Objective and subjective image quality of primary and recurrent squamous cell carcinoma on head and neck low-tube-voltage 80-kVp computed tomography

The Dose Optimization and Evaluation of Image Quality in the Adult Brain Protocols of Multi-Slice Computed Tomography: A Phantom Study

Computed tomography examinations have caused high radiation doses for patients, especially for CT scans of the brain. This study aimed to optimize the radiation dose and image quality in adult brain CT protocols. Images were acquired using a Catphan 700 phantom. Radiation doses were recorded as CTDIvol and dose length product (DLP). CT brain protocols were optimized by varying parameters such as kVp, mAs, signal-to-noise ratio (SNR) level, and Clearview iterative reconstruction (IR). The image quality was also evaluated using AutoQA Plus v.1.8.7.0 software. CT number accuracy and linearity had a robust positive correlation with the linear attenuation coefficient (µ) and showed more inaccurate CT numbers when using 80 kVp. The modulation transfer function (MTF) showed a higher value in 100 and 120 kVp protocols (p < 0.001), while high-contrast spatial resolution showed a higher value in 80 and 100 kVp protocols (p < 0.001). Low-contrast detectability and the contrast-to-noise ratio (CNR) tended to increase when using high mAs, SNR, and the Clearview IR protocol. Noise decreased when using a high radiation dose and a high percentage of Clearview IR. CTDIvol and DLP were increased with increasing kVp, mAs, and SNR levels, while the increasing percentage of Clearview did not affect the radiation dose. Optimized protocols, including radiation dose and image quality, should be evaluated to preserve diagnostic capability. The recommended parameter settings include kVp set between 100 and 120 kVp, mAs ranging from 200 to 300 mAs, SNR level within the range of 0.7-1.0, and an iterative reconstruction value of 30% Clearview to 60% or higher.

Evaluating the Image Quality of Neck Structures Scanned on Chest CT with Low-Concentration-Iodine Contrast Media

BACKGROUND

The purpose of this study was to investigate and compare the image quality of low-concentration-iodine (240 mgI/mL) contrast media (CM) and high-concentration-iodine (320 mgI/mL) CM according to the radiation dose.

METHODS

A total of 366 CT examinations were examined. Based on an assessment of quantitative and qualitative parameters by two radiologists, the quality was compared between Group A (low-concentration-iodine CM) and Group B (high-concentration-iodine CM) images of thyroid gland, sternocleidomastoid muscle (SCM), internal jugular vein (IJV), and common carotid artery (CCA). Another subgroup analysis compared Group a, (using ≤90 kVp in Group A), and Group b, (using ≥100 kVp in Group B) for finding the difference in image quality when the tube voltage is lowered.

RESULTS

Image quality did not differ between Groups A and B or between Groups a and b. The signal-to-noise ratio and contrast-to-noise ratio were significantly higher for Group B than Group A for the thyroid gland, IJV, and CCA. No statistical differences were found in the comparison of all structures between Groups a and b.

CONCLUSION

There was no significant difference in image quality based on CM concentration with variable radiation doses. Therefore, if an appropriate CT protocol is applied, clinically feasible neck CT images can be obtained even using low-concentration-iodine CM.

Improvement of image quality of laryngeal squamous cell carcinoma using noise-optimized virtual monoenergetic image and nonlinear blending image algorithms in dual-energy computed tomography

BACKGROUND

Dual-energy computed tomography (DECT) has been used to improve image quality of head and neck squamous cell carcinoma (SCC). This study aimed to assess image quality of laryngeal SCC using linear blending image (LBI), nonlinear blending image (NBI), and noise-optimized virtual monoenergetic image (VMI+) algorithms.

METHODS

Thirty-four patients with laryngeal SCC were retrospectively enrolled between June 2019 and December 2020. DECT images were reconstructed using LBI (80 kV and M_0.6), NBI, and VMI+ (40 and 55 keV) algorithms. Contrast-to-noise ratio (CNR), tumor delineation, and overall image quality were assessed and compared.

RESULTS

VMI+ (40 keV) had the highest CNR and provided better tumor delineation than VMI+ (55 keV), LBI, and NBI, while NBI provided better overall image quality than VMI+ and LBI (all corrected p < 0.05).

