Hyun Woo Goo1, Dong Soo Suh. 1. Department of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1 Poongnap-2dong, Songpa-gu, Seoul, 138-736, South Korea. hwgoo@amc.seoul.kr
Abstract
BACKGROUND: For the optimum application of tube current modulation in paediatric CT it is important to know the influences of different imaging parameters on it. OBJECTIVE: This phantom study was performed to evaluate the influences of tube voltage and scan direction on combined tube current modulation, which is a combination of angular and z-axis modulation. MATERIALS AND METHODS: Sixteen-slice spiral CT with combined tube current modulation was performed using four different phantoms (one adult-size anthropomorphic phantom and three cone-shaped acryl phantoms) at three different tube voltages (80, 100 and 120 kVp) and two scan directions (craniocaudal and caudocranial). Effective tube current-time product (mAs) was chosen to maintain a consistent CTDIvol for each phantom. Other parameters, including detector collimation, slice width, pitch, reconstruction algorithm, scan field of view, and scan range were identical for each phantom. Changes in CTDIvol and mAs resulting from the modulation were calculated and compared. RESULTS: Changes in CTDIvol and mAs resulting from the modulation were different among the three tube voltages. In larger phantoms the greatest reductions (-6.1+/-3.9% in CTDIvol and -12.5+/-4.0% in mAs) were obtained with 120 kVp, whereas in smaller phantoms they were obtained with 80 kVp (-2.8+/-0.9% in CTDIvol and -2.5+/-4.9% in mAs). Smaller CTDIvol (2.4+/-0.9 mGy vs. 2.5+/-1.0 mGy, P=0.017) and mAs (57.2+/-40.4 mAs vs. 61.4+/-43.2 mAs, P=0.002) were used in caudocranial scans than in craniocaudal scans with the modulation. CONCLUSION: Combined tube current modulation is influenced by tube voltage and scan direction depending on phantom profile.
BACKGROUND: For the optimum application of tube current modulation in paediatric CT it is important to know the influences of different imaging parameters on it. OBJECTIVE: This phantom study was performed to evaluate the influences of tube voltage and scan direction on combined tube current modulation, which is a combination of angular and z-axis modulation. MATERIALS AND METHODS: Sixteen-slice spiral CT with combined tube current modulation was performed using four different phantoms (one adult-size anthropomorphic phantom and three cone-shaped acryl phantoms) at three different tube voltages (80, 100 and 120 kVp) and two scan directions (craniocaudal and caudocranial). Effective tube current-time product (mAs) was chosen to maintain a consistent CTDIvol for each phantom. Other parameters, including detector collimation, slice width, pitch, reconstruction algorithm, scan field of view, and scan range were identical for each phantom. Changes in CTDIvol and mAs resulting from the modulation were calculated and compared. RESULTS: Changes in CTDIvol and mAs resulting from the modulation were different among the three tube voltages. In larger phantoms the greatest reductions (-6.1+/-3.9% in CTDIvol and -12.5+/-4.0% in mAs) were obtained with 120 kVp, whereas in smaller phantoms they were obtained with 80 kVp (-2.8+/-0.9% in CTDIvol and -2.5+/-4.9% in mAs). Smaller CTDIvol (2.4+/-0.9 mGy vs. 2.5+/-1.0 mGy, P=0.017) and mAs (57.2+/-40.4 mAs vs. 61.4+/-43.2 mAs, P=0.002) were used in caudocranial scans than in craniocaudal scans with the modulation. CONCLUSION: Combined tube current modulation is influenced by tube voltage and scan direction depending on phantom profile.
Authors: Marco Das; Andreas Horst Mahnken; Georg Mühlenbruch; Achim Stargardt; Claudia Weiss; Dirk-Alexander Sennst; Thomas G Flohr; Rolf W Günther; Joachim Ernst Wildberger Journal: AJR Am J Roentgenol Date: 2005-05 Impact factor: 3.959
Authors: Mannudeep K Kalra; Michael M Maher; Thomas L Toth; Bernhard Schmidt; Bryan L Westerman; Hugh T Morgan; Sanjay Saini Journal: Radiology Date: 2004-10-21 Impact factor: 11.105
Authors: Mannudeep K Kalra; Michael M Maher; Thomas L Toth; Leena M Hamberg; Michael A Blake; Jo-Anne Shepard; Sanjay Saini Journal: Radiology Date: 2004-01-22 Impact factor: 11.105
Authors: Peter K T Hui; Hyun Woo Goo; Jing Du; Janice J K Ip; Suzu Kanzaki; Young Jin Kim; Supika Kritsaneepaiboon; Oktavia Lilyasari; Suvipaporn Siripornpitak Journal: Pediatr Radiol Date: 2017-04-24