistage concepts of 3D photographs in Cultural Heritage just started. Furthermore a revised list of the 3D visualization principles, claiming completeness, has been carried out. Beside others in an outlook <br><br> *It is highly recommended, to list every historical and current stereo view with relevance to Cultural Heritage in a global Monument Information System (MIS), like in google earth. <br><br> *3D photographs seem to be very suited, to complete and/or at least partly to replace manual archaeological sketches. In this concern the still underestimated 3D effect will be demonstrated, which even allows, e.g., the spatial perception of extremely small scratches etc... <br><br> *A consequent dealing with 3D Technology even seems to indicate, currently we experience the beginning of a new age of “real 3DPC- screens“, which at least could add or even partly replace the conventional 2D screens. Here the spatial visualization is verified without glasses in an all-around vitreous body. In this respect nowadays widespread lasered crystals showing monuments are identified as “Early Bird“ 3D products, which, due to low resolution and contrast and due to lack of color, currently might even remember to the status of the invention of photography by Niepce (1827), but seem to promise a great future also in 3D Cultural Heritage documentation. <br><br> *Last not least 3D printers more and more seem to conquer the IT-market, obviously showing an international competition.

Field research was conducted to determine the potential of hyperspectral and multispectral imagery for late-season discrimination and mapping of grass weed infestations in wheat. Differences in reflectance between weed-free wheat and wild oat, canarygrass, and ryegrass were statistically significant in most 25-nm-wide wavebands in the 400- and 900-nm spectrum, mainly due to their differential maturation. Visible (blue, B; green, G; red, R) and near infrared (NIR) wavebands and five vegetation indices: Normalized Difference Vegetation Index (NDVI), Ratio Vegetation Index (RVI), R/B, NIR-R and (R − G)/(R + G), showed potential for discriminating grass weeds and wheat. The efficiency of these wavebands and indices were studied by using color and color-infrared aerial images taken over three naturally infested fields. In StaCruz, areas infested with wild oat and canarygrass patches were discriminated using the indices R, NIR, and NDVI with overall accuracies (OA) of 0.85 to 0.90. In Florida–West, areas infested with wild oat, canarygrass, and ryegrass were discriminated with OA from 0.85 to 0.89. In Florida–East, for the discrimination of the areas infested with wild oat patches, visible wavebands and several vegetation indices provided OA of 0.87 to 0.96. Estimated grass weed area ranged from 56 to 71%, 43 to 47%, and 69 to 80% of the field in the three locations, respectively, with per-class accuracies from 0.87 to 0.94. NDVI was the most efficient vegetation index, with a highly accurate performance in all locations. Our results suggest that mapping grass weed patches in wheat is feasible with high-resolution satellite imagery or aerial photography acquired 2 to 3 wk before crop senescence.

The recent and continuous development of unmanned aerial vehicles (UAV) and small cameras with different spectral resolutions and imaging systems promotes new remote sensing platforms that can supply ultra-high spatial and temporal resolution, filling the gap between ground-based surveys and orbital sensors. This work aimed to monitor siltation in two large rural and urban reservoirs by recording water color variations within a savanna biome in the central region of Brazil using a low cost and very light unmanned platform. Airborne surveys were conducted using a Parrot Sequoia camera (~0.15 kg) onboard a DJI Phantom 4 UAV (~1.4 kg) during dry and rainy seasons over inlet areas of both reservoirs. Field measurements of total suspended solids (TSS) and water clarity were made jointly with the airborne survey campaigns. Field hyperspectral radiometry data were also collected during two field surveys. Bio-optical models for TSS were tested for all spectral bands of the Sequoia camera. The near-infrared single band was found to perform the best (R2: 0.94; RMSE: 7.8 mg L−1) for a 0–180 mg L−1 TSS range and was used to produce time series of TSS concentration maps of the study areas. This flexible platform enabled monitoring of the increase of TSS concentration at a ~13 cm spatial resolution in urban and rural drainages in the rainy season. Aerial surveys allowed us to map TSS load fluctuations in a 1 week period during which no satellite images were available due to continuous cloud coverage in the rainy season. This work demonstrates that a low-cost configuration allows dense TSS monitoring at the inlet areas of reservoirs and thus enables mapping of the sources of sediment inputs, supporting the definition of mitigation plans to limit the siltation process.

