Nasolacrimal Canal Research Articles

New cranial material ofDiscosauriscus pulcherrimus(Seymouriamorpha, Discosauriscidae) from the Lower Permian of the Boskovice Basin (Czech Republic)

ABSTRACTWe describe four newly discovered and three-dimensionally preserved specimens of the discosauriscid seymouriamorphDiscosauriscus pulcherrimusfrom the Lower Permian lacustrine sediments of the Boskovice Basin (Czech Republic). Their excellent preservation revealed new cranial features that allowed us to present a new skull reconstruction of middle-sized specimens of this tetrapod. The new features include: (1) the sculpturing of the anterior wedge-like process of the parasphenoid consisting of irregular ridges, grooves, low elevations and pits; and (2) the presence of a pair of semicircular crests on the posterodorsal surface of the parasphenoidal plate. We discuss the intraspecific variability of several characters, such as the type of dermal cranial ornamentation, and the morphology of the sensory grooves, nasolacrimal canal, dentition on the pterygoids and parasphenoid. The lengths of the skulls of four new specimens range from about 18 to 31mm and represent larval ontogenetic stages.

Prevalence of nasolacrimal canal obstruction and epiphora following maxillary orthognathic surgery

Acquired injuries of the nasolacrimal apparatus may be the result of craniomaxillofacial surgical procedures, facial trauma, or inflammation. Injury to the nasolacrimal duct system following maxillary orthognathic surgery is rarely reported. This study evaluated the importance of early diagnosis and treatment of epiphora developing after Le Fort I surgery. The records of 83 patients who underwent maxillary orthognathic surgery over a 2-year period were reviewed. The prevalence of postoperative epiphora was 3.6% and it persisted for a mean of 32.7 days. No patient required further surgical treatment of the nasolacrimal duct obstruction. Clinicians should evaluate the lacrimal canal position and schedule close postoperative follow-up of injuries to the nasolacrimal apparatus. These may become permanent, necessitating additional surgery.

CT in a Neonate with Nasal Obstruction

A three-day-old girl was referred to the radiology department by the otorhinolaryngologist for work-up of nasal obstruction as she presented with loud nasal respiration and respiratory distress during feeding. Nasal endoscopy revealed a bilateral intranasal mass. CT of the sinonasal region showed a bilateral soft-tissue mass at the medial canthus, with bilateral widening of the nasolacrimal canal, and revealed the presence of a bilateral endonasal mass below the inferior turbinate (Figures 1–3). This triad of imaging findings is diagnostic for a congenital dacryocystocoele. Endonasal wide marsupialisation using a microdebrider was performed, restoring patency of the nasolacrimal apparatus and resolving the symptoms.

Morphological evidence supporting the monophyly of the family Polynemidae (Teleostei: Perciformes) and its sister relationship with Sciaenidae

The monophyly of Polynemidae was evaluated and its sister relationship with Sciaenidae discussed, based on osteological and myological characters from 24 polynemid species in eight genera, with comparisons with acanthomorph fishes from literature and 86 species in 8 orders and 63 families examined. Polynemidae was inferred as a monophyletic group, strongly supported by 19 synapomorphies, including four unique characters (unnamed bone present on cephalic sensory canal extending from supratemporal, third actinost not supporting pectoral-fin rays, section A1 comprising lateral and medial elements, and division of obliquus inferioris present between lower postcleithrum and rod-like process on coracoid) in percoids. In addition, seven pectoral girdle characters were recognized, with the girdle possessing filament-like sensory rays, an adaptation to benthic life in muddy water. The sister relationship of Polynemidae and Sciaenidae was supported by six synapomorphies, including two rather rare (a single branchiostegal ray suspended by epihyal and posterior portions of pelvic bones on both sides interdigitated) and two unique characters (metapterygoid and quadrate interdigitated medially and anterior extension of the nasal canal).

Anatomical Characterization of the Nasolacrimal Canal Based on Computed Tomography in Children With Complex Congenital Nasolacrimal Duct Obstruction.

