Texture Features of Magnetic Resonance Images Predict Poststroke Cognitive Impairment: Validation in a Multicenter Study.

BACKGROUND: Imaging features derived from T1-weighted (T1w) images texture analysis were shown to be potential markers of poststroke cognitive impairment, with better sensitivity than atrophy measurement. However, in magnetic resonance images, the signal distribution is subject to variations and can limit transferability of the method between centers. This study examined the reliability of texture features against imaging settings using data from different centers. METHODS: Data were collected from 327 patients within the Stroke and Cognition Consortium from centers in France, Germany, Australia, and the United Kingdom. T1w images were preprocessed to normalize the signal intensities and then texture features, including first- and second-order statistics, were measured in the hippocampus and the entorhinal cortex. Differences between the data led to the use of 2 methods of analysis. First, a machine learning modeling, using random forest, was used to build a poststroke cognitive impairment prediction model using one dataset and this was validated on another dataset as external unseen data. Second, the predictive ability of the texture features was examined in the 2 remaining datasets by ANCOVA with false discovery rate correction for multiple comparisons. RESULTS: The prediction model had a mean accuracy of 90% for individual classification of patients in the learning base while for the validation base it was ≈ 77%. ANCOVA showed significant differences, in all datasets, for the kurtosis and inverse difference moment texture features when measured in patients with cognitive impairment and those without. CONCLUSIONS: These results suggest that texture features obtained from routine clinical MR images are robust early predictors of poststroke cognitive impairment and can be combined with other demographic and clinical predictors to build an accurate prediction model.

Performance Analysis of Optically Pumped 4He Magnetometers vs. Conventional SQUIDs: From Adult to Infant Head Models.

Optically pumped magnetometers (OPMs) are new, room-temperature alternatives to superconducting quantum interference devices (SQUIDs) for measuring the brain's magnetic fields. The most used OPM in MagnetoEncephaloGraphy (MEG) are based on alkali atoms operating in the spin-exchange relaxation-free (SERF) regime. These sensors do not require cooling but have to be heated. Another kind of OPM, based on the parametric resonance of 4He atoms are operated at room temperature, suppressing the heat dissipation issue. They also have an advantageous bandwidth and dynamic range more suitable for MEG recordings. We quantitatively assessed the improvement (relative to a SQUID magnetometers array) in recording the magnetic field with a wearable 4He OPM-MEG system through data simulations. The OPM array and magnetoencephalography forward models were based on anatomical MRI data from an adult, a nine-year-old child, and 10 infants aged between one month and two years. Our simulations showed that a 4He OPMs array offers markedly better spatial specificity than a SQUID magnetometers array in various key performance areas (e.g., signal power, information content, and spatial resolution). Our results are also discussed regarding previous simulation results obtained for alkali OPM.

Texture features of magnetic resonance images: A marker of slight cognitive deficits in Parkinson's disease.

BACKGROUND: Cognitive impairment is a frequent nonmotor symptom of Parkinson's disease. Depending on severity, patients are considered to have mild cognitive impairment or dementia. However, among the cognitively intact patients, some may have deficits in a less severe range. The early detection of such subtle symptoms may be important for the initiation of care strategies. OBJECTIVE: To identify imaging markers of early cognitive symptoms, potentially before usual signs, such as atrophy, become manifest. METHODS: A total of 102 patients with Parkinson's disease and 17 age-matched cognitively intact healthy controls underwent extensive neuropsychological assessment and T1-weighted magnetic resonance imaging. Parkinson's disease patients were separated into 3 groups according to their cognitive status: intact, with slight slowing, and with mild deficits in executive functions. Texture features as measured by first-order and second-order statistics were computed in the following 6 brain regions: the hippocampus, thalamus, amygdala, putamen, caudate nucleus, and pallidum. They were tested between the groups, and their correlation with cognition was examined. Volumetric measurements were made for comparison. RESULTS: Texture analysis showed significant between-group differences for 2 features-skewness and entropy in the hippocampus, the thalamus, and the amygdala-and the volume analysis revealed no between-group difference. These features were significantly correlated with cognitive performance. CONCLUSION: These results support the assumption that signal alterations associated with Parkinson's disease-related cognitive decline can be captured very early by texture analysis. As these changes appear to reflect clinical phenomena, texture analysis may be a promising marker for helping cognitive phenotyping in Parkinson's disease. © 2019 International Parkinson and Movement Disorder Society.

