Accurate dose definition is vital for ensuring optimal radiation therapy (RT) outcomes. The combination of ionizing radiation acoustic imaging (iRAI) and volumetric ultrasound imaging (US) holds the potential for real-time and precise determination of the radiation dose on anatomical structures. We developed an iRAI-US dual-modality system, utilizing a custom 2D matrix array transducer for iRAI and a commercial 2D MAT for US. The studies on phantoms quantified the system performance, and then the experiments using a rabbit liver model in vivo achieved online monitoring of dose on anatomy during RT in real time. These findings demonstrated the potential of iRAI-US combined imaging for personalized RT with improved efficacy and safety.
Ionizing radiation acoustic imaging (iRAI) provides the potential to map the radiation dose during radiotherapy in real time. Described here is the development of iRAI volumetric imaging system in mapping the three-dimensional (3D) radiation dose deposition of clinical radiotherapy treatment plan with patient receiving radiation to liver tumor. The real-time visualizations of radiation dose delivered have been archived in patients with liver tumor under a clinical linear accelerator. This proof-of-concept study demonstrated the potential of iRAI to map the dose distribution in deep body during radiotherapy, potentially leading to personalized radiotherapy with optimal efficacy and safety.
Ionizing radiation acoustic imaging (iRAI) provides the potential to map the radiation dose during radiotherapy in real time. Described here is our recent development of an iRAI volumetric imaging system in mapping the three-dimensional (3D) radiation dose deposition of a complex clinical radiotherapy treatment plan. Temporal 3D dose accumulation of a treatment plan was first imaged in a phantom. Then, semi-quantitative iRAI measurements were verified with rabbit liver model in vivo. Finally, for the first time, real-time visualization of radiation dose delivered deep in a patient with liver metastases was successfully performed. These studies demonstrate the potential of iRAI to map the dose distribution in deep body during radiotherapy, potentially leading to personalized radiotherapy with optimal efficacy and safety.
This erratum corrects an error in “Measuring temporal stability of positron emission tomography standardized uptake value bias using long-lived sources in a multicenter network,” by D. Byrd et al.
Radiomics is the process of analyzing radiological images by extracting quantitative features for monitoring and diagnosis of various cancers. Analyzing images acquired from different medical centers is confounded by many choices in acquisition, reconstruction parameters and differences among device manufacturers. Consequently, scanning the same patient or phantom using various acquisition/reconstruction parameters as well as different scanners may result in different feature values. To further evaluate this issue, in this study, CT images from a physical radiomic phantom were used. Recent studies showed that some quantitative features were dependent on voxel size and that this dependency could be reduced or removed by the appropriate normalization factor. Deep features extracted from a convolutional neural network, may also provide additional features for image analysis. Using a transfer learning approach, we obtained deep features from three convolutional neural networks pre-trained on color camera images. An we examination of the dependency of deep features on image pixel size was done. We found that some deep features were pixel size dependent, and to remove this dependency we proposed two effective normalization approaches. For analyzing the effects of normalization, a threshold has been used based on the calculated standard deviation and average distance from a best fit horizontal line among the features’ underlying pixel size before and after normalization. The inter and intra scanner dependency of deep features has also been evaluated.
Positron emission tomography (PET) is a quantitative imaging modality, but the computation of standardized uptake values (SUVs) requires several instruments to be correctly calibrated. Variability in the calibration process may lead to unreliable quantitation. Sealed source kits containing traceable amounts of Ge68 / Ga68 were used to measure signal stability for 19 PET scanners at nine hospitals in the National Cancer Institute’s Quantitative Imaging Network. Repeated measurements of the sources were performed on PET scanners and in dose calibrators. The measured scanner and dose calibrator signal biases were used to compute the bias in SUVs at multiple time points for each site over a 14-month period. Estimation of absolute SUV accuracy was confounded by bias from the solid phantoms’ physical properties. On average, the intrascanner coefficient of variation for SUV measurements was 3.5%. Over the entire length of the study, single-scanner SUV values varied over a range of 11%. Dose calibrator bias was not correlated with scanner bias. Calibration factors from the image metadata were nearly as variable as scanner signal, and were correlated with signal for many scanners. SUVs often showed low intrascanner variability between successive measurements but were also prone to shifts in apparent bias, possibly in part due to scanner recalibrations that are part of regular scanner quality control. Biases of key factors in the computation of SUVs were not correlated and their temporal variations did not cancel out of the computation. Long-lived sources and image metadata may provide a check on the recalibration process.
Large variability in computed tomography (CT) radiomics feature values due to CT imaging parameters can have subsequent implications on the prognostic or predictive significance of these features. Here, we investigated the impact of pitch, dose, and reconstruction kernel on CT radiomic features. Moreover, we introduced correction factors to reduce feature variability introduced by reconstruction kernels. The credence cartridge radiomics and American College of Radiology (ACR) phantoms were scanned on five different scanners. ACR phantom was used for 3-D noise power spectrum (NPS) measurements to quantify correlated noise. The coefficient of variation (COV) was used as the variability assessment metric. The variability in texture features due to different kernels was reduced by applying the NPS peak frequency and region of interest (ROI) maximum intensity as correction factors. Most texture features were dose independent but were strongly kernel dependent, which is demonstrated by a significant shift in NPS peak frequency among kernels. Percentage improvement in robustness was calculated for each feature from original and corrected %COV values. Percentage improvements in robustness of 19 features were in the range of 30% to 78% after corrections. We show that NPS peak frequency and ROI maximum intensity can be used as correction factors to reduce variability in CT texture feature values due to reconstruction kernels.
