Fiberoptic Thermometry Research Articles

Measurement, calibration, and verification on the critical ignition temperature of hot bridge wire electro-explosive device

To address the problem of the difference in temperature between the exposed and amorce-filled state of the bridge wire in the fiber optic thermometry, this paper proceeds from a mathematical model of the temperature rise of the hot bridge wire electro-explosive device (EED), the relationship between the critical ignition temperature and the current of hot bridge wire EED is discussed. Combining thermal ignition theory, the technique of measurement and calibration the critical ignition temperature of hot bridge wire EED is proposed, and the technique is validated by injection versus radiation. The results show that the critical ignition temperature of the tested hot bridge wire EED obtained by testing and calibration is 337.53 °C. The 50% ignition field strength of the hot bridge wire EED under radiation conditions obtained by the up-and-down method test is 1271 V m−1, while the equivalent ignition field strength determined from the critical ignition temperature under the same radiation conditions is 1345 V m−1, the error between the two is only 0.49 dB, which demonstrates the high accuracy of the proposed measurement and calibration technique.

Estimation of Bacteriophage MS2 Inactivation Parameters During Microwave Heating of Frozen Strawberries

Frozen berries have been repeatedly linked to acute gastroenteritis caused by norovirus, the most common cause of foodborne illness in the United States. Many guidelines recommend that frozen berries be microwaved for at least 2 min, but it is unclear if this thermal treatment is effective at inactivating norovirus. The objective of this study was to model the effect of microwave heating at varying power levels on the survival of bacteriophage MS2, a norovirus surrogate, when inoculated onto frozen strawberries. Bacteriophage MS2 was inoculated onto the surface of frozen strawberries with a starting concentration of approximately 10 log PFU/g. Samples (either 3 or 5 whole strawberries) were heated in a 1300-Watt domestic research microwave oven (frequency of 2450 MHz) at power levels of 30, 50, 70, and 100% (full power), for times ranging from 15 to 300 s to determine inactivation. Temperatures at berry surfaces were monitored during heating using fiberoptic thermometry. All experiments were conducted in triplicate. The primary model for thermal inactivation was a log-linear model of logN vs. time. The secondary model was for a D-value decreasing linearly with temperature and an added term that was path-dependent on the thermal history. Parameters in the model were estimated using dynamic temperature history at the surface of the berry, via nonlinear regression using all data simultaneously. The root mean square error was ∼0.5 PFU/g out of a total 6-log reduction. Log reductions of 1.1 ± 0.4, 1.5 ± 0.5, 3.1 ± 0.1, and 3.8 ± 0.2 log PFU/g were observed for 30, 50, 70, and 100% microwave power levels when three berries were heated for 60 s. D-values were 21.4 ± 1.95 s and 10.6 ± 1.1 s at 10 and 60°C, respectively. This work demonstrates an approach to estimate inactivation parameters for viruses from dynamic temperature data during microwave heating. These findings will be useful in predicting the safety effect of microwave heating of berries in the home or food service.

Resonant fiber-optic thermometry with high resolution and wide range.

We report a high-resolution and wide-range thermometer using a fiber Bragg grating Fabry-Perot cavity (FBG-FP) combined with beat frequency interrogation. Two distributed feedback (DFB) lasers are locked to the FBG-FP sensing head and a hydrogen cyanide H13C14N (HCN) gas cell, respectively, both using the Pound-Drever-Hall (PDH) technique. The light beams from two lasers are brought together to interfere on a photodetector producing a beat frequency signal which provides a measure of the temperature change. Our sensor exhibits a dynamic range of ∼109 °C, a high resolution of 2×10-4 °C with an averaging time of 1 s. By introducing the reference frequency, the sensor has demonstrated good long-term stability. This sensor provides a useful tool for those fields where resolving slight temperature changes is crucial, such as deep ocean temperature measurement.