The number of panicles per unit area is a common indicator of rice yield and is of great significance to yield estimation, breeding, and phenotype analysis. Traditional counting methods have various drawbacks, such as long delay times and high subjectivity, and they are easily perturbed by noise. To improve the accuracy of rice detection and counting in the field, we developed and implemented a panicle detection and counting system that is based on improved region-based fully convolutional networks, and we use the system to automate rice-phenotype measurements. The field experiments were conducted in target areas to train and test the system and used a rotor light unmanned aerial vehicle equipped with a high-definition RGB camera to collect images. The trained model achieved a precision of 0.868 on a held-out test set, which demonstrates the feasibility of this approach. The algorithm can deal with the irregular edge of the rice panicle, the significantly different appearance between the different varieties and growing periods, the interference due to color overlapping between panicle and leaves, and the variations in illumination intensity and shading effects in the field. The result is more accurate and efficient recognition of rice-panicles, which facilitates rice breeding. Overall, the approach of training deep learning models on increasingly large and publicly available image datasets presents a clear path toward smartphone-assisted crop disease diagnosis on a global scale.

Thermokarst waterbodies caused by permafrost thawing and degradation are ubiquitous in many subarctic and Arctic regions. They are globally important components of the biogeochemical carbon cycle and have potential feedback effects on climate. These northern waters are mostly small lakes and ponds, and although they may be mapped using very high-resolution satellites or aerial photography, these approaches are generally not suitable for monitoring purposes, due to the cost and limited availability of such images. In this study we evaluated the potential use of widely available high-resolution imagery from Sentinel-2 (S2) for the characterization of the spectral reflectance of thermokarst lakes and ponds. Specifically, we aimed to define the minimum lake area that could be reliably imaged, and to identify challenges and solutions for remote sensing of such waters in the future. The study was conducted in subarctic Canada, in the vicinity of Whapmagoostui-Kuujjuarapik (Nunavik, Québec), an area in the sporadic permafrost zone with numerous thermokarst waterbodies that vary greatly in size. Ground truthing lake reflectance data were collected using an Unmanned Aerial System (UAS) fitted with a multispectral camera that collected images at 13 cm resolution. The results were compared with reflectance from Sentinel-2 images, and the effect of lake area on the reflectance response was assessed. Our results show that Sentinel-2 imagery was suitable for waterbodies larger than 350 m2 once their boundaries were defined, which in the two test sites would allow monitoring from 11% to 30% of the waterbodies and 73% to 85% of the total lake area. Challenges for remote sensing of small lakes include the confounding effects of water reflection (both direct radiation and diffuse), wind and shadow. Given the small threshold area and frequent revisit time, Sentinel-2 provides a valuable approach towards the continuous monitoring of waterbodies, including ponds and small lakes such as those found in thermokarst landscapes. UASs provide a complementary approach for ground truthing and boundary definition.

Chlorophyll content in plant leaves is an essential indicator of the growth condition and the fertilization management effect of naked barley crops. The soil plant analysis development (SPAD) values strongly correlate with leaf chlorophyll contents. Unmanned Aerial Vehicles (UAV) can provide an efficient way to retrieve SPAD values on a relatively large scale with a high temporal resolution. But the UAV mounted with high-cost multispectral or hyperspectral sensors may be a tremendous economic burden for smallholder farmers. To overcome this shortcoming, we investigated the potential of UAV mounted with a commercial digital camera for estimating the SPAD values of naked barley leaves. We related 21 color-based vegetation indices (VIs) calculated from UAV images acquired from two flight heights (6.0 m and 50.0 m above ground level) in four different growth stages with SPAD values. Our results indicated that vegetation extraction and naked barley ears mask could improve the correlation between image-calculated vegetation indices and SPAD values. The VIs of ‘L*,’ ‘b*,’ ‘G − B’ and ‘2G − R − B’ showed significant correlations with SPAD values of naked barley leaves at both flight heights. The validation of the regression model showed that the index of ‘G-B’ could be regarded as the most robust vegetation index for predicting the SPAD values of naked barley leaves for different images and different flight heights. Our study demonstrated that the UAV mounted with a commercial camera has great potentiality in retrieving SPAD values of naked barley leaves under unstable photography conditions. It is significant for farmers to take advantage of the cheap measurement system to monitor crops.

