Matrix 3D ultrasound-assisted thyroid nodule volume estimation and radiofrequency ablation: a phantom study.

BACKGROUND: Two-dimensional (2D) ultrasound is well established for thyroid nodule assessment and treatment guidance. However, it is hampered by a limited field of view and observer variability that may lead to inaccurate nodule classification and treatment. To cope with these limitations, we investigated the use of real-time three-dimensional (3D) ultrasound to improve the accuracy of volume estimation and needle placement during radiofrequency ablation. We assess a new 3D matrix transducer for nodule volume estimation and image-guided radiofrequency ablation. METHODS: Thirty thyroid nodule phantoms with thermochromic dye underwent volume estimation and ablation guided by a 2D linear and 3D mechanically-swept array and a 3D matrix transducer. RESULTS: The 3D matrix nodule volume estimations had a lower median difference with the ground truth (0.4 mL) compared to the standard 2D approach (2.2 mL, p < 0.001) and mechanically swept 3D transducer (2.0 mL, p = 0.016). The 3D matrix-guided ablation resulted in a similar nodule ablation coverage when compared to 2D-guidance (76.7% versus 80.8%, p = 0.542). The 3D mechanically swept transducer performed worse (60.1%, p = 0.015). However, 3D matrix and 2D guidance ablations lead to a larger ablated volume outside the nodule than 3D mechanically swept (5.1 mL, 4.2 mL (p = 0.274), 0.5 mL (p < 0.001), respectively). The 3D matrix and mechanically swept approaches were faster with 80 and 72.5 s/mL ablated than 2D with 105.5 s/mL ablated. CONCLUSIONS: The 3D matrix transducer estimates volumes more accurately and can facilitate accurate needle placement while reducing procedure time.

Operator Radiation Exposure in Cone-Beam Computed Tomography Guidance.

OBJECTIVES: Quantitative analysis of operator dose in cone-beam computed tomography guidance (CBCT-guidance) and the effect of protective shielding. METHODS: Using a Rando phantom, a model was set-up to measure radiation dose for the operator hand, thyroid and gonad region. The effect of sterile radiation-absorbing drapes and ceiling/couch shielding was measured. Using this model we calculated the dose, based on relevant clinical parameters. The procedures were divided in thoracic and abdominal group. Furthermore, dosimetry measurements were performed during clinical cases to correlate with our calculations. RESULTS: One hundred thirteen procedures were included between December 2007 and January 2010 (47 thoracic, 66 abdominal). The mean hand doses were 34.2 and 54.6 µSv (thoracic/abdominal respectively). The thyroid and gonad regions doses were 83.2 and 34.3 µSv in the thoracic, and 66.2 and 47.2 µSv in the abdominal group. Combined shielding reduced the dose by 98.2-98.9% (p<0.05). The radiation dose in clinical setting in the thoracic group (n=17) was 32.9 µSv (hand), 11.4 µSv (thyroid) and 16.0 µSv (gonad region). In the abdominal group (n=20) the doses were 43.4, 21.7 and 18.8 µSv respectively. CONCLUSION: The operator dose in CBCT-guidance without shielding is quite low, compared to the literature. Based on our data, between 375-830 cases can be performed staying below the yearly limit of 20 mSv effective whole-body dose.

Cone beam CT guidance provides superior accuracy for complex needle paths compared with CT guidance.

