An Optical Sensory System for Assessment of Residual Cancer Burden in Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy.

Breast cancer patients undergoing neoadjuvant chemotherapy (NAC) require precise and accurate evaluation of treatment response. Residual cancer burden (RCB) is a prognostic tool widely used to estimate survival outcomes in breast cancer. In this study, we introduced a machine-learning-based optical biosensor called the Opti-scan probe to assess residual cancer burden in breast cancer patients undergoing NAC. The Opti-scan probe data were acquired from 15 patients (mean age: 61.8 years) before and after each cycle of NAC. Using regression analysis with k-fold cross-validation, we calculated the optical properties of healthy and unhealthy breast tissues. The ML predictive model was trained on the optical parameter values and breast cancer imaging features obtained from the Opti-scan probe data to calculate RCB values. The results show that the ML model achieved a high accuracy of 0.98 in predicting RCB number/class based on the changes in optical properties measured by the Opti-scan probe. These findings suggest that our ML-based Opti-scan probe has considerable potential as a valuable tool for the assessment of breast cancer response after NAC and to guide treatment decisions. Therefore, it could be a promising, non-invasive, and accurate method for monitoring breast cancer patient's response to NAC.

Commissioning a four-dimensional Computed Tomography Simulator for minimum target size due to motion in the Anterior-Posterior direction: a procedure and treatment planning recommendations.

The purpose of this work is to develop a procedure for commissioning four-dimensional computed tomography (4DCT) algorithms for minimum target reconstruction size, to quantify the effect of anterior-posterior (AP) motion artifacts on known object reconstruction for periodic and irregular breathing patterns, and to provide treatment planning recommendations for target sizes below a minimum threshold. A mechanical platform enabled AP motion of a rod and lung phantom during 4DCT acquisition. Static, artifact-free scans of the phantoms were first acquired. AP sinusoidal and patient breathing motion was applied to obtain 4DCT images. 4DCT reconstruction artifacts were assessed by measuring the apparent width and angle of the rod. Comparison of known tumor diameters and volumes between the static image parameters with the 4DCT image sets was used to quantify the extent of AP reconstruction artifact and contour deformation. Examination of the rod width, under sinusoidal motion, found it was best represented during the inhale and exhale phases for all periods and ranges of motion. From the gradient phases, the apparent width of the rod decreased with increasing amplitude and decreasing period. The rod angle appeared larger on the reconstructed images due to the presence of motion artifact. The apparent diameters of the spherical tumors on the gradient phases were larger/equivalent than the true values in the AP/LR direction, respectively, while the exhale phase consistently displayed the spheres at the approximately correct diameter. The Eclipse calculated diameter matched closely with the true diameter on the exhale phase and was found to be larger on the inhale, MIP, and Avg scans. The procedure detailed here may be used during the acceptance and commissioning period of a computed tomography simulator or retroactively when implementing a SBRT program to determine the minimum target size that can be reliably reconstructed.

An approach for measuring the spatial orientations of a computed-tomography simulation system.

The quality assurance tests for measuring the spatial orientations between tabletop, external patient positioning lasers, couch longitudinal moving direction, and imaging plane in a CT simulation system are a complicated and time-consuming process. We proposed a simple and efficient approach to acquire the angular deviations of spatial orientations between these components. An in-house cross-jig was used in this study. We found a relationship between the orientations of the jig's arms shown on the CT images and the orientations of the components in a CT simulator. We verified this relationship with 16 misalignment orientations of known errors, to simulate all possible deviation situations. Generally, the tabletop and external lasers system are mounted separately in a CT simulation system; the former is on the couch trail, the later is on the wall and ceiling. They are independent to each other and will cause different effects on CT images. We only need two scans to acquire the angular deviations of our system: i) when aligning the cross-jig with tabletop, we can check the orientations between the tabletop, couch longitudinal moving direction, and imaging plane; ii) while aligning the cross-jig with the external axial lasers, we will know the angular deviation between the lasers, couch longitudinal moving direction, and imaging plane. The CT simulator had been carefully examined by performing the QA procedures recommended by the AAPM Task Group 66. The measurements of the spatial orientations using the proposed method agree well with TG 66 recommendations. However, the time taken to perform the QA using our method is considerably shorter than the method described in TG 66--5 minutes versus 30 minutes. The deliberate misalignment orientations tests with known errors were detected successfully by our in-house analysis program. The maximum difference between the known errors and the measured angles is only 0.07°. We determined that the relationship between the orientations of the jig's arms and the orientations of the CT components. By means of quantifying the deviations in degree we can correct the errors accurately. This approach can also be used to inspect the spatial orientations of other imaging systems, such as PET-CT and MRI.

