Can dual-energy CT improve the assessment of tumor margins in oral cancer?

doi:10.1016/j.oraloncology.2013.12.001

Oral Oncology

Volume 50, Issue 3, March 2014, Pages 221-227

https://doi.org/10.1016/j.oraloncology.2013.12.001 Get rights and content

Summary

Objectives

The aim was to investigate the image quality of dual-energy computed-tomography (DECT) compared to single-energy images at 80 kV and 140 kV in oral tumors.

Materials and methods

Forty patients underwent a contrast-enhanced DECT scan on a definition flash-CT. Four reconstructions (80 kV, 140 kV, mixed (M), and optimum-contrast (OC)) were assessed by four blinded readers for subjective image quality (10-point scale/10 = best). For objective quality assessment, linear attenuation measurements (line density profiles (LDP)) were positioned at the tumor margin, and the difference between minimum and maximum was calculated. Signal-to-noise ratios (SNR) were measured in the tongue.

Results

The mean image quality for all readers was 5.1 ± 0.3, 8.4 ± 0.3, 8.1 ± 0.2, and 8.3 ± 0.2 for the 140 kV, 80 kV, M, and OC, respectively (P < 001 between 140 kV and all others). The mean difference between the minimum and maximum within the LDP was 139.4 ± 59.0, 65.7 ± 29.5, 105.1 ± 46.5, and 118.7 ± 59.4 for the 80 kV, 140 kV, M, and OC, respectively (P < 001). The SNR for the tongue was 3.8 ± 2.1, 3.8 ± 2.1, 4.2 ± 2.4, and 4.1 ± 2.3 for the 80 kV, 140 kV, M, and OC, respectively.

Discussion

DECT of oral tumors offers high image quality, with subjectively rated image quality and attenuation contrast at the tumor margin similar to that of 80 kV; DECT, however, provides a significantly higher SNR compared to 80 kV.

Introduction

In the diagnosis of oral cancer, multi-detector computed tomography (MDCT) is a first-line diagnostic device because of its broad availability, the ability to perform whole-body tumor staging, and an overall good sensitivity and specificity for the detection of oral cancer [1]. For both the radiologist and the surgeon, the information provided by the image enables accurate tumor staging and treatment planning for the resection of the tumor. The primary site, the size of the primary tumor, and the proximity to the bone, are all factors that influence the choice of initial treatment [2]. However, due to the complex anatomy in the oral cavity and the metal artifacts of dental restoration, imaging of oral cancer is challenging [3].

The recently introduced technology of dual-energy computed tomography (DECT) has been reported to provide an improved image quality compared to standard single-energy CT at 120 kV. Initial work using the first- and the second-generation of DECT scanners analyzed image quality in the abdomen and even in the head and neck region, and found an overall improved image quality based on a subjective analysis [4], [5], [6].

To date, these studies have focused on the subjective analysis of image quality, and usually do not have the low-dose CT images for comparison. Furthermore, these studies focus on the image quality in healthy subjects and do not provide data about the image quality of the tumor region.

The aim of this study was to analyze the image quality, as well as the ability to identify the tumor margins subjectively and objectively in patients with oral cancer, using a second-generation dual-energy CT, and compare these results to images acquired with 80 kV and 140 kV. As a secondary aim, we wanted to compare the two common dual-energy reconstruction techniques, called ‘mixed’ and the ‘optimum contrast’. Finally, we wanted to evaluate the image noise in images with streaking artifacts caused by dental fillings.

Section snippets

Materials and methods

The research protocol for this prospective study was approved by the Institutional Review Board of our institution (Medical University of Vienna, Vienna, Austria; protocol 1014/2009) and was conducted in accordance with the ethical standards of the World Medical Association (Declaration of Helsinki). All patients gave written, informed consent to participate in the study. All patient data were completely anonymized at the start of the study and were not de-blinded for the duration of the study.

Patient population

From April 2010 to May 2011, 40 patients, 23–90 years of age (mean age, 62.4 years ± 12.8 [standard deviation]), 25 males (mean age, 59.8 years ± 11.9) and 15 females (mean age, 66.7 years ± 12.8; P = 099), were enrolled in this study. The mean body mass index (BMI) was 25.3 ± 5.0 (male, 26.3 ± 5.2 and female, 24.3 ± 4.3).

All patients underwent clinical examination and were referred for a CT scan for the evaluation and staging of an oral carcinoma. They also had a bioptic verification of the malignancy. The

Discussion

In this study of the assessment of oral tumors with DECT, we found that the subjective image quality between low kV images (80 kV) and dual-energy images (OC and M reconstructions) was comparable. The contrast at the tumor margins was significantly higher for 80 kV, M, and OC reconstructions, compared to the high kV (140 kV) images. In addition, the 80 kV image offered the highest image noise, whereas the signal-to-noise ratio was best for the dual-energy reconstructions. For images with streaking

Conclusion

The determination of the correct size and position of oral tumors is challenging. Low kV CT of the head and neck region provides excellent image quality and allows a distinct depiction of the tumor margins; however the image itself is prone to image noise and metal artifacts. Dual-energy CT, combining a high tissue contrast and a lower image noise, can help to improve the image quality with a similar ability to delineate the tumor margins. Due to the possibility of using 80 kV for the low kV

Conflict of interest statement

None declared.

