Non-enhanced ultrasound is not a satisfactory modality for measuring necrotic ablated volume after radiofrequency ablation of benign thyroid nodules: a comparison with contrast-enhanced ultrasound

Effectiveness of microvascular flow imaging for radiofrequency ablation in recurrent thyroid cancer: comparison with power Doppler imaging

OBJECTIVES

To compare microvascular flow imaging (MVFI) and power Doppler ultrasonography imaging (PDUS) for detecting intratumoral vascularity in recurrent thyroid cancer both before and after radiofrequency ablation (RFA).

METHODS

This retrospective study included 80 patients (age, 57 ± 12 years; 54 women) with 110 recurrent tumors who underwent RFA between January 2021 and June 2023. A total of 151 PDUS and MVFI image sets were analyzed (85 pre-RFA, 66 post-RFA). Two readers assessed vascularity on the images using a four-point scale with a 2-week interval between PDUS and MVFI to estimate inter-reader agreement. Intra-reader agreement was determined by reinterpreting images in reverse order (MVFI-PDUS) after a 1-month gap. Additionally, diagnostic performance for identifying viable tumors after RFA was assessed in 44 lesions using thyroid-protocol CT as a reference standard.

RESULTS

MVFI demonstrated higher vascular grades than PDUS, both before (reader 1: 3.04 ± 1.15 vs. 1.93 ± 1.07, p < 0.001; reader 2: 3.20 ± 0.96 vs. 2.12 ± 1.07, p < 0.001) and after RFA (reader 1: 2.44 ± 1.28 vs. 1.67 ± 1.06, p < 0.001; reader 2: 2.62 ± 1.23 vs. 1.83 ± 0.99, p < 0.001). Inter-reader agreement was substantial (κ = 0.743) and intra-reader agreement was almost perfect (κ = 0.840). MVFI showed higher sensitivity (81.5%-88.9%) and accuracy (84.1%-86.4%) than PDUS (sensitivity: 51.9%, p < 0.01; accuracy: 63.6-70.5%, p < 0.04), without sacrificing specificity.

CONCLUSION

MVFI was superior to PDUS for assessing intratumoral vascularity and showed good inter- and intra-reader agreement, highlighting its clinical value for assessing pre-RFA vascularity and accurately identifying post-RFA viable tumors in recurrent thyroid cancer.

CLINICAL RELEVANCE STATEMENT

Microvascular flow imaging (MVFI) is superior to power-Doppler US for assessing intratumoral vascularity; therefore, MVFI can be a valuable tool for assessing vascularity before radiofrequency ablation (RFA) and for identifying viable tumors after RFA in patients with recurrent thyroid cancer.

KEY POINTS

The value of microvascular flow imaging (MVFI) for evaluating intratumoral vascularity is unexplored. MVFI demonstrated higher vascular grades than power Doppler US before and after ablation. Microvascular flow imaging showed higher sensitivity and accuracy than power Doppler US without sacrificing specificity.

Comparative outcomes of ultrasound-guided radiofrequency ablation vs. microwave ablation for patients with T1N0M0 papillary thyroid carcinoma: a retrospective cohort study

OBJECTIVE

To compare the clinical outcomes between radiofrequency ablation (RFA) and microwave ablation (MWA) for the treatment of T1N0M0 papillary thyroid carcinoma (PTC) in a large cohort.

MATERIALS AND METHODS

This retrospective study included 1111 patients with solitary T1N0M0 PTC treated with RFA (n = 894) or MWA (n = 215) by experienced physicians. A propensity score matching was used to compare disease progression, including lymph node metastases (LNM), recurrent tumors and persistent tumors, recurrence-free survival (RFS), volume reduction ratio (VRR), and complications between the RFA and MWA groups. The subgroup outcomes of T1a and T1b tumors treated with RFA and MWA were also compared.

RESULTS

During a mean follow-up period of 41.7 ± 12.6 months, the overall incidence rates of disease progression, LNM, recurrent tumors, and persistent tumors were 2.1%, 0.7%, 1.2%, and 0.2%, respectively. Eight patients (0.7%) experienced transient voice change and recovered within 3 months. After 1:1 matching, there were no significant differences in disease progression (3.3% vs. 3.7%, p = 0.793), LNM (1.4% vs. 1.9%, p = 1.000), recurrent tumor (1.4% vs. 1.9%, p = 1.000), persistent tumors (0.5% vs. 0%, p = 0.317), RFS rates (96.7% vs. 96.3%, p = 0.821), VRR (99.3 ± 3.0% vs. 98.3 ± 8.5%, p = 0.865), tumor disappearance rate (87.9% vs. 81.4%, p = 0.061) and complications (1.4% vs. 1.9%, p = 1.000) between the RFA and MWA groups. For T1a and T1b tumors, clinical outcomes were comparable between RFA and MWA.

