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Method for automatic tube current selection for obtaining a consistent image quality and dose optimization in a cardiac multidetector CT.

Qi W, Li J, Du X - Korean J Radiol (2009 Nov-Dec)

Bottom Line: Image quality was evaluated using score scale of 1 to 5 with a score of 3 or higher being clinically acceptable.Using the formula, we obtained an average CT image noise of 28.55 Hounsfield unit (HU), with a standard deviation of only 1.7 HU, as opposed to a target value of 28 HU.Image quality scores were 4.03 and 4.27 for images in Groups A and B, respectively, and there was no statistical difference between the image quality scores between the two groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Peking University People's Hospital, Beijing, China. cyanage8@gmail.com

ABSTRACT

Objective: To evaluate a quantitative method for individually adjusting the tube current to obtain images with consistent noise in electrocardiogram (ECG)-gated CT cardiac scans.

Materials and methods: The image noise from timing bolus and cardiac CT scans of 80 patients (Group A) who underwent a 64-row multidetector (MD) CT cardiac examination with patient-independent scan parameters were analyzed. A formula was established using the noise correlation between the timing bolus and cardiac scans. This formula was used to predict the required tube current to obtain the desired cardiac CT image noise based on the timing bolus noise measurement. Subsequently, 80 additional cardiac patients (Group B) were scanned with individually adjusted tube currents using an established formula to evaluate its ability to obtain accurate and consistent image noise across the patient population. Image quality was evaluated using score scale of 1 to 5 with a score of 3 or higher being clinically acceptable.

Results: Using the formula, we obtained an average CT image noise of 28.55 Hounsfield unit (HU), with a standard deviation of only 1.7 HU, as opposed to a target value of 28 HU. Image quality scores were 4.03 and 4.27 for images in Groups A and B, respectively, and there was no statistical difference between the image quality scores between the two groups. However, the average CT dose index (CTDIvol) was 30% lower for Group B.

Conclusion: Adjusting the tube current based on timing bolus scans may provide a consistent image quality and dose optimization for cardiac patients of various body mass index values.

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Related in: MedlinePlus

Example of coronary CT angiography images with fixed (650 mA, left) and adaptive mA (330 mA, right) for patients from Groups A and B, respectively. Body mass index and image noise were 30.1 kg/m2 and 28.5 HU for Group A and 23.4 kg/m2 and 26.9 HU for Group B. Both images were rated excellent (score of 5). However, for patient in Group B, where tube current was adjusted based on timing bolus noise measurement, dose saving of about 50% was achieved compared to when fixed mA was used.
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Figure 6: Example of coronary CT angiography images with fixed (650 mA, left) and adaptive mA (330 mA, right) for patients from Groups A and B, respectively. Body mass index and image noise were 30.1 kg/m2 and 28.5 HU for Group A and 23.4 kg/m2 and 26.9 HU for Group B. Both images were rated excellent (score of 5). However, for patient in Group B, where tube current was adjusted based on timing bolus noise measurement, dose saving of about 50% was achieved compared to when fixed mA was used.

Mentions: Figure 6 shows an example of the CCTA images with a fixed (left) and an adaptive mA (right) for patients in Groups A and B, respectively. Both images were rated excellent (score of 5). However, for patients in group B, where the tube currents were adjusted based on the TB noise measurement, a lower tube current. Effectively, a lower tube current was required to achieve an excellent image quality for smaller sized patients, which resulted in dose saving of about 50% in this particular patient compared using a fixed mA.


Method for automatic tube current selection for obtaining a consistent image quality and dose optimization in a cardiac multidetector CT.

Qi W, Li J, Du X - Korean J Radiol (2009 Nov-Dec)

Example of coronary CT angiography images with fixed (650 mA, left) and adaptive mA (330 mA, right) for patients from Groups A and B, respectively. Body mass index and image noise were 30.1 kg/m2 and 28.5 HU for Group A and 23.4 kg/m2 and 26.9 HU for Group B. Both images were rated excellent (score of 5). However, for patient in Group B, where tube current was adjusted based on timing bolus noise measurement, dose saving of about 50% was achieved compared to when fixed mA was used.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2770833&req=5

Figure 6: Example of coronary CT angiography images with fixed (650 mA, left) and adaptive mA (330 mA, right) for patients from Groups A and B, respectively. Body mass index and image noise were 30.1 kg/m2 and 28.5 HU for Group A and 23.4 kg/m2 and 26.9 HU for Group B. Both images were rated excellent (score of 5). However, for patient in Group B, where tube current was adjusted based on timing bolus noise measurement, dose saving of about 50% was achieved compared to when fixed mA was used.
Mentions: Figure 6 shows an example of the CCTA images with a fixed (left) and an adaptive mA (right) for patients in Groups A and B, respectively. Both images were rated excellent (score of 5). However, for patients in group B, where the tube currents were adjusted based on the TB noise measurement, a lower tube current. Effectively, a lower tube current was required to achieve an excellent image quality for smaller sized patients, which resulted in dose saving of about 50% in this particular patient compared using a fixed mA.

Bottom Line: Image quality was evaluated using score scale of 1 to 5 with a score of 3 or higher being clinically acceptable.Using the formula, we obtained an average CT image noise of 28.55 Hounsfield unit (HU), with a standard deviation of only 1.7 HU, as opposed to a target value of 28 HU.Image quality scores were 4.03 and 4.27 for images in Groups A and B, respectively, and there was no statistical difference between the image quality scores between the two groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Peking University People's Hospital, Beijing, China. cyanage8@gmail.com

ABSTRACT

Objective: To evaluate a quantitative method for individually adjusting the tube current to obtain images with consistent noise in electrocardiogram (ECG)-gated CT cardiac scans.

Materials and methods: The image noise from timing bolus and cardiac CT scans of 80 patients (Group A) who underwent a 64-row multidetector (MD) CT cardiac examination with patient-independent scan parameters were analyzed. A formula was established using the noise correlation between the timing bolus and cardiac scans. This formula was used to predict the required tube current to obtain the desired cardiac CT image noise based on the timing bolus noise measurement. Subsequently, 80 additional cardiac patients (Group B) were scanned with individually adjusted tube currents using an established formula to evaluate its ability to obtain accurate and consistent image noise across the patient population. Image quality was evaluated using score scale of 1 to 5 with a score of 3 or higher being clinically acceptable.

Results: Using the formula, we obtained an average CT image noise of 28.55 Hounsfield unit (HU), with a standard deviation of only 1.7 HU, as opposed to a target value of 28 HU. Image quality scores were 4.03 and 4.27 for images in Groups A and B, respectively, and there was no statistical difference between the image quality scores between the two groups. However, the average CT dose index (CTDIvol) was 30% lower for Group B.

Conclusion: Adjusting the tube current based on timing bolus scans may provide a consistent image quality and dose optimization for cardiac patients of various body mass index values.

Show MeSH
Related in: MedlinePlus