Comparison of the effect of two different bone-targeted radiofrequency ablation (RFA) systems alone and in combination with percutaneous vertebroplasty (PVP) on the biomechanical stability of the metastatic spine.

INTRODUCTION: Radiofrequency ablation (RFA) and percutaneous vertebroplasty (PVP) are used independently and in combination to treat metastatically involved vertebrae with the aim of relieving pain, reducing tumour burden and providing bony mechanical stabilization. PURPOSE: The aim of this work was to characterize the effect of two bone-targeted RFA devices, alone and in combination with PVP, to improve strength and mechanical stability in vertebrae with osteolytic metastatic disease. METHODS: Simulated spinal metastases (n = 12) were treated with one of two bone-targeted RFA devices (bipolar cooled or bone coil RF electrodes), followed by PVP. Under axial compressive loading, spinal canal narrowing was measured in the intact specimen, after tumour simulation, post-RFA and post-PVP. RESULTS: RFA alone resulted in successful tumour shrinkage and cavitation, but further increased canal narrowing under loading. RFA combined with PVP significantly reduced posterior wall stability in samples where sufficient tumour shrinkage and cavitation were coupled with a pattern of cement deposition which extended to posterior vertebral body. CONCLUSIONS: RFA combined with cement deposition in the posterior vertebral body demonstrates significantly more stable vertebrae under axial loading.

The opportunity and strategy for quality and health-system improvement now and in the future.

Since 2004, Cancer Care Ontario (CCO) has played a leadership role in linking funding to quality of care, and in using evidence and administrative and clinical data to drive performance and quality improvement. This article describes how CCO has used its cancer and renal health system strategies to establish an environment of continuous health system improvement. The article also describes how CCO's Corporate Strategy is driving organizational improvement: evolving CCO's capacity and capability to drive quality and value across healthcare settings, and its ability to advance broader health system transformation in support of cancer and renal patients.

Provincial and regional accountability for performance is critical in non-integrated health systems.

Clinical integration based on care paths and clinical information at the patient level is critical to ensure quality care. Moreover, effective clinical integration can occur in non-integrated health delivery systems. However, one of the challenges of a lack of integration at the system level is that no one organization or provider is responsible for an individual patient's journey. For the benefits of local clinical integration to be realized, clear accountability for performance at the regional and provincial level must be established.

The value of collecting population-based cancer stage data to support decision-making at organizational, regional and population levels.

The stage of a patient's cancer at diagnosis is essential to predict the prognosis and plan the treatment. Since 2008, stage data have been collected on all Ontario patients with breast, colorectal, lung and prostate cancers and are linked to other data collected by Cancer Care Ontario. Here, an analysis of such data is presented. How it can be used to assess the value of screening programs, inform resource allocation, evaluate compliance with treatment guidelines, compare survival trends and enhance the spectrum of cancer control activities across the province is demonstrated. International comparisons can also be made.

Radiofrequency coil for the creation of large ablations: ex vivo and in vivo testing.

PURPOSE: Various radiofrequency (RF) ablation electrode designs have been developed to increase ablation volume. Multiple heating cycles and electrode positions are often required, thereby increasing treatment time. The objective of this study was to evaluate the performance of a high-frequency monopolar induction coil designed to produce large thermal lesions (>3 cm) with a single electrode insertion in a treatment time of less than 10 minutes. MATERIALS AND METHODS: A monopolar nitinol interstitial coil operated at 27.12 MHz and 200 W was evaluated. Ex vivo performance was tested in excised bovine liver (n = 22). In vivo testing (n = 10) was conducted in livers of seven Yorkshire pigs. Visual inspection, contrast-enhanced computed tomography (CT), and pathologic evaluation of ablation zones were performed. RESULTS: Average ablation volumes in ex vivo and in vivo tests were 60.5 cm(3) ± 14.1 (5.9 × 4.4 × 4.4 cm) and 57.1cm(3) ± 13.8 (6.1 × 4.5 × 4.1cm), with average treatment times of 9.0 minutes ± 3.0 and 8.4 minutes ± 2.7, respectively. Contrast-enhanced CT ablation volume measurements corresponded with findings of gross inspection. Pathologic analysis showed morphologic and enzymatic changes suggestive of tissue death within the ablation zones. CONCLUSIONS: The RF ablation coil device successfully produced large, uniform ablation volumes in ex vivo and in vivo settings in treatment times of less than 10 minutes. Ex vivo and in vivo lesion sizes were not significantly different (P = .53), suggesting that the heating efficiency of this higher-frequency coil device may help to minimize the heat-sink effect of perfusion.

