RSS-Feed abonnieren
DOI: 10.1055/s-0029-1245789
© Georg Thieme Verlag KG Stuttgart · New York
Estimation of the Minimum Dose Required to Measure Ventricular Width in Follow-Up Cranial Computed Tomography (CCT) in Children with Hydrocephalus
Abschätzung der für computertomografische Verlaufskontrollen der Ventrikelweite bei Kindern mit Hydrozephalus erforderlichen MindestdosisPublikationsverlauf
received: 24.4.2010
accepted: 16.9.2010
Publikationsdatum:
22. Oktober 2010 (online)
![](https://www.thieme-connect.de/media/roefo/201012/lookinside/thumbnails/10.1055-s-0029-1245789-1.jpg)
Zusammenfassung
Ziel: Die für computertomografische Verlaufskontrollen der Ventrikelweite bei Kindern mit Hydrozephalus erforderliche Mindestdosis abzuschätzen. Material und Methoden: Als Messphantom verwendeten wir eine mit Gelatine gefüllte kindliche Kalotte, in die als Seitenventrikel die zentralen Faserbündel von 2 Möhren eingebettet waren. Das Phantom wurde mit 2 Mehrschicht-Computertomografen (LightSpeed Ultra, GE und Somatom Sensation, Siemens) jeweils 10-mal untersucht, wobei ein Röhrenstrom von 400, 350, 300, 250, 200, 150 und 100 mAs sowie eine Röhrenspannung von 140, 120, 100 und 80 kV verwendet wurden. Die Ventrikelweite wurde an 4 Stellen gemessen. Die bei 380 mAs/ 400 mAs und 140 kV (LightSpeed/Somatom) gemessenen Ventrikelweiten dienten als Referenz. Messwerte erhielten einen Punkt, wenn sie um maximal 0,5 mm von der Referenz abwichen. Ergebnisse: Die Strahlendosis konnte beim LightSpeed von 60,9 mGy auf 9,2 mGy (15,1 %) und beim Somatom von 55,0 mGy auf 8,0 mGy (14,6 %) reduziert werden, ohne die Verlässlichkeit der Messungen zu beeinträchtigen. Allerdings gab es bei beiden Geräten bestimmte Kombinationen von Röhrenstrom und -spannung, die trotz höherer Dosis und geringeren Pixelrauschens weniger verlässliche Messergebnisse lieferten. Schlussfolgerung: Es gibt keine einheitliche Mindestdosis oder bestimmte Kombination von Röhrenstrom und -spannung, die für beide Computertomografen verlässliche Messungen der Ventrikelweite bei geringst möglicher Strahlendosis garantiert. Als Faustregel kann der Röhrenstrom des Standardprotokolls auf 100 kV reduziert werden, ohne die Messgenauigkeit zu beeinträchtigen.
Abstract
Purpose: To estimate the minimum dose needed at follow-up cranial computed tomography (CCT) to reliably determine ventricular width in children with hydrocephalus. Materials and Methods: For the study, a phantom was created using the calvarium of an infant which was filled with gelatin and the shaped inner cones of two carrots serving as lateral ventricles. The phantom was scanned ten times with two multi-slice CTs (LightSpeed Ultra, GE, and Somatom Sensation, Siemens), using a tube current of 400, 350, 300, 250, 200, 150, and 100 mA, and a tube voltage of 140, 120, 100, and 80 kV. The width of both lateral ventricles was measured at 4 sites. The values derived from scans performed at 380 / 400 mA and 140 kV (LightSpeed/Somatom) served as a reference. Measurements scored 1 point if they did not differ by more than 0.5 mm from the reference values. Results: The radiation dose can be reduced from 61.0 mGy to 9.2 mGy (15.1 %) with LightSpeed and from 55.0 mGy to 8.0 mGy (14.6 %) with Somatom without impairing the reliability of ventricular width measurements. However, in the case of both scanners, certain combinations of tube voltage and current yielded less reliable measurements although the dose was higher and the pixel noise was lower. Conclusion: There is no single cut-off dose or setting for tube voltage and current which guarantees reliable ventricular width measurements with the least radiation exposure for both scanners. As a guideline, it is safe to use the standard protocols with a reduced tube current of 100 kV.