CONCLUSIONS

RFA and MWA did not show significant differences in clinical outcomes for T1N0M0 PTC. The choice between RFA and MWA could depend on physician expertise and resources of local center resources. A qualified and experienced physician with extensive knowledge of the modalities is recommended when thermal ablation is performed.

KEY POINTS

Question With radiofrequency ablation (RFA) and microwave ablation (MWA) used worldwide for T1N0M0 papillary thyroid carcinoma (PTC), is one of them superior to the others? Findings There were no significant differences in disease progression, recurrence-free survival, volume reduction ratio, tumor disappearance, or complications between techniques for solitary T1N0M0 papillary thyroid carcinoma. Clinical relevance The choice between RFA and MWA could depend on physician expertise and resources of the local center resources. A qualified and experienced physician with extensive knowledge of the modalities is recommended when thermal ablation is performed.

Overview of Therapeutic Ultrasound Applications and Safety Considerations: 2024 Update

A 2012 review of therapeutic ultrasound was published to educate researchers and physicians on potential applications and concerns for unintended bioeffects (doi: 10.7863/jum.2012.31.4.623). This review serves as an update to the parent article, highlighting advances in therapeutic ultrasound over the past 12 years. In addition to general mechanisms for bioeffects produced by therapeutic ultrasound, current applications, and the pre-clinical and clinical stages are outlined. An overview is provided for image guidance methods to monitor and assess treatment progress. Finally, other topics relevant for the translation of therapeutic ultrasound are discussed, including computational modeling, tissue-mimicking phantoms, and quality assurance protocols.

Complications of ultrasound-guided thermal ablation of thyroid nodules and associated risk factors: an experience from 9667 cases

OBJECTIVES

To evaluate the safety of ultrasound-guided thermal ablation (UGTA) for thyroid nodules (TNs) by analysing complications and related risks.

MATERIALS AND METHODS

This retrospective, single-centre study reviewed patients who underwent UGTA (microwave or radiofrequency ablation) between January 2018 and March 2023. The incidence of complications was recorded and assessed during and immediately after ablation,1-3 h later, and at 1 month, 3 months, and 6 months. Univariate and multivariate analyses were performed to identify risk factors for hoarseness and haemorrhagic complications.

RESULTS

We reviewed 9667 cases in this study. Overall, 4494 (46.49%) cases underwent microwave ablation, while 5173 (53.51%) cases underwent radiofrequency ablation. The overall complication rate was 4.43%. The incidence of major complications was 1.94% (haemorrhage, 1.32%; hoarseness, 0.54%; and symptomatic aseptic necrosis, 0.08%). The incidence of minor complications was 2.45%. A large nodule volume, radiofrequency ablation, hyper-enhancing nodules, benign nodules, higher preoperative blood pressure, hyperthyroidism, and higher ablation power were independent risk factors for haemorrhage. Dorsal nodules and a higher ablation power were independent risk factors for hoarseness. All complications were resolved.

CONCLUSION

This study suggests that UGTA is a safe treatment for TNs. Several risk factors for haemorrhage and hoarseness should be considered before performing UGTA. Different ablation modalities should be considered for patients with different conditions.

CLINICAL RELEVANCE STATEMENT

Thermal ablation may be a safe treatment for eligible patients with TNs.

KEY POINTS

We analysed the complications and risk factors associated with UGTA in 9667 cases. The complication rate was 4.43%; 1.94% were major complications. Risk factors of haemorrhage and hoarseness should be considered. UGTA was a safe method for the treatment of TNs.

Efficacy and safety of percutaneous ultrasound-guided thermal ablation in the treatment of cervical metastatic lymph nodes from papillary thyroid carcinoma

OBJECTIVE

To evaluate the efficacy and safety of percutaneous ultrasound-guided thermal ablation in the treatment of cervical metastatic lymph nodes (LNs) from papillary thyroid carcinoma (PTC).

MATERIALS AND METHODS

A total of 77 patients with 79 LNs ablated by microwave ablation (MWA) or radiofrequency ablation (RFA) between September 2018 and October 2022 were enrolled in this study. After treatment, patients were followed up with measurement of diameters of LNs and serum thyroglobulin (s-Tg) at 1, 3, 6, and 12 months and annually thereafter. The paired t-test was used to compare the changes of s-Tg level, diameters of LNs before and after ablation.