Creating a system for performance improvement in cancer care: Cancer Care Ontario's clinical governance framework.

BACKGROUND: Good governance, clinician engagement, and clear accountabilities for achieving specific outcomes are crucial components for improving the quality of care at both an organizational and health system level. METHODS: This article describes the benefits and results reported by Cancer Care Ontario (CCO) in transforming from a direct provider of cancer services to an organization whose responsibilities include improving the quality of care across the province's cancer system. The significant challenges in establishing accountability in the absence of direct operational authority are discussed. Case examples illustrate how the structures and processes created through CCO's clinical governance framework achieved measurable improvements in cancer care outcomes. RESULTS: Challenges in establishing accountability were addressed through the creation of a clinical governance framework that integrated clinical accountability with administrative accountability in an ongoing performance improvement cycle. The performance improvement cycle includes four key steps: (1) the collection of system-level performance data and the development of quality indicators, (2) the synthesis of data, evidence, and expert opinion into clear clinical and organizational guidance, (3) knowledge transfer through a coordinated program of clinician engagement, and (4) a comprehensive system of performance management through the use of contractual agreements, financial incentives, and public reporting. CONCLUSIONS: CCO has succeeded in developing a clinical governance and performance improvement system that measures and improves access to care in the treatment phase of the care continuum. Future efforts will need to focus on expanding quality improvement initiatives to all phases of cancer care, measuring the appropriateness of care, and improving the measurement and management of the patient cancer care experience.

Treatment planning and dose analysis for interstitial photodynamic therapy of prostate cancer.

With the development of new photosensitizers that are activated by light at longer wavelengths, interstitial photodynamic therapy (PDT) is emerging as a feasible alternative for the treatment of larger volumes of tissue. Described here is the application of PDT treatment planning software developed by our group to ensure complete coverage of larger, geometrically complex target volumes such as the prostate. In a phase II clinical trial of TOOKAD vascular targeted photodynamic therapy (VTP) for prostate cancer in patients who failed prior radiotherapy, the software was used to generate patient-specific treatment prescriptions for the number of treatment fibres, their lengths, their positions and the energy each delivered. The core of the software is a finite element solution to the light diffusion equation. Validation against in vivo light measurements indicated that the software could predict the location of an iso-fluence contour to within approximately +/-2 mm. The same software was used to reconstruct the treatments that were actually delivered, thereby providing an analysis of the threshold light dose required for TOOKAD-VTP of the post-irradiated prostate. The threshold light dose for VTP-induced prostate damage, as measured one week post-treatment using contrast-enhanced MRI, was found to be highly heterogeneous, both within and between patients. The minimum light dose received by 90% of the prostate, D(90), was determined from each patient's dose-volume histogram and compared to six-month sextant biopsy results. No patient with a D(90) less than 23 J cm(-2) had complete biopsy response, while 8/13 (62%) of patients with a D(90) greater than 23 J cm(-2) had negative biopsies at six months. The doses received by the urethra and the rectal wall were also investigated.

Doctors and Canadian Medicare: Improving Accountability and Performance.

Physician compensation has been a rapidly growing segment of healthcare costs in Canada since the late 1990s. In comparative terms, Canadian physicians are now well compensated compared to physicians in other high-income countries. This has caused provincial governments to begin constraining physician remuneration. However, physician payment should be examined in a larger governance context, including the potentially changing role of physicians, as provincial governments try to improve quality, increase coordination and improve overall health system performance. Although limited progress has been made through primary care reforms in a few jurisdictions, substantive improvement has been hampered by a misalignment between the policy goals and intentions of provincial governments and existing governance and accountability structures. This creates an environment in which both administrators and physicians feel they have limited input or control, seeding an adversarial rather than a collaborative relationship. Effective reform will require addressing governance and accountability at the same time as physician payment.