To characterize anatomical variations of the nasolacrimal canal in patients with complex congenital nasolacrimal duct obstruction. Retrospective case series of 25 children with congenital nasolacrimal duct obstruction. All children had failed probings and were examined by computed tomography. An analysis of imaging data is presented. Anomalous development of the nasolacrimal canal was confirmed on computed tomography. Two main types of malformations were observed: fundamental (20 patients) and special (5 patients). In the fundamental type, the upper portion of the nasolacrimal canal was relatively normal and became significantly stenotic, or even atretic, at the middle and terminal segments. In the special type, the upper portion of the nasolacrimal duct was malformed. Only the special type showed an association with systemic abnormalities. In patients with unilateral fundamental type malformation (11 patients), the transverse and anteroposterior diameters of the upper segment of the nasolacrimal canal on the affected side were significantly larger than that of the normal side (P = .000). The height of the nasolacrimal canal on the normal side was significantly larger than that of the affected side (P = .000). Computed tomography is useful for delineation of anatomical characteristics of the nasolacrimal canal and to diagnose nasolacrimal canal malformation. Malformed nasolacrimal canals are of two main types: fundamental and special. Hydrostatic pressure in the lacrimal duct appears to the underlying mechanism as enlargement of the nasolacrimal canal in the unilateral fundamental type. [J Pediatr Ophthalmol Strabismus. 2017;54(4):238-243.].

The radiologic study of the nasolacrimal duct decompression surgery for treatment of chronic

Objective:To explore the possibility of endoscopic nasolacrimal duct decompression surgery for the treatment of chronic dacryocystitis.Method:①Twenty-two eyes with chronic dacryocystitis were treated with 30% iohexol injection for lacrimal sac lithography. Contrast agents were taken from the lacrimal canal reflux to stop the injection. The CT scan for the lacrimal passage was performed immediately. ②Three-dimensional reconstruction of lacrimal duct and its surrounding structures was performed with Sinuses Trachea Ⅰ software. ③The lacrimal sac and nasolacrimal canal were cut and depressed using this software simulation.Result:①The incidence of lacrimal duct obstruction were 4.5% (1/22, in lacrimal duct), 22.7%(5/22, in lacrimal sac), 13.6%(3/22, transition section), 36.4%(8/22, in nasocrimal duct), and 22.7%(5/22, in Hasner valve) separately. The transitional section, nasolacrimal duct, Hasner valve section 72.7%(16/22) totally. ②The lateral wall of the nasolacrimal duct in 3D visual model is constructed of maxillary lacrimal process. The interior wall of the nasolacrimal duct is made of drop process of lacrimal bone and ascending lacimal process of the inferior turbinate. ③Observed from the inferior meatus, hard nasolacrimal duct is surrounded by inferior turbinate bone, and forms the inside wall of openings of the lacrimal duct. ④The removal of the front parts of the inferior turbinate attached to the lateral nasal can lead to the deperession of the membranous nasolacrimal duct sufficiently, and create the efficient space to eliminate nasolacrimal duct obstruction. Conclusion:Endoscopic nasolacrimal duct decompression surgery is efficacy for the treatment of chronic dacryocystitis. The integrity of the membranous lacrimal duct was reserved, and the complication such as lacrimal sac granulation hyperplasia, lacrimal duct obstruction again caused by scar formation was avoided.

The original method for the endonasal surgical access to the maxillary sinus through crista conchalis of the maxillary bone

The objective of the present work was to develop a technique for the endonasal surgical access to the maxillary sinus through crista conchalis of the maxillary bone and to evaluate the effectiveness and safety of the surgical treatment by this method. A total of 210 patients underwent the CT-assisted examination of the paranasal sinuses. The data obtained made it possible to characterize the detailed anatomical structure of crista conchalis of a maxillary bone that forms the anterior part of the medial wall of the maxillary sinus. The syntopy in relation to the distal end of the nasolacrimal canal and the cavity of the maxillary sinus was investigated. The results of the study were used to develop the original technique for endonasal antrotomy that included the 0.5-1.0 cm long vertical section of the mucous membrane at the level of the anterior end of the inferior turbinated bone approximately 1 mm from the edge of the bone aperture of the nose which exposed crista conchalis up to the place of fixation of the inferior turbinated bone. Then, the diamond drill burr was use to carry out trepanation of the medial wall of the maxillary sinus in the region of crista conchalis of the maxillary bone; sanitation of the of the sinus was followed by the apposition of the edges of the incision and their fixation with two sutures. The safety of the proposed surgical technique was confirmed by results of the repeated CT examinations of the paranasal sinus and its effectiveness by the clinical follow-up observations.

