Defining the Shape of the Mylohyoid Muscle: A Morphometric Imaging Study.

OBJECTIVES: Implantable hypoglossal nerve stimulation (HNS) therapy is an evolving therapeutic alternative for patients with refractory obstructive sleep apnea (OSA). The muscular anatomy of this region has implications for surgical access through this zone as well as positioning and anchoring of hardware in this area. The purpose of this study was to radiologically describe the topography of the mylohyoid muscle and adjacent structures across a wide age spectrum. METHODS: We retrospectively evaluated computed tomography scans of the neck in 102 patients who were imaged for reasons unrelated to the floor of mouth or submental space. Patients with prior surgery or pathology in the area of interest were excluded. Fourteen relevant muscle measurements were made on a midline sagittal image and a coronal image positioned at the midpoint between the hyoid bone and the mandible. RESULTS: We included 49 men and 53 women with an average age of 44 years (range 19-70). The average mylohyoid length was 42 mm; the average distance between the anterior digastric bellies was 17 mm. The average angle of the central mylohyoid was 174° in the sagittal plane and 164° in the coronal plane. Several measurements were significantly correlated with patient age, including the angle measurements and the distance between the digastric muscles. Aberrant digastric anatomy was common. CONCLUSIONS: The mylohyoid muscle has multiple radiologically distinct segments with predictable curvatures. An understanding of submental muscular anatomy, along with its variability between patients, may be beneficial to the development of bilateral implantable neurostimulation technology for the treatment of refractory OSA. LEVEL OF EVIDENCE: N/A Laryngoscope, 134:2970-2975, 2024.

Inverse Problem Algorithm-Based Time-Resolved Imaging of Head and Neck Computed Tomography Angiography Contrast Kinetics with Clinical Testification.

This study mitigated the challenge of head and neck CT angiography by IPA-based time-resolved imaging of contrast kinetics. To this end, 627 cerebral hemorrhage patients with dizziness, brain aneurysm, stroke, or hemorrhagic stroke diagnosis were randomly categorized into three groups, namely, the original dataset (450), verification group (112), and in vivo testified group (65), in the Affiliated BenQ Hospital of Nanjing Medical University. In the first stage, seven risk factors were assigned: age, CTA tube voltage, body surface area, heart rate per minute, cardiac output blood per minute, the actual injected amount of contrast media, and CTA delayed trigger timing. The expectation value of the semi-empirical formula was the CTA number of the patient's left artery (LA). Accordingly, 29 items of the first-order nonlinear equation were calculated via the inverse problem analysis (IPA) technique run in the STATISTICA 7.0 program, yielding a loss function and variance of 3.1837 and 0.8892, respectively. A dimensionless AT was proposed to imply the coincidence, with a lower AT indicating a smaller deviation between theoretical and practical values. The derived formula was confirmed for the verification group of 112 patients, reaching high coincidence, with average ATavg and standard deviation values of 3.57% and 3.06%, respectively. In the second stage, the formula was refined to find the optimal amount of contrast media for the CTA number of LA approaching 400. Finally, the above procedure was applied to head and neck CTA images of the third group of 65 patients, reaching an average CTA number of LA of 407.8 ± 16.2 and finding no significant fluctuations.

Image quality improvement in head and neck CT angiography: Individualized post-trigger delay versus fixed delay.

PURPOSE: To compare the contrast media opacification of head and neck CT angiography (CTA) between conventional fixed trigger delay and individualized post-trigger delay (PTD). METHODS: In this prospective study (April-October 2022), 196 consecutive participants were randomly divided into two groups to perform head and neck CTA in bolus tracking with either an individualized PTD (Group A) or a fixed 4-second PTD (Group B). All CT and contrast media protocol parameters were consistent between the two groups. One reader evaluated objective image quality, while two readers rated subjective image quality. Objective image quality was compared between groups via two-sample t-test, while the subjective ratings were compared with chi-square analysis. RESULTS: Participants' clinical information including sex, age, weight, body weight index (BMI), and heart rate were not statistically different between two groups (all p > 0.05). Individualized PTD ranging from 3.5 to 7.9 s (average 5.6 s), which is shorter than fixed delays (p < 0.05). Both readers rated better subjective image quality for the Group A (p < 0.05). The mean vessel enhancement was significantly higher in Group A in all vessels (all p < 0.05). CONCLUSIONS: Compared to the fixed post-trigger delay in bolus tracking technique, individualized post-trigger delay could achieve reliable scan timing, optimize vessel opacification and obtain better image quality for head and neck CT angiography.