OBJECTIVE: To determine the accuracy of cone beam CT (CBCT) guidance and CT guidance in reaching small targets in relation to needle path complexity in a phantom. METHODS: CBCT guidance combines three-dimensional CBCT imaging with fluoroscopy overlay and needle planning software to provide real-time needle guidance. The accuracy of needle positioning, quantified as deviation from a target, was assessed for inplane, angulated and double angulated needle paths. Four interventional radiologists reached four targets along the three paths using CBCT and CT guidance. Accuracies were compared between CBCT and CT for each needle path and between the three approaches within both modalities. The effect of user experience in CBCT guidance was also assessed. RESULTS: Accuracies for CBCT were significantly better than CT for the double angulated needle path (2.2 vs 6.7 mm, p<0.001) for all radiologists. CBCT guidance showed no significant differences between the three approaches. For CT, deviations increased with increasing needle path complexity from 3.3 mm for the inplane placements to 4.4 mm (p=0.007) and 6.7 mm (p<0.001) for the angulated and double angulated CT-guided needle placements, respectively. For double angulated needle paths, experienced CBCT users showed consistently higher accuracies than trained users [1.8 mm (range 1.2-2.2) vs 3.3 mm (range 2.1-7.2) deviation from target, respectively; p=0.003]. CONCLUSION: In terms of accuracy, CBCT is the preferred modality, irrespective of the level of user experience, for more difficult guidance procedures requiring double angulated needle paths as in oncological interventions. ADVANCES IN KNOWLEDGE: Accuracy of CBCT guidance has not been discussed before. CBCT guidance allows accurate needle placement irrespective of needle path complexity. For angulated and double-angulated needle paths, CBCT is more accurate than CT guidance.

Real-Time 3D fluoroscopy guidance during needle interventions: technique, accuracy, and feasibility.

OBJECTIVE: Real-time 3D fluoroscopy guidance using cone beam CT with dedicated needle path planning software is a promising new interventional technique. The objective of this study was to evaluate the procedure and to assess the accuracy and feasibility of this technique for use in needle interventions. SUBJECTS AND METHODS: All procedures were performed using a flat panel-based fluoroscopy system capable of acquiring cone beam CT images and dedicated needle path-planning software. This new technology allows the use of fluoroscopy coregistered with a 3D data set reconstructed from the acquired attenuation information. The needle trajectory is planned in the 3D data set using the needle path-planning software. The calculated trajectory is then projected on to the real-time fluoroscopy image. Fluoroscopy time, accuracy, technical success of the procedures, median procedure time, and complications were recorded in 145 interventions. RESULTS: One hundred forty-five needle interventions were performed in 139 patients using real-time 3D fluoroscopy guidance. Procedures were divided into five groups according to anatomic region: upper thoracic (n = 19; 13.1%), lower thoracic (n = 18; 12.4%), upper abdominal (n = 65; 44.8%), lower abdominal (n = 13; 9.0%), and musculoskeletal (n = 30; 20.7%). Thirty needle interventions were therapeutic, and 115 were diagnostic biopsies. All interventions were within the predefined 5-mm safety margin and achieved 100% technical success. A histopathologic diagnosis could be made in 91.4% of the diagnostic biopsies. The median interventional procedure time was 28.5 minutes, and the median fluoroscopy time was 2 minutes 58 seconds. There were minor complications in six patients (4.3%) and one major complication (0.7%). CONCLUSION: Real-time 3D fluoroscopy guidance is a new, promising, and feasible technique providing high accuracy in needle interventions.

Percutaneous embolization on hereditary hemorrhagic telangiectasia patients with severe epistaxis.

OBJECTIVES: To evaluate the results of embolization in patients with hereditary hemorrhagic telangiectasia (HHT) because of severe epistaxis. METHODS: All HHT patients who underwent an embolization (between 1992 and 2006) were asked to participate in this retrospective study. Twelve patients who had in total 19 embolization procedures were interviewed. A questionnaire was used assessing the frequency, severity, duration of epistaxis and their Impact on Lifestyle (IoL). Haemoglobin values were collected from the patients' records. Embolization of the pathologically enhancing lesions was performed using PVA particles. RESULTS: The direct effect of the embolization is very good in 95% of patients. The Impact factor (daily frequency x severity) of epistaxis improved in the first month (p = 0.000) and one year after embolization (p = 0.009). Eleven embolizations (61%) were still associated with significant improvement. There was a reduction in the duration of epistaxis by 16 minutes per day one month after embolization (p = 0.005). However, this reduction was not found one year after embolization. Mean haemoglobin rose significantly after 1 year by an average of 0.8 mmol/l (p = 0.045). Impact on Lifestyle improved in 68% of the procedures and was unchanged in 32%. CONCLUSION: Embolizations remain a therapeutic option in experienced hands. The indication should be made carefully, because of possible (major) complications.