Leafy spurge can be detected during flowering with either aerial photography or hyperspectral remote sensing because of the distinctive yellow-green color of the flower bracts. The spectral characteristics of flower bracts and leaves were compared with pigment concentrations to determine the physiological basis of the remote sensing signature. Compared with leaves of leafy spurge, flower bracts had lower reflectance at blue wavelengths (400 to 500 nm), greater reflectance at green, yellow, and orange wavelengths (525 to 650 nm), and approximately equal reflectances at 680 nm (red) and at near-infrared wavelengths (725 to 850 nm). Pigments from leaves and flower bracts were extracted in dimethyl sulfoxide, and the pigment concentrations were determined spectrophotometrically. Carotenoid pigments were identified using high-performance liquid chromatography. Flower bracts had 84% less chlorophylla, 82% less chlorophyllb, and 44% less total carotenoids than leaves, thus absorptance by the flower bracts should be less and the reflectance should be greater at blue and red wavelengths. The carotenoid to chlorophyll ratio of the flower bracts was approximately 1:1, explaining the hue of the flower bracts but not the value of reflectance. The primary carotenoids were lutein, β-carotene, and β-cryptoxanthin in a 3.7:1.5:1 ratio for flower bracts and in a 4.8:1.3:1 ratio for leaves, respectively. There was 10.2 μg g−1fresh weight of colorless phytofluene present in the flower bracts and none in the leaves. The fluorescence spectrum indicated high blue, red, and far-red emission for leaves compared with flower bracts. Fluorescent emissions from leaves may contribute to the higher apparent leaf reflectance in the blue and red wavelength regions. The spectral characteristics of leafy spurge are important for constructing a well-documented spectral library that could be used with hyperspectral remote sensing.

Abstract. The requirement for very high-resolution satellite imagery by different applications has been increasing continuously. Several commercial and government-supported missions provide sub-meter spatial resolutions from optical sensors aboard Earth Observation (EO) satellites. The MAXAR satellite constellation acquires images with up to 30 cm Ground Sampling Distances (GSDs); and the High-Definition (HD) image production technology developed by MAXAR doubles the resolution by using artificial intelligence methods. Although the spatial resolution is one of the most important image quality metrics, several other factors indicated by diverse radiometric and geometric characteristics may circumscribe the usability of data in different projects. As part of mandatory activities of European Space Agency (ESA), Earthnet Programme provides a framework for integrating Third-Party Missions into the overall EO strategy and promotes the international use of the data. The Earthnet Data Assessment Pilot (EDAP) project aims at assessing the quality and the suitability of TPMs, and provides a communication platform between mission providers to ensure the coherence of the systems. In this study, the radiometric quality of the MAXAR HD products was evaluated within the EDAP project framework by using several General Image-Quality Equation (GIQE) metrics, visual inspections, and comparative assessments with orthophotos obtained from an Unmanned Aerial Vehicle (UAV) platform and with the original (non-HD) orthophotos with 30 cm resolutions. The results show that the spatial resolution improvements are observable in urban areas, where sharp edges are present. However, blurring and color noise patterns also occured in the HD images.

Predicting the crop nitrogen (N) nutrition status is critical for optimizing nitrogen fertilizer application. The present study examined the ability of multiple image features derived from unmanned aerial vehicle (UAV) RGB images for winter wheat N status estimation across multiple critical growth stages. The image features consisted of RGB-based vegetation indices (VIs), color parameters, and textures, which represented image features of different aspects and different types. To determine which N status indicators could be well-estimated, we considered two mass-based N status indicators (i.e., the leaf N concentration (LNC) and plant N concentration (PNC)) and two area-based N status indicators (i.e., the leaf N density (LND) and plant N density (PND)). Sixteen RGB-based VIs associated with crop growth were selected. Five color space models, including RGB, HSV, L*a*b*, L*c*h*, and L*u*v*, were used to quantify the winter wheat canopy color. The combination of Gaussian processes regression (GPR) and Gabor-based textures with four orientations and five scales was proposed to estimate the winter wheat N status. The gray level co-occurrence matrix (GLCM)-based textures with four orientations were extracted for comparison. The heterogeneity in the textures of different orientations was evaluated using the measures of mean and coefficient of variation (CV). The variable importance in projection (VIP) derived from partial least square regression (PLSR) and a band analysis tool based on Gaussian processes regression (GPR-BAT) were used to identify the best performing image features for the N status estimation. The results indicated that (1) the combination of RGB-based VIs or color parameters only could produce reliable estimates of PND and the GPR model based on the combination of color parameters yielded a higher accuracy for the estimation of PND (R2val = 0.571, RMSEval = 2.846 g/m2, and RPDval = 1.532), compared to that based on the combination of RGB-based VIs; (2) there was no significant heterogeneity in the textures of different orientations and the textures of 45 degrees were recommended in the winter wheat N status estimation; (3) compared with the RGB-based VIs and color parameters, the GPR model based on the Gabor-based textures produced a higher accuracy for the estimation of PND (R2val = 0.675, RMSEval = 2.493 g/m2, and RPDval = 1.748) and the PLSR model based on the GLCM-based textures produced a higher accuracy for the estimation of PNC (R2val = 0.612, RMSEval = 0.380%, and RPDval = 1.601); and (4) the combined use of RGB-based VIs, color parameters, and textures produced comparable estimation results to using textures alone. Both VIP-PLSR and GPR-BAT analyses confirmed that image textures contributed most to the estimation of winter wheat N status. The experimental results reveal the potential of image textures derived from high-definition UAV-based RGB images for the estimation of the winter wheat N status. They also suggest that a conventional low-cost digital camera mounted on a UAV could be well-suited for winter wheat N status monitoring in a fast and non-destructive way.