Virtual monoenergetic imaging in photon-counting CT of the head and neck.

PURPOSE: Advantages of virtual monoenergetic images (VMI) have been reported for dual energy CT of the head and neck, and more recently VMIs derived from photon-counting (PCCT) angiography of the head and neck. We report image quality metrics of VMI in a PCCT angiography dataset, expanding the anatomical regions evaluated and extending observer-based qualitative methods further than previously reported. METHODS: In a prospective study, asymptomatic subjects underwent contrast enhanced PCCT of the head and neck using an investigational scanner. Image sets of low, high, and full spectrum (Threshold-1) energies; linear mix of low and high energies (Mix); and 23 VMIs (40-150 keV, 5 keV increments) were generated. In 8 anatomical locations, SNR and radiologists' preferences for VMI energy levels were measured using a forced-choice rank method (4 observers) and ratings of image quality using visual grading characteristic (VGC) analysis (2 observers) comparing VMI to Mix and Threshold-1 images. RESULTS: Fifteen subjects were included (7 men, 8 women, mean 57 years, range 46-75). Among all VMIs, SNRs varied by anatomic location. The highest SNRs were observed in VMIs. Radiologists preferred 50-60 keV VMIs for vascular structures and 75-85 keV for all other structures. Cumulative ratings of image quality averaged across all locations were higher for VMIs with areas under the curve of VMI vs Mix and VMI vs Threshold-1 of 0.67 and 0.68 for the first reader and 0.72 and 0.76 for the second, respectively. CONCLUSION: Preferred keV level and quality ratings of VMI compared to mixed and Threshold-1 images varied by anatomical location.

Current approaches to the diagnosis and management of odontogenic abscesses / Odontogén tályogok diagnosztikája és kezelése a nemzetközi ajánlások tükrében

A wide scale of medical professionals including general practitioners, dentists, maxillofacial surgeons, otolaryngologists or even emergency physicians frequently encounter patients suffering from abscesses of odontogenic origin. These dental infections spreading along the fascial planes into the adjacent anatomical spaces or by the lymphatic vessels and veins may result in life-threatening situations. It is essential to prevent and - in the case of an evolved disease pattern - to treat them properly, since improper or delayed treatment may entail avoidable burdens on the healthcare system. Our aim was to review the current literature regarding the development, diagnostics and treatment of odontogenic infections. A review of the English and Hungarian literature was performed. Considerations regarding the surgical management of dental abscesses have well-tried, traditional routes. Prompt intervention is considered mandatory with surgical decompression of the swelling by performing incision and drainage. A rapid improvement of radiology has provided the possibility to realize and avoid fatal consequences of this disorder. The administration route, necessity and duration of empiric antibiotic therapy are still debated, protocols vary across studies. Based on inconsistency in findings among the studies and lack of high-quality prospective studies, future research should evaluate evidence-based and effective management of dental abscesses.

Initial Referring Physician and Radiologist Experience with Neck Imaging Reporting and Data System.

OBJECTIVES/HYPOTHESIS: Neck Imaging Reporting and Data System (NI-RADS) is a radiology reporting system developed for head and neck cancer surveillance imaging, using standardized terminology, numeric levels of suspicion, and linked management recommendations. Through a multidisciplinary, interdepartmental quality improvement initiative, we implemented NI-RADS for the reporting of head and neck cancer surveillance CT. Our objective is to summarize our initial experience from the standpoints of head and neck cancer providers and radiologists. STUDY DESIGN: Quality improvement study. METHODS: Before and 3 months post-implementation, surveys were offered to referring physicians (n = 21 pre-adoption; 22 post-adoption) and radiologists (n = 17 pre- and post-adoption). NI-RADS utilization was assessed over time. RESULTS: Survey response rates were 62% (13/21) and 73% (16/22) for referring physicians pre- and post-adoption, respectively, and 94% (16/17) for radiologists pre- and post-adoption. Among post-adoption provider respondents, 100% (16/16) strongly agreed or agreed with "I want our radiologists to continue using NI-RADS," "The NI-RADS numerical rating of radiologic suspicion is helpful," and "The language and style of NI-RADS neck CT reports are clear and understandable." Among radiologist respondents, 88% (14/16) strongly agreed or agreed with "NI-RADS improves consistency among our radiologists in the reporting of surveillance neck CTs." Radiologist NI-RADS utilization increased over time (46% month 1; 72% month 3). CONCLUSIONS: Most referring physicians and radiologists preferred NI-RADS. Head and neck cancer providers indicated that NI-RADS reports are clear, understandable, direct, and helpful in guiding clinical management. Radiologists indicated that NI-RADS improves radiologist consistency in the reporting of surveillance neck CT, and radiologists increasingly used NI-RADS over time. LEVEL OF EVIDENCE: 4 Laryngoscope, 132:349-355, 2022.