Value for Money through Effective Stewardship.

The respondents all raised valuable, informative points in response to our Invited Essay. There was convergence around the need to alter governance structures at the same time as payment arrangements for physicians to achieve higher-performing health systems within Canada. At the same time, there were different views on how best to address the disconnect between levels of physician remuneration and accountability for healthcare performance and delivery. In addition to ongoing efforts to improve governance, such as the recent amendments to the government-physician agreement in Alberta, individual provincial governments can and should take the lead in initiating and evaluating further payment and governance experiments.

Fast B-flow imaging: a method for improving frame rate in Golay coded B-flow imaging.

A technique for Golay coded B-flow imaging, called fast B-flow imaging, has been developed. This technique improves the frame rate of Golay coded B-flow imaging. In this technique, three instead of four input pulses are used to produce each scan line. A standard Golay pulse-pair is used as two of the three inputs, and pulse compression is performed upon receive returning the echoes from stationary (tissue) objects in the image. The third input is a repetition of one of the first two inputs. Upon receive, this pulse is cross correlated with an inverted copy of its input pulse. Addition of the cross-correlated signals produced from the identical input pulses results in the cancellation of the strong tissue echoes, and enables visualization of the weaker/moving blood echoes. Combining a small fraction of the tissue echoes with the weaker blood echoes allows both to be visualized in the same gray scale image. By using three instead of four input pulses, this technique can achieve a frame rate improvement of 33% compared with standard Golay coded B-flow imaging, with some loss in signal-to-noise ratio. The impact of axial and lateral motion on these techniques is examined. A quantitative comparison of both techniques is presented.

Characterization of changes in therapeutic ultrasound transducer performance over time using the angular spectrum method.

Strongly focused large aperture transducers used in high-intensity focused ultrasound treatments are prone to manufacturing defects and degradation. Current methods for evaluating transducer quality measure only bulk physical changes of transducers. We have determined the pressure distribution at the transducer surface, using the angular spectrum method, to detect defects of the transducer. Three therapeutic transducers were investigated. The pressure distribution at the focal plane of each transducer was measured and input into a back-projection algorithm to calculate the pressure distribution at the transducer surface. A number of scan window sizes were used for the pressure distribution measurement at the focal plane to determine the effect on the resolution of the calculated pressure distribution at the transducer surface. Results showed that one transducer might have suffered manufacturing defects. The second transducer degraded over 1 year of use with one half of the transducer suffering a partial loss of efficiency. The third transducer remained unchanged over 1 year. The scan window of 40 mm X 40 mm at the focal plane was required to identify defects 6 mm in diameter on the transducer surface. The results demonstrate that the angular spectrum method could be a useful tool for evaluating transducer quality.

Golay pulse encoding for microbubble contrast imaging in ultrasound.

We present a technique that uses Golay phase encoding, pulse inversion, and amplitude modulation (GPIAM) for microbubble contrast agent imaging with ultrasound. This technique improves the contrast-to-tissue ratio (CTR) by increasing the time-bandwidth product of the insonating waveforms. A nonlinear pulse compression algorithm is used to compress the signal energy upon receive. A 6.5-dB improvement in CTR was observed using an 8-chip GPIAM sequence compared to a conventional pulse-inversion amplitude-modulation sequence. The CTR improvement comes at the cost of a reduction in frame rate: GPIAM coding uses four input pulses whereas most contrast imaging sequences require two or three pulses. Our results showed that the microbubble response can be phase encoded and subsequently compressed using a nonlinear matched-filtering algorithm, in order to enhance the signal from the contrast agent, while maintaining resolution and suppressing the tissue signal.

Development of a novel loosely wound helical coil for interstitial radiofrequency thermal therapy.