System for delivering microwave ablation to subcutaneous tumors in small-animals under high-field MRI thermometry guidance

Purpose Bio-effects following thermal treatments are a function of the achieved temperature profile in tissue, which can be estimated across tumor volumes with real-time MRI thermometry (MRIT). Here, we report on expansion of a previously developed small-animal microwave hyperthermia system integrated with MRIT for delivering thermal ablation to subcutaneously implanted tumors in mice. Methods Computational models were employed to assess suitability of the 2.45 GHz microwave applicators for delivering ablation to subcutaneous tumor targets in mice. Phantoms and ex-vivo tissues were heated to temperatures in the range 47–67 °C with custom-made microwave applicators for validating MRIT with the proton resonance frequency shift method against fiberoptic thermometry. HAC15 tumors implanted in nude mice (n = 6) were ablated in vivo and monitored with MRIT in multiple planes. One day post ablation, animals were euthanized, and excised tumors were processed for viability assessment. Results Average absolute error between temperatures from fiberoptic sensors and MRIT was 0.6 °C across all ex-vivo ablations. During in-vivo experiments, tumors with volumes ranging between 5.4–35.9 mm3 (mean 14.2 mm3) were ablated (duration: 103–150 s) to achieve 55 °C at the tumor boundary. Thermal doses ≥240 CEM43 were achieved across 90.7–98.0% of tumor volumes for four cases. Ablations were incomplete for remaining cases, attributed to motion-affected thermometry. Thermal dose-based ablative tumor coverage agreed with viability assessment of excised tumors. Conclusions We have developed a system for delivering microwave ablation to subcutaneous tumors in small animals under MRIT guidance and demonstrated its performance in-vivo.

Magnetic resonance temperature imaging of laser-induced thermotherapy using proton resonance frequency shift: evaluation of different sequences in phantom and porcine brain at 7T.

The present study aimed to evaluate magnetic resonance (MR) thermometry using proton resonance frequency shift (PRFS) during laser-induced thermotherapy (LITT), and to compare the results of using different sequences at a field strength of 7-Tesla to identify the optimal for use in ablation so that the surrounding healthy tissues may be protected from damaging in real time. LITT was applied to agarose gel phantoms and ex-vivo porcine brains. We reconstructed both magnitude and phase images to perform MR thermometry based on PRFS methods. We tested four different sequences: a gradient-echo (GRE), a segmented gradient-echo echoplanar imaging (EPI-GRE), a fast-low angle shot (FLASH), and a true fast imaging with steady precession (TRUFI). Temperature was monitored and verified using a fiber-optic thermometry device. All sequences showed good linear correlations (R = 0.97-0.99) between the measured temperature and the calculated MR-thermometry measurements. The phantom/porcine brain experiments revealed the temperature precisions at 1.53/0.69°C (GRE), 0.61/0.43°C (EPI-GRE), 1.64/1.32°C (FLASH), and 0.58/1.52°C (TRUFI), respectively. Furthermore, we performed a Bland-Altman analysis and the temperature accuracies were found to be - 1.32/- 0.60°C (GRE), 0.42/- 0.33°C (EPI-GRE), - 1.28/- 0.98°C (FLASH), and 0.14/0.46°C (TRUFI) in the phantom/porcine brain experiments, respectively. Our experiments recommend that EPI-GRE sequence be the best of the all sequences for MR temperature imaging with PRFS in the LITT on 7T magnetic resonance imaging (MRI) systems because of its relatively higher precision and accuracy.

