3D ultrasonography is as accurate as low-dose CT in thyroid volumetry

3D ultrasound guidance for radiofrequency ablation in an anthropomorphic thyroid nodule phantom

BACKGROUND

The use of two-dimensional (2D) ultrasound for guiding radiofrequency ablation (RFA) of benign thyroid nodules presents limitations, including the inability to monitor the entire treatment volume and operator dependency in electrode positioning. We compared three-dimensional (3D)-guided RFA using a matrix ultrasound transducer with conventional 2D-ultrasound guidance in an anthropomorphic thyroid nodule phantom incorporated additionally with temperature-sensitive albumin.

METHODS

Twenty-four phantoms with 48 nodules were constructed and ablated by an experienced radiologist using either 2D- or 3D-ultrasound guidance. Postablation T2-weighted magnetic resonance imaging scans were acquired to determine the final ablation temperature distribution in the phantoms. These were used to analyze ablation parameters, such as the nodule ablation percentage. Further, additional procedure parameters, such as dominant/non-dominant hand use, were recorded.

RESULTS

Nonsignificant trends towards lower ablated volumes for both within (74.4 ± 9.1% (median ± interquartile range) versus 78.8 ± 11.8%) and outside of the nodule (0.35 ± 0.18 mL versus 0.45 ± 0.46 mL), along with lower variances in performance, were noted for the 3D-guided ablation. For the total ablation percentage, 2D-guided dominant hand ablation performed better than 2D-guided non-dominant hand ablation (81.0% versus 73.2%, p = 0.045), while there was no significant effect in the hand comparison for 3D-guided ablation.

CONCLUSION

3D-ultrasound-guided RFA showed no significantly different results compared to 2D guidance, while 3D ultrasound showed a reduced variance in RFA. A significant reduction in operator-ablating hand dependence was observed when using 3D guidance. Further research into the use of 3D ultrasound for RFA is warranted.

RELEVANCE STATEMENT

Using 3D ultrasound for thyroid nodule RFA could improve the clinical outcome. A platform that creates 3D data could be used for thyroid diagnosis, therapy planning, and navigational tools.

KEY POINTS

Twenty-four in-house-developed thyroid nodule phantoms with 48 nodules were constructed. RFA was performed under 2D- or 3D-ultrasound guidance. 3D- and 2D ultrasound-guided RFAs showed comparable performance. Real-time dual-plane imaging may offer an improved overview of the ablation zone and aid electrode positioning. Dominant and non-dominant hand 3D-ultrasound-guided RFA outcomes were comparable.

Artificial Intelligence-powered automatic volume calculation in medical images - available tools, performance and challenges for nuclear medicine

Volumetry is crucial in oncology and endocrinology, for diagnosis, treatment planning, and evaluating response to therapy for several diseases. The integration of Artificial Intelligence (AI) and Deep Learning (DL) has significantly accelerated the automatization of volumetric calculations, enhancing accuracy and reducing variability and labor. In this review, we show that a high correlation has been observed between Machine Learning (ML) methods and expert assessments in tumor volumetry; Yet, it is recognized as more challenging than organ volumetry. Liver volumetry has shown progression in accuracy with a decrease in error. If a relative error below 10 % is acceptable, ML-based liver volumetry can be considered reliable for standardized imaging protocols if used in patients without major anomalies. Similarly, ML-supported automatic kidney volumetry has also shown consistency and reliability in volumetric calculations. In contrast, AI-supported thyroid volumetry has not been extensively developed, despite initial works in 3D ultrasound showing promising results in terms of accuracy and reproducibility. Despite the advancements presented in the reviewed literature, the lack of standardization limits the generalizability of ML methods across diverse scenarios. The domain gap, i. e., the difference in probability distribution of training and inference data, is of paramount importance before clinical deployment of AI, to maintain accuracy and reliability in patient care. The increasing availability of improved segmentation tools is expected to further incorporate AI methods into routine workflows where volumetry will play a more prominent role in radionuclide therapy planning and quantitative follow-up of disease evolution.