We have developed a novel, radiofrequency thermal therapy device designed to improve local control of large solid tumours using heat in the range 55-90 degrees C. The device is a solenoid or helical coil designed to be loosely wound inside a tumour and excited with radiofrequency energy. Typically, we associate a uniform axially directed magnetic field with a solenoid coil, which when time varying, results in an electric field inside the coil, which lies mainly in the circumferential direction. In addition to this magnetically induced electric field, there exists a less familiar axially directed electric field inside the coil. Previous investigators have demonstrated the presence of this secondary axial electric field both experimentally and theoretically. Our design exploits the size and uniformity of these electric fields, for heating and coagulating a large tissue volume with a single applicator. The loosely wound solenoid is constructed from Nitinol, an electrically conductive shape memory alloy that permits the minimally invasive percutaneous insertion of the coil through a single cannulating delivery needle. To demonstrate the potential of this device and to determine the optimal frequency of operation, phantom tissue models and finite-element calculation models using COMSOL 3.2 were used to characterize frequency- and geometry-dependent trends in absorption rate density (ARD), which is proportional to electric field intensity. Radial and axial ARD profiles were measured, calculated and evaluated to determine the frequency and geometry best suited for producing large, homogenous coagulation volumes. Based on the trade-off between radial and axial uniformities of the ARD profiles, a 2 cm diameter coil with a 4 cm length and 1 cm pitch, operated at 27.12 MHz, produced the optimal heating pattern, as determined using tissue-mimicking phantom models.

The use of a dispersive ground electrode with a loosely wound helical coil for interstitial radiofrequency thermal therapy.

We have developed a novel, thermal therapy device designed to improve local control of large solid tumours using heat in the range 55-90 degrees C. The device is a helical coil designed to be loosely wound inside a tumour and excited with radiofrequency energy at 27.12 MHz. This design exploits the size and uniformity of the electric fields generated by magnetic induction inside this solenoidal geometry for heating and coagulating a large target volume. The use of the electrically conductive shape memory alloy Nitinol for the coil and an external ground plane permit the minimally invasive percutaneous insertion of the coil through a single cannulating delivery needle. To demonstrate the feasibility of this device, phantom models and finite-element models using COMSOL 3.2 were used to characterize uniformity of the radial and axial ARD (absorption rate density) profiles of different monopolar coil geometries. COMSOL 3.2 was also used to calculate temperature profiles and distributions produced by these coils in a non-perfused tissue-mimicking domain following a 10 min heating period. ARD results showed that optimum radial and axial uniformities were achieved with a 0.75 cm pitch and 3 cm length for a 1.5 cm diameter coil, and a 1.4 cm pitch and 4.2 cm length for a 2 cm diameter coil. These coils were able to produce lesions in excised bovine liver of 4 cm x 4.5 cm and 3.5 cm x 6.5 cm, respectively. Predicted temperature profiles showed similar profile sizes and shapes in a non-perfused domain, with the absolute temperature rise determined by the source input to the coil. These results demonstrate the potential of this interstitial, monopolar induction coil device for heating large tumours using a single applicator delivered through a single needle insertion.

High-frequency ultrasound for monitoring changes in liver tissue during preservation.

Currently the only method to assess liver preservation injury is based on liver appearance and donor medical history. Previous work has shown that high-frequency ultrasound could detect ischemic cell death due to changes in cell morphology. In this study, we use high-frequency ultrasound integrated backscatter to assess liver damage in experimental models of liver ischemia. Ultimately, our goal is to predict organ suitability for transplantation using high-frequency imaging and spectral analysis techniques. To examine the effects of liver ischemia at different temperatures, livers from Wistar rats were surgically excised, immersed in phosphate buffer saline and stored at 4 and 20 degrees C for 24 h. To mimic organ preservation, livers were excised, flushed with University of Wisconsin (UW) solution and stored at 4 degrees C for 24 h. Preservation injury was simulated by either not flushing livers with UW solution or, before scanning, allowing livers to reach room temperature. Ultrasound images and corresponding radiofrequency data were collected over the ischemic period. No significant increase in integrated backscatter (approximately 2.5 dBr) was measured for the livers prepared using standard preservation conditions. For all other ischemia models, the integrated backscatter increased by 4-9 dBr demonstrating kinetics dependent on storage conditions. The results provide a possible framework for using high-frequency imaging to non-invasively assess liver preservation injury.

Helical coil electrode radiofrequency ablation designed for application in osteolytic vertebral tumors--initial evaluation in a porcine model.

