DIGITAL IMAGE STORAGE

Digital image archival requires less physical storage space, allows for rapid storage and retrieval and avoids loss in image quality over time or with image duplication compared with film storage. Because medical imaging data are critically important and, by law, must be stored in a safe, accessible manner, it is imperative not to have one computer error destroy all copies of the image data. Several options for image storage media are available including magnetic tape, optical media, spinning disks and solid state. Other considerations include on-site vs. off-site storage, redundancy, on-line vs. off-line storage, and removable storage media for disaster recovery. The different storage media can be used in different configurations to provide sufficient protection of digital data. Choose a storage system that will keep your data safe from unauthorized access, hardware failure, and clinic disasters.     

DIGITAL IMAGE PROCESSING

Image processing or digital image manipulation is one of the greatest advantages of digital radiography (DR). Preprocessing depends on the modality and corrects for system irregularities such as differential light detection efficiency, dead pixels, or dark noise. Processing is manipulation of the raw data just after acquisition. It is generally proprietary and specific to the DR vendor but encompasses manipulations such as unsharp mask filtering within two or more spatial frequency bands, histogram sliding and stretching, and gray scale rendition or lookup table application. These processing steps have a profound effect on the final appearance of the radiograph, but they can also lead to artifacts unique to digital systems. Postprocessing refers to manipulation of the final appearance of the radiograph by the end-user and does not involve alteration of the raw data.     

RADIOGRAPHY AND IMAGE-INTENSIFIED FLUOROSCOPY OF BARIUM PASSAGE THROUGH THE GASTROINTESTINAL TRACT IN SIX HEALTHY AMAZON PARROTS (AMAZONA AESTIVA)

Gastrointestinal contrast studies were performed in six clinically healthy blue-fronted Amazon parrots (Amazona aestiva) using radiography and image-intensified fluoroscopy. During examination, the birds were confined in a perspex cage. The quality of the lateral radiographs was adequate for assessment of the contrast medium-filled gastrointestinal tract. Thirty minutes after administration of 20 mL/kg of a 25% barium sulphate suspension directly in the crop, in all birds the ventriculus was totally outlined by barium. After 60 min, the small intestine was filled in five of six birds. After 180 min, the crop was empty in all birds. The barium-outlined ventriculus had differences in shape on radiographs of individual birds and also between birds. The colon and cloaca had further filling after 120 to 300 min. With image-intensified fluoroscopy, gastrointestinal motility was evaluated. Contractions of the crop were seen, and boluses of contrast medium passing through the esophagus toward the proventriculus were easily identified. Proventricular contractions were rarely noted, but ventriculus motility was present and clearly defined. The ventriculus had a mean of 3.7 contraction cycles/min. In the duodenum and small intestine, rapid antegrade and retrograde peristaltic movements in combination with segmental contractions were seen. In the colon, occasionally very slow peristaltic activity, mainly of segmental nature, was present. During the examinations, no defeacation was recorded. Confinement in a small perspex cage provides an adequate and handy radiological set-up for evaluation of gastrointestinal passage and motility in birds, minimizing the influences of stress and anesthesia.     

COMPARISON OF FLUOROSCOPY AND COMPUTED TOMOGRAPHY FOR TRACHEAL LUMEN DIAMETER MEASUREMENT AND DETERMINATION OF INTRALUMINAL STENT SIZE IN HEALTHY DOGS

Tracheal collapse is a progressive airway disease that can ultimately result in complete airway obstruction. Intraluminal tracheal stents are a minimally invasive and viable treatment for tracheal collapse once the disease becomes refractory to medical management. Intraluminal stent size is chosen based on the maximum measured tracheal diameter during maximum inflation. The purpose of this prospective, cross‐sectional study was to compare tracheal lumen diameter measurements and subsequent selected stent size using both fluoroscopy and CT and to evaluate inter‐ and intraobserver variability of the measurements. Seventeen healthy Beagles were anesthetized and imaged with fluoroscopy and CT with positive pressure ventilation to 20 cm H₂O. Fluoroscopic and CT maximum tracheal diameters were measured by three readers. Three individual measurements were made at eight predetermined tracheal sites for dorsoventral (height) and laterolateral (width) dimensions. Tracheal diameters and stent sizes (based on the maximum tracheal diameter + 10%) were analyzed using a linear mixed model. CT tracheal lumen diameters were larger compared to fluoroscopy at all locations (P‐value < 0.0001). When comparing modalities, fluoroscopic and CT stent sizes were statistically different. Greater overall variation in tracheal diameter measurement (height or width) existed for fluoroscopy compared to CT, both within and among observers. The greater tracheal diameter measured with CT and lower measurement variability has clinical significance, as this may be the imaging modality of choice for appropriate stent selection to minimize complications in veterinary patients.     

