Test-retest reliability of mandibular morphology measurements on cone-beam computed tomography-synthesized cephalograms with random head positioning errors

Evaluation of Upper Airway in Children with Obstructive Sleep Apnea Using Cone-Beam Computed Tomography

OBJECTIVE

Cone-beam computed tomography (CBCT) offers three-dimensional structures in assessing upper airway of patients. This study aims to compare the cone-beam computerized tomography scan measurements between children with obstructive sleep apnea (OSA) and primary snoring.

STUDY DESIGN

Case-control study.

METHODS

This prospective study was conducted in a tertiary referral center. Thirty-six children with moderate-to-severe OSA (with apnea-hypopnea index [AHI] > 5 events/hour) and 36 age-, gender-, and obesity-matched children with primary snoring (AHI <1) were enrolled. The measurements in CBCT parameters were compared between children with moderate-to-severe OSA and primary snorers by conditional logistic regression model.

RESULTS

A total of 72 children (mean age, 7.9 ± 2.8 years; 64% male) were included. Children with moderate-to-severe OSA had a significantly smaller nasopharyngeal (2900 ± 1400 vs. 3800 ± 1800 mm³ , P = .017) and oropharyngeal airway volume (5600 ± 2700 vs. 7400 ± 4000 mm³ , P = .026) than those with primary snoring. Children with moderate-to-severe OSA, as compared to primary snorers, also had a significantly smaller minimal airway area in nasopharynx (77.4 ± 37.7 vs. 107.7 ± 52.0 mm² , P = .006) and oropharynx (66.6 ± 61.9 vs. 101.6 ± 65.8 mm² , P = .023). Moreover, the airway length was not significantly different between children with moderate-to-severe OSA and primary snoring.

CONCLUSIONS

The three-dimensional CBCT airway analysis could be used as a useful tool to evaluate upper airway in children with OSA.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:680-685, 2021.

A consistency evaluation of signal-to-noise ratio in the quality assessment of human brain magnetic resonance images

Background

Quality assessment of medical images is highly related to the quality assurance, image interpretation and decision making. As to magnetic resonance (MR) images, signal-to-noise ratio (SNR) is routinely used as a quality indicator, while little knowledge is known of its consistency regarding different observers.

Methods

In total, 192, 88, 76 and 55 brain images are acquired using T₂^*, T₁, T₂ and contrast-enhanced T₁ (T₁C) weighted MR imaging sequences, respectively. To each imaging protocol, the consistency of SNR measurement is verified between and within two observers, and white matter (WM) and cerebral spinal fluid (CSF) are alternately used as the tissue region of interest (TOI) for SNR measurement. The procedure is repeated on another day within 30 days. At first, overlapped voxels in TOIs are quantified with Dice index. Then, test-retest reliability is assessed in terms of intra-class correlation coefficient (ICC). After that, four models (BIQI, BLIINDS-II, BRISQUE and NIQE) primarily used for the quality assessment of natural images are borrowed to predict the quality of MR images. And in the end, the correlation between SNR values and predicted results is analyzed.

Results

To the same TOI in each MR imaging sequence, less than 6% voxels are overlapped between manual delineations. In the quality estimation of MR images, statistical analysis indicates no significant difference between observers (Wilcoxon rank sum test, p_w ≥ 0.11; paired-sample t test, p_p ≥ 0.26), and good to very good intra- and inter-observer reliability are found (ICC, p_icc ≥ 0.74). Furthermore, Pearson correlation coefficient (r_p) suggests that SNR_wm correlates strongly with BIQI, BLIINDS-II and BRISQUE in T₂^* (r_p ≥ 0.78), BRISQUE and NIQE in T₁ (r_p ≥ 0.77), BLIINDS-II in T₂ (r_p ≥ 0.68) and BRISQUE and NIQE in T₁C (r_p ≥ 0.62) weighted MR images, while SNR_csf correlates strongly with BLIINDS-II in T₂^* (r_p ≥ 0.63) and in T₂ (r_p ≥ 0.64) weighted MR images.

Conclusions

The consistency of SNR measurement is validated regarding various observers and MR imaging protocols. When SNR measurement performs as the quality indicator of MR images, BRISQUE and BLIINDS-II can be conditionally used for the automated quality estimation of human brain MR images.

Efficient Segmentation of a Breast in B-Mode Ultrasound Tomography Using Three-Dimensional GrabCut (GC3D)

As an emerging modality for whole breast imaging, ultrasound tomography (UST), has been adopted for diagnostic purposes. Efficient segmentation of an entire breast in UST images plays an important role in quantitative tissue analysis and cancer diagnosis, while major existing methods suffer from considerable time consumption and intensive user interaction. This paper explores three-dimensional GrabCut (GC3D) for breast isolation in thirty reflection (B-mode) UST volumetric images. The algorithm can be conveniently initialized by localizing points to form a polygon, which covers the potential breast region. Moreover, two other variations of GrabCut and an active contour method were compared. Algorithm performance was evaluated from volume overlap ratios ( T O , target overlap; M O , mean overlap; F P , false positive; F N , false negative) and time consumption. Experimental results indicate that GC3D considerably reduced the work load and achieved good performance ( T O = 0.84; M O = 0.91; F P = 0.006; F N = 0.16) within an average of 1.2 min per volume. Furthermore, GC3D is not only user friendly, but also robust to various inputs, suggesting its great potential to facilitate clinical applications during whole-breast UST imaging. In the near future, the implemented GC3D can be easily automated to tackle B-mode UST volumetric images acquired from the updated imaging system.

Comparison of measurements of mandible growth using cone beam computed tomography and its synthesized cephalograms

BACKGROUND

The current study aimed to compare the measurements of the mandible morphology using 3D cone beam computed tomography (CBCT) images with those using 2D CBCT-synthesized cephalograms; to quantify errors in measurements based on 2D synthesized cephalograms; and to clarify the effects such errors have on the description of the mandibular growth.

METHODS

Mandibles of six miniature pigs were scanned monthly using CBCT over 12 months and the data were used to reconstruct the 3D bone models. Five anatomical landmarks were identified on each bone model, and the inter-marker distances and monthly distance changes were calculated and taken as the gold standard. Synthetic 2D cephalograms were also generated for each bone model using a digitally reconstructed radiography (DRR)-generation method. Errors in cephalogram measurements were determined as the differences between the calculated variables in cephalograms and the gold standard. The variations between cephalograms and the gold standard were also compared using paired t-tests.

RESULTS

While the inter-marker distance increases varied among the marker pairs, all marker pairs increased their inter-marker distances gradually every month, reaching 50% of the total annual increases during the fourth and fifth months, and then slowing down in the subsequent months. The 2D measurements significantly underestimated most of the inter-marker distances throughout the monitoring period, in most of the monthly inter-marker distance changes during the first four months, and in the total growth (p < 0.05).

CONCLUSIONS

Significant errors exist in the measurements using 2D synthesized cephalogram, underestimating the mandibular dimensions and their monthly changes in the early stages of growth, as well as the total annual growth. These results should be considered in dental treatment planning at the beginning of the treatment in order to control more precisely the treatment process and outcome.