High flow arteriovenous malformations (AVMs) are infiltrative, invading tissue planes and structures and may be life threatening when they bleed.1 They have a feeding artery and an anomalous capillary bed shunting blood from the arterial system to the venous system.1 The present trend of management of small AVMs is surgical excision with a high success rate. The problematic cases are diffuse AVMs infiltrating structures that render them impossible to totally extirpate surgically without causing much blood loss and tissue damage. The mainstay of management is embolization, surgical resection and reconstruction.2 Ligation or proximal embolization (alone) of feeding vessels should never be done because such maneuvers result in rapid recruitment of new vessels from adjacent arteries to supply the AVM nidus.2 Incomplete surgical excision definitely leads to recurrences, making this type of AVM very difficult to manage. What is the point of this paper? The complete destruction of the “nidus” of the AVM, from the artery to the capillary to the venous component, is the only potential cure.3 Well and good if there could be a way of doing this by sclerosing the entire vascular malformation. But since sclerosis only works well in low flow vascular malformations and tumors like hemangiomas, and poorly or not at all in high flow lesions,4 we have to convert this high flow AVM into a “no-flow” or “low flow” AVM by ligating the feeding and draining vessel and injecting the sclerosant intra-arterially thereafter at a dose sufficient enough to blanch out the AVM even up to its peripheral branches. This paper aims to demonstrate how we do this. Definition of Terms Vascular malformation: They are a result of abnormal development of vascular elements during embryonic or fetal stages of life.2 They originate from mesenchymal cells at an early stage of embryogenesis.3 and most are present at birth but there are several case reports of these lesions presenting after trauma in adults.1 Some AVMs appear as part of a familial genetic disorder called angiomatous syndrome i.e. Rendu-Osler-Weber Syndrome presenting with telangiectasia of the skin and mucous membranes.3 Some propose that a defect in vascular stabilization like TGF-beta signaling could be a cause of AVM development.5,6 Still, progesterone receptors have been isolated in AVMs explaining their expansion during puberty.7 Hemangioma: These are vascular tumors that exhibit endothelial proliferation.2 A hemangioma of infancy usually undergoes 3 stages: a proliferative phase of rapid growth up to 10 to 12 months of age; an involuting phase where growth slows down and signs of regression appear usually at 1 to 7 years; and an involuted phase.2 Sclerosants: Agents used in sclerotherapy that induce a toxic effect on the vascular endothelium and results in fibrosis. There are 3 types: Detergents that disrupt cell membranes by protein theft desaturation ie: ethanolamine oleate, sodium morrhuate, polidocanol, sodium tetradecyl sulfate; Osmotic agents ie: sclerodex; and Chemical irritants that damage cell walls by direct contact ie: chromatin glycerine, polyiodinated iodine.8 Sclerodex: an osmotic sclerosant that is a combination of dextrose monohydrate 250mg/ml and sodium chloride 100mg/ml. It shifts water balance through cellular gradient (osmotic) dehydration that leads to endothelial destruction. Since component materials are naturally occurring bodily, it has no molecular toxicity in calibrated dosages. If extravasated, it could cause tissue necrosis.8 It is manufactured by OMEGA Laboratories, Ltd. Montreal, QC, Canada. REVIEW OF PRESENT PRACTICE AND LITERATURE The first task of the physician is to establish a diagnosis, whether the lesion is a vascular malformation or a vascular tumor. Taking the history of the patient could point to a diagnosis as vascular tumors like hemangiomas usually proliferate and involute from the time of infancy to about the age of 10. Vascular malformations grow as the child grows and do not involute. Vascular malformations have an arterial supply and a venous drainage and are classified into high or low flow. Capillary, venous and lymphatic types are low flow while arteriovenous malformations are usually high flow. A high flow AVM has an arterial blood supply and a venous drainage. In rare instances, a vascular malformation could co-exist with a hemangioma forming a mass effect.2 On physical examination, a bruit and a strong pulsation (thrill) is appreciated. The head and neck is the most common location of AVMs at 70%. When fully developed, they are deeper in color with increasing erythema, local warmth, palpable mass and a bruit.9 These malformations are composed of vascular channels lined by flat mature epithelium and are not hypercellular and not proliferative.10 