Comparison of lateral neck X-ray to neck CT in patients with suspicious bone impaction: "Old habits die hard".

OBJECTIVE: Bone impaction (BI) is a common cause for emergency room visits. Among foreign bodies, fish bone is considered the most common. The sensitivity of symptoms in predicting BI is relatively low, making imaging a central tool to aid diagnosis. Current imaging practices include both neck plain film radiography and none-contrast CT scans of the neck. We evaluated the accuracy of neck plain film radiography and CT scans of the neck for the diagnosis of BI. METHODS: Retrospective review of all patients who presented to the emergency room between 2009 and 2016 with a suspicious history of BI whom underwent plain film neck radiography or CT. All Images were reviewed by two neuro-radiologist blinded to the clinical symptoms and findings. Symptoms, clinical findings and images results were compared to the final diagnosis. RESULTS: 89 patients (30.7%), out of 290 patients who presented with complaints of BI, were diagnosed with BI. Mean age was 44.7 years old. Plain film neck radiography failed to predict BI (sen. 14.4%, spe 89.8% accuracy 63.2%), neck CT has an improved accuracy and sensitivity in locating BI (sen. 83.3%, spe. 94.1% accuracy 92.5%). Interobserver agreement between the two neuro-radiologists was moderate (0.46) and substantial (0.77) in neck radiography and CT images, respectively. Neck radiography missed 60 (out of 61) oropharyngeal BI's. CONCLUSION: Neck radiography has high inter-observer variability and low sensitivity for the diagnosis of BI. Neck CT should be the first imaging modality in patients with suspicious complaints for BI and negative physical exam.

Clinical, CT scan, and laboratory changes of abscess patients with odontogenic origin admitted to Shiraz acute surgical care center, Iran.

INTRODUCTION: Rapid diagnosis of maxillofacial abscess with the odontogenic origin is effective in the treatment of patients. This study aimed to check the clinical evaluation, head, and neck computed tomography (CT) scan, and microbial sensitivity of hospitalized patients diagnosed with maxillofacial abscess admitted to the Maxillofacial Surgery Ward Shaheed Rajaie Surgical Acute Care Center of Shiraz, Iran from 2019-2021. METHOD: A cross-sectional study was conducted. The sample included patients diagnosed with the abscess of odontogenic origin. Data collection tools included personal profile registration form, chief complainant and clinical evaluation, laboratory test results, pus culture, antibiogram results, and head and neck CT scan changes form. Data was reported with descriptive statistics by SPSS-16 software. RESULTS: The majority of patients were male; infection duration was 10 days; maximum mouth opening size was less than 20 mm in more than half of patients. The scan revealed 41.8% abscess, 36.4% cellulite, and 21.8% mixed abscess and cellulitis. There was 29.1% involvement of salivary glands. The majority of abscesses were unifocal involved in the submandibular space, and the least involvement was in peri mandibular space and carotid sheath. The most common organism causing was staphylococcal abscess coagulase-negative. CONCLUSION: In patients with maxillofacial abscess requiring hospitalization, the most common clinical features were trismus, toxic appearance, and dysphagia, and the most common source of abscess in scanning patients with mandibular molars was the most involved submandibular space and pterygomandibular space. Vancomycin, cotrimoxazole, and cefazolin had the greatest effect in the treatment of odontogenic infections in terms of antibiogram results and microbial culture.

FocusNetv2: Imbalanced large and small organ segmentation with adversarial shape constraint for head and neck CT images.