Minimally invasive medial maxillectomy and the position of nasolacrimal duct: the CT study

Several minimally invasive modifications of endoscopic medial maxillectomy have been proposed recently, with the least traumatic techniques utilizing the lacrimal recess as a route to enter the sinus. The aim of the study was to analyze the anatomy of medial maxillary wall in the region of nasolacrimal canal and, thus, to determine the capability of performing minimally invasive approach to the maxillary sinus leading through the lacrimal recess. The course of nasolacrimal canal and the distance between the anterior maxillary wall and the nasolacrimal canal (the width of lacrimal recess) were evaluated in 125 randomly selected computed tomography (CT) head examinations. The proportion of cases with unfavorable anatomical conditions (lacrimal recess too narrow to accept a 4 mm optic) to perform minimally invasive middle maxillectomy was assessed. The width of lacrimal recess, measured at the level of the inferior turbinate attachment, varied between 0 and 15.2 mm and was related to slanted course of nasolacrimal canal. The more perpendicular the axis of the canal to the nasal flor, the narrower the lacrimal recess. In about 16% of cases, lacrimal recess width was less than 4 mm and in 14.4% it was missing. The endoscopic approach to maxillary sinus leading through lacrimal recess is possible in about 70% of patients. In the remaining group of patients when the lacrimal recess is too narrow, this type of approach may be difficult to perform without damaging the piriform aperture rim or bony framework of nasolacrimal duct, or it may be impracticable when lacrimal recess is missing.

Squamous papilloma of the lacrimal sac and the nasolacrimal canal (clinical case report)

The article gives a detailed description of the clinical case of a rather rare eye disease - tumors of the lacrimal SAC and nasolacrimal duct, that usualy is difficult in diagnosis and treatment. We used computer tomography, dacryocystography, endoscopy for examination. The operation of removing tumor of the lacrimal SAC is well described and illustrated. Distinctive appearance of squamous papilloma, which is different from the prevailing views of papilloma attracts attention. Also we noted the number of postopertive features. The paper includes review of the literature concerning tumors of the lacrimal SAC and nasolacrimal duct, analisys of criteria for differential diagnostics of tumors of the lacrimal SAC, classification of malignant tumors of the lacrimal SAC in stages. The information obtained can contribute to the proper diagnosis and treatment of patients with pathology of the lacrimal drainage than will be useful for clinical ophthalmologists.

Imaging Features of Malignant Lacrimal Sac and Nasolacrimal Duct Tumors.

The purpose of this study was to present the imaging features of primary and secondary malignant lacrimal sac and nasolacrimal duct tumors and their pattern of tumor spread in 18 patients. The most common tumor histology in our series was squamous cell carcinoma. In 15/18 patients, tumor involved both the lacrimal sac and duct at the time of diagnosis. In 11/16 patients on CT, the nasolacrimal bony canal was smoothly expanded without erosive changes. The medial canthus region (16/18) was a frequent site of direct tumor spread. Two patients had intraconal orbital spread of tumor. Tumor spread to the sinus or nasal cavity was observed in 5/13 primary tumors. Only 1 patient presented with nodal metastasis. There was no intracranial tumor extension, perineural tumor spread along the infraorbital nerve, distant metastasis, or dacryocystocele formation in any of the patients at the time of diagnosis.

Application of implantation of high-density porous polyethylene artificial nasolacrimal canal for complex orbital fracture combined with lacrimal duct obstruction

Objective To evaluate the curative effect of high-density porous polyethylene artificial nasolacrimal canal (medpor) implantation for complex orbital fracture combined with lacrimal duct obstruction. Methods Seventeen eyes of 17 patients with traumatic lacrimal duct obstruction were treated with artificial nasolacrimal canal implantation. The patients were followed up for 6-36 months after the surgery. Results The epiphora disappeared or improved in all the patients. Postoperative complications including granulation hyperplasia and polyps growing in conjunctival side of the artificial nasolacrimal canal happened in 2 cases(11.8%) and scar covering around the nasolacrimal canal happened in 2 cases (11.8%). Conclusion Artificial nasolacrimal canal (medpor) implantation can obviously improve epiphora in patients with traumatic lacrimal duct obstruction. The method is safe and effective. Key words: Lacrimal duct obstruction, traumatic; Orbital fracture, complex; Artificial nasolacrimal canal(medpor)

Three-Dimensional Reconstruction of the Bony Nasolacrimal Canal by Automated Segmentation of Computed Tomography Images.

