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Alternating magnetic field (AMF) tissue interaction models are generally not validated. Our aim was to develop and validate a coupled electromagnetic and thermal model for estimating temperatures in large organs during magnetic nanoparticle hyperthermia (MNH). Coupled finite element electromagnetic and thermal model validation was performed by comparing the results to experimental data obtained from temperatures measured in homogeneous agar gel phantoms exposed to an AMF at fixed frequency (155 ± 10 kHz). The validated model was applied to a three-dimensional (3D) rabbit liver built from computed tomography (CT) images to investigate the contribution of nanoparticle heating and nonspecific eddy current heating as a function of AMF amplitude. Computed temperatures from the model were in excellent agreement with temperatures calculated using the analytical method (error < 1%) and temperatures measured in phantoms (maximum absolute error <2% at each probe location). The 3D rabbit liver model for a fixed concentration of 5 mg Fe/cm3 of tumor revealed a maximum temperature ∼44 °C in tumor and ∼40 °C in liver at AMF amplitude of ∼12 kA/m (peak). A validated coupled electromagnetic and thermal model was developed to estimate temperatures due to eddy current heating in homogeneous tissue phantoms. The validated model was successfully used to analyze temperature distribution in complex rabbit liver tumor geometry during MNH. In future, model validation should be extended to heterogeneous tissue phantoms, and include heat sink effects from major blood vessels. [ABSTRACT FROM AUTHOR]

Purpose/objective:The aim of this study was to develop and investigate the properties of a magnetic iron oxide nanoparticle–ethiodised oil formulation for image-guided thermal therapy of liver cancer. Materials and methods:The formulation comprises bionised nano-ferrite (BNF) nanoparticles suspended in ethiodised oil, emulsified with polysorbate 20 (BNF-lip). Nanoparticle size was measured via photon correlation spectroscopy and transmission electron microscopy.In vivothermal therapy capability was tested in two groups of male Foxn1numice bearing subcutaneous HepG2 xenograft tumours. Group I (n = 12) was used to screen conditions for group II (n = 48). In group II, mice received one of BNF-lip (n = 18), BNF alone (n = 16), or PBS (n = 14), followed by alternating magnetic field (AMF) hyperthermia, with either varied duration (15 or 20 min) or amplitude (0, 16, 20, or 24 kA/m). Image-guided fluoroscopic intra-arterial injection of BNF-lip was tested in New Zealand white rabbits (n = 10), bearing liver VX2 tumours. The animals were subsequently imaged with CT and 3 T MRI, up to 7 days post-injection. The tumours were histopathologically evaluated for distribution of BNF-lip. Results:The BNF showed larger aggregate diameters when suspended in BNF-lip, compared to clear solution. The BNF-lip formulation produced maximum tumour temperatures with AMF >20 kA/m and showed positive X-ray visibility and substantial shortening of T1 and T2 relaxation time, with sustained intratumoural retention up to 7 days post-injection. On pathology, intratumoural BNF-lip distribution correlated well with CT imaging of intratumoural BNF-lip distribution. Conclusion:The BNF-lip formulation has favourable thermal and dual imaging capabilities for image-guided thermal therapy of liver cancer, suggesting further exploration for clinical applications. [ABSTRACT FROM PUBLISHER]

Background: Dacryoscintigraphy is a noninvasive method frequently used for assessment of the lacrimal drainage system. Sometimes conflicting results with patients' complaints are obtained, which have no clear explanation. In our hypothesis, follow-up of patients evaluated with dacryoscintigraphy could be helpful in determining possible explanations for these conflicting results. Method: Thirty-eight consecutive patients (76 eyes) who had not previously undergone dacryocystorhinostomy or probing were entered in the study. Following instillation of 4 MBq 99mTc-pertechnetate, a routine procedure of dacryoscintigraphy was performed. After a mean follow-up time of 1.2 ± 0.3 years (range 0.9-1.6 years), all patients were reassessed clinically. Results: Using initial patients' symptoms as the gold standard, the sensitivity, specificity, NPV, and PPV of dacryoscintigraphy were calculated to be 82.1%, 75%, 60%, and 90.1%, respectively. The kappa value as a measure of agreement was 0.52. Considering the follow-up study as the gold standard, the sensitivity, specificity, NPV, and PPV were calculated as follows, respectively: 96.3%, 90.4%, 96.3%, and 90.4%. The kappa value was 0.86. There were three initially symptom-free eyes with obstructive pattern on the scans, which developed epiphora on the follow-up. In fact, these eyes were initially classified as false positive, but follow-up assessment showed that they were true-positive scans in a subclinical state. Conclusion: Despite certain drawbacks inherent to the technique, dacryoscintigraphy provides valuable independent information and allows more accurate management decisions. In some patients, data obtained from lacrimal scintigraphy could be predictive, and it makes possible determination of subclinical nasolacrimal duct obstructions. [ABSTRACT FROM AUTHOR]

Background: At the present time, only visual analysis is implemented on dacryoscintigraphic images and quantitative assessments are not routinely obtained. The authors have designed a novel, simple, quantitative method for the diagnosis of sac and post-sac obstructions based on the dacryoscintigraphic images. Method: Fifty-nine patients with severe unilateral epiphora were included and the contralateral asymptomatic eyes were used as controls. After ocular instillation of 0.1 cc isotonic saline containing 4 MBq 99mTcO4, dynamic images were obtained for 20 minutes. Visual interpretation was done by two blinded specialists in nuclear medicine. A Time-Activity Curve (TAC) was generated for each eye and its pattern was divided to plateau type, shallow-down sloping and deep-down sloping. The excretion ratio (expressed as the percentage of drained activity) in the 2nd, 3rd, 5th, 7th, 10th, 15th and 20th minute of the study was calculated based on the following formula: (the total count in the region of interest (ROI) in the 1st minute - the total ROI count in the 2nd, 3rd, 5th, 7th, 10th, 15th or 20th minute/the total ROI count in the 1st minute) × 100. The results of the quantitative analysis were compared with the clinical symptoms, visual analysis and TAC pattern. Results: At the optimal cut-off points for the 2nd, 3rd, 5th and 7th minute, the sensitivity of the prediction of obstruction was 76%, 72%, 71% and 69%, respectively. The correlation between visual interpretation and the TAC pattern was statistically significant. Conclusion: The quantitative evaluation of dacryoscintigraphic images would contribute greatly to achieving an easier and more objective interpretation of the scintigraphic results and also provides a reliable tool for inter-individual comparison and the follow-up of patients. As it is the first time that this innovative method has been examined clinically, it will be necessary to investigate its clinical utility in a larger series of patients. [ABSTRACT FROM AUTHOR]