An integrated method for contained laparoscopic specimen removal

Efforts at minimizing pain following minimally invasive (MIS) hysterectomy were hampered by the absence of simple, reliable methods to extract specimens following the 2014 FDA safety warning discouraging power morcellation. To address this gap, an integrated method intended to provide reliable specimen containment with a multi-layer bag, segmentation using bipolar energy, and tissue extraction during laparoscopic gynecological surgical procedures was developed. This report details the pre-clinical studies demonstrating specimen containment integrity, and thermal and electrical safety of the Eximis™ CS (Contained Segmentation) Procedure. All experiments were performed in pigs and approved by the research facility's institutional animal care committee and met USDA and AAALAC guidelines. The study design was composed of three experimental groups; Bovine tongue muscle to simulate normal uterine tissue, bovine tendon draped in a “sausage casing” to simulate hard-thick myoma tissues, and a polymer block wrapped with bacon strips to simulate a severely calcified fibroid. Additionally, there were two control groups: one negative and one positive (heat gun). Each experimental group was tested in four Eximis Capture Bags (8 cuts each) for a total of 24 electromechanical cuts. Thermal evaluation of the small bowel adjacent to the capture bag during device activation was performed with a Micronor FOTEMP4-PLUS-P0-V-B fiberoptic thermometry system. Specimens were then harvested for histology and graded by a blinded pathologist using the Histopathology Scoring Criteria (edema/necrosis/inflammation); 0-4; none to marked. Electrical testing evaluated high frequency electrical leakage current by an independent laboratory with the electrosurgical generator set to 200 W output power, the maximum output setting allowable. Finally, Eximis Capture Bags were tested after segmentation using a proprietary leak test that can detect leaks < a 1 μm hole size. The test group simulating normal uterine tissue (bovine tongue) had small bowel histopathology not different from the negative control group. The calcified fibroid and myoma test groups demonstrated statistically more mucosal edema than the negative control group, but differences were not observed in the submucosa or muscularis layers that were closer to the containment bag. The Eximis Capture Bag measured leakage current directly through the bag of 1.01 mA well below the maximum allowable standard of 150 mA. No evidence of leaks was detected. These studies demonstrate that the Eximis CS is thermally and electrically safe to surrounding tissues and that tissue segmentation and extraction do not impact Eximis Capture Bag’s integrity. Clinical evaluation during human and robotic gynecologic procedures for benign disease is warranted. Additionally, these results suggest the system may be beneficial in other MIS procedures where large specimens are removed.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Fiber optic quench detection for large-scale HTS magnets demonstrated on VIPER cable during high-fidelity testing at the SULTAN facility

Fiber-optic thermometry has the potential to provide rapid and reliable quench detection for emerging large-scale, high-field superconducting magnets fabricated with high-temperature-superconductor (HTS) cables. Developing non-voltage-based quench detection schemes, such as fiber Bragg grating (FBG) technology, are particularly important for applications such as magnetic fusion devices where a high degree of induced electromagnetic noise impose significant challenges on traditional voltage-based quench detection methods. To this end, two fiber optic quench detection techniques—FBG and ultra-long FBG (ULFBG)—were incorporated into two vacuum pressure impregnated, insulated, partially transposed, extruded, and roll-formed (VIPER) high-current HTS cables and tested in the SULTAN facility, which provides high-fidelity operating conditions to large-scale superconducting magnets. During surface heater induced quench-like events under a variety of operating conditions, FBG and ULFBG demonstrated strong signal-to-noise ratios (SNRs) ranging from 4 to 32 and measured single-digit temperature excursions; both the SNR and temperature sensitivity increase with temperature. Fiber thermal response times ranged between effectively instantaneous to a few seconds depending on the operating temperature. Strain sensitivity dominates the thermal sensitivity in the conditions achievable at SULTAN; however, measurements at higher quench evolution temperatures, coupled to future work to increase the thermal-to-strain signal, show promise for quench detection capability in full-scale magnets where temperature and strain may occur simultaneously. Overall, FBG and ULFBG were proven capable to quickly and reliably detect small temperature disturbances which induced quench initiation events for high current VIPER HTS conductors in realistic operating conditions, motivating further work to develop FBG and ULFGB quench detection systems for full-scale HTS magnets.

Luminescence of YAG:Dy and YAG:Dy,Er crystals to 1700 °C

Reported here are measurements aimed at development of high temperature luminescence-based fibre optic thermometry for temperatures up to at least 1700 °C. Cylindrical crystal samples of YAG:Dy(1%) and YAG:Dy(1.5%),Er(0.5%) were fabricated by the co-precipitation method. The optical system was comprised of Nd:YAG 355 nm laser light injected into one leg of flexible bifurcated optical fibre connected to a sapphire light pipe. The input end is water cooled and the sensing end is inside a furnace in proximity to the crystal. The emission originates from the Dy3+ dopant. Decay times for the 4I15/2–6H15/2 (456 nm) transition in the YAG:Dy,Er host ranged from 856 ns at 1600 °C to 401 ns at 1700 °C. Signals taken at 10 °C intervals were clearly resolvable. Decay times appeared constant at 800 °C and below with average values of 863 µs for YAG:Dy and 734 µs for YAG:Dy,Er. Decay times from these two materials appear to converge to the same value at high temperatures. These results were achieved with laser excitation of 100 to 150 µJ. The results were compared to physical models both of which yielded reasonable empirical agreement for the limited amount of data. Thermal sensitivity determined from a multiphonon model shows that decay times change by 1% per degree at 1400 °C and 0.9% at 1700 °C. Dy emission was also detected at 405, 400 and 389 nm at 1575 °C and 1700 °C and showed the expected temperature dependence.