CONCLUSIONS

VMI+ (40 keV) and NBI improve image quality of laryngeal SCC and may be preferable in DECT examination.

Comparison of tumor delineation using dual energy computed tomography versus magnetic resonance imaging in head and neck cancer re-irradiation cases

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GTVs on the 60 kV and 140 kV from DECT, and the T1c and T2 from MRI were compared.

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Delineation was the most consistent using T1c (no interobserver difference in DSC).

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T1c MRI provided higher interobserver agreement for skull base tumors.

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60 kV DECT provided higher interobserver agreement for non-skull base tumors.

In treatment planning, multiple imaging modalities can be employed to improve the accuracy of tumor delineation but this can be costly. This study aimed to compare the interobserver consistency of using dual energy computed tomography (DECT) versus magnetic resonance imaging (MRI) for delineating tumors in the head and neck cancer (HNC) re-irradiation scenario. Twenty-three patients with recurrent HNC and had planning DECT and MRI were identified. Contoured tumor volumes by seven radiation oncologists were compared. Overall, T1c MRI performed the best with median DSC of 0.58 (0–0.91) for T1c. T1c MRI provided higher interobserver agreement for skull base sites and 60 kV DECT provided higher interobserver agreement for non-skull base sites.

3D printing of anatomically realistic phantoms with detection tasks to assess the diagnostic performance of CT images

Objectives

Detectability experiments performed to assess the diagnostic performance of computed tomography (CT) images should represent the clinical situation realistically. The purpose was to develop anatomically realistic phantoms with low-contrast lesions for detectability experiments.

Methods

Low-contrast lesions were digitally inserted into a neck CT image of a patient. The original and the manipulated CT images were used to create five phantoms: four phantoms with lesions of 10, 20, 30, and 40 HU contrast and one phantom without any lesion. Radiopaque 3D printing with potassium-iodide-doped ink (600 mg/mL) was used. The phantoms were scanned with different CT settings. Lesion contrast was analyzed using HU measurement. A 2-alternative forced choice experiment was performed with seven radiologists to study the impact of lesion contrast on detection accuracy and reader confidence (1 = lowest, 5 = highest).

Results

The phantoms reproduced patient size, shape, and anatomy. Mean ± SD contrast values of the low-contrast lesions were 9.7 ± 1.2, 18.2 ± 2, 30.2 ± 2.7, and 37.7 ± 3.1 HU for the 10, 20, 30, and 40 HU contrast lesions, respectively. Mean ± SD detection accuracy and confidence values were not significantly different for 10 and 20 HU lesion contrast (82.1 ± 6.3% vs. 83.9 ± 9.4%, p = 0.863 and 1.7 ± 0.4 vs. 1.8 ± 0.5, p = 0.159). They increased to 95 ± 5.7% and 2.6 ± 0.7 for 30 HU lesion contrast and 99.5 ± 0.9% and 3.8 ± 0.7 for 40 HU lesion contrast (p < 0.005).

Conclusions

A CT image was manipulated to produce anatomically realistic phantoms for low-contrast detectability experiments. The phantoms and our initial experiments provide a groundwork for the assessment of CT image quality in a clinical context.

Key Points

• Phantoms generated from manipulated CT images provide patient anatomy and can be used for detection tasks to evaluate the diagnostic performance of CT images.

• Radiologists are unconfident and unreliable in detecting hypodense lesions of 20 HU contrast and less in an anatomical neck background.

• Detectability experiments with anatomically realistic phantoms can assess CT image quality in a clinical context.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-06808-7) contains supplementary material, which is available to authorized users.

Radiation Dose and Image Quality in Pediatric Neck CT

BACKGROUND AND PURPOSE

Optimization of pediatric neck CT protocols is of critical importance in order to maintain good diagnostic image quality while reducing the radiation burden. Our aim was to evaluate the image quality of pediatric neck CT studies before and after the implementation of a low radiation dose protocol.