Electroencephalography-based machine learning for cognitive profiling in Parkinson's disease: Preliminary results.

BACKGROUND: Cognitive symptoms are common in patients with Parkinson's disease. Characterization of a patient's cognitive profile is an essential step toward the identification of predictors of cognitive worsening. OBJECTIVE: The aim of this study was to investigate the use of the combination of resting-state EEG and data-mining techniques to build characterization models. METHODS: Dense EEG data from 118 patients with Parkinson's disease, classified into 5 different groups according to the severity of their cognitive impairments, were considered. Spectral power analysis within 7 frequency bands was performed on the EEG signals. The obtained quantitative EEG features of 100 patients were mined using 2 machine-learning algorithms to build and train characterization models, namely, support vector machines and k-nearest neighbors models. The models were then blindly tested on data from 18 patients. RESULTS: The overall classification accuracies were 84% and 88% for the support vector machines and k-nearest algorithms, respectively. The worst classifications were observed for patients from groups with small sample sizes, corresponding to patients with the severe cognitive deficits. Whereas for the remaining groups for whom an accurate diagnosis was required to plan the future healthcare, the classification was very accurate. CONCLUSION: These results suggest that EEG features computed from a daily clinical practice exploration modality in-that it is nonexpensive, available anywhere, and requires minimal cooperation from the patient-can be used as a screening method to identify the severity of cognitive impairment in patients with Parkinson's disease. © 2018 International Parkinson and Movement Disorder Society.

Quantified analysis of histological components and architectural patterns of gleason grades in apparent diffusion coefficient restricted areas upon diffusion weighted MRI for peripheral or transition zone cancer locations.

PURPOSE: To quantify and compare the histological components and architectural patterns of Gleason grades in cancerous areas with restriction on apparent diffusion coefficient (ADC) maps. MATERIALS AND METHODS: Twelve consecutive cases with 14 separate ADC restriction areas, positive for cancer in the peripheral zone (PZ) and transition zone (TZ) were included. All had 3 Tesla MRI and radical prostatectomy. Ten regions of interest (ROIs) within and outside the 14 ADC restriction areas positive for cancer were selected. For each ROI, we performed quantitative analysis of (a) prostate benign and malignant histological component surface ratios, including stroma, glands, epithelium, lumen, cellular nuclei; (b) percent of Gleason grades and measures of ADC values. Means of histological components according to ADC restriction for cancerous area were compared with analyses of variance with repeated measures. RESULTS: Independent predictors of the probability of cancer were median epithelium/ROI ratio (P = 0.001) and nuclei/ROI ratio (P = 0.03). Independent predictors of the probability of ADC restriction were malignant glands/ROI and luminal space/ROI (P < 0.0001). Effect of malignant glands/ROI area was different according to the localization of the ROI (P = 0.03). We observed an overall difference between the means for all of the histological components for the comparison of true positive and false negative (P < 0.0001), except for the percent of Gleason grade 4 (P = 0.18). In TZ cancers, a predominant grade 3 pattern was associated with low ADC values. In PZ cancers, a predominant grade 4 pattern was associated with low ADC values. CONCLUSION: Determinants of low ADC were high ratio of malignant glands/ROI area which may be seen in Gleason grades 3 or 4 cancers. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1786-1796.

Focal therapy as primary treatment for localized prostate cancer: definition, needs and future.