RESULTS

There were no serious complications related to ablation while one case of incomplete ablation in MWA was found during follow-up. The mean longest and shortest diameter of the ablated LNs reduced from 11.6 ± 4.3 mm to 5.0 ± 4.1 mm (p < 0.001), and from 6.1 ± 1.9 mm to 3.0 ± 2.5 mm (p < 0.001) at the last follow-up visit. Besides, the final volume reduction rate (VRR) was 61.8 ± 56.4% (range, -67.0 -100%). The complete disappearance rate was 46.8%, but there were 4 (5.1%) LNs becoming bigger than before. The average s-Tg level was 9.2 ± 26.6 ng/mL, a data significantly decreased to 3.7 ± 7.0 ng/mL at the last follow-up, but no statistical difference was shown.

CONCLUSION

Thermal ablation is an effective and safe modality for the treatment of metastatic LNs from PTC.

Sonographic Evolution and Pathologic Findings of Papillary Thyroid Cancer After Radiofrequency Ablation: A Five-Year Retrospective Cohort Study

Background: The criteria for determining technical efficacy of thermal ablation for papillary thyroid carcinoma (PTC) are not clearly defined. We analyzed the involution process of the ablation zone with clear pathologic results on core-needle biopsy (CNB) to clarify the relationship between sonographic changes and pathologic findings. Methods: This retrospective cohort study included 382 patients with unifocal T1N0M0 PTC who underwent radiofrequency ablation (RFA) between May 2014 and August 2021. Patients with a single ablation zone biopsy (recommended at 3 or 6 months for T1a and 6 or 12 months for T1b) and regular neck ultrasound (US)/contrast-enhanced ultrasound imaging follow-up at 1, 3, 6, and 12 months and every 6-12 months thereafter after RFA were included. Patients also underwent yearly chest computed tomography. CNB was performed in the target lesion ablation zone's central, peripheral, and surrounding thyroid parenchyma to detect the presence of tumor cells. If the thyrotropin (TSH) was >2 mU/L, levothyroxine was prescribed with the intention of keeping the TSH 0.5-2 mU/L. Technical efficacy was defined as tumor disappearance by imaging follow-up together with the pathologically confirmed absence of tumor cells in the ablation zone. Results: During the mean follow-up period of 67.8 ± 18.2 months (22-110 months), the overall incidence of persistent disease and the technical efficacy rate were 3.9% (15/382; 2.9% of T1a, and 12.2% of T1b) and 96.1%, respectively. Tumor size (p = 0.03) and subcapsular location (p = 0.04) were risk factors associated with persistent disease. The technical success rate was 100%. Of the 367 ablation zones with benign CNB results, 336 (91.6%) showed tumor disappearance on US and no re-emergence of imaging-visible tumors during follow-up. Male sex (p = 0.006), age <40 years (p = 0.003), T1a tumor (p < 0.01), and energy per milliliter (p < 0.03) were significantly associated with tumor disappearance. Conclusions: US-guided RFA is an effective treatment for small low-risk PTC. Tumor disappearance on US after RFA may suggest an excellent prognosis and confirm complete ablation of the macroscopic tumor, but this sonographic finding is generally late and requires histological confirmation.

Analysis and prediction of regrowth in benign thyroid nodules undergoing radiofrequency ablation: a retrospective study with a 5-year follow-up

OBJECTIVES

To evaluate the 5-year follow-up results of radiofrequency ablation (RFA) for benign thyroid nodules (BTNs), and construct pre- and postablation nomogram models to predict regrowth in BTNs undergoing RFA.

METHODS

According to the occurrence of regrowth, BTNs were divided into two subgroups, the regrowth group and the nonregrowth group, and the variables were compared between these two subgroups. Then, univariate and multivariate Cox regression analyzes were utilized to filter the independent prognostic factors of regrowth, which then were introduced into the pre- and postablation prognostic nomograms, respectively. The discrimination powers and prediction performances of the nomograms were appraised by receiver operating characteristic (ROC) curves and calibration charts.

RESULTS

The 5-year mean volume reduction rate was 88.80%, with a complication rate of 0.35% (7/200). Within 5 years of follow-up, the regrowth rate was 19% (38/200). Pre- and postablation prognostic nomograms were established to predict the probability of nonregrowth at 1, 3, and 5 years after RFA. The preablation nomogram included initial volume, perinodular vascularity, and high enhancement ring. The postablation nomogram incorporated total volume, perinodular vascularity, and energy applied per volume. The area under the ROC curves and concordance index values of these models were all above 0.7, indicating that the prognostic nomograms achieved satisfactory discrimination powers and prediction performances.

