3D Multislice CT Angiography in Post-Aortic Stent Grafting: A Pictorial Essay

Helical CT angiography has been widely used in both pre- and post-aortic stent grafting and it has been confirmed to be the preferred modality when compared to conventional angiography. The recent development of multislice CT (MSCT) has further enhanced the applications of CT angiography for aortic stent grafting. One of the advantages of MSCT angiography over conventional angiography is that the 3D reconstructions, based on the volumetric CT data, provide additional information during follow-up of aortic stent grafting. While endovascular repair has been increasingly used in clinical practice, the use of 3D MSCT imaging in endovascular repair continues to play an important role. In this pictorial essay, we aimed to discuss the diagnostic performance of 3D MSCT angiography in post aortic stent grafting, including the most commonly used surface shaded display, curvilinear reformation, the maximum intensity projection, volume rendering and virtual endoscopy. The advantages and disadvantages of each 3D reconstruction are also explored.

Impact of Image Post-Processing on PACS Workstation: Dynamic Range Suppression(DRS) of Chest Radiographs

PURPOSE: To investigate the impact of post-processing on a PACS workstation before and after use of thedynamic range suppression method for the normal chest radiographs. MATERIALS AND METHODS: Forty normal chestradiographs of healthy adult volunteers aged 20 to 33 (average 27; M:F = 29:11) were acquired by FCR using adigital interface and then transferred to an in-house-developed PACS workstation. The image size of computed chestradiographs was 7.5MB with 1760 x 2140 matrix. An image enhancement processing named DRS, developed by theauthors, was applied to the acquired images and generated a total of 40 chest radiographs. These were presented tothree groups of observers, each consisting of one radiologist and one technician on the PACS workstation, whichhad two monitors of 1712 x 2100 resolution. So that external light would not affect the visibility of imagesduring observation, these were displayed in a light-controlled room. The J.J.Vucich method, suitably modified, wasused to evaluate the anatomical structures and physical parameters of processed and unprocessed radiographs. Usinga percentage scale, the observers evaluated both anatomical sections (seven anatomical items : cortical margins ofribs, left diaphragms, thoracic vertebrae, trachea, pulmonary vasculature, trabeculae of ribs and clavicle,diaphragm outline) and physical sections (four items : contrast, graininess, density, detail). The results for thethree groups, both before and after DRS processing, were then compared. RESULTS: There was a statisticallysignificant difference between the three groups: in the anatomical section, 78.64 before DRS and 82.55 after ; andin the physical section, 75.48 and 79.78 (p<0.05). The average values of all items were 77.06 before DRS and 81.17after (p<0.05). CONCLUSION: Post-processing of computed chest radiographs on the PACS workstation improves boththe visibility of anatomical features and general image quality. Thus, in a PACS environment, it can be a usefultool for enhancing the diagnostic efficacy of radiography.

Impact of Image Post-Processing on PACS Workstation: Dynamic Range Suppression(DRS) of Chest Radiographs

PURPOSE: To investigate the impact of post-processing on a PACS workstation before and after use of thedynamic range suppression method for the normal chest radiographs. MATERIALS AND METHODS: Forty normal chestradiographs of healthy adult volunteers aged 20 to 33 (average 27; M:F = 29:11) were acquired by FCR using adigital interface and then transferred to an in-house-developed PACS workstation. The image size of computed chestradiographs was 7.5MB with 1760 x 2140 matrix. An image enhancement processing named DRS, developed by theauthors, was applied to the acquired images and generated a total of 40 chest radiographs. These were presented tothree groups of observers, each consisting of one radiologist and one technician on the PACS workstation, whichhad two monitors of 1712 x 2100 resolution. So that external light would not affect the visibility of imagesduring observation, these were displayed in a light-controlled room. The J.J.Vucich method, suitably modified, wasused to evaluate the anatomical structures and physical parameters of processed and unprocessed radiographs. Usinga percentage scale, the observers evaluated both anatomical sections (seven anatomical items : cortical margins ofribs, left diaphragms, thoracic vertebrae, trachea, pulmonary vasculature, trabeculae of ribs and clavicle,diaphragm outline) and physical sections (four items : contrast, graininess, density, detail). The results for thethree groups, both before and after DRS processing, were then compared. RESULTS: There was a statisticallysignificant difference between the three groups: in the anatomical section, 78.64 before DRS and 82.55 after ; andin the physical section, 75.48 and 79.78 (p<0.05). The average values of all items were 77.06 before DRS and 81.17after (p<0.05). CONCLUSION: Post-processing of computed chest radiographs on the PACS workstation improves boththe visibility of anatomical features and general image quality. Thus, in a PACS environment, it can be a usefultool for enhancing the diagnostic efficacy of radiography.