Focal therapy (FT) may offer a promising treatment option in the field of low to intermediate risk localized prostate cancer. The aim of this concept is to combine minimal morbidity with cancer control as well as maintain the possibility of retreatment. Recent advances in MRI and targeted biopsy has improved the diagnostic pathway of prostate cancer and increased the interest in FT. However, before implementation of FT in routine clinical practice, several challenges are still to overcome including patient selection, treatment planning, post-therapy monitoring and definition of oncologic outcome surrogates. In this article, relevant questions regarding the key steps of FT are critically discussed and the main available energy modalities are analyzed taking into account their advantages and unmet needs.

Impact of arterial input function selection on the accuracy of dynamic contrast-enhanced MRI quantitative analysis for the diagnosis of clinically significant prostate cancer.

PURPOSE: Using a limited temporal resolution dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) dataset to assess the impact of the arterial input function (AIF) choice on the transfer constant (K(trans) ) to distinguish prostate carcinoma (PCa) from benign tissue. MATERIALS AND METHODS: Thirty-eight patients with clinically important peripheral PCa (≥0.5 cc) were retrospectively studied. These patients underwent 1.5T multiparametric prostate MR with PCa and benign regions of interest (ROIs) selected using a visual registration with morphometric reconstruction obtained from radical prostatectomy. Using three pharmacokinetic (PK) analysis software programs, the mean K(trans) of ROIs was computed using three AIFs: an individual AIF (Ind-AIF) and two literature population average AIFs of Weinmann (W-AIF) and of Fritz-Hansen (FH-AIF). A pairwise comparison of the area under the receiver operating characteristic curves (AUROCC) obtained with different AIFs was performed. RESULTS: AUROCCs obtained with W-AIF (ranging from 0.801 to 0.843) were significantly higher than FH-AIF (ranging from 0.698 to 0.780, 0.002 ≤ P ≤ 0.045) and similar to or higher than Ind-AIF (ranging from 0.591 to 0.839, 0.014 ≤ P ≤ 0.9). Ind-AIF and FH-AIF provided similar AUROCC (0.34 ≤ P ≤ 0.81). The pairwise correlation of K(trans) values was moderate to very strong when comparing W-AIF with FH-AIF (the Spearman's correlation coefficients [SCCs] ranged from 0.55 to 0.93) and very weak to moderate when comparing W-AIF with Ind-AIF (the SCCs ranged from 0.018 to 0.59) or FH-AIF with Ind-AIF (the SCCs ranged from 0.30 to 0.51). CONCLUSION: W-AIF yielded a higher performance than FH-AIF and a similar or higher performance than Ind-AIF in distinguishing PCa from benign tissue.

Understanding the pathological implications of MRI: application to focal therapy planning.

PURPOSE OF REVIEW: The current challenge in prostate cancer (PCa) focal therapy indication and planning is how to accurately estimate tumor parameters such as volume, extent and grade. In addition to biopsy results, MRI provides an estimation of PCa contour, volume and histopathological characteristics such as presence of high Gleason grade. Among MRI sequences, diffusion-weighted imaging with apparent diffusion coefficient map is the sequence that showed the best results for cancer aggressiveness characterization. RECENT FINDINGS: It was shown that the higher the Gleason score, the lower the apparent diffusion coefficient value. However, accuracy is not sufficient for peripheral zone cancers to be validated for clinical decision and it was not enough investigated for transition zone cancers. Analysis of tumor extent showed a significant underestimation of tumor volume by imaging and this finding should be taken into consideration when planning focal therapy procedures. SUMMARY: Pathological implications of MRI for focal therapy planning are significant but not mature enough to be validated. Future research should aim to quantify cellularity and architectural patterns of PCa Gleason system in correlation with signal abnormalities for better assessment of tumor aggressiveness and extent, and to compare the boundaries of tumors between MRI and histopathological evaluation in order to define an optimal treatment margin.

Fischer 344 Rat: A Preclinical Model for Epithelial Ovarian Cancer Folate-Targeted Therapy.