CONCLUSION

RFA for BTNs has long-term efficacy and safety under the influence of key techniques. The pre- and postablation nomograms constructed in the present study might facilitate clinical decision-making before RFA and for the follow-up management after RFA.

KEY POINTS

• Perinodular vascularity, rather than intranodular vascularity was an independent predictor of regrowth, both before and after the RFA procedure. • A high enhancement ring on preablation contrast-enhanced ultrasound was an independent predictor of regrowth. • Pre- and postablation nomograms might facilitate clinical decision-making before RFA and follow-up management after RFA.

Value of CEUS combined with feeding artery ablation in the microwave ablation of large solid benign thyroid nodules

OBJECTIVES

To investigate the value of contrast-enhanced ultrasound (CEUS) combined with feeding artery ablation in the microwave ablation (MWA) of large solid benign thyroid nodules (LSBTNs) with a diameter ≥ 4 cm.

METHODS

We retrospectively analyzed 122 patients with LSBTN ≥ 4 cm in diameter treated with MWA. During evaluations before and after MWA, 53 patients who underwent conventional ultrasound examination were classified as the routine group, and 69 patients who underwent CEUS combined with feeding artery ablation were classified as the union group. The differences in ablation energy required per milliliter (AERPM), complication rate, regrowth rate, and volume reduction rate (VRR) were compared between the two groups.

RESULTS

The AERPM of the union group was significantly less than that of the routine group (956.3 ± 38.5 J/mL vs. 1025.9 ± 121.5 J/mL, p < 0.001). The complication rate of the routine group was significantly higher than that of the union group (13.2% vs. 2.9%, p = 0.031). The regrowth rate of the routine group (22.6%, 12/53) was significantly higher than that of the union group (7.2%, 5/69) (p = 0.015). At the 1st, 3rd, 6th, 12th, 18th, and 24th month after ablation, the mean VRRs of the routine group were significantly less than those of the union group, with p values of < 0.001, < 0.001, 0.002, 0.007, 0.013, and < 0.001, respectively.

CONCLUSIONS

The application of CEUS combined with feeding artery ablation in the MWA of LSBTNs is helpful to reduce the regrowth rate, improve the ablation efficiency, and reduce bleeding.

KEY POINTS

• CEUS combined with feeding artery ablation in MWA of LSBTNs is helpful to reduce regrowth rate. • CEUS combined with feeding artery ablation can help improve ablation efficiency than conventional ultrasound in LSBTNs. • CEUS combined with feeding artery ablation helps reduce the incidence of bleeding during MWA.

Intraobserver and Interobserver Consistency Evaluation of Carotid Plaque Volume Measured by Different 3-Dimensional Ultrasound Methods

ABSTRACT

This study aims to evaluate the accuracy of the semiautomatic planimetric measurement (SAPM) method and the necessity of manually adjusted boundary measurement in 3-dimensional ultrasound measurement of plaque volume. A total of 50 patients with 82 plaques in the common carotid arteries between December 2020 and March 2021 were included in this study. Two observers measured the 3-dimensional volume of plaque for each patient in 3 different methods (contour tracing method [CTM], SAPM method without manually adjusted boundary [SAPM1], and SAPM method with manually adjusted boundary [SAPM2]). The difference in measurement time between the 3 methods was evaluated by Kruskal-Wallis H test. Intraclass correlation coefficient and 95% confidence interval were used to evaluate the intraobserver and interobserver reliability of the 3 measurement modes. The Bland-Altman analysis was used to assess the agreement, which was expressed as the mean difference with the 95% limits of agreement (LOA). The difference in measurement time between the 3 methods was statistically significant ( P < 0.001). Both observers' intraobserver and interobserver reliability showed well in the 3 methods (all of the intraclass correlation coefficients were >0.75). The mean differences of the plaque volume measurement were 38.17, 26.42, and 11.75 mm 3 , respectively. The agreement between CTM and SAPM2 was the best, and LOA was -57.00 to 80.51. The agreement between SAPM1 and SAPM2 and the agreement between SAPM1 and CTM were similar, and the LOAs were -126.10 to 202.40 and -158.00 to 210.80, respectively. The SAPM method may be recommended to measure plaque volume in clinical practice.