Translation of a portable diffuse optical breast scanner probe for clinical application: a preliminary study.

Most breast cancer lesions absorb higher levels of near-infrared (NIR) radiation compared to healthy breast tissue due to its increased vascularity. Oxy-hemoglobin (HbO2) and deoxy-hemoglobin (Hb) primarily found in cancerous vascular lesions, absorbs higher levels of radiation in the 650 nm to 850 nm wavelength range than the surrounding fatty tissue and water in the human breast. NIR diffuse optical spectroscopy (DOS) provides real-time functional and compositional information based on the optical properties of biological tissues, which cannot be accomplished by other portable breast imaging modalities. Here we present the first set of clinical trials using a non-invasive, hand-held diffuse optical breast scanner (DOB-Scan probe3) to capture in vivo cross-sectional images of the breast. The scanner uses four NIR illuminating sources with different wavelengths, 690 nm, 750 nm, 800 nm, and 850 nm, to determine the concentrations of the four main constituents of breast tissue, oxy-hemoglobin (HbO2), deoxy-hemoglobin (Hb), water (H2O), and fat. In this paper, we briefly explain the hardware design and image reconstruction algorithm of the DOB-Scan probe, the data collection process, and the imaging results of four different participants, selected from twenty, all who are diagnosed with breast cancer. For each patient, images were scanned from two locations, the first over the cancerous lesion and the second over the same region on the contralateral healthy breast, as a means of establishing controls for comparison. During each scan, four cross-sectional images of the breast, corresponding to four different NIR wavelengths, are reconstructed and displayed on a user interface for reference. Clinical results confirm that the absorption coefficients of cancerous lesions are significantly higher than the normal surrounding tissue. We propose to deploy the probe to effectively identify cancerous breast tissue at an early stage in a primary care setting, which could increase the efficiency of screening programs.

Automated air kerma strength quality assurance of permanent seed implant prostate brachytherapy sources using vendor autoradiographs.

PURPOSE: To develop a novel quality assurance (QA) program to determine the air kerma strength (AKS) of brachytherapy seeds within preloaded needles using autoradiographs alone, without jeopardizing sterility or necessitating procedural changes either by the vendor or in the operating room. METHODS AND MATERIALS: Digital autoradiographs of QA seed orders and sterile preloaded needles were acquired. Regions of interest of each preloaded seed were determined through an iterative scanning process identifying changes from background levels to radioactivity exposure. Average exposure values through the center of each region of interest were fitted with a Gaussian curve and Full Width at Half Maximums (FWHMs) were calculated. The two-dimensional exposure-scaled FWHM (Exp2D) measurements for the QA seed orders were plotted against measured AKS values and related using a linear curve fit that was adjusted using the third-party assay average AKS and applied as a calibration curve to convert Exp2D to AKS. RESULTS: Estimated seed AKS was found to have a strong dependence on position within the holding tray because of imager positioning inconsistencies. Calculated seed AKS for patient-specific seed orders using the curve scaling factor varied from the nominal order AKS by 1.1 ± 0.9% and from the third-party assay measurements by 0.0 ± 0.4%. CONCLUSIONS: This work depicts a clinically useful tool to aid in QA of preloaded brachytherapy permanent seed implant needles without compromising sterility or increasing clinical workloads. With this procedure, each individual seed's AKS can be verified automatically before a patient's scheduled implant or retroactively when auditing patient records.

Validation of Three-dimensional Electronic Portal Imaging Device-based PerFRACTION™ Software for Patient-Specific Quality Assurance.