MULTISCALE IMAGE PROCESSING AND ANTISCATTER GRIDS IN DIGITAL RADIOGRAPHY

Scatter radiation is a source of noise and results in decreased signal-to-noise ratio and thus decreased image quality in digital radiography. We determined subjectively whether a digitally processed image made without a grid would be of similar quality to an image made with a grid but without image processing. Additionally the effects of exposure dose and of a using a grid with digital radiography on overall image quality were studied. Thoracic and abdominal radiographs of five dogs of various sizes were made. Four acquisition techniques were included (1) with a grid, standard exposure dose, digital image processing; (2) without a grid, standard exposure dose, digital image processing; (3) without a grid, half the exposure dose, digital image processing; and (4) with a grid, standard exposure dose, no digital image processing (to mimic a film-screen radiograph). Full-size radiographs as well as magnified images of specific anatomic regions were generated. Nine reviewers rated the overall image quality subjectively using a five-point scale. All digitally processed radiographs had higher overall scores than nondigitally processed radiographs regardless of patient size, exposure dose, or use of a grid. The images made at half the exposure dose had a slightly lower quality than those made at full dose, but this was only statistically significant in magnified images. Using a grid with digital image processing led to a slight but statistically significant increase in overall quality when compared with digitally processed images made without a grid but whether this increase in quality is clinically significant is unknown.     

DEEP DIGITAL FLEXOR TENDONITIS IN THE EQUINE FOOT DIAGNOSED BY LOW-FIELD MAGNETIC RESONANCE IMAGING IN THE STANDING PATIENT: 18 CASES

Injury to the distal aspects of the deep digital flexor tendon (DDFT) is an important cause of lameness in horses. The purpose of this study was to review the magnetic resonance imaging (MRI) findings of 18 horses affected by DDFT injuries in the foot. The MRI was performed with the horses standing using an open low-field (0.21 T) MRI scanner. The results were compared with those previously reported for horses using high-field MRI. Eighteen of 84 horses (21%) with undiagnosed forefoot pain were found to have lesions affecting the DDFT. The history, clinical findings and results of radiography, diagnostic ultrasonography and nuclear scintigraphy of these horses were reviewed. The duration of lameness ranged from 1 to 12 months, and the severity varied from 1/10 to 6/10. Fifteen horses had unilateral lameness (right fore in nine, left fore in six), whereas three horses were bilaterally foreleg lame. Radiological changes, considered of equivocal significance, were found in six of 18 horses. Ultrasonographic changes involving the DDFT were identified in only one of nine horses. DDFT lesions were detected in both T1- and T2-weighted MRI sequences. Four different types of lesions were identified: core lesions, sagittal splits, dorsal border lesions, and insertional lesions. Combinations of different lesion types within the same horse were common. The types and locations of the DDFT lesions were similar to those previously reported using high-field MRI. The use of low-field standing MRI avoids the necessity for general anesthesia and access to conventional high-field MRI scanners. However, studies comparing the results of standing low-field MRI with high-field MRI (and other imaging procedures) are required before the sensitivity and specificity of the technique can be assessed.     

DC元数据在中国数字图书馆建设中的应用之我见

最新版本的DCMI元数据术语规定了元数据元素、元素限定词和编码体系修饰词定义的必备属性和有则必备属性。本文区分了DC元数据标准中关于修饰词的几个概念，介绍了DCMI元数据术语定义规范和DC元数据在数字图书馆建设中的优势，探讨了本地应用纲要制定中应注意的问题。     

COMPARISON OF THE IMAGE QUALITY OF A HIGH‐RESOLUTION SCREEN–FILM SYSTEM AND A DIGITAL FLAT PANEL DETECTOR SYSTEM IN AVIAN RADIOGRAPHY