Development and validation of a nomogram model for predicting residue of partially cystic thyroid nodules after ultrasound-guided ethanol and thermal ablation

Objectives

To develop and validate a nomogram model for predicting residue of partially cystic thyroid nodules (PCTNs) after ethanol and thermal ablation.

Materials and Methods

From July 2015 to August 2022, a total of 97 patients (age 40.78 ± 12.61 years) with 107 treated benign PCTNs receiving ethanol and thermal ablation were enrolled. Pre-ablative laboratory test results and the ultrasound (US) and contrast-enhanced ultrasound (CEUS) features of lesions were collected. They were categorized into non-residue group and residue group according to the CEUS examination assessment after ablation. Univariate and multivariate logistic regression analysis were adopted to build a nomogram. The nomogram was validated by internal stratified fivefold cross-validation. The calibration, discrimination and clinical utility of the nomogram were investigated to assess the performance of the model.

Results

Residue was reported in 30 out of 107nodules (28.0%). Multivariate logistic regression analysis revealed initial volume (OR=1.12, 95%CI 1.06-1.19) and presence of septum (OR=3.19, 95%CI 1.09-9.36) were predictors of residue of PCTNs. The nomogram developed by the above factors showed good calibration and discrimination. The area under the curve (AUC), sensitivity and specificity of this model were 0.832, 86.7% and 68.8%, respectively. When applied to internal validation, the model revealed good generalizability with stratified fivefold cross-validation in the cohort (mean AUC = 0.821).

Conclusions

The nomogram model has good performance for predicting the residue of PCTNs undergoing ethanol and thermal ablation. This could play a role in the decision of treatment and follow-up in clinical practice.

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.

Contrast-enhanced ultrasound improves the potency of fine-needle aspiration in thyroid nodules with high inadequate risk

Background

This study aims to determine the clinical value of contrast enhanced ultrasound (CEUS) for fine-needle aspiration (FNA) of high inadequate risky thyroid nodules.

Methods

During April 2018 and April 2021, consecutive 3748 thyroid nodules underwent FNA were retrospectively analyzed. CEUS guided FNA (CEUS-FNA) was applied in 115 nodules with high inadequate risk in Lingnan Campus. Ten nodules underwent CEUS-FNA presented non-enhancing, and would be further analyzed independently. Other 105 partial or total enhancing nodules were included as CEUS-FNA group, and 210 nodules with high inadequate risk in Tianhe Campus were match as the US-FNA control group. FNA specimens were collected for liquid-based preparation. Cytological results were classified following the Bethesda System for Reporting Thyroid Cytopathology.

Results

The overall FNA specimen inadequate rate in our center was 6.6%. All of the ten non-enhancing nodules under CEUS have an inadequate result in cytopathological analyzes. The subsequent postoperative pathology and follow-up ultrasonography showed the non-enhancing nodules were benign or stable without further malignant features. Total specimen inadequate rate of high inadequate risk thyroid nodules in CEUS-FNA group was significantly lower than US-FNA group (6.7% vs. 16.7%, P = 0.014). Further stratified analyzed shown that FNA under US guidance, the inadequate rates in cystic, predominantly cystic, predominantly solid and solid sub-groups were 28.1%, 17.1%, 10.0% and 9.2% (P = 0.019). In contrast, the inadequate rates in cystic, predominantly cystic, predominantly solid and solid sub-groups were 7.4%, 6.7%, 5.6% and 6.7% (P = 0.996) in CEUS-FNA group.

Conclusions

CEUS can improve the specimen adequacy of FNA in high inadequate risk thyroid nodules by avoiding unnecessary FNAs of the non-enhancing nodules, and accurately locating the viable tissue and precise guidance in real-time. CEUS is a recommend modality for FNA guidance of high inadequate risk thyroid nodules.

A Review of Imaging Methods to Assess Ultrasound-Mediated Ablation

Ultrasound ablation techniques are minimally invasive alternatives to surgical resection and have rapidly increased in use. The response of tissue to HIFU ablation differs based on the relative contributions of thermal and mechanical effects, which can be varied to achieve optimal ablation parameters for a given tissue type and location. In tumor ablation, similar to surgical resection, it is desirable to include a safety margin of ablated tissue around the entirety of the tumor. A factor in optimizing ablative techniques is minimizing the recurrence rate, which can be due to incomplete ablation of the target tissue. Further, combining focal ablation with immunotherapy is likely to be key for effective treatment of metastatic cancer, and therefore characterizing the impact of ablation on the tumor microenvironment will be important. Thus, visualization and quantification of the extent of ablation is an integral component of ablative procedures. The aim of this review article is to describe the radiological findings after ultrasound ablation across multiple imaging modalities. This review presents readers with a general overview of the current and emerging imaging methods to assess the efficacy of ultrasound ablative treatments.