Magnetic Resonance Mediated Radiofrequency Ablation.

To introduce magnetic resonance mediated radiofrequency ablation (MR-RFA), in which the MRI scanner uniquely serves both diagnostic and therapeutic roles. In MR-RFA scanner-induced RF heating is channeled to the ablation site via a Larmor frequency RF pickup device and needle system, and controlled via the pulse sequence. MR-RFA was evaluated with simulation of electric and magnetic fields to predict the increase in local specific-absorption-rate (SAR). Temperature-time profiles were measured for different configurations of the device in agar phantoms and ex vivo bovine liver in a 1.5 T scanner. Temperature rise in MR-RFA was imaged using the proton resonance frequency method validated with fiber-optic thermometry. MR-RFA was performed on the livers of two healthy live pigs. Simulations indicated a near tenfold increase in SAR at the RFA needle tip. Temperature-time profiles depended significantly on the physical parameters of the device although both configurations tested yielded temperature increases sufficient for ablation. Resected livers from live ablations exhibited clear thermal lesions. MR-RFA holds potential for integrating RF ablation tumor therapy with MRI scanning. MR-RFA may add value to MRI with the addition of a potentially disposable ablation device, while retaining MRI's ability to provide real time procedure guidance and measurement of tissue temperature, perfusion, and coagulation.

Fiber-optic thermometer application of thermal radiation from rare-earth end-doped SiO₂ fiber.

Visible light thermal radiation from SiO2 glass doped with Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu were studied for the fiber-optic thermometer application based on the temperature dependence of thermal radiation. Thermal radiations according to Planck's law of radiation are observed from the SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu at the temperature above 1100 K. Thermal radiations due to f-f transitions of rare-earth ions are observed from the SiO2 fibers doped with Nd, Dy, Ho, Er, Tm, and Yb at the temperature above 900 K. Peak intensities of thermal radiations from rare-earth doped SiO2 fibers increase sensitively with temperature. Thermal activation energies of thermal radiations by f-f transitions seen in Nd, Dy, Ho, Er, Tm, and Yb doped SiO2 fibers are smaller than those from SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu. Thermal radiation due to highly efficient f-f transitions in Nd, Dy, Ho, Er, Tm, and Yb ions emits more easily than usual thermal radiation process. Thermal radiations from rare-earth doped SiO2 are potentially applicable for the fiber-optic thermometry above 900 K.

Fiber-optic thermometry using thermal radiation from Tm end doped SiO2 fiber sensor.

Fiber-optic thermometry based on temperature dependence of thermal radiation from Tm(3+) ions was studied using Tm end doped SiO2 fiber sensor. Visible light radiation peaks due to f-f transition of Tm(3+) ion were clearly observed at λ = 690 and 790 nm from Tm end doped SiO2 fibers sensor at the temperature above 600 °C. Thermal radiation peaks are assigned with f-f transition of Tm(3+) ion, (1)D2-(3)H6, and (1)G4-(3)H6. Peak intensity of thermal radiation from Tm(3+) ion increases with temperature. Intensity ratio of thermal radiation peaks at λ = 690 nm against that at λ = 790 nm, I790/690, is suitable for the temperature measurement above 750 °C. Two-dimensional temperature distribution in a flame is successfully evaluated by Tm end doped SiO2 fiber sensor.

Non-invasive measurement of brain temperature using radiometric thermometry: experimental validation and clinical observations in asphyxiated newborns.