A conventional high‐resolution screen–film system was compared with a digital detector system. A total of 20 birds (14 pigeons and six psittacine birds) with an average body mass of 533 g were examined in dorsoventral as well as lateral projections. Digital radiographs were acquired with the same mAs as well as half the mAs used for the conventional radiographs. Three criteria and one overall assessment were defined for each of four anatomic regions and assessed by five veterinarians using a score system. Comparison of the ratings was done by visual grading analysis. For the majority of criteria, there was no significant difference regarding image quality between the digital and screen–film projections. However, for certain criteria the quality of the digital images was significantly superior. Using the same mAs as for the conventional radiographs, the humeral joint surfaces and the honeycomb structure of the lung were assessed as superior with the digital imaging system. The tracheal rings and the delineation of the trachea from the surrounding tissue were also superior with the digital system. Assessment of the trabecular structure of the humerus was superior when the full mAs was used compared with the reduced mAs. In conclusion the digital technique is equal or superior to the conventional screen–film high‐resolution system for pet birds of a medium size. With some limitations, a dose reduction is possible with the digital system.     

RADIOGRAPHIC, COMPUTED TOMOGRAPHIC AND MAGNETIC RESONANCE IMAGING EVALUATION OF A CHRONIC LONG DIGITAL EXTENSOR TENDON AVULSION IN A DOG

Long digital extensor tendon avulsion is reported in a 5 month old Great Dane. Clinically the dog presented with a unilateral weight-bearing pelvic limb lameness. Joint effusion was present and there was pain and crepitance associated with flexion of the stifle. Orthopedic evaluation and radiographs were suggestive of a long digital extensor tendon injury which was confirmed by computed tomography and magnetic resonance imaging.The injury was surgically repaired with screw and spiked washer fixation.     

THE NETWORK AND ITS ROLE IN DIGITAL IMAGING AND COMMUNICATIONS IN MEDICINE IMAGING

The elements of a digital imaging system are bound together by the network, so careful attention must be paid to this essential component. Networking hardware and cable choice will affect the speed of image transmission between devices within a network. Wireless networking offers convenience at the expense of speed and potentially, security. If a facility allows its network to connect to the Internet, security precautions are essential. Firewalls prevent unauthorized and destructive access to the network; virtual private networks allow encrypted communication with the network; and email and web browser encryption allow data transmitted from the network to other users on the Internet safely. This article presents an overview of this broad array of technologies. Readers are encouraged to seek additional depth as needed to address individual networking needs.     

MAGNETIC RESONANCE IMAGING FINDINGS IN THE EQUINE DEEP DIGITAL FLEXOR TENDON AND DISTAL SESAMOID BONE IN ADVANCED NAVICULAR DISEASE—AN EX VIVO STUDY

We describe the abnormal magnetic resonance (MR) imaging findings in the deep digital flexor tendon (DDFT) and distal sesamoid bone in horses with radiographic changes compatible with navicular syndrome. Thirteen postmortem specimens were examined using a 1.5-T magnetic field, with spin echo (SE) T1-weighted, turbo SE (TSE) proton density-weighted (with and without fat saturation), and fat saturation TSE T2-weighted sequences. The limbs were then dissected to compare the MR findings with the gross assessment and histologic examination of the DDFT and distal sesamoid bones. Tendonous abnormalities were detected by MR imaging in 12 DDFTs and confirmed at necropsy. Most tendon lesions were located at the level of the distal sesamoid bone and the proximal recess of the podotrochlear bursa. Tendon lesions were classified based on their MR imaging features as core lesions, dorsal lesions, dorsal abrasions, and parasagittal splits. Areas of increased MR signal in the DDFTs were characterized by tendon fiber disturbance and lack of continuity of the collagen fibers, foci of edema, hemorrhages, and formation of lakes containing eosinophilic plasma-like material or amphophilic material of low density. Bone marrow signal alterations in the distal sesamoid bone were seen in all digits. Two main phenomena were responsible for the abnormal signal, respectively, in T1-weighted (decreased signal) and in T2-weighted fat-suppressed images (increased signal): a decrease in the fat marrow content in the trabecular spaces and an increase in the fluid content. Histologic examination revealed foci of bone marrow edema, hemorrhage, necrosis, and fibrosis. Cyst formation and trabecular abnormalities (disorganization, thinning, remodelling) were also observed in areas of abnormal signal intensity. Increased bone density because of trabecular thickening induced a decrease in signal in all sequences.     

