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 The real-time visualizations of radiation dose delivered have been archived in patients with liver tumor under a clinical linear accelerator.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.
KEYWORDS: Radiotherapy, Associative arrays, Real time imaging, Acoustics, Ionizing radiation, In vivo imaging, 3D modeling, Transducers, Tissues, Liver
Ironizing radiation acoustic imaging (iRAI) is a novel imaging concept with the potential to map the radiation dose delivery in real time during external beam radiation therapy. In this study, iRAI volumetric dose mapping was achieved with 2D matrix transducer array using a C-shape 3D conformal treatment plan with clinically relevant setting and a moving beam plan in both phantoms and rabbit model in vivo. With the unique ability to map the volumetric dose delivery in real time, iRAI 3D dose mapping can be developed into a new tool for quantifying the accuracy of dose delivery of radiation therapy.
As a newly invented technology, ionizing radiation acoustic imaging (iRAI) provides a potential solution for in vivo dosimetry and real-time online monitoring of radiation beam position during external beam radiotherapy, including both conventional and FLASH radiotherapy. In this study, the dose resolution as low as 1% from a single pulse was achieved, demonstrating a clinically acceptable sensitivity of iRAI in mapping the dose deposition. The relative displacement of the radiation beam with respect to the target tissue can be visualized in real time by our clinically ready iRAI and ultrasound (US) dual-modality imaging system.
The strategy of Intensity-modulated radiotherapy (IMRT) is to deliver precise radiation doses to targeted area while minimizing the dose to surrounding healthy tissue. The intrafractional variations such as the movement of the patient or the respiratory motion, which most likely to cause misalignment during a session of radiotherapy, may compromise the outcome of the detailed dose delivery. This study examines the feasibility of real-time monitoring the alignment of the X-ray beam relative to treatment target during radiotherapy based on ultrasound (US) and X-ray acoustic (XA) dual-modality imaging. A dual-modality imaging system, which utilizes the US phase array for both US imaging and XA signal acquisition, was established based on the Verasonics US system. 2D US image achieved can be used to locate the target cancerous tissue, while 2D XA image acquired will show the shape and location of the X-ray field inside the same imaging plane quasi simultaneously. A phantom holding a large piece of veal liver, where parts of the liver tissue were removed from the middle and embedded with different types of bio-tissues (muscle, fat or kidney), was shot by the beams generated and modulated by a medical linear accelerator. The fusion images integrated with XA and US images quantitatively demonstrated whether the X-ray beam was delivered to the embedded bio-tissue with any mismatch in its shape or any shifts off the accurate position. The experiment results suggest that the US-XA dual-modality imaging is a potential tool for real-time monitoring the geometric alignment during radiotherapy.
To improve the precision in radiation therapy and optimize treatment strategies during the radiotherapy, in vivo radiation dosimetry monitoring which measures the actual dose received in and around target region during treatment becomes necessary. Given the fact that X-ray induced acoustic amplitude is proportionally correlating to X-ray absorption, we propose applying X-ray acoustic computed tomography (XACT) to monitor X-ray dosimetry during radiotherapy. A prototype X-ray acoustic (XA) detection system with single immersion ultrasound transducer, which was positioned by a motor controlled rotation stage, was synchronized with a medical linear accelerator to acquire the XA signal at each rotating position. A porcine gel phantom, which is embedded with equally spaced lard made cylindrical indicators, was shot by different X-ray beams modulated by physical wedge filters (with wedge angles of 15°, 30°, 45° and 60°). The reconstructed 2D XACT images not only showed the positions of the indicators but also displayed the different intensity profiles for each indicator, which had good correlations with the corresponding dose distributions captured in radiochromic film tests. A dose difference as small as 3.6% can be determined. Moreover, a phantom imitating complex scenario of body, which has lard made indicators covered by different materials (bone, muscle and air-gap), was shot by uniform beam. The variances of dose delivered to target regions suffering different attenuations were successfully presented in XACT images. The results of phantom experiments have proved that XACT can be a promising technique in monitoring the 2D dosimetry during radiotherapy with high sensitivity and good accuracy.
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