Therapeutic hypothermia (HT) has been shown to decrease death and severe disability in infants with hypoxic-ischemic encephalopathy (HIE). Rectal temperature (RT) is used to determine the temperature set-points for treatment with HT, however experimental studies have shown significant differences between RT and brain temperature during HT. Knowledge of actual brain temperature during HT might allow better determination of optimal degree of cooling and improve outcomes. To compare measurements of brain temperature obtained by non-invasive radiometric thermometry (RadT) to direct tissue measurements in an experimental model of HT, and to use RadT in newborn infants with HIE undergoing HT. RadT measurements of brain temperature were compared to fiber optic (Luxtron) thermometry measurements placed at a depth of 1.5 centimeters into the brain of cooled miniswine. Following validation studies, brain RadT and RT measurements were continuously recorded in thirty infants with HIE during HT and rewarming. RadT and Luxtron probe temperatures were comparable in miniswine throughout a temperature range similar to therapeutic HT. RadT measurements of brain temperature were higher than RT in 60% of infants with HIE undergoing HT. Higher RadT measurements compared to RT were associated with cerebral white matter abnormalities (p = 0.01). RadT provides a safe, passive and non-invasive way to measure brain temperature that can be used in the clinical setting. RadT may be helpful in determining the optimal degree of cooling and identifying infants at highest risk of brain injury.

Oncologic Outcomes Using Real-Time Peripheral Thermometry-Guided Radiofrequency Ablation of Small Renal Masses

With the increased incidence of low-stage renal cancers, thermal ablation technology has emerged as a viable treatment option for extirpation in selected persons and is supported by the current American Urological Association guidelines. We present a 9-year, single institution experience with radiofrequency ablation (RFA) using real-time peripheral temperature monitoring of small renal masses focusing on oncologic outcomes. We reviewed our prospectively collected database of patients with renal masses who were treated between November 2001 and January 2011 with laparoscopic (LRFA) or CT-guided percutaneous RFA (CTRFA) with simultaneous real-time peripheral fiberoptic thermometry. Patients were followed radiographically at 1 month, 6 months, 1 year, and then annually. Clinicopathologic outcomes were collected and analyzed. A total of 274 patients (211 male) aged 18 to 88 years (mean 67 years) with 292 renal tumors underwent LRFA (112) or CTRFA (180). Mean tumor size was 2.5 cm (0.7-5.3 cm). An intraoperative preablation biopsy showed 197 (67.4%) renal-cell carcinomas (RCC), and 77 (26.4%) benign tumors. Mean follow-up was 26 months (1-98 mos). The single ablation treatment radiographic success rate was 96% for all tumors and 94% for RCC. Metastatic RCC developed in one patient, who died. The Kaplan-Meier (KM) 3-year and 5-year cancer-specific survival was 100% and 98.6%, respectively. The KM 3-year and 5-year overall survival was 90.4% and 74.2%, respectively. RFA is a clinically effective and safe nephron-sparing treatment of patients with small renal masses. Our large cohort and intermediate-term experience adds to the building evidence for the efficacy of RFA for small renal cancers.

Radio-frequency ablation helps preserve nephrons in salvage of failed microwave ablation for a renal cancer in a solitary kidney

Recurrent tumors after renal ablative therapy present a challenge for clinicians. New ablative modalities, including microwave ablation (MWA), have very limited experience in methods of retreating ablation failures. Additionally, in MWA, no long-term outcomes have been reported. In patients having local tumor recurrence, options for surveillance or surgical salvage must be assessed. We present a case to help assess radio-frequency ablation (RFA) for salvage of failed MWA. We report a 63-year-old male with a 4.33-cm renal mass in a solitary kidney undergoing laparoscopic MWA with simultaneous peripheral fiber-optic thermometry (Lumasense, Santa Clara, CA, USA) as primary treatment. Follow-up contrast-enhanced computed tomography (CT) scan was performed at 1 and 4.3 months post-op with failure occurring at 4.3 months as evidenced by persistent enhancement. Subsequently, a laparoscopic RFA (LRFA) with simultaneous peripheral fiber-optic thermometry was performed as salvage therapy. Clinical and radiological follow-up with a contrast-enhanced CT scan at 1 and 11 months post-RFA showed no evidence of disease or enhancement. Creatinine values pre-MWA, post-MWA, and post-RFA were 1.01, 1.14, and 1.17 mg/ml, respectively. This represents a 15% decrease in estimated glomerular filtration rate (eGFR) (79 to 67 ml/min) post-MWA and no change in eGFR post-RFA. Local kidney tumor recurrence often requires additional therapy and a careful decisionmaking process. It is desirable not only to preserve kidney function in patients with a solitary kidney or chronic renal insufficiency, but also to achieve cancer control. We show the feasibility of RFA for salvage treatment of local recurrence of a T1b tumor in a solitary kidney post-MWA.