Computed Radiogra p hy in Skeletal Imaging: Visual Assessment of Compressed Image Quality

PURPOSE: To evaluate the effect of lossy image compression on skeletal images and to determine the compression ratio which does not lead to difficulties when images are interpreted for diagnostic purposes. MATERIALS AND METHODS: Thirty-two computed radiographs (CR) of osteolytic bone tumors were obtained from Picture Archiving and Communication System. They were compressed to three different levels (Q factor 30, 70, 120) using the JPEG (Joint Photographic Expert Group) technique. Ninety-six pairs of uncompressed and compressed images were randomly ordered and then serially displayed on two high-resolution monitors. During a side-by-side review, three radiologists independently compared each pair of uncompressed and compressed images, and these were rated once using a five-category ordinal scale for tumor-related findings, linear structures, and soft tissues. The reviewers were then obliged to decide which image in each pair was of better quality, and finally, they were asked to evaluate the influence of image compression on diagnostic accuracy. RESULTS: The reviewers found no significant difference in image quality between uncompressed and compressed images with a Q factor 30. Compressed images with a Q factor of 70 or 120, however, revealed clinically relevant degradation. Among 96 observations of compressed images, 15 with a Q factor of 70 and 35 with a Q factor of 120 were considered inadequate for clinical purposes. CONCLUSION: If the JPEG technique is used, compressed CR skeletal images with a Q factor of 30 are acceptable for clinical application. Compressed images with a Q factor of 70 or 120 may, however, cause diagnostic difficulty and thus cannot be used for clinical purposes.

Transmission of DICOM 3.0 type MR data to the personal computer in the hospital without PACS

PURPOSE: To transmit DICOM data to a personal computer in the hospital without PACS, and estimate theusefulness of digital image management and its convenience for physicians through transmitted file size,transmission time and quality of transmitted images. MATERIALS AND METHODS: The raw data of three brain MRI andlumbar spine MRI were transmitted from an MR system to a personal computer via Ethernet TCP/IP connection. Thefile size and transmission time of transmitted images were measured according to the matrix number. Threeboard-certified radiologists compared the image quality of the transmitted and scanned images. RESULTS: Thetransmission of DICOM data to the personal computer was successful and the transmitted images and their headerinformation were displayed by various personal computer-based DICOM viewing programs. The file size andtransmission time of the 256 and 512 matrix images were 136 Kbyte, 2.17 seconds/slice and 520 Kbyte, 4.37seconds/slice, respectively. All radiologists regarded the transmitted brain MRI images as superior. Oneradiologist considered the transmitted lumbar spine MRI images superior, while others decided that the quality oftransmitted and scanned images was the same. CONCLUSION: The transmission of DICOM format image data to apersonal computer through an appropriate DICOM receiving program is useful for managing digital images andconvenient for physicians in the hospital without PACS.

Image Viewing Station for MR and SPECT: Using Personal Computer

PURPOSE: Macro language was programmed to analyze and process on Macintosh personal computers GE MR imagesdigitally transferred from the MR main computer, with special interest in the interpretation of information such as patients data and imaging parameters under each image header. By this method, raw data(files) of certain patients may be digitally stored on a hard disk or CD ROM, and the quantitative analysis, interpretation anddisplay is possible. MATERIALS AND METHODS: Patients and images were randomly selected. 4.X MR images were transferred through FTP using the ethernet network. 5.X and SPECT images were transferred using floppy diskets. Toprocess transferred images, an freely distributed software for Macintosh namely NIH Image, with its macrolanguage, was used to import images and translate header information. To identify necessary information, aseparate window named "Info-txt", was made for each image series. MacLC, Centris650, and PowerMac 6100/CD,7100/CD, 8100/CD models with 256 color and RAM over 8 Mbyte were used. RESULTS: Different versions of MR images and SPECT images were displayed simultaneously and a separate window named "Info-txt" was used to show all necessary information(name of the patient, unit number, date, TR, TE, FOV etc.). Additional information(diagnosis,pathologic report etc.) was stored in another text box in "Info-txt". The size of the file for each image planewas about 149 Kbytes and the images were stored in a step-like file folders. CONCLUSION: 4.X and 5.X GE Signa 1.5T images were successfully processed with Macintosh computer and NIH Image. This result may be applied to manyfields and there is hope of a broader area of application with the linkage of NIH Image and a database program.