A moving liver phantom in an anthropomorphic thorax for SPECT MP imaging

Cranio-caudal respiratory motion and liver activity cause a variety of complex myocardial perfusion (MP) artifacts, especially in the inferior myocardial wall, that may also mask cardiac defects. To assess and characterise such artifacts, an anthropomorphic thorax with moving thoracic phantoms can be utilised in SPECT MP imaging. In this study, a liver phantom was developed and anatomically added into an anthropomorphic phantom that also encloses an ECG beating cardiac phantom and breathing lungs’ phantom. A cranio-caudal respiratory motion was also developed for the liver phantom and it was synchronised with the corresponding ones of the other thoracic phantoms. This continuous motion was further divided into isochronous dynamic respiratory phases, from end-exhalation to end-inspiration, to perform SPECT acquisitions in different respiratory phases. The new motions’ parameters and settings were measured by mechanical means and also validated in a clinical environment by acquiring CT images and by using two imaging software packages. To demonstrate the new imaging capabilities of the phantom assembly, SPECT/CT MP acquisitions were performed and compared to previous phantom and patients studies. All thoracic phantoms can precisely perform physiological motions within the anthropomorphic thorax. The new capabilities of the phantom assembly allow to perform SPECT/CT MP acquisitions for different cardiac-liver activity ratios and cardiac-liver proximities in supine and, for first time, in prone position. Thus, MP artifacts can be characterised and motion correction can be performed due to these new capabilities. The impact of artifacts and motion correction on defect detection can be also investigated.

Stereotactic navigation versus ultrasound guidance in placing IRE applicators in a liver phantom

The aim of this study was to compare the accuracy of stereotactic CT-guided navigation and ultrasound guided navigation for placing electrodes in Irreversible electroporation in a liver phantom. A liver phantom with multiple tumours was used and interventionists placed four IRE electrodes around each tumour guided either by stereotactic CT-guided navigation or ultrasound. The goal was to place them in a perfect 20 × 20 mm square with parallel electrodes. After each treatment, a CT-scan was performed. The accuracy in pairwise electrode distance, pairwise parallelism and time per tumour was analysed. Eight interventionists placed four electrodes around 55 tumours, 25 with ultrasound and 30 with stereotactic CT-guided navigation. 330 electrode pairs were analysed, 150 with ultrasound and 180 with stereotactic CT-navigation. The absolute median deviation from the optimal distance was 1.3 mm (range 0.0 to 11.3 mm) in the stereotactic CT-navigation group versus 7.1 mm (range 0.3 to 18.1 mm) in the Ultrasound group (p < 0.001). The mean angle between electrodes in each pair was 2.7 degrees (95% CI 2.4 to 3.1 degrees) in the stereotactic CT-navigation group and 5.5 degrees (95% CI 5.0 to 6.1 degrees) in the Ultrasound group (p < 0.001). The mean time for placing the electrodes was 15:11 min (95% CI 13:05 to 17:18 min) in the stereotactic CT-navigation group and 6:40 min (95% CI 5:28 to 7:52 min) in the Ultrasound group. The use of stereotactic CT-navigation in placing IRE-electrodes in a liver phantom is more accurate, but more time consuming, compared to ultrasound guidance.

Soft-tissue-mimicking using silicones for the manufacturing of soft phantoms by fresh 3D printing

Purpose The purpose of this study is to use the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) additive manufacturing (AM) technique for manufacturing a liver phantom which can mimic the corresponding soft living tissue. One of the possible applications is surgical planning. Design/methodology/approach A thermo-reversible Pluronic® F-127-based support bath is used for the FRESH technique. To verify how three-dimensional (3D)-printed new materials can mimic liver tissue, dynamic mechanical analysis and oscillation shear rheometry tests are carried out to identify mechanical characteristics of different 3D printed silicone samples. Additionally, the differential scanning calorimetry was done on the silicone samples. Then, a validation of a 3D printed silicone liver phantom is performed with a 3D scanner. Finally, the surface topography of the 3D printed liver phantom was fulfiled and microscopy analysis of its surface. Findings Silicone samples were able to mimic the liver, therefore obtaining the first soft phantom of the liver using the FRESH technique. Practical implications Because of the use of soft silicones, surgeons could practice over these improved phantoms which have an unprecedented degree of living tissue mimicking, enhancing their rehearsal experience before surgery. Social implications An improvement in surgeons surgery skills would lead to a bettering in the patient outcome. Originality/value The first research study was carried out to mimic soft tissue and apply it to the 3D printing of organ phantoms using AM FRESH technique.