OBJECTIVE: Ovarian cancer prognosis remains dire after primary therapy. Recurrence rates are disappointingly high as 60% of women with advanced epithelial ovarian cancer considered in remission will develop recurrent disease within 5 years. Special attention to undetected peritoneal metastasis and residual tumorous cells during surgery is necessary as they are the main predictive factors of recurrences. Folate receptor α (FRα) shows promising prospects in targeting ovarian cancerous cells. Our aim was to determine if the Fischer model described by Rose et al could be used to evaluate folate-targeted therapies in preclinical studies. METHODS: NuTu-19 epithelial ovarian cancer cell line was used to induce peritoneal carcinomatosis in female Fischer 344 rats. FRα expression by NuTu-19 cells was assessed in vitro by immunofluorescence using "Cytospin®" protocol. In vitro folate-targeted compound uptake by NuTu-19 cells was evaluated by incubation of FRα-positive ovarian cancer cell lines (NuTu-19/SKOV-3/OVCAR-3/IGROV-1) with or without (control) a folate-targeted photosensitizer. Intracellular incorporation was assessed by confocal microscopy. Determination of in vivo FRα tissue expression by several organs of the peritoneal cavity was studied by immunohistochemistry. RESULTS: NuTu-19 cells express FRα which allows intracellular incorporation of folate-targeted compound by endocytosis. FRα is expressed in tumor tissue, ovary, and liver. Peritoneum, colon, small intestine, and kidney do not express the receptor. CONCLUSIONS: Female Fischer 344 rat is an inexpensive reproducible and efficient preclinical model to study ovarian peritoneal carcinomatosis folate-targeted therapies.

The role of MRI-targeted and confirmatory biopsies for cancer upstaging at selection in patients considered for active surveillance for clinically low-risk prostate cancer.

PURPOSE: The purpose of this study was to assess the roles of MRI-targeted biopsies (TB) and confirmatory biopsies for cancer upstaging at selection in patients considered for active surveillance (AS) for low-risk prostate cancer (PCa) based on the first systematic biopsy (SB) series in another centre. METHODS: From 2009 to 2012, 41 patients with PCa diagnosed within the last 4 months and eligible for AS [clinical stage ≤T2a, prostate-specific antigen (PSA) <10 ng/ml, ≤2 positive biopsy cores with no Gleason pattern 4 or 5 and ≤5 mm involvement of any biopsy core] underwent pre-biopsy MRI, confirmatory transrectal ultrasound 12-core SB and MRI-TB of suspicious lesions. A contingency table assessed the accuracy of MRI to predict cancer upstaging. RESULTS: Median age and PSA were 63.5 years and 5.3 ng/ml, respectively. Overall, 24 patients (59 %) were upstaged. This upstaging was obtained at a confirmatory SB in 16 patients (39 %) based on the Gleason score (9), on cancer length (8) or both (7) and at MRI-TB in 17 patients (41 %) based on the Gleason score (14), cancer length (9) or both (6). Nine patients were upstaged at both SB and TB (22 %). The added value of MRI-TB was 20 % (8/41). The positive and negative predictive values of MRI for predicting cancer upstaging were 79 and 70.5 %, respectively. CONCLUSION: MRI-TB and confirmatory SB upstaged 59 % of cases, improving the selection of patients considered for AS at the first series of SB. Variation in histologic grade assignation between centres and better cancer sampling may explain this high upstaging rate.

New treatment techniques for axillary hyperhidrosis.