ObjectiveTo apply a fully automated method to quantify the 3D structure of the bony nasolacrimal canal (NLC) from CT scans whereby the size and main morphometric characteristics of the canal can be determined.DesignCross-sectional study.Subjects36 eyes of 18 healthy individuals.MethodsUsing software designed to detect the boundaries of the NLC on CT images, 36 NLC reconstructions were prepared. These reconstructions were then used to calculate NLC volume. The NLC axis in each case was determined according to a polygonal model and to 2nd, 3rd and 4th degree polynomials. From these models, NLC sectional areas and length were determined. For each variable, descriptive statistics and normality tests (Kolmogorov-Smirnov and Shapiro-Wilk) were established.Main Outcome MeasuresTime for segmentation, NLC volume, axis, sectional areas and length.ResultsMean processing time was around 30 seconds for segmenting each canal. All the variables generated were normally distributed. Measurements obtained using the four models polygonal, 2nd, 3rd and 4th degree polynomial, respectively, were: mean canal length 14.74, 14.3, 14.80, and 15.03 mm; mean sectional area 15.15, 11.77, 11.43, and 11.56 mm2; minimum sectional area 8.69, 7.62, 7.40, and 7.19 mm2; and mean depth of minimum sectional area (craniocaudal) 7.85, 7.71, 8.19, and 8.08 mm.ConclusionThe method proposed automatically reconstructs the NLC on CT scans. Using these reconstructions, morphometric measurements can be calculated from NLC axis estimates based on polygonal and 2nd, 3rd and 4th polynomial models.

Bilateral infraorbital maxillary air cells: recess-derived non-Haller cells

Abstract BACKGROUND. The infraorbital recess of the maxillary sinus can reach in front of the nasolacrimal duct to become prelacrimal recess. During a routine Cone Beam CT (CBCT) study of a male patient of 72 years old, there were bilaterally found infraorbital maxillary air cells (IMACs) resulted after the almost complete closure of infraorbital recesses of the maxillary sinuses. Only that on the left side was reaching in front of the nasolacrimal canal. The closure of each infraorbital recess leaded to a narrow draining passage opened in the terminal end of the maxillary infundibulum, thus proximal to the maxillary sinus ostium. On the left side, a small cell of the lacrimal bone was interposed between the IMAC drainage pathway and the nasolacrimal canal. On the right side, the nasolacrimal canal was communicating with the ethmoidal infundibulum. Such an anatomic variation in the infraorbital angle of the maxillary sinus can impede the endoscopic procedures which use the anterior lacrimal pathway.

Nasolacrimal System Aeration on Computed Tomographic Imaging: Sex and Age Variation.

To investigate variation in aeration of the nasolacrimal drainage system between age groups and genders, and to report the reliability of repeated aeration grading and nasolacrimal canal measurements on CT. Retrospective review of CT images from 92 individuals, 60 female and 32 male, was conducted by 3 independent reviewers for the presence of air within the nasolacrimal drainage system. Diameter and area measurements were also obtained at the smallest identifiable portion of the nasolacrimal canal by 2 independent reviewers. When air is present on CT, it is seen more fully throughout the nasolacrimal system in men as compared to women. Age data demonstrate that patients from the third and fourth decade have significantly more aeration than older patients. Diameter and area of the nasolacrimal duct within the canal at its narrowest point revealed no correlation with sex, age, or nasolacrimal system aeration. Inter-reviewer reliability shows strong repeatability of aeration grading and nasolacrimal duct measurements between multiple reviewers. The results suggest CT is reliable and repeatable modality to assess nasolacrimal system aeration and nasolacrimal duct diameter. Decreased aeration of the nasolacrimal system in females and the elderly mirrors epidemiologic trends for those at risk to develop primary acquired nasolacrimal duct obstruction. Variables in nasolacrimal drainage system anatomy, specifically nasolacrimal duct diameter and area, did not vary between sexes or age groups, suggesting aeration may be an overlooked variable in nasolacrimal system function.

One-and-a-half nostril endoscopic transsphenoidal approach for pituitary adenomas-a technical report.