EFFECT OF DEEP DIGITAL FLEXOR TENDON ORIENTATION ON MAGNETIC RESONANCE IMAGING SIGNAL INTENSITY IN ISOLATED EQUINE LIMBS—THE MAGIC ANGLE EFFECT

Ten normal equine isolated limbs were imaged using a knee coil in a 1.5 Tesla magnetic field, with short echo time sequences (TE < 15 ms). Magnetic resonance imaging was performed on each isolated limb in different positions, with and without extension of the metacarpophalangeal joint. Deep digital flexor tendon orientation ranged from 20 to 60 degrees in relation to the static magnetic field. Increased intratendinous signal intensity was observed when the angle between the deep digital flexor tendon and the constant magnetic field approached 55 degrees ("magic angle"). The increased signal intensity was independent from extension of the metacarpophalangeal joint. Recognition of the magic angle phenomenon is essential for proper evaluation of magnetic resonance imaging studies of the equine foot.     

USE OF CONTRAST-ENHANCED COMPUTED TOMOGRAPHY TO ASSESS ANGIOGENESIS IN DEEP DIGITAL FLEXOR TENDONOPATHY IN A HORSE

We compared contrast-enhanced computed tomography (CT) and high field magnetic resonance (MR) imaging in a horse with deep digital flexor tendonopathy. Lesions in the distal extremity were documented grossly and histopathologically. In contrast-enhanced CT, the deep digital flexor tendon lesions were markedly contrast enhancing with evidence of angiogenesis in the core and dorsal border lesions. The lesion morphology was clearly delineated on MR imaging, but without contrast media angiogenesis cannot be identified. Gross examination, histopathologic examination, and CD31 immunohistochemistry confirmed the tendonopathy and an increased presence of small blood vessels. In this horse, deep digital flexor tendon lesions appeared similarly on contrast-enhanced CT and MR imaging. Contrast-enhanced CT may be an alternative to MR imaging for assessing tendon and ligament injury in the digit of the horse.     

DIGITAL RADIOGRAPHY ARTIFACTS

Radiographic artifacts may mimic a clinical feature, impair image quality, or obscure abnormalities. With the development of digital radiography (DR), a new set of artifacts is introduced. Regardless of the technology, the classic technical errors that occur with film screen radiography still occur using DR. Artifacts created using computed radiography, DR, and incorrect image processing are discussed. Methods for correction of the artifacts are presented.     

TECHNICAL PARAMETERS AFFECTING IMAGE CHARACTERISTICS IN IN VIVO MR MICROSCOPY OF THE MOUSE

The aim of the study was to assess the effects of changing acquisition parameters used for high-resolution in vivo magnetic resonance (MR) microscopy on image quality and scan time. The head or abdomen of 11 normal and 1 glioblastoma-bearing anesthetized BALB/c mice were imaged using a high-resolution 7.0-Tesla magnet. Scan parameters such as matrix size (MTX), slice thickness (ST), number of excitations (NEX), pulse sequence type including repetition time (TR) and echo time (TE), respiratory gating, and intraperitoneal contrast medium administration were altered to assess their actual effect on signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) as compared to calculated effects. As expected, SNR increased with increasing ST or NEX and with decreasing MTX. However, although the empirical increase in SNR was similar to that expected for increased ST, it was less than that anticipated for increasing NEX or decreasing MTX. Increasing NEX and applying respiratory gating both increased SNR and reduced the image degradation associated with respiratory motion in images of the abdomen. Intraperitoneal contrast medium administration produced a marked increase in CNR in the subject with the implanted glioblastoma, suggesting that this route is satisfactory for the enhancement of lesions disrupting the blood-brain barrier. The consequence of improving image quality in terms of spatial and contrast resolution is increased scan time. However, the actual increase in SNR when altering acquisition parameters may not be as much as predicted by theory.     