Hyperhidrosis is a medical problem defined as perspiration in excess of what is normally needed to cool the body. The excessive production of sweat by the sudoriferous glands is independent of the process of thermoregulation. Techniques have recently appeared that make use of energy sources, in particular microwave devices and light (pulsed flashlamp or laser). The aim is to obtain very long-lasting efficacy without notable side effects. Thermal Nd:YAG lasers used with an interstitial fiber, microwave devices, and photodynamic therapy appear to offer new treatment options for axillary hyperhidrosis. However, insertion of a laser fiber into tissue by means of a cannula may lead to complications if the procedure is not well mastered, as has been shown by numerous studies on laser lipolysis. The only microwave device available on the market is certainly interesting. Photodynamic therapy using eosin gel is an attractive technique. The energy source is a pulsed flashlamp, which many physicians have. Eosin gel is relatively easy to produce and these gels are already marketed in several countries. However, further clinical studies of larger series of patients and with longer follow-up are still needed to reach a definitive conclusion as to the value of this approach.

New treatment options for onychomycosis.

Onychomycosis is the most common nail disorder. The causative pathogens are not only dermatophytes in the majority of cases (Trichophyton rubrum and T. mentagrophytes), but also yeasts of the genus Candida and molds. A wide variety of topical antifungal agents are proposed for first-line treatment of superficial onychomycosis, when the matrix is not involved. New treatment options using light were recently introduced, such as thermal lasers, non-thermal lasers, and photodynamic therapy. For thermal lasers, a temperature increase in the nail of around 50 °C seems to be a prerequisite for success. For non-thermal lasers, the clinical data are very debatable and their mechanism of action still remains mysterious. For photodynamic therapy, 5-aminolevulinic acid is used. The therapy consists of exciting protoporphyrin IX with red light that penetrates relatively deeply. Further clinical studies of larger series of patients and with longer follow-up are still needed to reach a definitive conclusion on the value of these devices.

Qualitative versus quantitative assessment of electroencephalography in cognitive decline: Comparison in a clinical population.

This study aimed to compare the diagnostic performance of visual assessment of electroencephalography (EEG) using the Grand Total EEG (GTE) score and quantitative EEG (QEEG) using spectral analysis in the context of cognitive impairment. This was a retrospective study of patients with mild cognitive impairment, with (MCI+V) or without (MCI) vascular dysfunction, and patients with dementia including Alzheimer's disease, Lewy Body Dementia and vascular dementia. The results showed that the GTE is a simple scoring system with some potential applications, but limited ability to distinguish between dementia subtypes, while spectral analysis appeared to be a powerful tool, but its clinical development requires the use of artificial intelligence tools.

Numerical simulation of endovenous laser treatment of the incompetent great saphenous vein with external air cooling.

Endovenous laser treatment (ELT) has been proposed as an alternative in the treatment of reflux of the great saphenous vein. Before the procedure, peri-saphenous subcutaneous tumescent saline solution infiltration is usually performed. However, diffusion of this tumescent fluid is rapidly observed and can potentially reduce the efficacy as a heat sink. External skin cooling with cold air was proposed as an alternative solution. The objective of this study is to compare endovenous laser treatment without and with air cooling by realistic numerical simulations. An optical-thermal damage model was formulated and implemented using finite element modeling. The general model simulated light distribution using the diffusion approximation of the transport theory, temperature rise using the bioheat equation, and laser-induced injury using the Arrhenius damage model. Parameters, used in clinical procedures, were considered: power, 15 W; pulse duration, 1 s; fiber pull back, 3-mm increments every second; cold air applied in continuous mode during ELT; and no tumescent anesthesia. Simulations were performed for vein locations at 5, 10, and 15 mm in depth, with and without air cooling. For a vein located at 15 mm in depth, no significant difference was observed with and without cooling. For a vein located at 10 mm in depth, surface temperature increase up to 45 °C is observed without cooling. For a vein located at 5 mm, without cooling, temperature increase leads to irreversible damage of dermis and epidermis. Conversely, with air cooling, surface temperature reaches a maximum of 38 °C in accordance with recordings performed on patients. ELT of the incompetent great saphenous vein with external air cooling system is a promising therapy technique. Use of cold air on the skin continuously flowing in the area of laser shot decreased significantly the heat extent and the thermal damage in the perivenous tissues and the skin.