Schobinger proposed a staging system for Head and Neck AVM. Stage 1 are AVMs that are quiescent and remain stable for long periods of time. Stage 2 is a time for expansion followed by pain and bleeding. Stage 3 is heralded by destruction of adjacent tissues and ulceration. Stage 4 is presented by decompensation where symptoms of cardiac failure are present.11 Ultrasound with color Doppler imaging, Magnetic Resonance Imaging and Phlebography (arteriography/venography) contribute to diagnosis, classification and management.3 In our setting were we do not have the facilities, we use CT- angiography. These imaging modalities should be used to evaluate the characteristics of the lesion, such as size, flow velocity, flow direction, relation to surrounding structures and lesion content.3 Ultrasound demonstrates flow rates, contrast-enhanced magnetic resonance imaging (MRI) shows presence or absence of a mass, and CT angiography reveals the arborization (the blood supply and drainage) of the vascular anomaly. Vascular tumors like hemangioma, if located in non-strategic areas where function is not impaired can be observed over its developmental phases until involution at about 10 years old.2 For hemangiomas that impair function or are possibly life threatening because of potential hemorrhage, these tumors are treated with the following modalities: 1. Intralesional corticosteroids ie: triamcinolone; 2.Systemic corticosteroids in a tapered dose like prednisolone and some second choice pharmacotherapeutics like interferon, vincristine; and 3. Propranolol. Surgery is indicated in ulcerating, bleeding, and life threatening lesions like airway obstruction.2 Over 90% demonstrate dramatic reduction in size of hemangioma in one to two weeks from the above medical therapeutic modalities. Propranolol has been successfully used as hemangioma treatment since 2008 and is believed to have an antiproliferative effect on the vascular endothelium. The mechanism of action may involve the regulation of growth factors.1 Low flow vascular malformations are treated with sclerotherapy or surgical excision for accessible tumors. These malformations do not regress like hemangioma but grow in time. High flow AVMs are treated with surgical excision if they have limited extent and are surgically accessible. Embolization before surgery decreases bleeding and is the standard. Embolization followed by repeated sclerotherapy is recommended for surgically inaccessible areas.4 There is a 64 to 96% response rate , defined as improvement in symptoms or a reduction in the lesion size after ethanol sclerotherapy of venous low flow malformations.3 Partial surgical excision leads to only temporary improvement followed by re-expansion of tumor overtime.9 Sometimes, complete resection is not possible in diffuse or infiltrating AVMs and surgery can result in severe disfigurement and impairment of function of involved structures.9 METHODS After establishing the diagnosis of a high flow AVM with identification of an arterial feeding vessel and a venous draining vessel, surgery is commenced away from the malformation to expose the arterial and venous supplies. The procedure is done under general anesthesia because sclerotherapy of large malformations and vascular tumors is very painful. We do this because we have no interventional radiology services in our hospital. We ligate the feeding artery and if possible, the draining vein to convert the AVM into a “ low or no flow” and to allow ample contact time between the sclerosant (sclerogen) and the vessel endothelium. The sclerosant is then injected intravascularly distal to the ligation until all visible malformation blanches out. Aspirating the blood content of the ligated (arterial supply and venous drainage) malformation before introduction of the sclerosant will further potentiate the action of the sclerosant. While injecting the sclerosant slowly, the patient’s vital signs are monitored. A drop in the pulse rate is a signal to stop or slow down the injection of the sclerosant because it may be a sign that some sclerosant is escaping the venous drainage and reaching the general circulation in a concentration picked up by the sensors of the vascular system. Injections resume in a slower manner as the vital signs revert to normal. Our sclerosing agent sclerogen is an osmotic agent composed of sodium chloride and dextrose which are naturally present in our body so they are not toxic in manageable concentrations. Other sclerosants can be nephrotoxic so we must be very careful in injecting not to overload the vascular system. The objective is to push the sclerosant to all branches of the malformation to eliminate all possible nidus. The end point of injection is when all cutaneous or mucosal components of the malformation blanch out. Injection