BACKGROUND CONTEXT: Radiofrequency ablation (RFA) is emerging as a complementary treatment for vertebral metastases. Traditional RFA induces frictional heating leading to local tissue necrosis but often yields small, incomplete, and inhomogeneous zones of ablation in bone. We have developed a new bone-specific RFA electrode that uses a nontraditional frequency (27.12 MHz) and geometry (helical), exploiting a magnetic field and an electric field to generate larger and more comprehensive treatment zones. PURPOSE: The purpose of the study was to evaluate the feasibility and safety of the Bone Coil RFA electrode in the spine. STUDY DESIGN: This is a preclinical in vivo study based on basic science. METHODS: Under institutional approval, six healthy Yorkshire pigs received a sham and an RF treatment in two adjacent cervical vertebrae. To deploy the Bone Coil RFA device in dense porcine vertebrae, a surgical approach was required; an irrigated coring drill bit created a cylindrical path in the vertebral bodies through which the RFA electrodes were placed. The electronic circuit was completed by four grounding pads. Treatment was delivered for 10 minutes at 20 W (n=1), 25 W (n=1), and 30 W (n=4). To monitor the thermal rise and for safety, fiber-optic probes recorded temperatures in the center of each coil and near the spinal foramen. After the procedure, animals were monitored for 2 weeks. Magnetic resonance imaging (MRI) was completed immediately after treatment and at 14 days. Magnetic resonance image segmentation and histology were used to evaluate the ablation volume. RESULTS: Comprehensive treatment of the porcine vertebrae was demonstrated by temperature monitoring, MRI, and histology. Large zones of RF ablation were obtained (RF: 3.72±0.73 cm3 vs. sham: 1.98±0.16 cm3, p<.05), confined within the vertebral body. Internal temperatures were elevated with RF (66.1 °C-102.9 °C), without temperature rise outside of the vertebrae (38.2 °C ± 1.5 °C). Mobility, neurological responses, and behavior were normal, consistent with preprocedural examination. Magnetic resonance imaging best visualized ablation at Day 14. Histology revealed comprehensive homogeneous coagulative necrosis with little peripheral sign of repair. CONCLUSIONS: The Bone Coil RFA device created large intravertebral ablation volumes with no neurologic sequelae. Radiofrequency thermal ablation (clearly distinguished from the much smaller effects arising from core drilling) corresponded to the homogeneous necrosis visible on histology.

Theoretical evaluation of moderately focused spherical transducers and multi-focus acoustic lens/transducer systems for ultrasound thermal therapy.

Impractically long treatment times are required for highly focused spherical transducers to destroy large tumours because thermal lesions generated by these transducers are small and a large number of such lesions are required. Moderately focused spherical transducers and multi-focus acoustic lens/transducer systems can generate larger thermal lesions compared to those produced by highly focused spherical transducers, and therefore shorter treatment times can be expected. The decrease in total treatment time by the use of moderately focused spherical transducers and acoustic lens/transducer systems was quantified in this study. A 3D ultrasound thermal model was developed to predict thermal lesion volumes generated by ultrasound transducers. A target model was constructed in order to compare various transducer designs under identical treatment conditions and with identical treatment goals. A design method was developed to determine the thickness of lens elements for production of specified multi-focus fields. Then, a highly focused and a moderately focused spherical transducer, and an acoustic lens/transducer system were compared in terms of total time required to treat a tumour. These transducers had identical apertures and operating frequencies. The radius of curvature of the moderately focused spherical transducer was chosen such that the length of thermal lesions it generated over 10 s single exposures was slightly greater than that of the target. The lens/transducer system was designed to produce a 9 focus field. The simulation results show that for the treatment of a 2 x 2 x 2 cm3 tumour at a depth of 5 cm in the body, the highly focused spherical transducer, the moderately focused spherical transducer and the lens/transducer system required 150, 42 and 30 min, respectively.

Optimization of a beam shaping bolus for superficial microwave hyperthermia waveguide applicators using a finite element method.

