Effects of Image Compression on Linear Measurements of Digital Panoramic Radiographs

Abstract This study aimed to evaluate the accuracy of panoramic radiographs obtained by digital system based on charge coupled device (CCD) and a phosphor storage plate (PSP) system with two different file formats, JPEG irreversible type and BMP. Linear measurements of artificial bony defects were made in dry mandibles with a digital caliper. Measures of digital panoramic radiographs were taken in ImageJ(r) software. Each measurement was performed twice by an experienced examiner. The intra-rater agreement was considered very strong (Pearson's correlation coefficient of 0.97). There was no significant difference between the linear measurements of dry mandibles, considered the gold standard, in relation to measurements obtained from digital radiographs (p=0.47). The error of these measures for the CCD was 1.04 mm (9.97%) for JPEG images and 1.03 mm (9.99%) for those with BMP format. For the PSP images, these values were 1.48 mm (14.94%) and 1.43 mm (14.43%), respectively. Although there was no statistical difference between the images with JPEG and BMP format, for both digital systems (p=1.00 for CCD and p=0.98 for PSP system), errors made on radiographs obtained by PSP system were significantly higher than those of CCD (p<0.05). The size of the files saved in JPEG was also significantly lower (p=0.005) compared with the files saved in BMP. It may be concluded that the digital radiographs, both saved in JPEG and BMP formats, are accurate, regardless the used digital system, and JPEG images are more suitable for teleradiology.

Resumo Este estudo teve como objetivo avaliar a acurácia de radiografias panorâmicas digitais obtidas por sistema digital baseado em dispositivo acoplador de carga (DAC) e por sistema de placa de fósforo (PF) com duas diferentes extensões de arquivo (JPEG e BMP, sendo o primeiro do tipo compactador irreversível). Medidas lineares de defeitos ósseos foram realizadas em mandíbulas secas com paquímetro digital. As medidas correspondentes nas radiografias panorâmicas digitais foram realizadas no software ImageJ(r). As medidas foram realizadas duas vezes por um examinador. A concordância intraexaminador foi considerada muito forte (coeficiente de correlação de Pearson de 0,97). Não houve diferença significante entre as medidas lineares das mandíbulas secas, consideradas padrão-ouro, em relação às medidas obtidas das radiografias digitais (p=0,47). Os erros absolutos e relativos dessas medidas para o DAC foram de 1,04 mm (9,97%) para as imagens JPEG e de 1,03 mm (9,99%) para aquelas com extensão BMP. Para o sistema digital com PF esses valores foram de 1,48 mm (14,94%) e 1,43 mm (14,43%), respectivamente. Apesar de não ter havido diferença estatística entre as imagens com extensão JPEG e BMP, para ambos os sistemas digitais (p=1,00 para DAC e p=0,98 para a PF), os erros das medidas realizadas nas radiografias obtidas pelo sistema de PF foram significativamente maiores que os erros do DAC (p<0,05). O tamanho dos arquivos salvos em JPEG também foram significativamente menores (p=0,005) em comparação com os arquivos salvos em BMP. Pode-se concluir que as radiografias digitais tanto com extensão JPEG quanto BMP são acuradas, independente do sistema digital utilizado e as imagens salvas em JPEG são mais indicadas em telerradiologia.

Influence of Image Compression on the Interpretation of Optical Coherence Tomography in Diabetic Macular Edema

PURPOSE: To evaluate the influence of image compression on optical coherence tomography (OCT) images in eyes with diabetic macular edema (DME). METHODS: Twenty eyes of 30 patients diagnosed with DME were included in this retrospective observational case series. Horizontal OCT scans centered at the center of the fovea were conducted using spectral-domain OCT (Spectral OCT/SLO(R)). The images were exported to Tag Image File Format (TIFF) and then transformed to 10, 5, and 1 quality of Joint Photographic Experts Group (JPEG) format using Photoshop. OCT images were taken before and after intravitreal bevacizumab injection. The presence of intraretinal fluid, foveolar detachment, and photoreceptor inner segment/outer segment (IS/OS) disruption were evaluated in each image. RESULTS: The mean (+/- standard deviation) size of TIFF images and 10, 5 and 1 quality JPEG images were 1712.0, 183.3 +/- 6.8, 90.9 +/- 4.3, 42.8 +/- 1.4 kilobytes (KB), respectively, before the injection and 1712.0, 189.5 +/- 9.1, 94.9 +/- 5.6, 43.4 +/- 1.8 KB, respectively, after the injection. The presence of intraretinal fluid, foveolar detachment, and photoreceptor IS/OS disruption identified in TIFF images was also identified in the compressed JPEG images. CONCLUSIONS: Quality of retinal OCT image did not influence the estimation of DME despite the JPEG image being compressed to approximately 1/40 of the original TIFF image size.