Key words
brain - CT spiral - hydrocephalus - ventricles - radiation dose - children
References
- 1 Heyer C M, Peters S, Lemburg S. Structure of the meeting of the German radiological society and scientific discourse pertaining to radiation dose and dose reduction: An analysis of 1998 – 2008. Fortschr Röntgenstr. 2009; 181 1065-1072
- 2 Hietschold V, Koch A, Laniado M et al. Computed tomography: Influence of varying tube current on patient dose and correctness of effective dose calculations. Fortschr Röntgenstr. 2008; 180 430-439
- 3 Flohr T, Stierstorfer K, Bruder H et al. New technical developments in multislice CT Part 1: Approaching isotropic resolution with sub-millimeter 16-slice scanning. Fortschr Röntgenstr. 2002; 174 839-845
- 4 Seidenbusch M C, Regulla D, Schneider K. Radiation exposure of children in pediatric radiolog. Part 2: The paedos algorithm for computer-assisted dose reconstruction in pediatric radiology and results for x-ray examinations of the skull. Fortschr Röntgenstr. 2008; 180 522-539
- 5 Seidenbusch M C, Regulla D, Schneider K. Radiation exposure of children in pediatric radiology. Part 3: Conversion coefficients for reconstruction of organ doses achieved during chest x-ray examinations. Fortschr Röntgenstr. 2008; 180 1061-1081
- 6 Seidenbusch M C, Schneider K. Radiation exposure of children in pediatric radiology. Part 4: Entrance doses achieved during the x-ray examination of the chest. Fortschr Röntgenstr. 2008; 180 1082-1103
- 7 Seidenbusch M C, Schneider K. Radiation exposure of children in pediatric radiology. Part 5: Organ doses in chest radiography. Fortschr Röntgenstr. 2009; 181 454-471
- 8 Seidenbusch M C, Regulla D, Schneider K. Radiation exposure of children in pediatric radiology. Part 6: Conversion factors for reconstruction of organ dose in abdominal radiography. Fortschr Röntgenstr. 2009; 181 945-961
- 9 Seidenbusch M C, Regulla D, Schneider K. Radiation exposure of children in pediatric radiology. Part 7: Conversion factors for reconstruction of organ dose during thoracoabdominal babygrams. Fortschr Röntgenstr. 2010; 182 415-421
- 10 Schneider K, Seidenbusch M. Radiation exposure of children in pediatric radiology part 8: Radiation doses during thoracoabdominal babygram and abdominal x-ray examination of the newborn and young infants. Fortschr Röntgenstr. 2010; 182 479-492
- 11 Seidenbusch M C, Schneider K. Radiation exposure of children in pediatric radiology. Fortschr Röntgenstr. 2008; 180 410-422
- 12 Huda W, Vance A. Patient radiation doses from adult and pediatric CT. AJR. 2007; 188 540-546
- 13 Huda W, Lieberman K, Chang J et al. Patient size and x-ray technique factors in head computed tomography examinations. I. Radiation doses. Med Phys. 2004; 31 588-594
- 14 Boetticher von H, Lachmund J, Looe H K et al. 2007 recommendations of the IRCP change basis for estimation of the effective dose: What is the impact on radiation dose assessment of patient and personnel?. Fortschr Röntgenstr. 2008; 180 391-395
- 15 Hammer G P, Seidenbusch M C, Schneider K et al. Cancer incidence rate after diagnostic x-ray exposure in 1976 – 2003 among patients of a university children’s hospital. Fortschr Röntgenstr. 2010; 182 404-414
- 16 Brenner D J, Ellliston C D, Hall E J et al. Estimated risks of radiation-induced fatal cancer from pediatric ct. AJR. 2001; 176 289-296
- 17 Keil B, Wulff J, Schmitt R et al. Protection of eye lens in computed tomography – dose evaluation on an anthropomorphic phantom using thermo-luminescent dosimeters and Monte-Carlo simulations. Fortschr Röntgenstr. 2008; 180 1047-1053
- 18 Karcaaltincaba M, Karaosmanoglu D, Akata D et al. Dual energy virtual CT colonoscopy with dual source computed tomography: Initial experience. Fortschr Röntgenstr. 2009; 181 859-862
- 19 Kuettner A, Gehann B, Spolnik J et al. Strategies for dose-optimized imaging in pediatric cardiac dual source CT. Fortschr Röntgenstr. 2009; 181 339-348
- 20 Hein P A, Rogalla P, Klessen C et al. Computer-aided pulmonary nodule detection – performance of two CAD systems at different CT dose levels. Fortschr Röntgenstr. 2009; 181 1056-1064
- 21 Hein P A, Romano V C, Rogalla P et al. Linear and volume measurements of pulmonary nodules at different CT dose levels – intrascan and interscan analysis. Fortschr Röntgenstr. 2009; 181 24-31
- 22 Anders K, Baum U, Gauss S et al. Initial experience with prospectively triggered, CT coronary angiography on a 128-slice scanner. Fortschr Röntgenstr. 2009; 181 332-338
- 23 Huda W, Lieberman K, Chang J et al. Patient size and x-ray technique factors in head computed tomography examinations. II. Image quality. Med Phys. 2004; 31 595-601
- 24 McCollough C H, Bruesewitz M R, Kofler J M. CT dose reduction and dose management tools: Overview of available options. Radiographics. 2006; 26 503-512
- 25 Chan C Y, Wong Y C, Chau L F et al. Radiation dose reduction in paediatric cranial CT. Pediatr Radiol. 1999; 29 770-775
- 26 Shannon C E. Communication in the presence of noise. Proc IRE. 1949; 37 Reprint in: Proc IEEE 1998; 86: 447 – 457
- 27 Merimaa K, Järvinen H, Kortesniemi M et al. A direct method for air kerma-length product measurement in CT for verification of dose display calibrations. Radiat Prot Dosimetry. 2010; 140 274-280
Dr. Klaus Kirchhof
Institut und Poliklinik für Radiologische Diagnostik, Universitätsklinikum Carl Gustav Carus
Fetscherstr. 74, Haus 9
01307 Dresden
Germany
Telefon: ++ 49/3 51/45 81 82 22
Fax: ++ 49/3 51/4 58 43 21
eMail: Klaus.Kirchhof@uniklinikum-dresden.de