MATERIALS AND METHODS

We retrospectively reviewed 179 pediatric neck CT studies, 75 before and 104 after the implementation of low-dose protocols, performed in children 0-16 years of age. The 2 cohorts were divided into 3 age groups, 0-4, 5-9, and 10-16 years. The signal-to-noise ratio was calculated using the axial image through the true vocal folds. Three neuroradiologists assessed the image quality of the same CT scan using a 5-point scoring system. We compared the CT dose index volume, dose-length product, image-quality ratings, and SNR of studies conducted at baseline and with low-dose protocols.

RESULTS

Image-quality ratings were lower in the low-dose than in the baseline cohort in children 10-16 years of age, but not in children 0-4 and 5-9 years of age. The SNR was lower in the low-dose cohort than in the baseline cohort in children 0-4 and 10-16 years of age, but not in children 5-9 years of age. Despite the decrease in image-quality scores in older children, 97% of the studies (73/75) in the baseline cohort and 96% of studies (100/104) in the low-dose cohort were considered of sufficient image quality.

CONCLUSIONS

Images acquired with the low-dose CT protocols were deemed to be of sufficient quality for making a clinical diagnosis. Our initial results suggest that there may be an opportunity for further radiation dose reduction without compromising diagnostic image quality using iterative reconstruction algorithms.

Third generation dual-energy CT with 80/150 Sn kV for head and neck tumor imaging

BACKGROUND

Dual-energy CT (DECT) provides additional image datasets which enable improved tumor delineation or reduction of beam hardening artifacts in patients with head and neck squamous cell carcinoma (SCC).

PURPOSE

To assess radiation dose and image quality of third-generation DECT of the head and neck in comparison to single-energy CT (SECT).

MATERIAL AND METHODS

Thirty patients with SCC who underwent both SECT (reference tube voltage 120 kVp) and DECT (80/150 Sn kVp) of the head and neck region for staging were retrospectively selected. Attenuation measurements of the sternomastoid muscle, internal jugular vein, submandibular gland and tongue were compared. Image noise was assessed at five anatomic levels. Subjective image quality was evaluated by two radiologists in consensus.

RESULTS

CTDI_vol was 55% lower with DECT (4.2 vs. 9.3 mGy; P = 0.002). Median image noise was equal or lower in DECT at all levels (nasopharynx: 3.9 vs. 5.8, P < 0.0001; floor of mouth: 3.6 vs. 4.5, P = 0.0002; arytenoids: 3.6 vs. 3.1, P = 0.096; lower thyroid: 4.4 vs. 5.7, P = 0.002; arch of aorta: 5.6 vs. 6.5, P = 0.001). Attenuation was significantly lower in DECT ( P < 0.05). Subjective image analysis revealed that DECT is equal or superior to SECT with regard to overall image quality (nasopharynx: 5 vs. 5, P = 1; floor of mouth: 5 vs. 5, P = 0.0041; arytenoids: 5 vs. 5, P = 0.6; lower thyroid: 5 vs. 3, P < 0.0001; arch of aorta: 5 vs. 4, P < 0.0001).

CONCLUSION

Head and neck imaging with third-generation DECT can reduce radiation dose by half compared to SECT, while maintaining excellent image quality.

Ultra-Low-Dose Neck CT With Low-Dose Contrast Material for Preoperative Staging of Thyroid Cancer: Image Quality and Diagnostic Performance

OBJECTIVE

Although CT has been used as a complementary diagnostic method for the preoperative diagnosis of thyroid cancer, it has the shortcomings of substantial radiation exposure and the use of contrast material (CM). The purpose of this article is to evaluate the image quality and diagnostic performance of 70-kVp thyroid CT with low volumes of CM versus conventional 120-kVp thyroid CT protocol.

MATERIALS AND METHODS

Eighty patients referred for preoperative thyroid CT were randomly divided into two groups (group A: 40 patients, 70 kVp, 60 mL of CM; group B: 40 patients, 120 kVp, 100 mL of CM). Quantitative and qualitative image quality and radiation doses for the two groups were compared using the Mann-Whitney U and chi-square tests. Degrees of agreement between preoperative CT staging and pathologic results were evaluated and compared using the Wald statistic.