A review of medical image compression techniques / 国际生物医学工程杂志

As the increasing of digital imagilag modalities,a close-at-hand challenge to deal with is the storage and transmission requirement of enormous data of medical images.Compression is one of the indispensable techniques to solve this problem.A comprehensive review and discussions are made in this paper over the medial image compression techniques applied in medical image domain,including the latest achievements in this field.Different compression algorithm including ROI-based coding,lossless compression,DWT,neural net are introduced and some quality evaluation methods are introduced.Foreground of the field is given from our point of view.

Evaluation of compression ratios using JPEG 2000 on diagnostic images in dentistry / 대한구강악안면방사선학회지

PURPOSE: To find out the proper compression ratios without degrading image quality and affecting lesion detectability on diagnostic images used in dentistry compressed with JPEG 2000 algorithm. MATERIALS AND METHODS: Sixty Digora periapical images, sixty panoramic computed radiographic (CR) images, sixty computed tomographic (CT) images, and sixty magnetic resonance (MR) images were compressed into JPEG 2000 with ratios of 10 levels from 5 : 1 to 50 : 1. To evaluate the lesion detectability, the images were graded with 5 levels (1: definitely absent; 2: probably absent; 3: equivocal; 4: probably present; 5: definitely present), and then receiver operating characteristic analysis was performed using the original image as a gold standard. Also to evaluate subjectively the image quality, the images were graded with 5 levels (1: definitely unacceptable; 2: probably unacceptable; 3: equivocal; 4: probably acceptable; 5: definitely acceptable), and then paired t-test was performed. RESULTS: In Digora, CR panoramic and CT images, compressed images up to ratios of 15 : 1 showed nearly the same lesion detectability as original images, and in MR images, compressed images did up to ratios of 25 : 1. In Digora and CR panoramic images, compressed images up to ratios of 5 : 1 showed little difference between the original and reconstructed images in subjective assessment of image quality. In CT images, compressed images did up to ratios of 10 : 1 and in MR images up to ratios of 15 : 1. CONCLUSION: We considered compression ratios up to 5 : 1 in Digora and CR panoramic images, up to 10 : 1 in CT images, up to 15 : 1 in MR images as clinically applicable compression ratios.

Comparison of JPEG and wavelet compression on intraoral digital radiographic images / 대한구강악안면방사선학회지

PURPOSE: To determine the proper image compression method and ratio without image quality degradation in intraoral digital radiographic images, comparing the discrete cosine transform (DCT) -based JPEG with the waveletbased JPEG 2000 algorithm. MATERIALS AND METHODS: Thirty extracted sound teeth and thirty extracted teeth with occlusal caries were used for this study. Twenty plaster blocks were made with three teeth each. They were radiographically exposed using CDR sensors (Schick Inc., Long Island, USA). Digital images were compressed to JPEG format, using Adobe Photoshop v.7.0 and JPEG 2000 format using Jasper program with compression ratios of 5 : 1, 9 : 1, 14 : 1, 28 : 1 each. To evaluate the lesion detectability, receiver operating characteristic (ROC) analysis was performed by the three oral and maxillofacial radiologists. To evaluate the image quality, all the compressed images were assessed subjectively using 5 grades, in comparison to the original uncompressed images. RESULTS: Compressed images up to compression ratio of 14 : 1 in JPEG and 28 : 1 in JPEG 2000 showed nearly the same the lesion detectability as the original images. In the subjective assessment of image quality, images up to compression ratio of 9 : 1 in JPEG and 14 : 1 in JPEG 2000 showed minute mean paired differences from the original images. CONCLUSION: The results showed that the clinically acceptable compression ratios were up to 9 : 1 for JPEG and 14 : 1 for JPEG 2000. The wavelet-based JPEG 2000 is a better compression method, comparing to DCT-based JPEG for intraoral digital radiographic images.

