1024 Matrix Image Reconstruction: Usefulness in High Resolution chest CT

PURPOSE: We tried to evaluate whether high resolution chest CT with a 1,024 matrix has a significant advantage in image quality compared to a 512 matrix. MATERIALS AND METHODS: Each set of 512 and 1024 matrix high resolution chest CT scans with both 0.625 mm and 1.25 mm slice thickness were obtained from 26 patients. Seventy locations that contained twenty-four low density lesions without sharp boundary such as emphysema, and forty-six sharp linear densities such as linear fibrosis were selected; these were randomly displayed on a five mega pixel LCD monitor. All the images were masked for information concerning the matrix size and slice thickness. Two chest radiologists scored the image quality of each arrowed lesion as follows: (1) undistinguishable, (2) poorly distinguishable, (3) fairly distinguishable, (4) well visible and (5) excellently visible. The scores were compared from the the aspects of matrix size, slice thickness and the different observers by using ANOVA tests. RESULTS: The average and standard deviation of image quality were 3.09 (+/-.92) for the 0.625 mmx512 matrix, 3.16 (+/-.84) for the 0.625 mmx1024 matrix, 2.49 (+/-1.02) for the 1.25 mmx512 matrix, and 2.35 (+/-1.02) for the 1.25 mmx1024 matrix, respectively. The image quality on both matrices of the high resolution chest CT scans with a 0.625 mm slice thickness was significantly better than that on the 1.25 mm slice thickness (p < 0.001). However, the image quality on the 1024 matrix high resolution chest CT scans was not significantly different from that on the 512 matrix high resolution chest CT scans (p = 0.678). The interobserver variation between the two observers was not significant (p = 0.691). CONCLUSION: We think that 1024 matrix image reconstruction for high resolution chest CT may not be clinically useful.

The Value of Coronal Image Reconstructions of HRCT using MDCT for the Assessment of Bronchiectasis: Experiment with 64 MDCTs

PURPOSE: The aim of our study was to evaluate the value of coronal image reconstructions of HRCT with using 64 MDCT scans for the assessment of bronchiectasis. MATERIALS AND METHODS: Chest CT scans (0.6-mm collimation, table speed of 14 mm/sec and a rotation time of 0.5 sec) that employed 64 MDCT images (Somatom Sensation 64, Siemens) without contrast media were performed in 56 patients (21 males and 35 females, mean age: 55 years) who displayed hemoptysis. The images were reconstructed with a 1 mm slice thickness in the axial (10 mm apart) and coronal (10 mm apart) planes with using a high frequency algorithm, and they were sent to PACS monitors. The axial images were assessed with and without the coronal images by two radiologists at two separate occasions. The presence of bronchiectasis was decided upon by consensus diagnosis of the two radiologists. The detection rates of bronchiectasis were compared between the readings with using the axial images alone and the readings with using both the axial and coronal images. RESULTS: The detection rate of bronchiectasis was significantly higher with using both the axial and coronal images than with using with axial images alone (82.1%, 46/56 patients Vs 64.3%, 36/56 patients, respectively, p=0.001). The detection rates for all the lobes, except for the superior division of the left upper lobe, were significantly improved with using both the axial and coronal images (RUL; p=0.013, RML; p=0.002, RLL; 0.024, Lt lingular segment; p=0.004, LLL; p=0.018). CONCLUSION: The coronal images of HRCT with using 64 MDCT improved the detection rate of bronchiectasis in the patients with hemoptysis when they were used in conjunction with the standard axial images. We suggest that HRCT with the coronal images should be obtained for the patients with hemoptysis, despite that the simple chest radiographs are often normal or they have non-specific findings.

The Value of Coronal Image Reconstructions of HRCT using MDCT for the Assessment of Bronchiectasis: Experiment with 64 MDCTs

PURPOSE: The aim of our study was to evaluate the value of coronal image reconstructions of HRCT with using 64 MDCT scans for the assessment of bronchiectasis. MATERIALS AND METHODS: Chest CT scans (0.6-mm collimation, table speed of 14 mm/sec and a rotation time of 0.5 sec) that employed 64 MDCT images (Somatom Sensation 64, Siemens) without contrast media were performed in 56 patients (21 males and 35 females, mean age: 55 years) who displayed hemoptysis. The images were reconstructed with a 1 mm slice thickness in the axial (10 mm apart) and coronal (10 mm apart) planes with using a high frequency algorithm, and they were sent to PACS monitors. The axial images were assessed with and without the coronal images by two radiologists at two separate occasions. The presence of bronchiectasis was decided upon by consensus diagnosis of the two radiologists. The detection rates of bronchiectasis were compared between the readings with using the axial images alone and the readings with using both the axial and coronal images. RESULTS: The detection rate of bronchiectasis was significantly higher with using both the axial and coronal images than with using with axial images alone (82.1%, 46/56 patients Vs 64.3%, 36/56 patients, respectively, p=0.001). The detection rates for all the lobes, except for the superior division of the left upper lobe, were significantly improved with using both the axial and coronal images (RUL; p=0.013, RML; p=0.002, RLL; 0.024, Lt lingular segment; p=0.004, LLL; p=0.018). CONCLUSION: The coronal images of HRCT with using 64 MDCT improved the detection rate of bronchiectasis in the patients with hemoptysis when they were used in conjunction with the standard axial images. We suggest that HRCT with the coronal images should be obtained for the patients with hemoptysis, despite that the simple chest radiographs are often normal or they have non-specific findings.