Optimization of Thyroid Volume Determination by Stitched 3D-Ultrasound Data Sets in Patients with Structural Thyroid Disease

Ultrasound (US) is the most important imaging method for the assessment of structural disorders of the thyroid. A precise volume determination is relevant for therapy planning and outcome monitoring. However, the accuracy of 2D-US is limited, especially in cases of organ enlargements and deformations. Software-based "stitching" of separately acquired 3D-US data revealed precise volume determination in thyroid phantoms. The purpose of this study is to investigate the feasibility and accuracy of 3D-US stitching in patients with structural thyroid disease. A total of 31 patients from the clinical routine were involved, receiving conventional 2D-US (conUS), sensor-navigated 3D-US (3DsnUS), mechanically-swept 3D-US (3DmsUS), and I-124-PET/CT as reference standard. Regarding 3DsnUS and 3DmsUS, separately acquired 3D-US images (per thyroid lobe) were merged to one comprehensive data set. Subsequently, anatomical correctness of the stitching process was analysed via secondary image fusion with the I-124-PET images. Volumetric determinations were conducted by the ellipsoid model (EM) on conUS and CT, and manually drawn segmental contouring (MC) on 3DsnUS, 3DmsUS, CT, and I-124-PET/CT. Mean volume of the thyroid glands was 44.1 ± 25.8 mL (I-124-PET-MC = reference). Highly significant correlations (all p < 0.0001) were observed for conUS-EM (r = 0.892), 3DsnUS-MC (r = 0.988), 3DmsUS-MC (r = 0.978), CT-EM (0.956), and CT-MC (0.986), respectively. The mean volume differences (standard deviations, limits of agreement) in comparison with the reference were -10.50 mL (±11.56 mL, -33.62 to 12.24), -3.74 mL (±3.74 mL, -11.39 to 3.78), and 0.62 mL (±4.79 mL, -8.78 to 10.01) for conUS-EM, 3DsnUS-MC, and 3DmsUS-MC, respectively. Stitched 3D-US data sets of the thyroid enable accurate volumetric determination even in enlarged and deformed organs. The main limitation of high time expenditure may be overcome by artificial intelligence approaches.

Ultrasound imaging in thyroid nodule diagnosis, therapy, and follow-up: Current status and future trends

Ultrasound, the primary imaging modality in thyroid nodule management, suffers from drawbacks including: high inter- and intra-observer variability, limited field-of-view and limited functional imaging. Developments in ultrasound technologies are taking place to overcome these limitations, including three-dimensional-Doppler, -elastography, -nodule characteristics-extraction, and novel machine-learning algorithms. For thyroid ablative treatments and biopsies, perioperative use of three-dimensional ultrasound opens a new field of research. This review provides an overview of the current and future applications of ultrasound, and discusses the potential of new developments and trends that may improve the diagnosis, therapy, and follow-up of thyroid nodules.

Tracked 3D ultrasound and deep neural network-based thyroid segmentation reduce interobserver variability in thyroid volumetry

Thyroid volumetry is crucial in the diagnosis, treatment, and monitoring of thyroid diseases. However, conventional thyroid volumetry with 2D ultrasound is highly operator-dependent. This study compares 2D and tracked 3D ultrasound with an automatic thyroid segmentation based on a deep neural network regarding inter- and intraobserver variability, time, and accuracy. Volume reference was MRI. 28 healthy volunteers (24—50 a) were scanned with 2D and 3D ultrasound (and by MRI) by three physicians (MD 1, 2, 3) with different experience levels (6, 4, and 1 a). In the 2D scans, the thyroid lobe volumes were calculated with the ellipsoid formula. A convolutional deep neural network (CNN) automatically segmented the 3D thyroid lobes. 26, 6, and 6 random lobe scans were used for training, validation, and testing, respectively. On MRI (T1 VIBE sequence) the thyroid was manually segmented by an experienced MD. MRI thyroid volumes ranged from 2.8 to 16.7ml (mean 7.4, SD 3.05). The CNN was trained to obtain an average Dice score of 0.94. The interobserver variability comparing two MDs showed mean differences for 2D and 3D respectively of 0.58 to 0.52ml (MD1 vs. 2), −1.33 to −0.17ml (MD1 vs. 3) and −1.89 to −0.70ml (MD2 vs. 3). Paired samples t-tests showed significant differences for 2D (p = .140, p = .002 and p = .002) and none for 3D (p = .176, p = .722 and p = .057). Intraobsever variability was similar for 2D and 3D ultrasound. Comparison of ultrasound volumes and MRI volumes showed a significant difference for the 2D volumetry of all MDs (p = .002, p = .009, p <.001), and no significant difference for 3D ultrasound (p = .292, p = .686, p = 0.091). Acquisition time was significantly shorter for 3D ultrasound. Tracked 3D ultrasound combined with a CNN segmentation significantly reduces interobserver variability in thyroid volumetry and increases the accuracy of the measurements with shorter acquisition times.