Radiotherapy is a treatment where radiation is used to eliminate cancer cells. The delineation of organs-at-risk (OARs) is a vital step in radiotherapy treatment planning to avoid damage to healthy organs. For nasopharyngeal cancer, more than 20 OARs are needed to be precisely segmented in advance. The challenge of this task lies in complex anatomical structure, low-contrast organ contours, and the extremely imbalanced size between large and small organs. Common segmentation methods that treat them equally would generally lead to inaccurate small-organ labeling. We propose a novel two-stage deep neural network, FocusNetv2, to solve this challenging problem by automatically locating, ROI-pooling, and segmenting small organs with specifically designed small-organ localization and segmentation sub-networks while maintaining the accuracy of large organ segmentation. In addition to our original FocusNet, we employ a novel adversarial shape constraint on small organs to ensure the consistency between estimated small-organ shapes and organ shape prior knowledge. Our proposed framework is extensively tested on both self-collected dataset of 1,164 CT scans and the MICCAI Head and Neck Auto Segmentation Challenge 2015 dataset, which shows superior performance compared with state-of-the-art head and neck OAR segmentation methods.

Obtaining the potential number of object models/atlases needed in medical image analysis.

Medical image processing and analysis operations, particularly segmentation, can benefit a great deal from prior information encoded to capture variations over a population in form, shape, anatomic layout, and image appearance of objects. Model/atlas-based methods are extant in medical image segmentation. Although multi-atlas/ multi-model methods have shown improved accuracy for image segmentation, if the atlases/models do not cover representatively the distinct groups, then the methods may not be generalizable to new populations. In a previous study, we have given an answer to address the following problem at image level: How many models/ atlases are needed for optimally encoding prior information to address the differing body habitus factor in a population? However, the number of models for different objects may be different, and at the image level, it may not be possible to infer the number of models needed for each object. So, the modified question to which we are now seeking an answer to in this paper is: How many models/ atlases are needed for optimally encoding prior information to address the differing body habitus factor for each object in a body region? To answer this question, we modified our method in the previous study for seeking the optimum grouping for a given population of images but focusing on the individual objects. We present our results on head and neck computed tomography (CT) scans of 298 patients.

How many models/atlases are needed as priors for capturing anatomic population variations?

Many medical image processing and analysis operations can benefit a great deal from prior information encoded in the form of models/atlases to capture variations over a population in form, shape, anatomic layout, and image appearance of objects. However, two fundamental questions have not been addressed in the literature: "How many models/atlases are needed for optimally encoding prior information to address the differing body habitus factor in that population?" and "Images of how many subjects in the given population are needed to optimally harness prior information?" We propose a method to seek answers to these questions. We assume that there is a well-defined body region of interest and a subject population under consideration, and that we are given a set of representative images of the body region for the population. After images are trimmed to the exact body region, a hierarchical agglomerative clustering algorithm partitions the set of images into a specified number of groups by using pairwise image (dis)similarity as a cost function. Optionally the images may be pre-registered among themselves prior to this partitioning operation. We define a measure called Residual Dissimilarity (RD) to determine the goodness of each partition. We then ascertain how RD varies as a function of the number of elements in the partition for finding the optimum number(s) of groups. Breakpoints in this function are taken as the recommended number of groups/models/atlases. Our results from analysis of sizeable CT data sets of adult patients from two body regions - thorax (346) and head and neck (298) - can be summarized as follows. (1) A minimum of 5 to 8 groups (or models/atlases) seems essential to properly capture information about differing anatomic forms and body habitus. (2) A minimum of 150 images from different subjects in a population seems essential to cover the anatomical variations for a given body region. (3) In grouping, body habitus variations seem to override differences due to other factors such as gender, with/without contrast enhancement in image acquisition, and presence of moderate pathology. This method may be helpful for constructing high quality models/atlases from a sufficiently large population of images and in optimally selecting the training image sets needed in deep learning strategies.

Assessment of radiation dose and iodine load reduction in head-neck CT angiography using two scan protocols with wide-detector.