[The outbreak of focal therapy for localized prostate cancer management]. / Emrergence des thérapies focales du cancer localisé de la prostate.

These last years, focal therapy is emerging as an intermediate management technique between radical approaches (radical prostatectomy, external beam radiation and brachytherapy) and active surveillance to manage some early stage prostate cancer. Different energy modalities are currently being developed. Prostatic tumour destruction can be achieved with different energies: freezing effect for cryotherapy, thermal effect using focalized ultrasound for HIFU and using thermal effect of light for FLA, and activation of a photosensitizer by light for PDT. Those techniques carry a low morbidity but clinical experience is limited regarding to oncologic outcome. Prospective clinical trials are needed to highlight the full potential of this promising treatment modality.

The contribution of executive control dysfunction to freezing of gait in Parkinson's disease.

OBJECTIVE: An executive dysfunction is supposed to contribute to freezing of gait (FoG) in Parkinson's disease. We aimed to investigate at a behavioral and cortical levels whether an attentional load (particularly, a conflicting situation) can specifically impact preparation and execution phases of step initiation in parkinsonian patients with FoG. METHODS: Fifteen patients with FoG, 16 without and 15 controls performed an adapted version of the Attention Network Test, with step initiation as response instead of the standard manual keypress. Kinetic and kinematic features of gait initiation as well as high-resolution electroencephalography were recorded during the task. RESULTS: Patients with FoG presented an impaired executive control. Step execution time was longer in parkinsonian patients. However, the executive control effect on step execution time was not different between all groups. Compared to patients, controls showed a shorter step initiation-locked alpha desynchronization, and an earlier, more intense and shorter beta desynchronization over the sensorimotor cortex. Even though controls were faster, the induced alpha and beta activity associated with the effect of executive control didn't differ between patients and controls. CONCLUSIONS: Tasks of conflict resolution lead to a comparable alteration of step initiation and its underlying brain activity in all groups. Links between executive control, gait initiation and FoG seem more complex than expected. SIGNIFICANCE: This study questions the cognitive hypothesis in the pathophysiology of freezing of gait. Executive dysfunction is associated with FoG but is not the main causal mechanism since the interaction between attention and motor preparation didn't provoke FoG.

Multi-approach comparative study of EEG patterns associated with the most common forms of dementia.

Electroencephalography's (EEG) sensitivity in discriminating dementia syndromes remains unclear. This study aimed to investigate EEG markers in patients with major cognitive disorders. The studied population included 4 groups of patients: Alzheimer's disease with associated vascular lesions, Alzheimer's disease without vascular lesions (AD-V), Lewy body disease and vascular dementia (VaD); and completed by a control group composed by cognitively unimpaired patients. EEGs were analysed quantitatively using spectral analysis, functional connectivity and micro-states. By comparison to the controls, expected slowing and alterations of functional connectivity were detected in patients with dementia. Among these patients, an overall increase in power in the alpha band was observed in the VaD group, mainly when compared to the 2 AD groups, while the Alzheimer's disease without vascular lesions group exhibited increased power in the beta-2 band and higher functional connectivity in the same frequency band. Micro-state analyses revealed differences in temporal dynamics for the VaD group. A number of EEG modifications reported as markers of some syndromes were found, but others were not reproduced.

Tri-axial rubidium and helium optically pumped magnetometers for on-scalp magnetoencephalography recording of interictal epileptiform discharges: a case study.