BackgroundBinostril endoscopic transsphenoidal approach (BETA) provides sufficient manipulation space and wide endoscopic vision, although it increases the trauma of nose. Mononostril endoscopic transsphenoidal approach (META) has minimal trauma of nose, at the expense of space within the operation. We describe a one-and-a-half nostril endoscopic transsphenoidal approach (OETA) that combines the advantages of BETA and META.MethodsWe introduced OETA for pituitary adenomas with a detailed technical description. A retrospective analysis was also performed on 57 consecutive patients who underwent one-and-a-half nostril endoscopic transsphenoidal surgery between March 2014 and June 2015 at Jinling hospital.ResultsThe gross total resection rate was 79%. The gross complete resection rate of Knosp grade 3 tumors were 63.6, and 27.3% in grade 4 tumors. Postoperative hormone remission was achieved in 14 out of 18 (77.8%) patients with secreting adenomas. Postoperative abnormal visual function improvement was achieved in 23 out of 32 patients (73%) with preoperative visual dysfunction. The overall intra-operative CSF leak was 17.5%, with the postoperative CSF leak decreased to 3.5% after the sellar reconstruction with the unilateral “rescue” nasoseptal flap procedure. The main sinonasal complaints 2 weeks after surgery were: loss of sense of smell (28%), decrease in sense of taste (4%), trouble breathing during the day (18%), thick nasal discharge (36%), post nasal discharge (8%), dried nasal material (6%), and headache (6%). Three months after surgery, there were no reports of decrease of taste, post nasal discharge, or dried nasal material. Other complaints were decreased significantly. Six months after surgery, the main complaints of sinonasal quality of life were negligible, and overall health status was near complete recovery to preoperative status.ConclusionsThe one-and-a-half nostril endoscopic transsphenoidal approach for pituitary adenomas is a simple and reliable technique. It provides not only a sufficient surgical corridor for a 2-surgeon/4 or 3-hands technique, but also ensures minimal invasion of the nasal canal.

Nasolacrimal System Fractures: A Description of Radiologic Findings and Associated Outcomes.

Fractures of the bony nasolacrimal system (NLS), including the lacrimal sac fossa and nasolacrimal canal, have not been comprehensively described in patients with facial trauma. Characterization of these injuries may help facial trauma surgeons better predict which patients will develop lacrimal outflow obstruction symptoms including epiphora and dacryocystitis and who may eventually need lacrimal surgery. CT images for all patients seen at the University of Wisconsin Hospital and Clinics for craniofacial trauma were reviewed from January 2001 to December 2005. Patients were included if they had a NLS fracture and at least 1 year of follow-up. Fracture patterns were described and correlated with clinical outcomes documented in the medical record. Outcomes, including the development of epiphora or dacryocystitis and the need for lacrimal surgery, were analyzed using Fisher exact test. We identified 104 patients with NLS fractures among 1980 patients with craniofacial trauma who had at least 1 year of follow-up. Eleven patients (10.6%) developed epiphora or dacryocystitis, and 2 patients (1.9%) required dacryocystorhinostomy (DCR). Ten radiographic injury patterns were characterized. Avulsion of the lacrimal crest, bone fragment in the lacrimal sac fossa or duct, duct compression greater than 50%, and nasomaxillary buttress displacement were significantly associated with the development of epiphora or dacryocystitis (P < 0.05). Nasomaxillary buttress displacement was significantly associated with the eventual need for DCR (P = 0.03). Patients with radiographic evidence of NLS fracture have an approximately 10% risk of developing epiphora or dacryocystitis. We describe 5 NLS fracture findings that are significantly associated with the development of lacrimal outflow obstruction. The presence of nasomaxillary buttress fracture and displacement suggests a significantly higher risk of eventually needing lacrimal surgery.

Transection of Nasolacrimal Duct in Endoscopic Medial Maxillectomy: Implication on Epiphora.