3-D Lossless Volumetric Medical Image Compression Using 3-D Integer Wavelet Transform and Lifting Steps / 대한의료정보학회지

This paper focuses on lossless medical image compression methods for medical images that operate on three-dimensional(3-D) irreversible integer wavelet transform. We offer an application of the Set Partitioning in Hierarchical Trees(SPIHT) algorithm to medical images, using a 3-D wavelet decomposition and a 3-D spatial dependence tree. The wavelet decomposition is accomplished with integer wavelet filters implemented with the lifting method, where careful scaling(square root 2) and truncations keep the integer precision and the transform unitary. We have tested our encoder on volumetric medical images using different integer filters and different coding unit sizes. The coding unit sizes of 16 slices save considerable dynamic memory(RAM) and coding delay from full sequence coding units used in previous works. Results show that, even with these small coding units, our algorithm with certain filters performs as well and better in lossless coding than previous coding systems using 3-D integer wavelet transforms on volumetric medical images.

Hospital Information Exchange System Using XML Document / 대한의료정보학회지

Recently many domestic hospitals computerize and automatize the process to manage their own medical data. These medical data should be shared among the departments in the hospital and be held in common in case of patients transfers or references to the remote hospitals. However, there is no simple method to share data among the management systems to be shared due to their heterogeneous platforms. Schema sharing with systems and standard format data transfer could be a solution. In this paper, we propose HIES(Hospital Information Exchange System), which uses XML as a standard medical data transfer method. HIES uses XML, which is currently recognized as the standard of electronic documents, for integrating and managing heterogeneous and distributed medical data. Information Sharing Manager to maintain consistent schema information for heterogeneous database systems in hospital systems as well as Image Compression/Partition Manager for efficient image data transfer and reemergence among the systems are implemented.

Optimum image compression rate maintaining diagnostic image quality of digital intraoral radiographs / 대한구강악안면방사선학회지

PURPOSE: The aims of the present study are to determine the optimum compression rate in terms of file size reduction and diagnostic quality of the images after compression and evaluate the transmission speed of original or each compressed images. MATERIALS AND METHODS: The material consisted of 24 extracted human premolars and molars. The occlusal surfaces and proximal surfaces of the teeth had a clinical disease spectrum that ranged from sound to varying degrees of fissure discoloration and cavitation. The images from Digora system were exported in TIFF and the images from conventional intraoral film were scanned and digitalized in TIFF by Nikon SF-200 scanner(Nikon, Japan). And six compression factors were chosen and applied on the basis of the results from a pilot study. The total number of images to be assessed were 336. Three radiologists assessed the occlusal and proximal surfaces of the teeth with 5-rank scale. Finally diagnosed as either sound or carious lesion by one expert oral pathologist. And sensitivity and specificity and kappa value for diagnostic agreement was calculated. Also the area(Az) values under the ROC curve were calculated and paired t-test and oneway ANOVA test was performed. Thereafter, transmission time of the image files of the each compression level were compared with that of the original image files. RESULTS: No significant difference was found between original and the corresponding images up to 7%(1:14) compression ratio for both the occlusal and proximal caries(p<0.05). JPEG3(1:14) image files are transmitted fast more than 10 times, maintained diagnostic information in image, compared with original image files. CONCLUSON: 1:14 compressed image file may be used instead of the original image and reduce storage needs and transmission time.

Web Browsing and Transmitting of DICOM Image in HIFU Remote Diagnosis System / 医疗卫生装备

Objective To transmit and browse DICOM images in HIFU remote diagnosis system in Web.Methods Mix-patterned programming of.NET and VC++ was used to create a multi-layers architecture.Results The online compression and web browsing of DICOM images were realized.Conclusion Treatment can be livingly played back and suggestions were proposed for doctors.Medical service in high quality can be provided for remote patients.[Chinese Medical Equipment Journal,2008,29(3):39-41]