of the sclerosant intravascularly is done under direct visualization to prevent extravascular introduction. A review of literature has this to say about sclerotherapy. Extravascular injection of the sclerosant causes tissue necrosis.4 Ethanol injection to high flow fistulous lesions is contraindicated because of high risk of” early wash “ into the systemic circulation.4 Sclerosants could cause hemolysis, denaturation of blood proteins, thrombus formation and nephrotoxicity.3,4,12 Ethanolamine oleate, in comparison to ethanol, has less effect in the deep vascular layer and no penetrative effect. It is not associated with neuronal side effects despite of the proximity of the nervous system to the vascular system.3 CASES Our first case was a 62-year-old woman with a pinna and periauricular vascular malformation, noted since 5 years prior to consultation. The inferior concha was bulging and pulsating with a strong bruit. The periauricular area was elevated with microvascular malformations in reddish discoloration. The left posterior auricular artery was identified as the feeding artery and the diagnosis was a high flow AVM. She consulted a hospital in Sacramento, California where she worked and was advised to have a resection of her left ear. She got frightened and decided to come home to the Philippines for a second opinion. I suggested our procedure which she gladly accepted but warned her of possible pinna necrosis. At least, she said, it is just a possibility and not an outright pinna loss. I dissected 1 cm below the malformation avoiding any of its extensions below the pinna and mandibular angle and moved towards the external carotid. I immediately located the pulsating, abnormally dilated posterior auricular artery feeding vessel and ligated it. Further dissection deep towards the styloid process revealed the venous drainage that penetrated the mastoid bone toward the direction of the sigmoid sinus. I too did the venous drainage ligation. I injected sclerogen distal to the posterior artery ligation after aspiration of 8 cc of AVM blood until all the malformation main mass and the peripheral branches blanched out. Total volume of sclerosant was 10 cc. There was no change in the vital signs as I slowly introduced the sclerosant. I closed the surgical defect and observed the patient for three days in the hospital. There was post-operative pain and swelling in the sclerosed malformation, relieved by ice packs and celecoxib 200 mg every 12 hours. After three days, the swelling started to subside and the pain lessened so the patient was sent home. She followed up in a week and the malformation had shrunk. Sutures were removed. Two weeks post-operatively, the malformation was just a trace skin discoloration with no tissue necrosis, no more bulge and pulsations and no pain. She asked permission to go back to work the following week in California. Our second case was a 13-year-old girl with a right tonsillar and hypopharyngeal vascular malformation. She had recurrent bleeding episodes necessitating blood transfusions in their province. I suggested our procedure which the parents and the patient consented to. We did surgery, ligating the right external carotid artery and external jugular vein and introduced the sclerosant (sclerogen) slowly until the tonsillar and hypopharyngeal malformation blanched out. There was no abnormal fluctuation of the patient’s vital signs. After closing the surgical access wound, I did tonsillectomy of the right since the bulging tonsillar malformation was obstructing the airway. There was very minimal bleeding and I was able to cauterize the remaining sclerosed malformation not included in the tonsil with ease. Two weeks post-surgery, she followed up with healed tonsillectomy wound and a disappearing malformation. She however had gastritis because of her co-amoxiclav antibiotic and her inability to eat well because of pain in swallowing. She eventually recovered from her gastric problems. At one-month follow-up, there was no trace of the malformation on visual examination. Looking back, doing tonsillectomy in an AVM would have been very bloody without sclerotherapy. Our third case was a nasopharyngeal AV malformation in a 35-year-old woman. She had episodes of severe bleeding requiring emergency tracheostomy, oral packing and blood transfusions. CT-angiography revealed two feeding vessels, one from the left external carotid artery and a minor one from the internal carotid artery. We decided to sclerose the left external carotid artery and see what happened to the internal carotid artery branch that could not be accessed. Since CT angiography did not identify the venous drainage, we introduced the sclerosant (sclerogen) very slowly, stopping when the pulse rate started to drop below 60 beats per minute and resuming slow injection when the pulse rate was normal. Oxygen saturation was noted to be stable at 98 to 100 %. We stopped when the AVM blanched out, injecting 15 ml of sclerosant. In two weeks time the AVM shrank except for a 1 x 1 cm bulge at the left posterior nasopharynx that was supplied by the internal carotid artery branch that could not be sclerosed at the time of surgery. The patient was decannulated from tracheostomy and was able to resume normal diet and activity. She is on regular follow-up and is being maintained with propranolol 40 mg once a day hoping that it may work as it does in hemangioma. 