OBJECTIVE: To compare image quality, radiation dose, and iodine intake of head-neck CT angiography (CTA) acquired by wide-detector with the gemstone spectral imaging (GSI) combination with low iodine intake or routine scan protocol. METHODS: Three hundred patients who had head-neck CTA were enrolled and divided into three groups according to their BMI values: group A (18.5 kg/m2 ≦ BMI <24.9 kg/m2), group B (24.9 kg/m2 ≦ BMI <29.9 kg/m2) and group C (29.9 kg/m2 ≦ BMI ≦ 34.9 kg/m2) with 100 patients in each group. Patients in each group were randomly divided into two subgroups (n = 50) namely, A1, A2, B1, B2, C1 and C2. The patients in subgroups A1, B1 and C1 underwent GSI with low iodine intake (270 mgI/ml, 50 ml) and combined with the ASiR-V algorithm. Other patients underwent three dimensional (3D) smart mA modulation with routine iodine intake (350 mgI/ml, 60 ml). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated after angiography. Images were then subjectively assessed using a 5-point scale. CT dose index of volume and dose-length product (DLP) was converted to the effective dose (ED) and then compared. RESULTS: The mean CT values, SNR, CNR and subjective image quality in subgroups A2, B2 and C2 are significantly lower than in subgroups A1, B1, and C1 (P < 0.01), respectively. The ED values in subgroup A1, B1, and C1 are 55.18%, 61.89%, and 69.64% lower than those in A2, B2, and C2, respectively (P < 0.01). The total iodine intakes in subgroups A1, B1, and C1 are 35.72% lower than those in subgroups A2, B2, and C2. CONCLUSIONS: The gemstone spectral imaging with monochromatic images at 53-57 keV combined with ASiR-V algorithm allows significant reduction in iodine load and radiation dose in head-neck CT angiography than those yielded in routine scan protocol. It also enhances signal intensity of head-neck CTA and maintains image quality.

Comparative analysis of radiation dose and image quality between organ dose modulation and 3D smart mA modulation during head-neck CT angiography.

OBJECTIVE: To assess the difference in absorbed organ dose and image quality for head-neck CT angiography using organ dose modulation compared with 3D smart mA modulation in different body mass indices (BMIs) using an adaptive statistical iterative reconstruction (ASiR-V) algorithm. METHODS: Three hundred patients underwent head-neck CTA were equally divided into three groups: A (18.5 kg/m2≦BMI < 24.9 kg/m2), B (24.9 kg/m2≦BMI < 29.9 kg/m2) and C (29.9 kg/m2≦BMI≦34.9 kg/m2). The groups were randomly subdivided into two subgroups (n = 50): A1-A2, B1-B2 and C1-C2. The patients in subgroups A1, B1 and C1 underwent organ dose modulation with the ASiR-V algorithm, while other patients underwent 3D smart mA modulation. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all head-neck CT angiography images were calculated. Images were then subjectively evaluated. Mean values of several indices including dose-length product (DLP) were computed. The DLP was converted to the effective dose (ED). SNR, CNR and ED in groups A, B, and C were compared in statistical data analysis. RESULTS: SNR, CNR, and subjective image scores show no statistical differences in three groups (P  >  0.05). However, there is significant difference of ED values (P  <  0.05) . For example, in subgroup A1 mean ED values are 15.30% and 23.66% lower than those in subgroup A2 at thyroid gland and eye lens, respectively. Similar patterns also exist in groups B (B1 vs. B2) and C (C1 vs. C2). CONCLUSIONS: Using organ dose modulation and applying the ASiR-V algorithm can more effectively reduce the radiation dose in head-neck CT angiography than using 3D smart mA modulation, while maintaining image quality. Thus, using organ-based dose modulation has the additional benefit of reducing dose to the thyroid gland and eye lens.

A preliminary study on the combination of high iodine flow rate and high noise index in reducing the radiation dose of CT angiography for head and neck / 中国医学装备

Objective:To carry out preliminarily study on the combination of high iodine flow rate (IDR) and high noise index (NI) in reducing radiation dose of CT angiography (CTA) for head and neck.Methods:A total of 120patients with lesions on head and neck who underwent head and neck CTA in the hospital were divided into high IDR combined with high NI group (high IDR+NI group, 50 cases) , middle IDR combined with middle NI group (middle IDR+NI group, 40 cases) and low IDR combined with low NI group (low IDR+NI group, 30 cases) according to the random number table method.The scanned images were reconstructed by the iterative reorganization algorithm (ASiR) 2.0.The CT values of head and neck, signal to noise ratio (SNR) , contrast noise ratio (CNR) of all images in three groups were analyzed objectively and scored subjectively.And the CT dose index (CTDI) , dose length product (DLP) , effective radiation dose (ED) of the iodine intake and radiation dose were recorded.Results:The differences of CT value of ascending aorta, upper common carotid artery or lower internal carotid artery among the three groups were no significant, respectively.The SNR and CNR in high IDR+NI group were significantly higher than those in middle IDR+NI group and low IDR+NI group (F=47.908, F=52.525, P<0.05) , respectively.And there was no significant difference in subjective scores among the three groups.The differences of CTDI, DLP and ED in high IDR+NI group were significantly lower than those in middle IDR+NI group and low IDR+NI group (F=224.861, F=199.610, F=412.443, P<0.05) , respectively.Conclusion:The combination of high IDR and high NI for patients who undergoes head and neck CT can reduce the radiation dose when ensure the image quality, and it is worthy in clinical application.

