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Equity, Diversity, and Inclusion Are Essential in Medical Physics [Editorial]
Pollard-Larkin, Julianne M; Roth, Toni M; Seuntjens, Jan; Ngwa, Wilfred; Avery, Stephen; Osterman, Sunshine; Rivera, Judith; Perez-Andujar, Angelica; Castillo, Richard
PMID: 37179089
ISSN: 1879-355x
CID: 5542132
Replacing gamma knife beam-profiles on film with point-detector scans
Rudek, Benedikt; Bernstein, Kenneth; Osterman, Sunshine; Qu, Tanxia
PURPOSE/OBJECTIVE:Detector arrays and profile-scans have widely replaced film-measurements for quality assurance (QA) on linear accelerators. Film is still used for relative output factor (ROF) measurements, positioning, and dose-profile verification for annual Leksell Gamma Knife (LGK) QA. This study shows that small-field active detector measurements can be performed in the easily accessed clinical mode and that they are an effective replacement to time-consuming and exacting film measurements. METHODS:Beam profiles and positioning scans for 4-mm, 8-mm, and 16-mm-collimated fields were collected along the x-, y-, and z-axes. The Exradin W2-scintillator and the PTW microdiamond-detector were placed in custom inserts centered in the Elekta solid-water phantom for these scans. GafChromic EBT3-film was irradiated with single uniformly collimated exposures as the clinical-standard reference, using the same solid-water phantom for profile tests and the Elekta film holder for radiation focal point (RFP)/patient-positioning system (PPS) coincidence. All experimental data were compared to the tissue-maximum-ratio-based (TMR10) dose calculation. RESULTS:The detector-measured beam profiles and film-based profiles showed excellent agreement with TMR10-predicted full-width, half-maximum (FWHM) values. Absolute differences between the measured FWHM and FWHM from the treatment-planning system were on average 0.13 mm, 0.08 mm, and 0.04 mm for film, microdiamond, and scintillator, respectively. The coincidence between the RFP and the PPS was measured to be ≤0.5 mm with microdiamond, ≤0.41 mm with the W2-1 × 1 scintillator, and ≤0.22 mm using the film-technique. CONCLUSIONS:Small-volume field detectors, used in conjunction with a clinically available phantom, an electrometer with data-logging, and treatment plans created in clinical mode offer an efficient and viable alternative for film-based profile tests. Position verification can be accurately performed when CBCT-imaging is available to correct for residual detector-position uncertainty. Scans are easily set up within the treatment-planning-system and, when coupled with an automated analysis, can provide accurate measurements within minutes.
PMID: 35001499
ISSN: 1526-9914
CID: 5118292
Comparing ArcCHECK and Portal Dosimetry Gamma Index Scores for VMAT TBI [Meeting Abstract]
Rembish, J.; Taneja, S.; Osterman, K.; Bice, N.; Teruel, J.; Barbee, D.
ISI:000808579201049
ISSN: 0094-2405
CID: 5740962
Probabilistic Interpretation of a Single-Isocenter Multi-Target SRS Robustness Analysis [Meeting Abstract]
Bice, N.; Xue, J.; Osterman, K.; Barbee, D.; Galavis, P.; Qu, T.; Teruel, J.
ISI:000808579201035
ISSN: 0094-2405
CID: 5740942
Dosimetric Characterization of Patient Setup Uncertainty for Patients Treated with Craniospinal Irradiation Using a VMAT Approach [Meeting Abstract]
Osterman, K.; Barbee, D.; Teruel, J.; Taneja, S.; Cooper, B.; Zhang, J.
ISI:000808579200039
ISSN: 0094-2405
CID: 5740932
Streamlining complex multi-isocentric VMAT based treatment delivery using a newly developed software tool [Meeting Abstract]
Teruel, J; Galavis, P; Osterman, K; Taneja, S; Cooper, B; Gerber, N; Hitchen, C; Barbee, D
Purpose: Multi-isocentric treatment delivery for CSI and TBI poses specific challenges for treatment delivery. We have developed a software tool to streamline all aspects of delivery for therapists and physicists at the machine, as well as to inform attending physicians of setup variability and image residuals at different locations.
Method(s): Our institution delivers VMAT-based CSI and TBI with up to 3 and 7 isocenters, respectively. A software tool was developed to assist with treatment delivery including initial patient setup, patient imaging, automatic calculation of the optimal global shift based on each isocenter's ideal shift, and automatic calculation of each isocenter's couch coordinates. Initial treatment couch coordinates are queried via the Eclipse scripting API. The global shift was calculated prioritizing the head isocenter for CSI treatments and the chest isocenter for TBI treatments by first maximizing residual tolerance at any other location prior to accepting any residual deviation at these locations. Maximum residuals tolerance was determined based on target margins, plan uncertainty and as per physician instructions. Delivery parameters are reported to a document uploaded to ARIA via API.
Result(s): The developed tool was employed for 11 cases. The software tool replaced the need for plan shift comments or instructions for therapists. In particular, its use eliminated the need to provide isocenter shifts to therapists by directly providing final couch parameters for treatment, greatly reducing the risk of delivery errors. The software effectively informed the therapists if any expected tolerance was surpassed, triggering a patient setup evaluation.