Cryogenic magnetoencephalography (MEG) enhances the presurgical assessment of refractory focal epilepsy (RFE). Optically pumped magnetometers (OPMs) are cryogen-free sensors that enable on-scalp MEG recordings. Here, we investigate the application of tri-axial OPMs [87Rb (Rb-OPM) and 4He gas (He-OPM)] for the detection of interictal epileptiform discharges (IEDs). IEDs were recorded simultaneously with 4 tri-axial Rb- and 4 tri-axial He-OPMs in a child with RFE. IEDs were identified visually, isolated from magnetic background noise using independent component analysis (ICA) and were studied following their optimal magnetic field orientation thanks to virtual sensors. Most IEDs (>1,000) were detectable by both He- and Rb-OPM recordings. IEDs were isolated by ICA and the resulting magnetic field oriented mostly tangential to the scalp in Rb-OPMs and radial in He-OPMs. Likely due to differences in sensor locations, the IED amplitude was higher with Rb-OPMs. This case study shows comparable ability of Rb-OPMs and He-OPMs to detect IEDs and the substantial benefits of triaxial OPMs to detect IEDs from different sensor locations. Tri-axial OPMs allow to maximize spatial brain sampling for IEDs detection with a limited number of sensors.

Focal laser interstitial thermotherapy (LITT) at 980 nm for prostate cancer: treatment feasibility in Dunning R3327-AT2 rat prostate tumour.

OBJECTIVE: To examine the feasibility and reproducibility of laser interstitial thermotherapy (LITT) as a minimally invasive method for the treatment of prostate cancer. MATERIALS AND METHODS: Heterotopic tumours of prostatic adenocarcinoma (Dunning R3327-AT2) were induced in 10 male Copenhagen rats. After preoperative magnetic resonance imaging (MRI), a 10-mm cylindrical diffusing fibre developed by our research department was inserted under ultrasonographic guidance into the tumour. LITT was performed with a 980-nm diode laser (power 5 W) for 75 s (fluence rate of 1145 J/cm(2)). Non-enhanced T2-weighted and dynamic gadolinium-enhanced T1-weighted MRI examinations were performed at baseline, 1 and 48 h after the procedure and correlated with histological findings. RESULTS: The necrosis lesions induced by LITT were visible on MRI. The mean (SD) ellipsoid necrosis volumes were 0.748 (0.075) mL at 1 h and 0.982 (0.052) mL at 48 h after the LITT procedure, and significantly different (P < 0.001). Histological analysis showed a strong correlation (r = 0.87) with the mean necrosis volume obtained by MRI at 48 h after LITT. CONCLUSIONS: In a prostatic adenocarcinoma model, 980-nm LITT induces reproducible necrosis volumes. Further characterization of the response to LITT in an animal model and in human tissues will be important in establishing the efficacy of the procedure for prostate cancer focal therapy.

Laser interstitial thermotherapy of small breast fibroadenomas: numerical simulations.

BACKGROUND: Laser interstitial thermotherapy (LITT) is potentially a novel method to treat small breast fibroadenoma, without the need for surgical removal. Dosimetry planning and conformation of the treated area of tumor remain major issues, especially for a moving organ such as the breast. Pre-treatment simulation planning of this therapy is an effective method to predict the final thermal damage. In this study, a mathematical model is elaborated to simulate the heat distribution and the thermal damage. METHODS: The mathematical model was based on finite element method (FEM) to solve the light distribution, bioheat, and thermal damage equations. Six simulations were performed with the following powers: 5, 6, 7, 8, 9, and 10 W (λ = 980 nm), and for an irradiation time of 125 seconds, with a 50 °C iso-damage temperature. To validate these simulations, six turkey breast samples were irradiated with parameters used for simulations. Volumes of thermal damage were calculated by using formulas: spherical, Elliptical, and Carlsson volumes and compared to the simulated volumes. RESULTS: Differences between volumes were from 0.01 to 1 cm3. Interpolations between volumes from ex vivo experiments with corresponding powers were established. The relationship between the volume of the thermal damage and the laser power was described by a polynomial equation (R2 = 0.99). The power estimated by the interpolation to obtain 1 cm3 of thermal damage was 7.4 W (922 J) and the maximum corresponding temperature was 90 °C. CONCLUSION: In this study, a good correlation was established between simulation and ex vivo experiments of LITT for fibroadenoma breast cancer.