Radioiodine therapy of thyroid autonomy

Radioiodine therapy (RIT) of thyroid functional autonomy (TFA) is rapidly evolving, though it has been recognized for decades as a very effective treatment of toxic nodular varieties. Indeed, TFA is a frequent cause of persistent subclinical hyperthyroidism, which should be regarded as a new metabolic syndrome, with well-established adverse cardio-vascular consequences. Sensitive TSH assays and multiparametric ultrasounds are not accurate enough to reliably diagnose TFA and identify its main variants, unifocal, multifocal (UFA/MFA) and disseminated autonomy (DISA). Modern diagnostic tools are extensively presented and rely upon Thyroid Scan imaging and quantification. A new relationship allows predicting at baseline, an excess of 123I uptake as compared to the TSH stimulation in compensated TFA. Suppressed TS are useful with either isotope, otherwise. Diagnosis of the DISA variant is presented as compared to Graves' disease. Dosimetry has some specificity in TFA work-up. Indeed, the spatial distribution of the dose is as important as the mean value itself and can be eventually controlled by adjusting the TSH level with the smart use of LT3 or antithyroid drug therapy (ATD). A review of the different ways to determine the target mass from anatomical to functional approaches is presented. Main clinical and dosimetric published results of RIT are summarized according to clinical goals. Endogenous TSH stimulation using an ATD preparation has promising results in reducing big autonomously functioning goiters. Finally, we report preliminary successful results of preventive RIT using short term LT3 suppression in compensated TFA, with low administered activities and low rate of hypothyroidism.

[Three-dimensional reconstruction of cervical CT vs ultrasound for estimating residual thyroid volume]

OBJECTIVE

To compare the accuracy of three-dimensional reconstruction of cervical CT and ultrasound for estimating residual thyroid volume.

METHODS

We performed a retrospective analysis of 17 patients with 21 residual thyroid glands undergoing thyroidectomy surgery between February, 2017 and March, 2018 in our department. We compared the residual thyroid volume in preoperative ultrasound with the intraoperative measurement and the volume measured using threedimensional CT reconstruction before surgery.

RESULTS

The maximum vertical and anterioposterior diameters of the residual thyroid measured by preoperative ultrasound differed significantly from the volume data measured intraoperatively (P < 0.05), but the difference in the maximum left-right diameters was not statistically significant (P>0.05). The maximum vertical, leftright, and anteroposterior diameters estimated by three-dimensional reconstruction of cervical CT was all similar with those measured intraoperatively (P>0.05).

CONCLUSIONS

Compared with ultrasound examination, three-dimensional reconstruction of neck CT is more accurate for estimating the residual thyroid volume and provides more reliable evidence for clinical calculation of postoperative I131 dose for thyroid cancer.

US not bright but right method of thyroid volume estimation even in large and substernal extended goitres. Comparison of US and three methods of CT thyroid evaluation – prospective study

BACKGROUND

Ultrasound is nowadays a method of choice for thyroid volume assessment. However, its disadvantage is some inaccuracy, which is said to be higher in huge, especially substernally extended goitres.

AIMS

The aim of the study was to compare the US and CT thyroid volumetric measurements: multi-observers (CT MO) and one-observer (CT OO) to CT planimetry results (CT Pl) in patients with large goitres.

MATERIALS & METHODS

The study material comprised 70 thyroid imaging examinations obtained from 35 patients with nontoxic goitres, scanned twice before and after radioiodine treatment. Mean thyroid volume was 88·97 ± 60·21 ml. Thirty-three thyroid scans revealed the extension below the jugular notch (mean of 2·46 cm). Thyroid volume in US, CT MO and CT OO was estimated using the ellipsoid formula. CT Pl was established a reference method.

RESULTS

The mean thyroid volume in CT Pl was 88·97 ml (median 80·73, range 11·81 to 315·97). US underestimates thyroid volume by 7·55 ml (7·7%) with a sufficient correlation (R(2) = 0·89) and precision (20·37). CT OO is the closest and CT MO the most distant from CT Pl, with US between them in thyroid volume estimation. The percentage US bias is constant through all range of thyroid volume. There is no difference for percentage bias between US and CT Pl for goitres with (8·67%), and without (6·70%) substernal part.

CONCLUSION

US examination is sufficient for epidemiological studies, radioiodine activity calculation and goitre size assessment in everyday medical practice. Neither initial size of the goitre nor its substernal extension affects US assessment precision.