Temperature inhomogeneity in hyperthermia treatments often limits the total thermal dose that can be delivered to the tumour region. To reduce such inhomogeneities, a prototype dynamically modifiable square array of saline-filled patches which attenuate microwave energy was developed for superficial treatments that use external microwave applicators. The array was situated inside the coupling water bolus that is often used with external applicators. The prototype has been previously tested clinically with promising results. A more complete theoretical analysis of the performance of this new bolus design and improvements to its design by modelling are presented here. The analysis was performed by performing five iterative simulations of the SAR pattern produced inside a tissue structure by a waveguide applicator with a water bolus containing the dynamic patch array attached. Between iterations the patch array configuration was modified in an attempt to improve the ability of the bolus to confine heating to an 'L'-shaped tumour region. These simulations were performed using the finite element method. The steady-state temperature profile was then computed using a finite element method based simulation of heat transfer that assumed a given applicator power level and water bolus temperature. Several iterations of these heat transfer simulations were performed with varying applicator power level and water bolus temperature to improve the confinement of heating to the target region. The analysis showed that the dynamic patch array should be capable of conforming heating to an 'L'-shaped target tumour region while limiting the heating to the surrounding normal tissue to an acceptable level.

Theoretical modelling, experimental studies and clinical simulations of urethral cooling catheters for use during prostate thermal therapy.

Urethral cooling catheters are used to prevent thermal damage to the urethra during thermal therapy of the prostate. Quantification of a catheter's heat transfer characteristics is necessary for prediction of the catheter's influence on the temperature and thermal dose distribution in periurethral tissue. Two cooling catheters with different designs were examined: the Dornier Urowave catheter and a prototype device from BSD Medical Corp. A convection coefficient, h. was used to characterize the cooling ability of each catheter. The value of the convection coefficient (h = 330 W m(-2) C(-1) for the Dornier catheter. h = 160 W m(-2) C(-1) for the BSD device) was obtained by comparing temperatures measured in a tissue-equivalent phantom material to temperatures predicted by a finite element method simulation of the phantom experiments. The coefficient was found to be insensitive to the rate of coolant flow inside the catheter between 40 and 120 ml min(-1). The convection coefficient method for modelling urethral catheters was incorporated into simulations of microwave heating of the prostate. Results from these simulations indicate that the Dornier device is significantly more effective than the BSD catheter at cooling the tissue surrounding the urethra.

Changes in dielectric properties at 460 kHz of kidney and fat during heating: importance for radio-frequency thermal therapy.

We have developed a system to measure the changes due to heating to high temperatures in the dielectric properties of tissues in the radio-frequency range. A two-electrode arrangement was connected to a low-frequency impedance analyser and used to measure the dielectric properties of ex vivo porcine kidney and fat at 460 kHz. This frequency was selected as it is the most commonly used for radio-frequency thermal therapy of renal tumours. Tissue samples were heated to target temperatures between 48 and 78 degrees C in a hot water bath and changes in dielectric properties were measured during 30 min of heating and 15 min of cooling. Results suggest a time-temperature dependence of dielectric properties, with two separate components: one a reversible, temperature-dependent effect and the other a permanent effect due to structural events (e.g. protein coagulation, fat melting) that occur in tissues during heating. We calculated temperature coefficients of 1.3 +/- 0.1% degrees C(-1) for kidney permittivity and 1.6% degrees C(-1) for kidney conductivity, 0.9 +/- 0.1% degrees C(-1) for fat permittivity and 1.7 +/- 0.1% degrees C(-1) for fat conductivity. An Arrhenius model was employed to determine the first-order kinetic rates for the irreversible changes in dielectric properties. The following Arrhenius parameters were determined: an activation energy of 57 +/- 5 kcal mol(-1) and a frequency factor of (6 +/- 1) x 10(34) s(-1) for conductivity of kidney, an activation energy of 48 +/- 2 kcal mol(-1) and a frequency factor of 6 x 10(28) s(-1) for permittivity of kidney. A similar analysis led to an activation energy of 31 +/- 4 kcal mol(-1) and a frequency factor of (4.43 +/- 1) x 10(16) s(-1) for conductivity of fat, and an activation energy of 40 +/- 4 kcal mol(-1) and a frequency factor of 4 x 10(22) s(-1) for permittivity of fat. Structural events occurring during heating at different target temperatures as determined by histological analyses were correlated with the changes in the measured dielectric properties.