RESULTS

Calculated signal-to-noise ratios of different anatomic structures, calculated contrast-to-noise ratios, overall image quality, subjective noise, and streak artifacts were not significantly different between the two groups (all p > 0.05), and neither were the accuracies of preoperative CT staging (all p > 0.05). The estimated effective doses were significantly lower in group A (mean [± SD], 0.52 ± 0.14 mSv in group A and 2.28 ± 0.29 mSv in group B; p < 0.001).

CONCLUSION

Ultra-low-dose 70-kVp CT with a low volume of CM provides sufficient image quality for preoperative staging of thyroid cancer and substantially reduces the radiation dose compared with standard 120-kVp CT.

Comparison of dual- and single-source dual-energy CT in head and neck imaging

OBJECTIVES

The aim of this study was to compare image quality of single-source dual-energy CT (SS-DECT) with third-generation dual-source dual-energy CT (DS-DECT) in head and neck cancer.

MATERIALS AND METHODS

One hundred two patients with histologically proven head and neck cancer were prospectively randomized to undergo radiation dose-matched SS-DECT (n = 51, 120 kV, split-filter technique, 384 ref. mAs) or DS-DECT (n = 51, 80/Sn150 kV, tube A 100/tube B 67 ref. mAs). Inline default images (DI) and virtual monoenergetic images (VMI) for two different low energies (40 and 60 keV) were reconstructed. Objective image quality was evaluated as dose-normalized contrast to noise ratio (CNRD), and subjective image quality was rated on a 5-point Likert scale.

RESULTS

In both groups, highest CNRD values for vessel and tumor attenuation were obtained at 40 keV. DS-DECT was significantly better than SS-DECT regarding vessel and tumor attenuation. Overall subjective image quality in the SS-DECT group was highest on the DI followed by 40 keV and 60 keV. In the DS-DECT group, subjective image quality was highest at 40 keV followed by 60 keV and the DI. Forty kiloelectron volts and 60 keV were significantly better in the DS-DECT compared to the SS-DECT group (both p < 0.01).

CONCLUSIONS

In split-filter SS-DECT as well as in DS-DECT, highest overall image quality in head and neck imaging can be obtained with a combination of DI and low keV reconstructions. DS-DECT is superior to split-filter SS-DECT in terms of subjective image quality and vessel and tumor attenuation.

KEY POINTS

• Image quality was diagnostic with both dual-energy techniques; however, the dual-source technique delivered significantly better results. • Highest overall image quality in head and neck imaging can be obtained with a combination of default images and low keV reconstructions with both dual-energy techniques. • The results of this study may have relevance for the decision-making process regarding replacement of CT scanners and focused patient examination considering image quality and subsequent therapeutic decision-making.

Diagnostic yield of 90-kVp low-tube-voltage carotid and intracerebral CT-angiography: effects on radiation dose, image quality and diagnostic performance for the detection of carotid stenosis

OBJECTIVE

To investigate the impact of low-tube-voltage 90-kVp acquisition combined with advanced modeled iterative reconstruction algorithm (Admire) on radiation exposure, image quality, artifacts, and assessment of stenosis in carotid and intracranial CT angiography (CTA).

METHODS

Dual-energy CTA studies of 43 patients performed on a third-generation 192-slice dual-source CT were retrospectively evaluated. Intraindividual comparison of 90-kVp and linearly blended 120-kVp equivalent image series (M_0.6, 60% 90-kVp, 40% Sn-150-kVp) was performed. Contrast-to-noise and signal-to-noise ratios of common carotid artery, internal carotid artery, middle cerebral artery, and basilar artery were calculated. Qualitative image analysis included evaluation of artifacts and suitability for angiographical assessment at shoulder level, carotid bifurcation, siphon, and intracranial by three independent radiologists. Detection and quantification of carotid stenosis were performed. Radiation dose was expressed as dose-length product (DLP).

RESULTS

Contrast-to-noise values of all arteries were significantly increased in 90-kVp compared to M_0.6 (p < 0.001). Suitability for angiographical evaluation was rated excellent with low artifacts for all levels in both image series. Both 90-kVp and M_0.6 showed excellent accordance for detection and grading of carotid stenosis with almost perfect interobserver agreement (carotid stenoses in 32 of 129 segments; intraclass correlation coefficient, 0.94). dose-length product was reduced by 40.3% in 90-kVp (110.6 ± 32.1 vs 185.4 ± 47.5 mGy·cm, p < 0.001).