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Fifty-six patients with histologically confirmed untreated squamous cell carcinoma of the head and neck who underwent SDCT of the neck for staging purposes were included in this retrospective study. Attenuation, image noise as well as signal- and contrast-to-noise ratios (S-/CNR) in VMI_40–70keV were obtained from region of interest (ROI)-based measurements in the tumour and important anatomical landmarks (sternocleidomastoid muscle, subcutaneous fat, thyroid gland, submandibular gland, carotid artery, and jugular vein). Tumour conspicuity and delineation, as well as subjective image quality, were rated for conventional images, VMI_40–70keV, and iodine overlay maps using five-point Likert scales.
The CNR of the tumour versus the floor of the mouth and the CNR of the tumour versus the sternocleidomastoid muscle was significantly higher in VMI_40keV in comparison to conventional images (10.0 ± 7.3 versus 3.8 ± 3.3 and 11.3 ± 7.6 versus 3.6 ± 2.8; p<0.05 each). This was supported by qualitative results, as tumour conspicuity and delineation received superior ratings in iodine overlay maps and VMI_40keV compared to conventional images (5 [3–5] and 5 [4–5] versus 3 [2–5]; 5 [2–5] and 5 [3–5] versus 3 [2–4], respectively, all p<0.05). VMI_40keV yielded the highest score among all included image reconstructions for overall image quality (p<0.05 all).
Iodine overlay maps and low-energy VMI derived from SDCT improve initial assessment of primary squamous cell carcinoma of the head and neck compared to conventional images.
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Highest lesion enhancement and diagnostic confidence were observed in MEI+ 40 keV, with significant differences to CT_pv (p < 0.001), as well as for malignant lesions (highest conspicuity, noise, and sharpness in MEI+ 40 keV; p < 0.001). CNR calculations revealed highest values for MEI+ 40 keV followed by 60 keV with significant differences to CT_pv, and increasing energy levels. ROC analysis showed highest diagnostic accuracy for 40-keV MEI+ datasets regarding the detection of malignant/benign lesions with AUC values of 98.9% (95%-confidence interval: 96.5, 100) and a standard error of 1.2, further AUC values decreased to 83.6% for MEI+100.
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Citation Excerpt :
This technology allows tissue characterisation through material decomposition and voxel-to-voxel determination of iodine concentration, which can be used to derive a regional blood volume map [18,19]. The applications of DECT in head and neck cancer have been a growing area of interest, with several recent studies showing the benefit of iodine characterisation and virtual monoenergetic images for detection and delineation of head and neck tumor [20,21], differentiation between metastatic, inflammatory and benign cervical lymph nodes [22,23] or assessment of cartilage invasion [24,25]. However, the role of DECT-derived quantitative imaging to predict oncological outcomes in HNC has never been previously investigated.
To investigate the role of quantitative pre-treatment dual-energy computed tomography (DECT) for prediction of loco-regional recurrence (LRR) in patients with larynx/hypopharynx squamous cell cancer (L/H SCC).
Patients with L/H SCC treated with curative intent loco-regional radiotherapy and that underwent treatment planning with contrast-enhanced DECT of the neck were included. Primary and nodal gross tumor volumes (GTVp and GTVn) were contoured and transferred into a Matlab® workspace. Using a two-material decomposition, GTV iodine concentration (IC) maps were obtained. Quantitative histogram statistics (maximum, mean, standard deviation, kurtosis and skewness) were retrieved from the IC maps. Cox regression analysis was conducted to determine potential predictive factors of LRR.
Twenty-five patients, including 20 supraglottic and 5 pyriform sinus tumors were analysed. Stage I, II, III, IVa and IVb constituted 4% (1 patient), 24%, 36%, 28% and 8% of patients, respectively; 44% had concurrent chemo-radiotherapy and 28% had neodjuvant chemotherapy. Median follow-up was 21 months. Locoregional control at 1 and 2 years were 75% and 69%, respectively. For the entire cohort, GTVn volume (HR 1.177 [1.001-1.392], p = 0.05), voxel-based maximum IC of GTVp (HR 1.099 [95% CI: 1.001–1.209], p = 0.05) and IC standard deviation of GTVn (HR 9.300 [95% CI: 1.113–77.725] p = 0.04) were predictive of LRR. On subgroup analysis of patients treated with upfront radiotherapy +/- chemotherapy, both voxel-based maximum IC of GTVp (HR 1.127 [95% CI: 1.010–1.258], p = 0.05) and IC kurtosis of GTVp (HR 1.088 [95% CI: 1.014–1.166], p = 0.02) were predictive of LRR.
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¹: Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna/Vienna General Hospital, Waehringer Guertel 18-20, 1090 Vienna, Austria. Tel.: +43 1 40400 4818; fax: +43 1 40400 4898.

²: Department of Craniomaxillofacial and Oral Surgery, Medical University Vienna/Vienna General Hospital, Waehringer Guertel 18-20, 1090 Vienna, Austria. Tel.: +43 1 40400 4818; fax: +43 1 40400 4898.

³: Address: Carinagasse 47, 6807 Feldkirch, Austria. Tel.:05522 303 1500; fax: 05522 303 7552.

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Can dual-energy CT improve the assessment of tumor margins in oral cancer?

Summary

Objectives

Materials and methods

Results

Discussion

Introduction

Section snippets

Materials and methods

Patient population

Discussion

Conclusion

Conflict of interest statement

Radiother Oncol

Oral oncol

Acad Radiol

Acad Radiol

Eur J Radiol

Eur J Radiol

Image quality and radiation dose of dual-energy CT of the head and neck compared with a standard 120-kVp acquisition

AJNR Am J Neuroradiol

Dual source dual energy MDCT: comparison of 80 kVp and weighted average 120 kVp data for conspicuity of hypo-vascular liver metastases

Invest Radiol

Dual-energy CT of head and neck cancer: average weighting of low- and high-voltage acquisitions to improve lesion delineation and image quality-initial clinical experience

Invest Radiol