Detailing Radio Frequency Heating Induced by Coronary Stents: A 7.0 Tesla Magnetic Resonance Study

The sensitivity gain of ultrahigh field Magnetic Resonance (UHF-MR) holds the promise to enhance spatial and temporal resolution. Such improvements could be beneficial for cardiovascular MR. However, intracoronary stents used for treatment of coronary artery disease are currently considered to be contra-indications for UHF-MR. The antenna effect induced by a stent together with RF wavelength shortening could increase local radiofrequency (RF) power deposition at 7.0 T and bears the potential to induce local heating, which might cause tissue damage. Realizing these constraints, this work examines RF heating effects of stents using electro-magnetic field (EMF) simulations and phantoms with properties that mimic myocardium. For this purpose, RF power deposition that exceeds the clinical limits was induced by a dedicated birdcage coil. Fiber optic probes and MR thermometry were applied for temperature monitoring using agarose phantoms containing copper tubes or coronary stents. The results demonstrate an agreement between RF heating induced temperature changes derived from EMF simulations versus MR thermometry. The birdcage coil tailored for RF heating was capable of irradiating power exceeding the specific-absorption rate (SAR) limits defined by the IEC guidelines by a factor of three. This setup afforded RF induced temperature changes up to +27 K in a reference phantom. The maximum extra temperature increase, induced by a copper tube or a coronary stent was less than 3 K. The coronary stents examined showed an RF heating behavior similar to a copper tube. Our results suggest that, if IEC guidelines for local/global SAR are followed, the extra RF heating induced in myocardial tissue by stents may not be significant versus the baseline heating induced by the energy deposited by a tailored cardiac transmit RF coil at 7.0 T, and may be smaller if not insignificant than the extra RF heating observed under the circumstances used in this study.

Comparison of Safety, Renal Function Outcomes and Efficacy of Laparoscopic and Percutaneous Radio Frequency Ablation of Renal Masses

With the increased incidence of low stage renal cancers, thermal ablation technology has emerged as a viable treatment option. Current AUA (American Urological Association) guidelines include thermal ablation as a treatment modality for select individuals. We compared the laparoscopic and percutaneous approach for the radio frequency ablation of renal tumors under the guidance of urological surgeons. We reviewed our radio frequency ablation database of patients with renal masses undergoing laparoscopic or computerized tomography guided percutaneous radio frequency ablation with simultaneous peripheral fiberoptic thermometry from November 2001 to January 2011 at a single tertiary care center. Data were collected on patient demographics, and surgical and clinicopathological outcomes stratified by approach. A total of 298 patients with 316 renal tumors underwent laparoscopic (122 tumors) or computerized tomography guided (194 tumors) radio frequency ablation. There were no statistically significant differences between the laparoscopic and computerized tomography guided radio frequency ablation groups with respect to patient demographics, complication rates and renal functional outcomes (p>0.05). The 3-year Kaplan-Meier estimation of radiographic recurrence-free probability was 95% for computerized tomography guided radio frequency ablation and 94% for laparoscopic radio frequency ablation (p=0.84). Subanalysis of the 212 (67%) renal cell carcinoma tumors showed a 3-year Kaplan-Meier estimation of oncologic recurrence-free probability (post-ablation biopsy proven viable tumor) of 94% for computerized tomography guided radio frequency ablation and 100% for laparoscopic radio frequency ablation (p=0.16). Median followup was 21 months for laparoscopic radio frequency ablation) and 19 months for computerized tomography guided radio frequency ablation. Laparoscopic and computerized tomography guided radio frequency ablation appear safe and effective with statistically equivalent rates of complications and recurrence.