PURPOSE: PerFRACTION™ is a three-dimensional (3D) in vivo electronic portal imaging device-based dosimetry software. To validate the software, three phantoms with different inserts (2D array, ionization chamber, and inhomogeneity materials) were constructed to evaluate point dose and fluence map. MATERIALS AND METHODS: Phantoms underwent independent computed tomography simulation for planning and received repetitive fractions of volumetric modulated arc therapy, simulating prostate treatment. Fluence and absolute point dose measurements, PerFRACTION™ reconstructed doses, and the dose predictions of the planning system were compared. RESULTS: There was concordance between ionization chamber and PerFRACTION™ 3D absolute point dose measurements. Close agreement was also obtained between X- and Y-axis dose profiles with PerFRACTION™ calculated doses, MapCHECK measured doses, and planning system predicted doses. Setup shifts significantly influenced 2D gamma passing rates in PerFRACTION™ software. CONCLUSIONS: PerFRACTION™ appears reliable and valid under experimental conditions in air and with phantoms.

Dosimetric evaluation of Plastic Water Diagnostic-Therapy.

High-precision radiotherapy planning and quality assurance require accurate dosimetric and geometric phantom measurements. Phantom design requires materials with mechanical strength and resilience, and dosimetric properties close to those of water over diagnostic and therapeutic ranges. Plastic Water Diagnostic Therapy (PWDT: CIRS, Norfolk, VA) is a phantom material designed for water equivalence in photon beams from 0.04 MeV to 100 MeV; the material has also good mechanical properties. The present article reports the results of computed tomography (CT) imaging and dosimetric studies of PWDT to evaluate the suitability of the material in CT and therapy energy ranges. We characterized the water equivalence of PWDT in a series of experiments in which the basic dosimetric properties of the material were determined for photon energies of 80 kVp, 100 kVp, 250 kVp, 4 MV, 6 MV, 10 MV, and 18 MV. Measured properties included the buildup and percentage depth dose curves for several field sizes, and relative dose factors as a function of field size. In addition, the PWDT phantom underwent CT imaging at beam qualities ranging from 80 kVp to 140 kVp to determine the water equivalence of the phantom in the diagnostic energy range. The dosimetric quantities measured with PWDT agreed within 1.5% of those determined in water and Solid Water (Gammex rmi, Middleton, WI). Computed tomography imaging of the phantom was found to generate Hounsfield numbers within 0.8% of those generated using water. The results suggest that PWDT material is suitable both for regular radiotherapy quality assurance measurements and for intensity-modulated radiation therapy (IMRT) verification work. Sample IMRT verification results are presented.

Template-based Intensity-Modulated Radiation Therapy: A Cost-effective Intensity-Modulated Radiation Therapy Planning Procedure for Prostate Cancer.

INTRODUCTION: Intensity-modulated radiation therapy (IMRT) has been widely accepted for the treatment of prostate cancer. In comparison with traditional three-dimensional conformal radiation therapy (3D-CRT), it improves local control while minimizing side effects. However, IMRT comes at a significantly higher cost. In this report, we describe the development of template-based IMRT (TB-IMRT) planning for prostate cancer that does not require additional resources above 3D-CRT. METHODS: Twenty patients previously treated using 3D-CRT were retrospectively planned using the TB-IMRT planning technique. Planning target volume coverage, dose to organs at risk, and resource usage were compared between 3D-CRT and TB-IMRT techniques. RESULTS: All 3D-CRT and TB-IMRT plans met the planning guidelines. TB-IMRT compared better than 3D-CRT in terms of the homogeneity index (0.039 ± 0.007 vs. 0.052 ± 0.008) and conformity index (0.866 ± 0.024 vs. 0.752 ± 0.054). TB-IMRT also provided better sparing of organs at risk. Planning times were significantly less for TB-IMRT (average 13.43 ± 2.18 minutes) compared with conventional plans (45.4 ± 17.0 minutes). Times required for patient-specific quality assurance were similar between TB-IMRT and 3D-CRT. CONCLUSIONS: The TB-IMRT technique for prostate allows for all the potential benefits of IMRT without any additional resources above conventional 3D-CRT.

Fractionated stereotactic radiotherapy for the treatment of vestibular schwannomas: combined experience of the Toronto-Sunnybrook Regional Cancer Centre and the Princess Margaret Hospital.

