Pediatric digital echocardiography: a study of the analog-to-digital transition

John Sutton MG, Ferrari VA, Scott CH, Wiegers SE. Failure of digital echocardiography to accurately diagnose intracardiac shunts

BACKGROUND

Intravenous agitated saline injection during transthoracic echocardiography assists in the detection of right to left intracardiac and intrapulmonary shunts. Whether digital echocardiography offers comparable sensitivity and specificity to analog tape recording to assess shunts is unknown. Technical differences between methods could lead to significant differences in shunt detection.

METHODS

Agitated saline was injected intravenously at rest and with Valsalva in 189 consecutive patient studies (406 injections). Echocardiographers assessed presence and degree of left ventricle contrast on simultaneously recorded analog tape and digital echocardiography images in blinded fashion.

RESULTS

Digital echocardiography had low overall sensitivity (rest 0.50, valsalva 0.63, late 0.39) compared to analog tape. Longer clip lengths improved sensitivity for detection of late contrast passage (rest 0.50, valsalva 0.67, late 0.46).

CONCLUSION

Digital echocardiography saline contrast studies have poor sensitivity for assessment of intracardiac shunts versus analog tape, and increasing clip length only modestly increases sensitivity. Joint Photographic Experts Group digital compression losses may be an important cause of failure to detect intracardiac shunts, including patent foramen ovale.

High-grade video compression of echocardiographic studies: a multicenter validation study of selected motion pictures expert groups (MPEG)-4 algorithms

BACKGROUND

Large files produced by standard compression algorithms slow down spread of digital and tele-echocardiography. We validated echocardiographic video high-grade compression with the new Motion Pictures Expert Groups (MPEG)-4 algorithms with a multicenter study.

METHODS

Seven expert cardiologists blindly scored (5-point scale) 165 uncompressed and compressed 2-dimensional and color Doppler video clips, based on combined diagnostic content and image quality (uncompressed files as references). One digital video and 3 MPEG-4 algorithms (WM9, MV2, and DivX) were used, the latter at 3 compression levels (0%, 35%, and 60%).

RESULTS

Compressed file sizes decreased from 12 to 83 MB to 0.03 to 2.3 MB (1:1051-1:26 reduction ratios). Mean SD of differences was 0.81 for intraobserver variability (uncompressed and digital video files). Compared with uncompressed files, only the DivX mean score at 35% (P = .04) and 60% (P = .001) compression was significantly reduced. At subcategory analysis, these differences were still significant for gray-scale and fundamental imaging but not for color or second harmonic tissue imaging. Original image quality, session sequence, compression grade, and bitrate were all independent determinants of mean score.

CONCLUSIONS

Our study supports use of MPEG-4 algorithms to greatly reduce echocardiographic file sizes, thus facilitating archiving and transmission. Quality evaluation studies should account for the many independent variables that affect image quality grading.

A low-cost digital filing system for echocardiography data with MPEG4 compression and its application to remote diagnosis

The high cost of digital echocardiographs and the large size of data files hinder the adoption of remote diagnosis of digitized echocardiography data. We have developed a low-cost digital filing system for echocardiography data. In this system, data from a conventional analog echocardiograph are captured using a personal computer (PC) equipped with an analog-to-digital converter board. Motion picture data are promptly compressed using a moving pictures expert group (MPEG) 4 codec. The digitized data with preliminary reports obtained in a rural hospital are then sent to cardiologists at distant urban general hospitals via the internet. The cardiologists can evaluate the data using widely available movie-viewing software (Windows Media Player). The diagnostic accuracy of this double-check system was confirmed by comparison with ordinary super-VHS videotapes. We have demonstrated that digitization of echocardiography data from a conventional analog echocardiograph and MPEG 4 compression can be performed using an ordinary PC-based system, and that this system enables highly efficient digital storage and remote diagnosis at low cost.