CLINICAL AND DIAGNOSTIC IMAGING CHARACTERISTICS OF LATERAL DIGITAL FLEXOR TENDINITIS WITHIN THE TARSAL SHEATH IN FOUR HORSES

Lateral digital flexor tendonitis is a rarely reported cause of hind limb lameness in performance horses. The purpose of this retrospective study was to describe clinical and diagnostic imaging findings for a group of horses with lateral digital flexor tendinitis within the tarsal sheath. Equine cases with a diagnosis of lateral digital flexor tendonitis and magnetic resonance imaging (MRI) studies of the affected region were retrieved from North Carolina University's medical record database. Recorded data for included horses were signalment; findings from history, physical examination, lameness examination, and all diagnostic imaging studies; treatment administered; and outcome. Four horses met inclusion criteria. Lameness was mild/moderate in severity and insidious in onset in all patients. Responses to flexion tests were variable. All horses showed positive improvement (70–90%) in lameness after tarsal sheath analgesia. Radiographic, scintigraphic, and ultrasonographic findings were inconclusive. For all horses, MRI characteristics included increased T2, PD, and STIR signal intensity within the lateral digital flexor tendon in the area of the tarsal sheath. Tarsal sheath effusion was slight in three horses, and mild/moderate in one horse. With medical treatment, two horses were sound at 6‐month followup, one horse was sound at 1‐year followup, and one horse had a slight persistent lameness (grade 1/5) at 9‐month followup. Findings supported the use of MRI for diagnosing lateral digital flexor tendonitis within the tarsal sheath in horses. Affected horses may have a good prognosis for return to athletic performance following appropriate medical treatment.     

EVALUATION OF FATTY INFILTRATION OF THE LIVER IN DAIRY CATTLE THROUGH DIGITAL ANALYSIS OF HEPATIC ULTRASONOGRAMS

Ultrasonography of the liver of 49 Holstein-Friesian cows was performed, liver specimens were taken, examined microscopically and the fatty occupying rate (FOR) was calculated. Echoes from the hepatic B-mode ultrasonograms were quantified as histogram mean (Emean) and histogram mode (Emode) of echo amplitudes within various areas at a depth of 1–9 cm from the hepatic surface. Of the 49 animals, 26 had a normal liver and 23 had fatty infiltration of the liver, diagnosed through histopathological examination. Fatty occupying rate ranged from 1.7 to 64.5%, with 11 animals having 1–15% FOR (mild fatty infiltration), 6 having 15.1–30% FOR (moderate fatty infiltration) and 6 having > 30% FOR (severe fatty infiltration). At 1 cm, severe fatty infiltration had higher Emean and Emode than normal liver (p < 0.05). At 7 cm and 9 cm, moderate and severe fatty infiltration had lower Emeans and Emodes than normal liver (p < 0.001). The results suggest that digital analysis of hepatic ultrasonogram can be useful in the evaluation of the degree of fatty infiltration of the liver in dairy cattle.     

数字资源建设及其整合技术在图书馆的应用研究

针对数字图书馆的各类数字对象，构建数字资源的元数据库，并基于该元数据库，实现数字资源整合检索、资源调度、文献传递、信息推送等知识资源服务，从而提出了一个在分布环境下数字图书馆资源建设和资源服务的完整解决方案。     

DOPPLER SONOGRAPHIC EVALUATION OF THE DIGITAL BLOOD FLOW IN HORSES WITH LAMINITIS OR SEPTIC PODODERMATITIS

The aim of this study was to evaluate the use of Doppler ultrasonography to monitor vascular blood flow dynamics in defined diseases of the equine digit in a noninvasive way. Doppler sonography was used to evaluate medial digital artery blood flow in eight horses with septic pododermatitis and four horses with laminitis in comparison with 10 horses of a control group. Doppler sonographic measurement and lameness examinations were performed in lame horses before treatment (day 0) and at 3, 6, and 9 days following treatment. Before treatment, blood flow velocities, arterial diameter, and flow volume were significantly higher in the lame horses, while pulsatility indices (PIs) were significantly lower (P < 0.05). Compared with the control group, there was no significant difference of resistive indices (RI) in the septic pododermatitis group, but these indices were significantly lower in the laminitis group. No significant difference between the two lame groups was recorded. After treatment, blood flow velocities and flow volume decreased significantly and PIs increased significantly in both lame groups, while RI and arterial diameter did not change. No correlation between Doppler parameters and the degree of lameness was found. Doppler sonography can be used to monitor vascular blood flow dynamics in horses suffering from septic pododermatitis and laminitis, while blood flow velocities and PI can serve as parameters for monitoring the course of the disease.