Effect of Hashimoto's thyroiditis on the extent of the ablation zone in early stages of ultrasound-guided radiofrequency ablation for papillary thyroid microcarcinoma: a large cohort study of 772 patients

PURPOSE

To evaluate the effect of Hashimoto's thyroiditis (HT) on the extent of ablation zone in ultrasound (US)-guided radiofrequency ablation (RFA) for early stages of papillary thyroid microcarcinoma (PTMC).

METHOD

We selected 772 patients with 797 PTMCs who underwent with RFA from August 2017 to August 2020. They were subdivided into two groups as follows: (i) 216 patients (224 PTMCs) with HT in the 'HT + PTMC' group and (ii) 556 patients (573 PTMCs) with healthy thyroid in the 'PTMC' group. We assessed the extent (maximum diameter and volume) of the ablation zone by contrast-enhanced ultrasound (CEUS) immediately, one day, and 1 week following RFA.

RESULTS

The ablation zone of the 'HT + PTMC' group was smaller than that of the 'PTMC' group at 1 week of RFA (maximum diameter: 14.6 ± 3.1 mm vs. 15.2 ± 3.2 mm and volume: 0.932 ± 0.498 mL vs. 1.028 ± 0.540 mL, respectively, p < .05). However, there were no differences before, immediately, and one day post-RFA (p > .05). Life-threatening complications did not develop in any of the patients.

CONCLUSION

RFA-treated PTMCs were smaller in size in patients with HT than in those with a healthy thyroid at 1 week of RFA. However, the exact mechanism underlying this phenomenon and its clinical significance warrant further investigation.

A New Perspective for Predicting the Therapeutic Success of RFA in Solid BTNs: Quantitative Initial RFA Ratio by Contrast-Enhanced Ultrasound

OBJECTIVE

The short-term therapeutic success of radiofrequency ablation (RFA) in solid benign thyroid nodules is of great concern. The aim of this study was to investigate a new method, initial radiofrequency ablative ratio (IRAR) using contrast-enhanced ultrasound (CEUS), for predicting therapeutic success of RFA in solid benign thyroid nodules (BTNs) immediately and effectively after RFA.

METHODS

A total of 813 nodules in 776 patients with benign thyroid nodules were treated with RFA from January 2014 to August 2018, among which 120 patients (M:F=41:79) with 120 solid BTNs (small: ≤10ml, n=57; medium: 10-30ml, n=42; large: >30ml, n=21) were enrolled in our study according to the inclusion criteria. The IRAR was defined as the ablative volume ratio immediately after RFA displayed by CEUS. The therapeutic success was evaluated at the 6-month follow-up. The relationship between the IRAR and volume reduction ratio (VRR) at 6-month was analyzed. The marginal regrowth of solid BTNs was also examined by CEUS at the 6 and 12 months of follow-up.

RESULTS

In medium and large nodules, the IRAR was significantly and positively correlated with VRR (r= 0.69, P < 0.001) at 6 months after RFA. There was a tendency to achieve therapeutic success (50% VRR: 55/63, 87.3%) when the IRAR exceeded 75%, and marginal regrowth was also relatively slow within 12 months after a single session treatment. No significant correlation between IRAR and VRR of small nodules was found. In conclusion, IRAR is significantly and positively correlated with VRR, which may indicate therapeutic success when it exceeds 75%.

CONCLUSIONS

CEUS can be used to accurately quantify the IRAR, which is positively correlated with the VRR. Moreover, the IRAR may be used as a parameter to predict the short-term therapeutic success of RFA in solid BTNs.

Contrast-enhanced ultrasound is a reliable and reproducible assessment of necrotic ablated volume after radiofrequency ablation for benign thyroid nodules: a retrospective study

PURPOSE

To investigate the intra- and inter-observer reliability and agreement of contrast-enhanced ultrasound (CEUS) in measuring ablated volume (Va) after radiofrequency ablation (RFA) for benign thyroid nodules.

MATERIALS

This retrospective study evaluated 65 patients with 74 benign thyroid nodules who underwent RFA. Patients were followed up at 1, 3, 6, and 12 months and every 12 months thereafter. Two independent observers measured the Va using CEUS during the same follow-up visit. The intra- and inter-observer reliability was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval. The Bland-Altman analysis was used to evaluate the inter-observer agreement, which was expressed as a mean difference with 95% limit of agreement (LOA).

