Low-Tube-Voltage 80-kVp Neck CT: Evaluation of Diagnostic Accuracy and Interobserver Agreement

BACKGROUND AND PURPOSE:Low-tube-voltage acquisition has been shown to facilitate substantial dose savings for neck CT with similar image contrast compared with standard 120-kVp acquisition. However, its potential for the detection of neck pathologies is uncertain. Our aim was to evaluate the effects of low-tube-voltage 80-kV(peak) acquisitions for neck CT on diagnostic accuracy and interobserver agreement.MATERIALS AND METHODS:Three radiologists individually analyzed 80-kVp and linearly blended 120-kVp image series of 170 patients with a variety of pathologies who underwent dual-energy neck CT. Reviewers were unblinded to the clinical indication for CT but were otherwise blinded to any other data or images and were asked to state a final main diagnosis. Findings were compared with medical record charts, CT reports, and pathology results. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated for each observer. Interobserver agreement was evaluated by using intraclass correlation coefficients.RESULTS:Diagnoses were grouped as squamous cell carcinoma–related (n = 107, presence/absence of primary/recurrent squamous cell carcinoma), lymphoma-related (n = 40, presence/absence of primary/recurrent lymphoma), and benign (n = 23, eg, abscess). Cumulative sensitivity, specificity, positive predictive value, and negative predictive value for 80-kVp and blended 120-kVp images were 94.8%, 93.0%, 95.9%, and 91.1%, respectively. Results were also consistently high for squamous cell carcinoma–related (94.8%/95.3%, 89.1%/89.1%, 94.3%/94.4%, 90.1%/91.0%) and lymphoma-related (95.0%, 100.0%, 100.0%, 95.2%) 80-kVp/120-kVp image series. Global interobserver agreement was almost perfect (intraclass correlation coefficient, 0.82, 0.80; 95% CI, 0.76–0.74, 0.86–0.85). Calculated dose-length product was reduced by 48% with 80-kVp acquisitions compared with the standard 120-kVp scans (135.5 versus 282.2 mGy × cm).CONCLUSIONS:Low-tube-voltage 80-kVp CT of the neck provides sufficient image quality with high diagnostic accuracy in routine clinical practice and has the potential to substantially decrease radiation exposure.

CT is a standard imaging technique in routine clinical practice for detection, staging, and follow-up evaluation of various pathologies of the neck, including squamous cell carcinoma (SCC), cervical lymphoma or lymphadenopathy, and parapharyngeal or retropharyngeal abscess.^1–5 CT examinations contribute a substantial amount of cumulative radiation exposure to patients with cervical pathologies, especially if follow-up CT is required.⁶ Thus, various approaches for dose reduction of CT of the neck, brain, paranasal sinus, and the facial skeleton have been proposed, including reduction of tube current and tube potential, high-pitch acquisition, and application of automated exposure-control software.^7–10 The combination of such techniques with an iterative reconstruction algorithm can also provide similar image quality while substantially reducing exposure to ionizing radiation compared with the standard 120-kVp acquisitions.^11,12Several studies have demonstrated that low-tube-voltage acquisitions at 80 kVp can increase iodine attenuation and image contrast of soft-tissue structures and reduce radiation exposure.^13–15 However, only a few studies have investigated low-tube-voltage acquisition CT techniques for imaging of the neck.^16–18 We hypothesized that an 80-kVp acquisition may provide comparable image quality for evaluation of the neck region. To evaluate the efficacy of this technique in simulated routine clinical practice, we retrospectively assessed the diagnostic accuracy of low-tube-voltage 80-kVp image series from dual-energy neck CT (DECT) for evaluation of a variety of cervical pathologies, and the results were compared with linearly blended images representing a standard 120-kVp acquisition. We also assessed interobserver agreement and calculated the potential radiation dose reduction.