Clinical evaluation of dual-energy bone removal in CT angiography of the head and neck: comparison with conventional bone-subtraction CT angiography

doi:10.1016/j.crad.2009.01.007

Clinical Radiology

Volume 64, Issue 5, May 2009, Pages 534-541

https://doi.org/10.1016/j.crad.2009.01.007 Get rights and content

Aim

To evaluate the bone-subtraction effect of dual-energy bone removal in computed tomography angiography (CTA) of the head and neck in comparison with conventional bone-subtraction CTA.

Material and Methods

The study comprised 52 patients who were divided into two groups at random, and examined using dual-source CT for head and neck CTA. Dual-energy bone removal CTA and conventional bone-subtraction CTA were applied to each of the two groups, respectively. The bone subtraction was performed automatically in both methods. Vascular structures, as well as brain tissue remained visible. The subtracted images were further processed with maximum intensity projection (MIP) and volume-rendering technique (VRT) for image evaluation. Two experienced radiologists reviewed the resulting subtracted and non-subtracted volume data with respect to the delineation and detection of image quality and vascular pathology.

Results

The means of the weighted CT dose index (CTDIvol) for bone-removal dual-energy CTA and conventional bone-subtraction CTA were 20.56 ± 0.01 mGy and 25.57 ± 0.56 mGy, respectively. There was a significant difference between them. The percentage of carotid and vertebral arteries and all other vessels that could be successfully assessed with these two methods were 87.8, 68, and 83%, and 93.5, 91.8, and 92.6%, respectively. There were no significant differences in the visualization of the carotid arteries; however, there were significant differences in the visualization of the vertebral arteries.

Conclusion

Compared with conventional bone-subtraction CTA, dual-energy bone-removal CTA had a lower radiation dose. It eliminated most bones in the head and neck successfully; however, the bone subtraction effect around the vertebral artery was unsatisfactory. Dual-energy bone-removal CTA provides a new method for detecting vascular diseases in routine clinical work.

Introduction

Computed tomography angiography (CTA) is an important imaging method for the detection of cerebral aneurysms, arterial stenosis, and other vascular anomalies in head and neck arteries. Although conventional digital subtraction angiography (DSA) is still the reference standard for diagnosis because of its high spatial resolution and large field of view, it has the disadvantage of being invasive. With the improvement of the temporal and spatial resolution in CTA studies and workstation technology, CTA is increasingly considered as an alternative noninvasive imaging technique to DSA. However, the vasculature near the base of the skull and cervical vertebrae is not clearly displayed because of difficulties in separating vessels from bony structures.1, 2 To resolve this, there are different approaches for the removal of bone from the CTA datasets, such as a region-growing algorithm or section-by-section digital subtraction.³ However, even minor patient movements lead to insufficient subtraction and image quality with this approach. Initial results published by Venema et al.⁴ using selective bone removal using “matched mask bone elimination” were promising. Currently with dual-energy material differentiation (bone and iodine), it is possible to perform reliable bone and calcified-plaque subtraction from CTA volume data. Translocation between the two parallel images is extremely rare with the two-tube set-up.⁵ There have been no reports evaluating the bone-removal effect with dual-energy CTA of the head and neck. Consequently, the present study was undertaken to evaluate the effect of dual-energy bone-removal CTA in the head and neck compared with conventional bone-subtraction CTA.

Section snippets

Patients

Between November 2007 and April 2008, 52 patients who presented with clinically suspected vascular diseases of the head and neck underwent dual-source CT. These patients were divided into two groups randomly with each group comprising 26 patients. There were 18 men and eight women with a mean age of 49.8 years (range 18–79 years) in one group, designated the “DE-CTA” group. The other group, designated the “Neuro-DSA” group, included 17 men and nine women with a mean age of 49.1 years (range

Radiation dose

The radiation dose of the two groups is listed in Table 2. Because conventional bone-subtraction CTA needed to be scanned twice, the radiation dose was the sum of the two scans. Using the statistical method of the two-sample t-test for independent samples with SPSS 13.0 software, the t value was 45.77, p < 0.001. Therefore, the radiation doses of the two groups could be considered to be significantly different. The bone-removal DE-CTA had a smaller radiation dose than conventional

Discussion

Although DSA is still the reference standard for the diagnosis of aneurysms, stenosis, and vascular malformations, it is invasive, potentially time-consuming, operator-dependent, and carries a 4% risk of complications and 1% rate of persistent neurological deficit.⁶ Many studies have shown that CTA may be a cost-effective and minimally invasive alternative. Although innovations in magnetic resonance imaging (MRI), such as parallel acquisition techniques and high magnetic field strengths, have

Acknowledgements

The authors thank Drs Zhao-ping Cheng, Yan-hua Duan, and Da-wei Wu for help with patient recruitment. Similarly, the authors thank Jiu-hong Chen (CT Research Collaboration, Siemens Ltd, China, Medical Solutions) for editorial and writing assistance.

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Clinical evaluation of dual-energy bone removal in CT angiography of the head and neck: comparison with conventional bone-subtraction CT angiography

Aim

Material and Methods

Results

Conclusion

Introduction

Section snippets

Patients

Radiation dose

Discussion

Acknowledgements

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