Lens Dose Reduction by Patient Posture Modification During Neck CT.

OBJECTIVE: Radiation exposure of the lens during neck CT may increase a patient's risk of developing cataracts. Radiologists at the National Institutes of Health worked with technicians to modify the neck CT scanning procedure to include a reduction in the scanning range, a reduction in the tube potential (kilovoltage), and a change in neck positioning using a head tilt. We objectively quantified the organ dose changes after this procedure modification using a computer simulation. MATERIALS AND METHODS: We retrospectively analyzed CT images of 40 patients (20 men and 20 women) scanned before and after the procedure change. Radiation dose to the lens delivered before and after the procedure change was calculated using an in-house CT dose calculator combined with computational human phantoms deformed to match head tilt angles. We also calculated the doses to other radiosensitive organs including the brain, pituitary gland, eye globes, and salivary glands before and after the procedure change. RESULTS: Our dose calculations showed that modifying the neck position, shortening the scanning range, and reducing the tube potential reduced the dose to the lens by 89% (p < 0.0001). The median brain, pituitary gland, globes, and salivary gland doses also decreased by 59%, 52%, 66%, and 29%, respectively. We found that overranging significantly affects the lens dose. CONCLUSION: Combining head tilt and scanning range reduction is an easy and effective method that significantly reduces radiation dose to the lens and other radiosensitive head and neck organs.

Variation in algorithm implementation across radiomics software.

Given the increased need for consistent quantitative image analysis, variations in radiomics feature calculations due to differences in radiomics software were investigated. Two in-house radiomics packages and two freely available radiomics packages, MaZda and IBEX, were utilized. Forty 256 × 256 - pixel regions of interest (ROIs) from 40 digital mammograms were studied along with 39 manually delineated ROIs from the head and neck (HN) computed tomography (CT) scans of 39 patients. Each package was used to calculate first-order histogram and second-order gray-level co-occurrence matrix (GLCM) features. Friedman tests determined differences in feature values across packages, whereas intraclass-correlation coefficients (ICC) quantified agreement. All first-order features computed from both mammography and HN cases (except skewness in mammography) showed significant differences across all packages due to systematic biases introduced by each package; however, based on ICC values, all but one first-order feature calculated on mammography ROIs and all but two first-order features calculated on HN CT ROIs showed excellent agreement, indicating the observed differences were small relative to the feature values but the bias was systematic. All second-order features computed from the two databases both differed significantly and showed poor agreement among packages, due largely to discrepancies in package-specific default GLCM parameters. Additional differences in radiomics features were traced to variations in image preprocessing, algorithm implementation, and naming conventions. Large variations in features among software packages indicate that increased efforts to standardize radiomics processes must be conducted.

CT Dental Artifact: Comparison of an Iterative Metal Artifact Reduction Technique with Weighted Filtered Back-Projection.