Conclusion(s): The described software tool is a core component to our multi-isocenter treatment programs and has streamlined delivery of these complex techniques that would otherwise require complicated instructions, including multiple shifts and on-the-fly calculations of optimal image alignment based on multiple imaging locations. This has substantially reduced the possibility of delivery errors
EMBASE:635748300
ISSN: 0094-2405
CID: 4987622
Comparison of kV-CBCT dose measurement techniques for annual Linac QA [Meeting Abstract]
Rudek, B; Osterman, K; Xue, J
Purpose: Modern linear accelerators (LINACs) are equipped with kV-imaging systems for 2D-images and 3D-cone-beam CT (CBCT). The delivered single kV-CBCT-dose is small compared to the treatment dose but can add up to a cumulative dose of 1-3% for multi-fraction courses according to TG180. Thus, TG142 recommends an annual assessment of the imaging dose. The purpose of this project was to review the current practice, compare approaches suggested in recent literature and standardize annual kV-CBCT dose measurements.
Method(s): Current institutional practice is to measure the CBCT dose with the 10cmlong RaySafe X2 pencil-ion-chamber inserted in the center position of a CIRS lung phantom. We introduced the PMMA-CTDI phantom in a satellite-location for all measurements. Dose was measured at 3/6/9/12 o'clock and center positions of a 32cm-wide CTDI phantom to determine max dose heterogeneity for a half-trajectory imaging protocol and at the 12 o'clock and center position of either the head or abdomen phantom for 11 protocols ranging from 80kVp/100mAs to 140kVp/1688mAs using the Raysafe X2, the Standard Imaging A101 pencil-ion-chamber, and the A12 Farmer-ion-chamber. Measurements were repeated with decreased kV-tube-collimator opening as suggested by Varian.
Result(s): The dose discrepancy due to chamber position was largest between the 6 and 3 o'clock positions (10%) and the average was close to the peripheral measurement at 12 o'clock. All three detectors showed a linear dependency. Reducing CBCT beam collimation increased measurement complexity with only minimally improved agreement between measured and displayed CTDIw values. The standard deviation for dose measurements at different machines reduced from 22%/12% for the lung phantom to 7%/3% (max/mean) for the CTDI phantom.
Conclusion(s): Dose measurements at 12 o'clock and center position of CTDI-phantom have been defined as our new standard using un-modified treatment imaging protocols; conversion factors for center-only or lung-phantom measurements have been provided
EMBASE:635752640
ISSN: 0094-2405
CID: 4987602
Automatic treatment planning for VMAT-based total body irradiation using Eclipse scripting
Teruel, Jose R; Taneja, Sameer; Galavis, Paulina E; Osterman, K Sunshine; McCarthy, Allison; Malin, Martha; Gerber, Naamit K; Hitchen, Christine; Barbee, David L
The purpose of this work is to establish an automated approach for a multiple isocenter volumetric arc therapy (VMAT)-based TBI treatment planning approach. Five anonymized full-body CT imaging sets were used. A script was developed to automate and standardize the treatment planning process using the Varian Eclipse v15.6 Scripting API. The script generates two treatment plans: a head-first VMAT-based plan for upper body coverage using four isocenters and a total of eight full arcs; and a feet-first AP/PA plan with three isocenters that covers the lower extremities of the patient. PTV was the entire body cropped 5 mm from the patient surface and extended 3 mm into the lungs and kidneys. Two plans were generated for each case: one to a total dose of 1200 cGy in 8 fractions and a second one to a total dose of 1320 cGy in 8 fractions. Plans were calculated using the AAA algorithm and 6 MV photon energy. One plan was created and delivered to an anthropomorphic phantom containing 12 OSLDs for in-vivo dose verification. For the plans prescribed to 1200 cGy total dose the following dosimetric results were achieved: median PTV V100% = 94.5%; median PTV D98% = 89.9%; median lungs Dmean = 763 cGy; median left kidney Dmean = 1058 cGy; and median right kidney Dmean = 1051 cGy. For the plans prescribed to 1320 cGy total dose the following dosimetric results were achieved: median PTV V100% = 95.0%; median PTV D98% = 88.7%; median lungs Dmean = 798 cGy; median left kidney Dmean = 1059 cGy; and median right kidney Dmean = 1064 cGy. Maximum dose objective was met for all cases. The dose deviation between the treatment planning dose and the dose measured by the OSLDs was within ±4%. In summary, we have demonstrated that scripting can produce high-quality plans based on predefined dose objectives and can decrease planning time by automatic target and optimization contours generation, plan creation, field and isocenter placement, and optimization objectives setup.
PMID: 33565214
ISSN: 1526-9914
CID: 4779762
Dosimetry of Gamma-Knife Hybrid Shots With Film, Scintillator and the Microdiamond Detector [Meeting Abstract]
Rudek, B.; Bernstein, K.; Osterman, S.; Qu, T.
ISI:000582521501111
ISSN: 0360-3016
CID: 4686212
Initial Experience in MRI-Based Brain Metastases Detection Using Deep Learning [Meeting Abstract]
Teruel, J.; Bernstein, K.; Galavis, P.; Spuhler, K.; Silverman, J.; Kondziolka, D.; Osterman, K.
ISI:000699863600701
ISSN: 0094-2405
CID: 5320872