Absent posteroinferior and anterosuperior atrial septal defect rims: factors affecting nonsurgical closure of large secundum defects using the amplatzer occluder

Using transesophageal echocardiography, we sought to determine the anatomic characteristics of the secundum atrial septal defects (ASDs) that extend into the inferior sinus venosus and have no posteroinferior (PI) rim, to determine the factors related to potential closure with an Amplatzer occluder. We also sought to understand why large secundum ASDs with a PI but without an anterosuperior (AS) rim may require special techniques to reorient the left atrial disk before deployment of the waist and right atrial disk. We measured the lengths of 5 separate rims of the circumferences of 76 secundum ASDs, including anteroinferior, AS, superior, posterosuperior, and PI rims. We also measured anteroposterior and superoinferior defect diameters, total septal lengths, and the ratios of defect diameter to total septal length. The atrial depth was measured at the axial angle of the delivery sheath in 5 defects with no AS rim for which special techniques were required to achieve successful closure. Of 76 secundum ASDs, 13 (17%) had no PI rim. Each defect extended from the fossa ovalis into the inferior sinus venosus. Compared with defects with a PI rim, the factors related to potential closure included 100% larger defect diameters, shorter posterosuperior rim lengths, larger defect to total septal length ratios, and completely flat posterior atrial walls. When the AS rim was absent the factors related to the need for special techniques included diameters >/= 22 mm, atrial depth < the calculated Amplatzer occluder left atrial disk diameter, rigid wire/disk interface, and obligatory left atrial disk orientation more or less perpendicular to the atrial septal plane.

Conversion to digital technology improves efficiency in the pediatric echocardiography laboratory

BACKGROUND

Although the videotape method (VTM) is commonly used to record and intrepret ecocardiographic images, many pediatric echocardiographers are considering acquiring to, interpreting from, and storing their images to digital disk using the single-beat digital acquisition method (SBM). The paucity of image redundancy using SBM should translate into improved laboratory efficiency compared with VTM, but hard data are lacking. The purpose of this study was to test the hypothesis that the time to acquire images to videotape using VTM and to disk using SBM would be the same for normal hearts and corresponding congenital heart diseases, but interpretation times would be shorter using SBM.

METHODS

We measured the times to acquire and interpret 403 echocardiograms using standard VTM from Children's Hospital in Cincinnati, Ohio, and 352 echocardiograms acquired using SBM from Children's Hospital in San Diego, Calif. Diagnostic categories at each site included: (1) normal, (2) simple shunt or isolated valve disease, and (3) multiple-lesion disease.

RESULTS

As a group, SBM echocardiograms included more hemodynamic measurements and took more time to acquire (P <.037), but less time to read (P <.001) than corresponding images acquired using VTM. Using SBM, it took more time to acquire normals and isolated valve or shunt lesions, whereas the average time to acquire multiple-lesion disease was the same using both VTM and SBM. With SBM, in contrast, interpretation times were significantly less for all corresponding diagnoses.

CONCLUSION

SBM studies took longer to acquire because more hemodynamic measurements were acquired, but they were read in less time than corresponding VTM studies even though all videotapes were replayed in search fast-forward mode. Pediatric echocardiographers can increase their laboratory efficiency by converting from VTM to SBM.

Digital echocardiography 2002: now is the time

The ability to acquire echocardiographic images digitally, store and transfer these data using the DICOM standard, and routinely analyze examinations exists today and allows the implementation of a digital echocardiography laboratory. The purpose of this review article is to outline the critical components of a digital echocardiography laboratory, discuss general strategies for implementation, and put forth some of the pitfalls that we have encountered in our own implementation. The major components of the digital laboratory include (1) digital echocardiography machines with network output, (2) a switched high-speed network, (3) a high throughput server with abundant local storage, (4) a reliable low-cost archive, (5) software to manage information, and (6) support mechanisms for software and hardware. Implementation strategies can vary from a complete vendor solution providing all components (hardware, software, support), to a strategy similar to our own where standard computer and networking hardware are used with specialized software for management of image and measurement information.

Telecardiology: potential impact on acute care

Echocardiography is often used to diagnose and exclude important cardiac diagnoses in adults and children. Evolving telemedicine technology has the potential to improve access to echocardiography diagnoses in the intensive care unit, emergency room, and newborn nursery. The two primary modes of telemedicine practice are "store and forward" and "real-time" videoconferencing. A digital echocardiogram (often several one cardiac cycle loops) can be stored at one site and forwarded across a telemedicine network to a receiving station for review at a later time. Pediatric cardiologists often favor "real-time" telemedicine because of the ability to guide sonographers with limited experience in congenital heart disease. A complete telemedicine system requires a modified computer, a low- or high-speed connection, and telemedicine inputs. Several adult and pediatric clinical studies have shown telemedicine to be accurate and cost-effective, improve patient care, enhance echocardiogram quality and sonographer proficiency, and promote practice expansion. Obstacles to widespread implementation of telemedicine include lack of standardization of telemedicine components, confusing legal issues and licensure requirements, and poor reimbursement.