ABSTRACT
Objective@#To evaluate the reliability of CT measurements of muscle quantity and quality using variable CT parameters. @*Materials and Methods@#A phantom, simulating the L2–4 vertebral levels, was used for this study. CT images were repeatedly acquired with modulation of tube voltage, tube current, slice thickness, and the image reconstruction algorithm. Reference standard muscle compartments were obtained from the reference maps of the phantom. Cross-sectional area based on the Hounsfield unit (HU) thresholds of muscle and its components, and the mean density of the reference standard muscle compartment, were used to measure the muscle quantity and quality using different CT protocols. Signal-to-noise ratios (SNRs) were calculated in the images acquired with different settings. @*Results@#The skeletal muscle area (threshold, -29 to 150 HU) was constant, regardless of the protocol, occupying at least 91.7% of the reference standard muscle compartment. Conversely, normal attenuation muscle area (30–150 HU) was not constant in the different protocols, varying between 59.7% and 81.7% of the reference standard muscle compartment. The mean density was lower than the target density stated by the manufacturer (45 HU) in all cases (range, 39.0–44.9 HU). The SNR decreased with low tube voltage, low tube current, and in sections with thin slices, whereas it increased when the iterative reconstruction algorithm was used. @*Conclusion@#Measurement of muscle quantity using HU threshold was reliable, regardless of the CT protocol used. Conversely, the measurement of muscle quality using the mean density and narrow HU thresholds were inconsistent and inaccurate across different CT protocols. Therefore, further studies are warranted in future to determine the optimal CT protocols for reliable measurements of muscle quality.
ABSTRACT
Objective@#To evaluate the reliability of CT measurements of muscle quantity and quality using variable CT parameters. @*Materials and Methods@#A phantom, simulating the L2–4 vertebral levels, was used for this study. CT images were repeatedly acquired with modulation of tube voltage, tube current, slice thickness, and the image reconstruction algorithm. Reference standard muscle compartments were obtained from the reference maps of the phantom. Cross-sectional area based on the Hounsfield unit (HU) thresholds of muscle and its components, and the mean density of the reference standard muscle compartment, were used to measure the muscle quantity and quality using different CT protocols. Signal-to-noise ratios (SNRs) were calculated in the images acquired with different settings. @*Results@#The skeletal muscle area (threshold, -29 to 150 HU) was constant, regardless of the protocol, occupying at least 91.7% of the reference standard muscle compartment. Conversely, normal attenuation muscle area (30–150 HU) was not constant in the different protocols, varying between 59.7% and 81.7% of the reference standard muscle compartment. The mean density was lower than the target density stated by the manufacturer (45 HU) in all cases (range, 39.0–44.9 HU). The SNR decreased with low tube voltage, low tube current, and in sections with thin slices, whereas it increased when the iterative reconstruction algorithm was used. @*Conclusion@#Measurement of muscle quantity using HU threshold was reliable, regardless of the CT protocol used. Conversely, the measurement of muscle quality using the mean density and narrow HU thresholds were inconsistent and inaccurate across different CT protocols. Therefore, further studies are warranted in future to determine the optimal CT protocols for reliable measurements of muscle quality.
ABSTRACT
BACKGROUND AND PURPOSE: We had previously demonstrated by immunohistochemical study (IHS) that nm23-H1 gene may play an important role in disease prognosis as well as its participation in metastasis of urothelial cancer. The purpose of present study was 1) to reexamine the role of nm23-H1 gene in urothelial cancers at molecular level, 2) to identify the molecular mechanism of decreased immunoreactivity for nm23-H1 protein in metastatic urothelial cancers, and 3) to identify whether IHS is reliable in studying the expression of nm23-H1. MATERIALS AND METHODS: We studied expression level and mutation profiles of nm23-H1 gene in 25 fresh surgical specimens of urothelial cancer by reverse transcription polymerase chain reaction(RT-PCR)-Southern blotting analysis, and PCR of genomic DNA followed by single strand conformation polymorphism and sequencing analysis. The results of RT-PCR-Southern blotting were comparatively analyzed with those of IHS. RESULTS: mRNA transcript levels of nm23-H1 gene were significantly decreased in tumor tissues with metastasis as compared with those without metastasis. The transcript levels of nm23-H1 gene were also significantly decreased in metastatic tumor tissues as compared with primary tumor tissues. Point mutation of nm23-H1 gene was detected in only 1 of 13 urothelial cancer tissues with metastasis, whereas, mutation was observed in none of those without metastasis. The results of IHS corresponded with those of RT-PCR-Southern blotting analysis in 23 of 25 specimens. CONCLUSIONS: The nm23-H1 gene may play an important role in metastasis of urothelial cancer. Decreased transcription at mRNA level may be a major molecular mechanism of loss of immunoreactivity for nm23-H1 protein in urothelial cancer. IHS used in the present study may be a clinically useful method to study the expression of nm23-H1 and to predict metastasis potential and prognosis of urothelial cancers.