RESULTS

No significant difference was found in Va measurements by the two observers with a mean follow-up time of 41.17 ± 16.80 months (all p > 0.05). The intra- and inter-observer reliability were both excellent (ICC >0.90) at each follow-up period. The 95% LOA became wider over the follow-up period. The smallest 95% LOA was found at 1 month with a LOA from 0.8117 to 1.122, and the largest 95% LOA was from 0.5694 to 1.343 at 36 months.

CONCLUSIONS

CEUS could provide a reliable and reproducible assessment of Va after RFA for benign thyroid nodules. In clinical post-ablation follow-up, the irregular morphology of ablated area and the variation by different observers could not affect the assessment of Va by CEUS.

Correlation and agreement between superb micro-vascular imaging and contrast-enhanced ultrasound for assessing radiofrequency ablation treatment of thyroid nodules: a preliminary study

Background

To evaluate the correlation and agreement between superb micro-vascular imaging (SMI) mode and the contrast-enhanced ultrasound (CEUS) mode for the ablative completeness and the volumes of ablation lesions to determine the clinical application value of SMI in follow-up after radiofrequency ablation.

Methods

From April 2020 to June 2020, two radiologists used SMI and CEUS mode to measure the volume of the ablation lesion. We use intra-class correlation coefficient (ICC), scatter plots and Bland–Altman plots to evaluate the correlation and agreement of the two techniques. In addition, intra- and inter-observer reliability in volume measurement of ablation lesions with SMI mode was assessed.

Results

SMI mode and CEUS mode have good agreement in the evaluation of ablative completeness. The ICC was 0.876 and 0.928 of reader A and reader B between SMI mode and CEUS mode in terms of ablation lesions volume measurement. There was a strong correlation between the two modes in both reader A and reader B (r_A = 0.808; r_B = 0.882). The ICC was 0.836 for the inter-observer reliability of SMI technique. The scatter plot showed a good linear relation (r = 0.715). In the Bland–Altman plot, 4.35% (1/23) of the points was outside the 95% limits of agreement. The ICC was 0.965 for the intra-observer reliability of SMI technique, the scatter plot also showed a strong linear correlation (r = 0.965). In the Bland–Altman plot, 8.70% (2/23) of the points was outside the 95% limits of agreement.

Conclusions

SMI and CEUS have good agreement and correlation in the ablation volume measurement. SMI technology is expected to be applied as an alternative to CEUS in the clinical follow-up of ablation lesions.

Image-guided thermal ablation in autonomously functioning thyroid nodules. A retrospective multicenter three-year follow-up study from the Italian Minimally Invasive Treatment of the Thyroid (MITT) Group

OBJECTIVES

To report the results of a multicenter retrospective evaluation of the clinical outcomes of thermal ablation (TA) in a large series of autonomously functioning thyroid nodules (AFTN) with a follow-up protracted up to 3 years.

METHODS

Patients treated with single TA for an AFTN in Italy were included. Changes in nodule volume, TSH values, and ongoing anti-thyroid therapy were assessed at the 2-, 6-, 12-, 24-, and 36-month follow-up controls. Complications and need of any additional therapy after TA were also registered.

RESULTS

A total of 361 patients (244 females, 117 males, median age 58 years, IQR 46-70 years) were included. Nodule volume was significantly reduced at all time points (p < 0.001) (median volume reduction 58% at 6-month and 60% at 12-month). Serum TSH values increased significantly at all time points. After TA, anti-thyroid therapy was withdrawn in 32.5% of patients at 2 months, in 38.9% at 6 months, and in 41.3% at 12 months. A significant difference in the rate of patients who withdrawn medical therapy at 12 months was registered between small (< 10 mL) (74%), medium (49%), or large (> 30 mL) nodules (19%). A single major complication occurred (0.25%). Additional treatments were needed in 34/361 (9.4%) of cases including 4 (1.1%) surgical treatment.

CONCLUSIONS

Image-guided thermal ablation offers a further safe and effective therapeutic option in patients with AFTN. Clinical outcomes are significantly more favorable in small than in large size AFTN.

KEY POINTS

• Thermal ablations (TA) can be safely and effectively used in patients with autonomously functioning thyroid nodules (AFTN). • TA results in a clinically significant nodule volume reduction that is paralleled by TSH level normalization and anti-thyroid drug therapy discontinuation (after TA anti-thyroid therapy was withdrawn in 41.3% at 12 months). • Clinical outcomes after TA are more favorable in small nodules, and when a large amount of thyroid nodule tissue is ablated.