1 year post operatively, the bulge has not grown nor disappeared. Looking back, had we done surgery as suggested by colleagues, we could have encountered massive bleeding, inability to take the AVM all out, and eventual recurrence. Pondering upon the case of a second arterial blood supply of the AVM, the malformation could have recruited this second blood supply. The forward force of introduction of the sclerosant was not able to overcome the arterial pressure of the internal carotid artery feeding branch so the sclerotherapy effect stopped where the flow forces where at equilibrium. Note that in this case, we did not ligate the specific venous drainage as the CT-angiography did not identify it. DISCUSSION Managing AVMs that are diffuse and infiltrative can be very difficult. Surgical extirpation of all the nidus may not be possible and will surely lead to recurrences. Besides, malformations located in functionally strategic areas may present with structural deformities and functional disturbances when they are damaged by surgery. Small AVMs can be resected with high rates of success and no recurrences. In one series, all 16 patients with surgically accessible, localized, non-infiltrating AVMs who underwent angio-embolization with subsequent surgical excision demonstrated no evidence of recurrence on angiography during follow-up averaging 3 months.9 In low flow venous malformations, sclerotherapy administered by trans-arterial, trans-venous or direct puncture injection without embolization or feeding vessel ligation has a 64 to 96% response rate, defined as improvement in symptoms or reduction of the lesion and not necessarily cure.3 The cure rate for small malformations was 69% with excision only and 62% for extensive lesions with combined embolization and resection. At 6 years average follow-up, cure rate was 75% for stage 1; 67% for stage 2; and 48% for stage 3 malformations. The outcomes were not significantly affected by age at treatment, Schobinger stage, or treatment method.11 Embolo-sclerotherapy is a new therapeutic modality for surgically inaccessible lesions like diffuse and infiltrating AVMs.4 This procedure is done repeatedly since the embolus recanalizes and the sclerosant is injected distal to the embolus. This method is reserved as an adjunct to subsequent surgical resection.4 Our immediate results for ligation of feeding artery or draining vein before sclerotherapy were dramatic without functional or anatomic compromise. With sclerogen, whose components exist in the body naturally, we found no significant complications in our 3 cases. This technique could be ideal for diffuse and infiltrating AVMs. It is more effective if the feeding artery and the draining vein are identified and ligated so that the sclerosant can be pushed to all branches of the AVM. With a “no-flow or a slow-flow” AVM, we are able to prolong the contact of the sclerosant with the vascular endothelium thereby increasing the success rate of totally eliminating the nidus of the vascular malformation. More studies and experience are needed to prove the durability of this technique. Are we able to eliminate all the nidus of the AVM if we are able to ligate all feeding arteries and draining veins before sclerotherapy? Our center is not so equipped so more technically advanced institutions dealing with vascular tumors and malformations can validate the efficacy of this technique. After all, it might not be bane to ligate AVM feeding and draining vessels if we are able to destroy the entire nidus of the AVM by whatever means like sclerotherapy in this case. Acknowledgements I wish to acknowledge my anesthesiologist Dr. Julius Apostol who encouraged me to try new things and promised to research on management of possible egress of sclerosants in the systemic circulation as he puts my patients to sleep. My residents at the Department of Otolaryngology-Head and Neck Surgery, Baguio General Hospital did the pre- and post-operative patient care while I was away, and the photography: Dr. Carlo Pagalilauan, Chief Resident and photographer, Dr. Sherwin Valdez, Dr. Beverly Carbonel, Dr. Jeff Peckley and Dr. Wingleaf Yu who are my assistants. Thank you.