Clinical trials that evaluate cancer treatments may benefit from positron emission tomography (PET) imaging, which for many cancers can discriminate between effective and ineffective treatments. However, the image metrics used to quantify disease and evaluate treatment may be biased by many factors related to clinical protocols and PET system settings, many of which are site- and/or manufacturer-specific. An observational study was conducted using two surveys that were designed to record key sources of bias and variability in PET imaging. These were distributed to hospitals across the United States. The first round of surveys was designed and distributed by the American College of Radiology’s Centers of Quantitative Imaging Excellence program in 2011. The second survey expanded on the first and was completed by the National Cancer Institute’s Quantitative Imaging Network. Sixty-three sites responded to the first survey and 36 to the second. Key imaging parameters varied across participating sites. The range of reported methods for image acquisition and reconstruction suggests that signal biases are not matched between sites. Patient preparation was also inconsistent, potentially contributing additional variability. For multicenter clinical trials, efforts to control biases through standardization of imaging procedures should precede patient measurements.
KEYWORDS: Tumors, Tissues, Solids, Temperature metrology, Laser ablation, Mouse models, Ultrasonography, Breast cancer, In vivo imaging, Connective tissue
Purpose: Develop a new combination therapy consisting of cryoablation and conductive high-temperature
ablation for enhanced thermal ablation of solid tumors.
Methods: We have constructed an invasive probe that can be used for consecutive cryoablation and hightemperature
ablation (C/HTA), with a single insertion. The C/HTA probe was tested, in Balb/c mice bearing
solid 4T1 tumors, in comparison to cryoablation and high temperature ablation, only. Three days after
ablation, the diameter of the ablated zone was evaluated with pathological examination.
Results: The C/HTA device can be used to induce larger ablation zones, in comparison to high temperature or
cryoablation alone, and at lower thermal doses and temperatures than either modality alone.
Conclusions: The relatively high thermal conductivity of ice, in comparison to water and native tissue,
enables rapid heating of the ice-ball that result in improved conductive high temperature ablation. The new
dual thermal modality improves ablation outcomes at lower thermal doses in comparison to a single ablation
modality.
The effects of sweat gland ducts (SGD) on specific absorption rate and temperatures during millimeter wave
irradiation of skin were investigated with a high resolution finite differences time domain model consisting of
a 30 μm stratum corneum (SC), a 350 μm epidermis, 1000 μm dermis and five SGD (60 μm radius, 300 μm
height, 370 μm separation). The source was a WR-10 waveguide irradiating at 94 GHz. Without SGD, specific
absorption rate (SAR) and temperature maximum were in the dermis near epidermis. With SGD, a higher SAR
maximum was inside SGD in the epidermis while temperature maximum moved to the epidermis/stratumcorneum
junction. SGD significantly affected how GHz waves were absorbed in the skin. Implications of
these finding in nociceptive research will be discussed as well as other potential medical applications.
The SonoKnife is a scan-able high intensity line-focused ultrasound device for thermal ablation (52 - 60°C) of
superficially located advanced tumors or nodal disease in the head and neck. Based on preliminary simulation results, a
prototype cylindrical section transducer operating at 3.5 MHz, with a 60 mm radius of curvature, an elevation of 30 mm
and an aperture of 60 mm, was constructed for laboratory testing. The three-dimensional distribution of the acoustic field
was measured in water and compared to preliminary numerical results. Ablation experiments were performed in gel
phantoms, in porcine liver ex vivo and in live piglets. The experimental results agreed well with the theoretical
simulations and showed that the SonoKnife transducer had a narrow acoustic edge and is able to ablate living biological
tissues at practical power levels.
The purpose is to develop a patient-specific treatment planning method for a cylindrically-focused (i.e.,
SonoKnife) ultrasound thermal therapy system to optimize the thermal treatment of locally-advanced head and neck
squamous cell carcinomas (HNSCC) and/or positive lymph nodes. To achieve a more efficient and effective treatment, a
temperature-based treatment planning was devised, which was composed of : (1) a 3D acoustic-thermal model has been
developed to simulate the acoustic field, temperature distribution, and thermal dose coverage induced by the SonoKnife
applicator. (2) A 3D relevant anatomical structures (e.g. the H&N tumors, bones and cavities) were reconstructed based
on multislice CT scans. A step-and-shoot strategy was devised to perform the treatment, in which the initial applied
power levels, placement of the transducers, and sonication times per scan were determined by conducting a temperature-based
forward simulation. The maximum temperature, thermal dose coverage of target, and thermal exposure to
surrounding tissue were analyzed. For performance evaluation, the treatment planning was applied on representative
examples obtained from the clinical radiation therapy of HNSCC and positive lymph nodes. This treatment planning
platforms can be used to guide applicator placement, set-up configurations, and applied power levels prior to delivery of
a treatment or for post-procedure analysis of temperature distributions.
An ultrasonic system capable of Lateral Power Conformability, Penetration Depth Control (PDC), and the ability to deliver hyperthermia concomitantly with external beam radiation is being developed. PDC is achieved by simultaneously insonating with beams of low (1 MHz) and high (5 MHz) frequency. This paper presents a sono-thermal numerical evaluation of the impact of PDC on thermal dose in the treatment of chest wall volumes. The main goal is to assess the potential advantages of impedance-mismatched interface depth-mapping, using therapy transducers in A-scan mode, to select optimal relative output intensities of the beams as a function of bone and lung depths. Simulation results for a representative chest wall anatomy showed that there exists a strong relationship between optimal relative output intensities and bone/lung depth for maximum thermal dose and minimum muscle-bone interface temperature. Consequently, interface depth-mapping prior to a dual- frequency ultrasound hyperthermia treatment would provide patient-specific data useful for selecting PDC parameters that maximize thermal dose and minimize bone heating.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.