PURPOSE: To evaluate the efficacy and toxicity of fractionated stereotactic radiotherapy (FSRT) for vestibular schwannomas in patients treated at two university-affiliated hospitals. METHODS AND MATERIALS: Thirty-nine patients were treated between April 1996 and September 2000. The median age was 56 years (range: 29-80), and median maximal tumor diameter was 20 mm (range: 9-40). A total of 11 patients had fifth and/or seventh cranial nerve dysfunction before irradiation; 2 patients had only facial weakness, 5 patients had only facial numbness, and 4 patients had both facial weakness and numbness. Thirty-three patients were treated with primary FSRT, and 6 patients were treated for recurrent or persistent disease after previous surgery. All patients were treated with 6-MV photons using a stereotactic system with a relocatable frame. The 39 patients received 50 Gy in 25 fractions over 5 weeks. Median follow-up was 21.8 months (range: 4.4-49.6). RESULTS: Local control was achieved in 37 patients (95%). Two patients experienced deterioration of their symptoms at 3 and 20 months as a result of clinical progression in one case and tumor progression in the other and underwent surgery post FSRT. A total of 19/28 (67.9%) patients preserved serviceable hearing after FSRT. Deterioration of the facial and trigeminal nerves was observed in only 2 patients who were treated with surgery post FSRT. CONCLUSION: FSRT provided excellent tumor control with minimal morbidity and good hearing preservation in this cohort of patients. Longer follow-up is required to confirm long-term control rates.

Template-based breast IMRT planning for increased workload efficiency.

BACKGROUND: To be less resource intensive, we developed a template-based breast IMRT technique (TB-IMRT). This study aims to compare resources and dose distribution between TB-IMRT and conventional breast radiation (CBR). METHODS: Twenty patients with early stage breast cancer were planned using CBR and TB-IMRT. Time to plan, coverage of volumes, dose to critical structures and treatment times were evaluated for CBR and TB-IMRT. Two sided-paired t tests were used. RESULTS: TB-IMRT planning time was less than CBR (14.0 vs 39.0 min, p < 0.001). Fifteen patients with CBR needed 18 MV, and 11 of these were planned successfully with TB-IMRT using 6 MV. TB-IMRT provided better homogeneity index (0.096 vs 0.124, p < 0.001) and conformity index (0.68 vs 0.59, p = 0.003). Dose to critical structures were comparable between TB-IMRT and CBR, and treatment times were also similar (6.0 vs 7.8 min, p = 0.13). CONCLUSIONS: TB- IMRT provides reduction of planning time and minimizes the use of high energy beams, while providing similar treatment times and equal plans compared to CBR. This technique permits efficient use of resources with a low learning curve, and can be done with existing equipment and personnel.

A three-isocenter jagged-junction IMRT approach for craniospinal irradiation without beam edge matching for field junctions.

PURPOSE: Traditionally craniospinal irradiation treats the central nervous system using two or three adjacent field sets. We propose a technique using a three-isocenter intensity-modulated radiotherapy (IMRT) plan (jagged-junction IMRT) which overcomes problems associated with field junctions and beam edge matching and improves planning and treatment setup efficiencies with homogenous target dose distribution. METHODS AND MATERIALS: Treatments for 3 patients with a prescription of 36 Gy in 20 fractions were retrospectively planned with jagged-junction IMRT and compared to conventional treatment plans. Planning target volume (PTV) included the whole brain and spinal canal to the S3 vertebral level. The plan used three field sets, each with a unique isocenter. One field set with seven fields treated the cranium. Two field sets treated the spine, each set using three fields. Fields from adjacent sets were overlapped, and the optimization process smoothly integrated the dose inside the overlapped junction. RESULTS: For jagged-junction IMRT plans vs. conventional technique, the average homogeneity index equaled 0.08 ± 0.01 vs. 0.12 ± 0.02, respectively, and conformity number equaled 0.79 ± 0.01 vs. 0.47 ± 0.12, respectively. The 95% isodose surface covered (99.5 ± 0.3)% of the PTV vs. (98.1 ± 2.0)%, respectively. Both jagged-junction IMRT plans and the conventional plans had good sparing of organs at risk. CONCLUSIONS: Jagged-junction IMRT planning provided good dose homogeneity and conformity to the target while maintaining a low dose to organs at risk. Results from jagged-junction IMRT plans were better than or equivalent to those from the conventional technique. Jagged-junction IMRT optimization smoothly distributed dose in the junction between field sets. Because there was no beam matching, this treatment technique is less likely to produce hot or cold spots at the junction, in contrast to conventional techniques. The planning process is also simplified as only one IMRT plan is required for the entire target volume.