Multimodal Imaging of Hepatocellular Carcinoma Using Dynamic Liver Phantom

Liver phantom is used at various medical levels, such as detecting hepatocellular carcinoma (HCC) in the early stages, training medical staff to deal with HCC by taking biopsies, developing new sequences on medical imaging devices, confirming the image quality, applying treatments to HCC, and others. All of the trials should be applied before entering the real human body. The phantom includes properties very similar to those of the human body, as well as the properties of liver cancer and how it is treated within the body through its biological form. Therefore, the present chapter aims to provide comprehensive information to consider when fabricating HCC-containing phantoms and the characteristics of those phantoms in proportion to multimodal medical imaging to aid in understanding the main target of dynamic phantom for HCC.

Comparison of Y-90 and Ho-166 Dosimetry Using Liver Phantom: A Monte Carlo Study

Background: It is estimated that more than 1 million people are diagnosed with liver malignancy each year and one of the treatments is radioembolization with Y-90 and Ho-166. Objective: The aim of this study is to calculate the absorbed doses caused by Y-90 and Ho-166 in tumor and liver parenchyma using a phantom via Monte Carlo method. Methods: A liver model phantom including a tumor imitation of sphere (r =1.5cm) was defined in GATE. The total activity of 40 mCi Y-90 and Ho-166 was prescribed into tumor imitation as source and 2x2x2 mm3 voxel-sized DoseActors were identified at 30 locations. The simulation, performed to calculate the absorbed doses left by particles during 1 second for Y-90 and Ho-166, was run for a total of 10 days and 11 days, respectively. Total doses were calculated by taking the doses occurring in 1 second as a reference. Results: The maximum absorbed doses were found to be 2.334E+03±1.576E+01 Gy for Y-90 and 7.006E+02±6.013E-01 Gy for Ho-166 at the center of tumor imitation. The minimum absorbed doses were found to be 2.133E-03±1.883E-01 Gy for Y-90 and 1.152E-02±1.036E-03 Gy for Ho-166 at the farthest location from source. The mean absorbed doses in tumor imitation were found to be 1.50E+03±1.36E+00 Gy and 4.58E+02±4.75E-01 Gy for Y-90 and Ho-166, respectively. And, the mean absorbed doses in normal parenchymal tissue were found to be2.07E+01±9.58E-02 Gy and 3.79E+00±2.63E-02 Gy for Y-90 and Ho-166, respectively. Conclusion: Based on the results, Ho-166 is a good alternative to Y-90 according to dosimetric evaluation.

A Moving Liver Phantom in An Anthropomorphic Thorax for SPECT MP Imaging

Cranio-caudal respiratory motion and liver activity cause a variety of complex myocardial perfusion (MP) artifacts, especially in the inferior myocardial wall, that may also mask cardiac defects. To assess and characterize such artifacts, an anthropomorphic thorax with moving thoracic phantoms can be utilized in SPECT MP imaging. In this study, a liver phantom was developed, and anatomically added into an anthropomorphic phantom, that encloses an ECG beating cardiac phantom and breathing lungs phantom. A cranio-caudal respiratory motion was also developed for the liver phantom and it was synchronized with the corresponding ones of the cardiac and lungs phantoms. This continuous motion could also be further divided into dynamic respiratory phases, from end-exhalation to end-inspiration, to perform SPECT acquisitions in different respiratory phases. The motion parameters, displacements and volumes, were validated by the acquired CT slices, the OsiriX and Vitrea software. Sample SPECT/16-slice-CT myocardial MP acquisitions were also performed and compared to the literature. The cardiac, lungs and liver phantoms can precisely perform, in time interval of 0.1 sec, physiological thoracic motions within an anthropomorphic thorax. This dynamic phantom assembly can be utilized for SPECT MP supine and, for first time, prone imaging to access and characterize artifacts due to different cranio-caudal respiratory amplitudes and cardiac-liver activity ratios.

Soft Liver Phantom with a Hollow Biliary System

Hepatobiliary interventions are regarded as difficult minimally-invasive procedures that require experience and skills of physicians. To facilitate the surgical training, we develop a soft, high-fidelity and durable liver phantom with detailed morphology. The phantom is anatomically accurate and feasible for the multi-modality medical imaging, including computer tomography (CT), ultrasound, and endoscopy. The CT results show that the phantom resembles the detailed anatomy of real livers including the biliary ducts, with a spatial root mean square error (RMSE) of 1.7 ± 0.7 mm and 0.9 ± 0.2 mm for the biliary duct and the liver outer shape, respectively. The sonographic signals and the endoscopic appearance highly mimic those of the real organ. An electric sensing system was developed for the real-time quantitative tracking of the transhepatic puncturing needle. The fabrication method herein is accurate and reproducible, and the needle tracking system offers a robust and general approach to evaluate the centesis outcome.