BACKGROUND: Dental hardware produces streak artifacts on computed tomography (CT) images reconstructed with the standard weighted filtered back projection (wFBP) method. PURPOSE: To perform a preliminary evaluation of an iterative metal artifact reduction (IMAR) technique to assess its ability to improve anatomic visualization over wFBP in patients with dental amalgam or other hardware. MATERIAL AND METHODS: CT images from patients with dental hardware were reconstructed using wFBP and IMAR software and soft-tissue or bone window/level settings. The anatomy most affected by metal artifacts was identified. Two neuroradiologists determined subjective and objective imaging features, including overall metal artifact score (1 = severe artifacts, 5 = no artifacts), soft-tissue visualization score of the most-compromised structure, and artifact length along the skin surface. CT numbers were used to quantify artifact severity. RESULTS: Twenty-four patients were included. IMAR improved overall metal artifact score in 18/24 cases (median =2 ± 0.9 vs. 1 ± 0.6, P < 0.001). Mean CT number in the most-affected anatomical structure significantly improved with IMAR (94.6 vs. 219 HU, P = 0.002) and length of affected skin surface decreased (40.4 mm vs. 118.7 mm, P < 0.001). However, osseous/dental artifactual defects were found in 22/24 cases with IMAR vs. 11/24 with wFBP. CONCLUSION: IMAR software reduced metal artifact both subjectively and objectively and improved visualization of adjacent soft tissues. However, it produced a higher rate of artifactual defects in the teeth and bones than wFBP. Our findings support the use of IMAR as a valuable complement to, but not a replacement for, standard wFBP image reconstruction.

Thyroid Doses and Risks to Adult Patients Undergoing Neck CT Examinations.

OBJECTIVE: The purpose of this study was to estimate absorbed thyroid dose and consequent cancer risks in adult patients undergoing neck CT examinations. MATERIALS AND METHODS: We used data from neck CT examinations of 68 consecutive adult patients to calculate the thyroid dose and estimate the corresponding cancer risk. Age and sex were recorded along with the volume CT dose index (CTDIvol) that was used to perform the examination. CTDIvol values were used to estimate thyroid doses in the mathematic phantom used in the ImPACT patient CT dosimetry calculator. Corresponding doses in patients were estimated by modeling each patient's neck as an equivalent cylinder of water and applying correction factors for varying neck size and scanning length and the variation of radiation intensity due to automatic exposure control. RESULTS: The mean (± SD) adult patient age was 59 ± 16 years, and the mean equivalent water cylinder diameter used for modeling the patient neck was 19.4 ± 4.2 cm. The average adult patient neck size was about 3 cm larger than the mathematic anthropomorphic phantom (16.5 cm), decreasing the estimated thyroid doses by 15%. Thyroid doses were independent of age and sex, with an average of 50 ± 23 mGy. The average cancer risk for a 20-year-old woman was six times higher than the corresponding risk for a 20-year-old man. Increasing patient age of either sex from 40 to 60 years reduced the cancer risk by approximately an order of magnitude. CONCLUSION: Patient sex and age are the most important factors in determining thyroid cancer risk, with the thyroid dose being secondary.

Automated Tube Potential Selection as a Method of Dose Reduction for CT of the Neck: First Clinical Results.

OBJECTIVE: The objective of our study was to investigate whether the use of a software-based automated tube potential selection (ATPS) CT neck protocol can result in radiation dose reduction as compared with a set 120-kV protocol without a statistically significant reduction in image quality. MATERIALS AND METHODS: Three hundred sixty-four patients (median age, 52 years) underwent CT of the neck. Group 1 (n = 320) underwent CT with ATPS with 80, 100, or 120 kV. Group 2 (n = 44) was examined with the standard CT protocol at 120 kV. Attenuation, image background noise, signal-to-noise ratio (SNR), dose-length product (DLP), volume CT dose index (CTDIvol), body mass index (BMI [weight in kilograms divided by the square of height in meters]), and subjective image quality (5-point Likert scale, two readers in consensus) were analyzed. RESULTS: A tube potential of 100 kV was selected in 279 patients, 120 kV in 40 patients, and 80 kV in one patient of the ATPS group. A significant correlation was found for selected tube potential and BMI (80 kV, BMI = 20.4; 100 kV, mean BMI = 24.2; 120 kV, BMI = 28.6; r = 0.28, p < 0.01). The average radiation dose was significantly lower with ATPS activated than with the standard protocol (mean DLP, 259 vs 350 mGy × cm, respectively). Background noise did not differ between groups 1 and 2 at the levels of the mandibular angle and the upper mediastinum; however, attenuation and SNR increased significantly with lower tube potential settings. Subjective image quality did not suffer (mean image quality score: ATPS protocol vs standard protocol, 4.56 vs 4.61, respectively; p > 0.05) with good interobserver agreement (κ > 0.56). CONCLUSION: ATPS allows significant dose savings for CT of the neck compared with a standard protocol that uses a fixed 120-kV setting without a statistically significant reduction in image quality.