1527 RADIOFREQUENCY ABLATION OF SMALL RENAL MASSES: OVER 8 YEAR EXPERIENCE AT A SINGLE INSTITUTION

You have accessJournal of UrologyKidney Cancer: Localized1 Apr 20111527 RADIOFREQUENCY ABLATION OF SMALL RENAL MASSES: OVER 8 YEAR EXPERIENCE AT A SINGLE INSTITUTION Scott Castle, Vladislav Gorbatiy, Nelson Salas, Watid Karnjanawanichkul, and Raymond Leveillee Scott CastleScott Castle Miami, FL More articles by this author , Vladislav GorbatiyVladislav Gorbatiy Miami, FL More articles by this author , Nelson SalasNelson Salas Miami, FL More articles by this author , Watid KarnjanawanichkulWatid Karnjanawanichkul Miami, FL More articles by this author , and Raymond LeveilleeRaymond Leveillee Miami, FL More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.1520AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES With the increased incidence of low stage renal cancers, thermal ablation technology has emerged as a viable treatment option. Current AUA guidelines include thermal ablation as a treatment modality in select individuals. We present an 8-year, single institution experience with radiofrequency ablation (RFA) of small renal masses. METHODS We reviewed our prospectively collected RFA database of patients with renal masses treated from Nov 2001 to Aug 2010 undergoing laparoscopic or CT guided percutaneous RFA with or without simultaneous peripheral fiber-optic thermometry (Lumasense, Santa Clara, CA). Data was collected for patient demographics, surgical outcomes, and clinico-pathologic outcomes. RESULTS A total of 291 patients (208 male, 83 female) aged 31–88 years (mean 67) with 308 renal tumors underwent laparoscopic (116) or percutaneous (192) RFA with CT guidance. 11 patients had more than 1 tumor ablated during surgery (11 Lap, 6 CT, one patient with 6 ablations), and 38 (13%) had no peripheral thermometry. 115 complications occurred in 73 patients, where 74, 16, 11, 4 were Clavien grade I, II, III, IV respectively. 155 Right-sided and 153 Left sided tumors had a mean size of 2.6cm (0.8–5.3). Intraoperative biopsy, prior to ablation, was performed in 304/308 (98.7%) tumors, with 204 (67%) being Renal Cell Carcinoma (RCC), 84 (28%) benign tumors, 14 (4.6%) with an indeterminate biopsy, and 1 biopsy with metastatic lung cancer. Patients were followed by contrast enhanced CT scans at 1 month, 6 months, and annually with a mean follow-up of 20.6 months (0.5–84). Nine patients were followed with a non-contrast MRI due to renal insufficiency. 14/204 (6.9%) patients with RCC had persistent enhancement on follow-up imaging. Of those, 10 patients underwent re-ablation with concurrent biopsy whereas 3 patients chose to undergo a re-biopsy, and one refused biopsy. Six patients had persistent RCC on biopsy. Biopsy proven recurrence rate was 2.9%. Two patients died due to metastatic RCC, and 6 of other causes. Cancer free survival rate was 99.0% at mean follow up of 20.6 months. Patients had a no change in renal function based on preoperative and postoperative eGFR. CONCLUSIONS RFA has shown to be clinically effective, nephron-sparing and safe the treatment of small renal masses. Our large cohort adds to the building evidence for the efficacy of RFA for small renal masses. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e613 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Scott Castle Miami, FL More articles by this author Vladislav Gorbatiy Miami, FL More articles by this author Nelson Salas Miami, FL More articles by this author Watid Karnjanawanichkul Miami, FL More articles by this author Raymond Leveillee Miami, FL More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Initial Experience Using Microwave Ablation Therapy for Renal Tumor Treatment: 18-Month Follow-up