CONCLUSION

90-kVp carotid and intracranial CTA with Admire provides increased quantitative and similarly good qualitative image quality, while reducing radiation exposure substantially compared to M_0.6. Diagnostic performance for arterial stenosis detection and quantification remained excellent. Advances in knowledge: 90-kVp carotid and intracranial CTA with an advanced iterative reconstruction algorithm results in excellent image quality and reduction of radiation exposure without limiting diagnostic performance.

Comparison of MR Imaging and Dual-Energy CT for the Evaluation of Cartilage Invasion by Laryngeal and Hypopharyngeal Squamous Cell Carcinoma

BACKGROUND AND PURPOSE

Dual-energy CT can distinguish iodine-enhanced tumors from nonossified cartilage and has been investigated for evaluating cartilage invasion in patients with laryngeal and hypopharyngeal squamous cell carcinomas. In this study, we compared the diagnostic accuracy of MR imaging and of a combination of weighted-average and iodine overlay dual-energy CT images in detecting cartilage invasion by laryngeal and hypopharyngeal squamous cell carcinomas, in particular thyroid cartilage invasion.

MATERIALS AND METHODS

Fifty-five consecutive patients who underwent 3T MR imaging and 128-slice dual-energy CT for preoperative initial staging of laryngeal or hypopharyngeal squamous cell carcinomas were included. Two blinded observers evaluated laryngeal cartilage invasion on MR imaging and dual-energy CT using a combination of weighted-average and iodine-overlay images. Pathologic findings of surgically resected specimens were used as the reference standard for evaluating sensitivity, specificity, and the areas under the receiver operating characteristic curve of both modalities for cartilage invasion by each type of cartilage and for all cartilages together. Sensitivity and specificity were compared using the McNemar test and generalized linear mixed models.

RESULTS

Dual-energy CT showed higher specificity than MR imaging for diagnosing all cartilage together (84% for MR imaging versus 98% for dual-energy CT, P < .004) and for thyroid cartilage (64% versus 100%, P < .001), with a similar average area under the curve (0.94 versus 0.95, P = .70). The sensitivity did not differ significantly for all cartilages together (97% versus 81%, P = .16) and for thyroid cartilage (100% versus 89%, P = .50), though there was a trend toward increased sensitivity with MR imaging.

CONCLUSIONS

Dual-energy CT showed higher specificity and acceptable sensitivity in diagnosing laryngeal cartilage invasion compared with MR imaging.

Advanced dual-energy CT applications for the evaluation of the soft tissues of the neck

There are multiple emerging advanced computed tomography (CT) applications for the evaluation of the neck, many based on dual-energy CT (DECT). DECT is an advanced form of CT in which scan acquisition is performed at two different energies, enabling spectral tissue characterisation beyond what is possible with conventional single-energy CT and potentially providing a new horizon for quantitative analysis and tissue characterisation, particularly in oncological imaging. The purpose of this review is to familiarise the reader with DECT principles and review different clinical applications for the evaluation of the soft tissues of the neck. The article will begin with an overview of DECT scan acquisition, material characterisation, reconstructions, and basic considerations for implementation in the clinical setting. This will then be followed by a review of different clinical applications. The focus will be on oncological imaging, but artefact reduction and other miscellaneous applications will also be discussed.

Dual-Energy CT in Head and Neck Imaging

PURPOSE OF REVIEW

To explain the technique of Dual-energy CT (DECT) and highlight its applications and advantages in head and neck radiology.

RECENT FINDINGS

Using DECT, additional datasets can be created next to conventional images. In head and neck radiology, three material decomposition algorithms can be used for improved lesion detection and delineation of the tumor. Iodine concentration measurements can aid in differentiating malignant from nonmalignant lymph nodes and benign posttreatment changes from tumor recurrence. Virtual non-calcium images can be used for detection of bone marrow edema. Virtual mono-energetic imaging can be useful for improved iodine conspicuity at lower keV and for reduction of metallic artifacts and increase in signal-to-noise ratio at higher keV.

