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.

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.

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.

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.

Radiation dose reduction to the lens of eye with bismuth shielding in head and neck MSCT / 中华放射医学与防护杂志

Objective To explore the effects on image quality and dose reduction to the lens when using bismuth shielding in head and neck MSCT.Methods The standard phantom and the cadaveric head with none,1,2 and 3 layers of bismuth shielding were scanned with protocols of brain,temporal bone and paranasal sinuses using a 16-MDCT scanner.The organ dose to the lens in each scanning was measured with thermoluminescence dosimeters(TLD).The above scanning with sinus protocol was repeated with a sponge with thickness of 5,10,15 and 20 mm placed between the shielding and phantom/head.The CT attenuation of phantom with the distance of 2,4,6 and 8 cm to shielding were measured.The image quality was subjectively evaluated by 2 physicians.Results The organ doses of the lens with protocols of brain,temporal bone and sinuses were 24.31,27.60 and 20.01 mGy,respectively.The doses were decreased significantly when using bismuth shielding.With the increase of the shield gap,the degree of dose reduction was reduced,but the increasing degree of CT attenuation significantly reduced.Using 2-layer and 3-layer bismuth shield in brain and temporal bone CT scan,the radiation doses were reduced by 47.1％ and 59.1％,respectively while maintaining the diagnostic image quality.Using 1-layer shield without gap and 2-layer shield with 1.5 cm gap in sinus CT,the radiation doses were reduced by 31.5％ and 34.5％,respectively.Conclusions Reasonable usage of bismuth shielding can effectively reduce the radiation dose to the lens of eye in head and neck MSCT.