Management of the nasolacrimal system is usually recommended during medial maxillectomy via external approach because of reported higher rates of postoperative epiphora. Association of the endoscopic medial maxillectomy (EMM) with epiphora, however, is not clearly stated. In this study, we attempted to evaluate whether patients develop epiphora after simple transection of the nasolacrimal duct during EMM. Medical records of 26 patients who underwent endoscopic tumor resection for inverted papilloma (IP) were retrospectively reviewed. Patients who underwent EMM with nasolacrimal canal transection were included and recalled for lacrimal system evaluation. Twelve patients were eligible for inclusion and fluorescein dye disappearance test (FDDT) was performed for each patient. Patient demographics, tumor data, surgical procedures, and follow-up time were recorded. Of the 12 patients included in the study, 6 underwent canine fossa transantral approach concurrently with EMM. The mean duration of follow-up was 21.1 months (range, 6-84 months). Eight patients were graded as 0, whereas 4 patients were graded as 1 according to FDDT. All test results were interpreted as negative for epiphora. All patients were completely symptom free of epiphora. Epiphora after EMM with nasolacrimal canal transection among patients with sinonasal tumors appears to be uncommon. Therefore, prophylactic concurrent management of nasolacrimal system including stenting, dacryocystorhinostomy (DCR), or postoperative lacrimal lavage are not mandatory for all patients.

Idiopathic Bilateral Bloody Tearing

Bloody tear is a rare and distinct clinic phenomenon. We report a case presenting with the complaint of recurrent episodes of bilateral bloody tearing. A 16-year-old girl presented to our clinic with complaint of bloody tearing in both eyes for 3 months. Bloody tearing was not associated with her menses. A blood-stained discharge from the punctum was not observed during the compression of both nasolacrimal ducts. Nasolacrimal passage was not obstructed. Imaging studies such as dacryocystography and gradient-echo magnetic resonance imaging (MRI) of nasolacrimal canal were normal. Intranasal endoscopic evaluation was normal. We collected samples from bloody tears two times and pathological examination was performed. Pathological analysis showed lots of squamous cells and no endometrial cells; dysplastic cells were found. Further evaluations for underlying causes were unremarkable. No abnormalities were found in ophthalmologic, radiologic, and pathologic investigations. This condition is likely a rare abnormality and the least recognized aetiology for the idiopathic phenomenon.

Radiographic observation of nasolacrimal canal in congenital nasolacrimal canal agenesis

To explore the radiographic characteristics of nasolacrimal canals in congenital nasolacrimal canal agenesis. Retrospective case series study. The images of Computed Tomography of 18 children with unilateral congenital nasolacrimal canal agenesis who were treated in Beijing Children's Hospital from January 2009 to June 2013 were studied. The common features of abnormal lacrimal canals were analyzed. The heights of bilateral lacrimal canals, anterioposterior and transverse diameters at the original level of lacrimal canal were measured. The traverse diameters, anteroposterior diameters, heights of bony nasolacrimal duct between affected side and normal side were compared using paired t tests. The initial segment of abnormal nasolacrimal canal showed no obvious abnormalities, but it became significant stenosis or even atresia at the middle and terminal segments. The transverse (4.72 ± 0.79) mm and anterioposterior diameters (5.45 ± 1.07) mm of affected sides were larger than the values of normal sides (3.42 ± 0.67) mm, (4.35 ± 1.01) mm at the original level of nasolacrimal canal with statistically significance (t = 5.665, P = 0.000; t = 6.610, P = 0.000). However, the height of nasolacrimal canal of normal sides were larger than the affected sides (t = 5.931, P = 0.000). Atresia position of congenital nasolacrimal canal agenesis always located in the terminal segment. High pressure in the nasolacrimal duct caused by bony obstruction leaded to the enlargement of nasolacrimal canal in affected side.

Experimental induction of left abomasal displacement: a new educational technique

Summary The purpose of this study was to induce abomasal displacement to the left, and to let the undergraduate and post graduate students get used to the ping sounds of abomasum and other clinical manifestations. The procedure was carried out on eight young bulls, they were sedated and a 2 m flexible tube was inserted through the nasal canal into the rumen. By laparo-rumenotomy, 20 cm of the tube was inserted into the abomasums through the omaso-abomasal groove. The rumen wall and abdominal wall were apposed routinely. The animal was casted on its right side on the floor. The abomasum was inflated through the external end of the tube which was tied to bull’s horn base. Then the animal was allowed to stand on its feet. The gas filled abomasum was mobilized to the left flank between the body wall and the rumen. The left abomasal displacement was confirmed by ping and ultrasonography. Experimental induction of left abomasal displacement by inflating the abomasum using a nasal abomasal tube following rumenotomy is a safe and suitable technique for educational and research purposes.