SUMMARY

DECT and its additional reconstructions can play an important role in head and neck cancer patients, from initial diagnosis and staging, to therapy planning, evaluation of treatment response and follow-up. Moreover, it can be helpful in imaging of infections and inflammation and parathyroid imaging as supplementary reconstructions can be obtained at lower or equal radiation dose compared with conventional single energy scanning.

Change in Image Quality According to the 3D Locations of a CBCT Phantom

A patient's position changes in every CBCT scan despite patient alignment protocols. However, there have been studies to determine image quality differences when an object is located at the center of the field of view (FOV). To evaluate changes in the image quality of the CBCT scan according to different object positions, the image quality indexes of the Alphard 3030 (Alphard Roentgen Ind., Ltd., Kyoto, Japan) and the Rayscan Symphony (RAY Ind., Ltd., Suwon, Korea) were measured using the Quart DVT_AP phantom at the center of the FOV and 6 peripheral positions under four types of exposure conditions. Anterior, posterior, right, left, upper, and lower positions 1 cm offset from the center of the FOV were used for the peripheral positions. We evaluated and compared the voxel size, homogeneity, contrast to noise ratio (CNR), and the 10% point of the modulation transfer function (MTF10%) of the center and periphery. Because the voxel size, which is determined by the Nyquist frequency, was within tolerance, other image quality indexes were not influenced by the voxel size. For the CNR, homogeneity, and MTF10%, there were peripheral positions which showed considerable differences with statistical significance. The average difference between the center and periphery was up to 31.27% (CNR), 70.49% (homogeneity), and 13.64% (MTF10%). Homogeneity was under tolerance at some of the peripheral locations. Because the CNR, homogeneity, and MTF10% were significantly affected by positional changes of the phantom, an object's position can influence the interpretation of follow up CBCT images. Therefore, efforts to locate the object in the same position are important.

Advanced Modeled Iterative Reconstruction in Low-Tube-Voltage Contrast-Enhanced Neck CT: Evaluation of Objective and Subjective Image Quality

BACKGROUND AND PURPOSE

Dose-saving techniques in neck CT cause increased image noise that can be counteracted by iterative reconstruction. Our aim was to evaluate the image quality of advanced modeled iterative reconstruction (ADMIRE) in contrast-enhanced low-tube-voltage neck CT.

MATERIALS AND METHODS

Sixty-one patients underwent 90-kV(peak) neck CT by using third-generation 192-section dual-source CT. Image series were reconstructed with standard filtered back-projection and ADMIRE strength levels 1, 3, and 5. Attenuation and noise of the sternocleidomastoid muscle, internal jugular vein, submandibular gland, tongue, subscapularis muscle, and cervical fat were measured. Signal-to-noise and contrast-to-noise ratios were calculated. Two radiologists assessed image noise, image contrast, delineation of smaller structures, and overall diagnostic acceptability. Interobserver agreement was calculated.

RESULTS

Image noise was significantly reduced by using ADMIRE compared with filtered back-projection with the lowest noise observed in ADMIRE 5 (filtered back-projection, 9.4 ± 2.4 Hounsfield units [HU]; ADMIRE 1, 8.3 ± 2.8 HU; ADMIRE 3, 6.7 ± 2.0 HU; ADMIRE 5, 5.4 ± 1.7 HU; all, P < .001). Sternocleidomastoid SNR and internal jugular vein-sternocleidomastoid contrast-to-noise ratios were significantly higher for ADMIRE with the best results in ADMIRE 5 (all, P < .001). Subjective image quality and image contrast of ADMIRE 3 and 5 were consistently rated better than those for filtered back-projection and ADMIRE 1 (all, P < .001). Image noise was rated highest for ADMIRE 5 (all, P < .005). Delineation of smaller structures was voted higher in all ADMIRE strength levels compared with filtered back-projection (P < .001). Global interobserver agreement was good (0.75).

CONCLUSIONS

Contrast-enhanced 90-kVp neck CT is feasible, and ADMIRE 5 shows superior objective image quality compared with filtered back-projection. ADMIRE 3 and 5 show the best subjective image quality.