To assess efficacy and morbidity of microwave ablation (MWA) for small renal tumors in an initial cohort of patients. MWA is a recently introduced thermal needle ablation treatment modality with theoretical advantages compared with radiofrequency ablation, such as greater intratumoral temperatures, lack of a grounding pad, and superior convection profile. However, experience has been limited in the human kidney. Ten patients with a single, solid-enhancing renal tumor from June 2008 to November 2008 received laparoscopic or computed tomography-guided percutaneous MWA at a tertiary referral center with ≥14 months of follow-up. MWA was performed using the Valleylab Evident, 915-MHz MWA system at 45 W with intraoperative biopsy before ablation, and peripheral fiberoptic thermometry to determine the treatment endpoints. The patients were followed up with contrast-enhanced computed tomography at 1 month, 6 months to 1 year, and annually to monitor for tumor recurrence. The follow-up duration for the 6 male and 4 female patients (mean tumor size 3.65 cm, range 2.0-5.5; mean age 69.8 years) was 17.9 months. The recurrence rate, defined by persistent enhancement, was 38% (3 of 8). The intraoperative and postoperative complication rate was 20% and 40%, respectively. MWA resulted in poor oncologic outcomes with a significant complication rate at an intermediate level of follow-up. However, MWA has promising theoretical advantages and should not be discarded. Additional studies should be considered to better understand the microwave-tissue interaction and treatment endpoints for different size renal masses before widespread use.

Simultaneous microwave heating and three-dimensional MRI temperature mapping

Abstract In microwave processing a number of microwave specific factors cause non-uniform heating patterns with hot and cold spots. Hence, the quality and safety of food products can be compromised. Capabilities for creating three-dimensional temperature maps are therefore essential for control, optimisation and validation of microwave heating processes. This paper will discuss the advantages and shortcomings of different techniques for measuring temperatures in electromagnetic fields. The unique possibilities of applying non-invasive magnetic resonance imaging (MRI) for temperature mapping are demonstrated by experiments. In particular, in-situ measurements with three-dimensional isotropic resolution of 1 mm and a reasonable temporal resolution of 13 s are presented and compared with infrared thermography and fibre optic thermometry. Numerical simulations are employed to assess the extent of two kinds of systematic errors involved in the MRI experiment. Industrial relevance The presented approach for measuring temperatures volumetrically in-situ during a microwave heating process allows for the determination of three-dimensional temperature distributions; hence hot and cold spots in the products can be detected. Although the experiments in this study have been conducted in a high-resolution MRI tomograph with a small sample diameter, the same approach works in larger scale medical tomographs with bores up to 1 m diameter, making it also relevant for industrial scale applications. The costs of an MRI tomograph are still high; however, having premium products where quality would be adversely affected by overheating and safety compromised by under-processing, the application of such technology would be of great benefit for the food industry. Two approaches for applying this technology in industrial applications are possible: 1. In-situ temperature measurement would allow for a feed-back control of the process, which is essential for microwave applications to be applied to processing of high quality products. 2. The technology can be used for random tests, which in turn allows for evaluating temperature performance (level and uniformity), as well as fine-tuning of coupled electromagnetics/CFD models to simulate and optimise processing lines. No calibration of such system is needed and only a small amount of unbound water has to be present in the product for the methodology to be applied on or close to an industrial processing line. With a feed-back controlled microwave process, which can be simulations or real processes, the main advantage of such applications, the increase of process rates due to the volumetric heating can be utilised and at the same time the quality of the treated product can be optimised and product safety can be ensured by improving temperature uniformity. Furthermore, regulatory bodies can be satisfied.

Spread of Thermal Energy and Heat Sinks: Implications for Nerve-Sparing Robotic Prostatectomy

During nerve-sparing robot-assisted laparoscopic prostatectomy, nerve injury caused by thermal energy is a concern. Using a porcine model, we studied thermal spread and queried whether vessels such as the prostatic pedicle may act as a heat sink, reducing the spread of thermal energy. Monopolar (MP) and bipolar (BP) cautery was applied laparoscopically on the anterior abdominal wall surface of six pigs with the da Vinci robot. Using fiberoptic thermometry (Luxtron Inc. Santa Clara, CA), temperatures were recorded with and without the interposed inferior epigastric vessels to evaluate the heat sink effect. Interposition of the inferior epigastric vessels definitively demonstrated a heat sink phenomenon: at 7 mm from the MP/BP energy source, temperatures rose 10.7 degrees C to 13.8 degrees C without interposed vessels versus only 1.9 degrees C to 2.5 degrees C when vessels were interposed (P < 0.001). The heat sink phenomenon suggests that the prostatic vascular pedicle should be protective of the neurovascular bundle during transection of the bladder neck during laparoscopic prostatectomy.