Performance of Contrast-Enhanced Ultrasound in Thyroid Nodules: Review of Current State and Future Perspectives

Ultrasound has been established as a baseline imaging technique for thyroid nodules. The main advantage of adding CEUS is the ability to assess the sequence and intensity of vascular perfusion and hemodynamics in the thyroid nodule, thus providing real-time characterization of nodule features, considered a valuable new approach in the determination of benign vs. malignant nodules. Original studies, reviews and six meta-analyses were included in this article. A total of 624 studies were retrieved, and 107 were included in the study. As recognized for thyroid nodule malignancy risk stratification by US, for acceptable accuracy in malignancy a combination of several CEUS parameters should be applied: hypo-enhancement, heterogeneous, peripheral irregular enhancement in combination with internal enhancement patterns, and slow wash-in and wash-out curve lower than in normal thyroid tissue. In contrast, homogeneous, intense enhancement with smooth rim enhancement and "fast-in and slow-out" are indicative of the benignity of the thyroid nodule. Even though overlapping features require standardization, with further research, CEUS may achieve reliable performance in detecting or excluding thyroid cancer. It can also play an operative role in guiding ablation procedures of benign and malignant thyroid nodules and metastatic lymph nodes, and providing accurate follow-up imaging to assess treatment efficacy.

Efficacy and safety of ultrasound-guided radiofrequency ablation for low-risk papillary thyroid microcarcinoma in patients aged 55 years or older: a retrospective study

PURPOSE

To evaluate the efficacy and safety of radiofrequency ablation for low-risk papillary thyroid microcarcinoma (PTMC) in patients aged 55 years or older.

METHODS

This retrospective study included 95 patients aged 55 years or older who underwent radiofrequency ablation (RFA) for PTMCs between June 2014 and January 2019. Incidence and duration of postoperative complications were recorded and evaluated. Tumor volume and volume reduction rate (VRR) changes were calculated. Patients were also closely monitored for tumor recurrence, regrowth, and lymph node metastasis.

RESULTS

All nodules were completely ablated. The mean initial volume of the ablated thyroid nodules was 107.27 ± 99.10 mm³, and the volume decreased significantly during the follow-up time. The VRR in 1st, 3rd, 6th, 12th, 18th, 24th and 36th month were -591.64 ± 623.65%, -170.89 ± 319.51%, 9.74 ± 128.43%, 77.99 ± 45.26%, 99.35 ± 3.61%, 99.45 ± 3.05% and 99.78 ± 1.54%, respectively. No patient had any life-threatening complications. One patient had lymph node metastasis and one had a recurrence; both underwent a second radiofrequency ablation treatment and achieved satisfactory treatment results.

CONCLUSIONS

Our study suggests that radiofrequency ablation is a safe and effective option for low-risk PTMC in patients aged 55 years or older who are at a high risk of general anesthesia and postoperative complications or those who refuse surgery.

Current Status and Challenges of US-Guided Radiofrequency Ablation of Thyroid Nodules in the Long Term: A Systematic Review

BACKGROUND

US-guided minimally-invasive techniques, such as radiofrequency ablation (RFA) have emerged as an alternative treatment for benign and malignant thyroid nodules. This systematic review aims to provide an overview on the long-term outcomes of US-guided RFA in patients with benign and malignant thyroid nodules.

METHODS

We systematically searched PubMed/MEDLINE, EMBASE, and Scopus to identify articles reporting the outcomes of thyroid RFA after a follow-up of at least 3 years.

RESULTS

A total of 20 studies met the inclusion criteria and were included in the review. In patients with benign thyroid nodules, RFA significantly reduced nodule volume and this was generally maintained for the following 5 years. However, a small but not negligible proportion of nodules regrew and some of them required further treatments over time. In patients with malignant nodules, RFA has been used not only to treat differentiated thyroid cancer (DTC) neck recurrences, but also to treat papillary thyroid microcarcinoma (PTMC). In most patients with PTMC, RFA led to complete disappearance of the tumor. When it was compared to surgery, RFA was not inferior in terms of oncologic efficacy but it had a lower complication rate. However, RFA did not allow for final pathology, disease staging and accurate risk stratification.

CONCLUSIONS

US-guided RFA significantly reduces benign thyroid nodules and destroys most PTMC, and this is generally maintained for at least 5 years after the initial treatment. Further studies addressing the risk of regrowths in patients with benign thyroid nodules, as well as the risk of recurrence in patients with PTMC are needed.