Technical Note: Unified imaging and robotic couch quality assurance.

PURPOSE: To introduce a simplified quality assurance (QA) procedure that integrates tests for the linac's imaging components and the robotic couch. Current QA procedures for evaluating the alignment of the imaging system and linac require careful positioning of a phantom at isocenter before image acquisition and analysis. A complementary procedure for the robotic couch requires an initial displacement of the phantom and then evaluates the accuracy of repositioning the phantom at isocenter. We propose a two-in-one procedure that introduces a custom software module and incorporates both checks into one motion for increased efficiency. METHODS: The phantom was manually set with random translational and rotational shifts, imaged with the in-room imaging system, and then registered to the isocenter using a custom software module. The software measured positioning accuracy by comparing the location of the repositioned phantom with a CAD model of the phantom at isocenter, which is physically verified using the MV port graticule. Repeatability of the custom software was tested by an assessment of internal marker location extraction on a series of scans taken over differing kV and CBCT acquisition parameters. RESULTS: The proposed method was able to correctly position the phantom at isocenter within acceptable 1 mm and 1° SRS tolerances, verified by both physical inspection and the custom software. Residual errors for mechanical accuracy were 0.26 mm vertically, 0.21 mm longitudinally, 0.55 mm laterally, 0.21° in pitch, 0.1° in roll, and 0.67° in yaw. The software module was shown to be robust across various scan acquisition parameters, detecting markers within 0.15 mm translationally in kV acquisitions and within 0.5 mm translationally and 0.3° rotationally across CBCT acquisitions with significant variations in voxel size. Agreement with vendor registration methods was well within 0.5 mm; differences were not statistically significant. CONCLUSIONS: As compared to the current two-step approach, the proposed QA procedure streamlines the workflow, accounts for rotational errors in imaging alignment, and simulates a broad range of variations in setup errors seen in clinical practice.

Development of Two FhSAP2 Recombinant-Based Assays for Immunodiagnosis of Human Chronic Fascioliasis.

In the United States, infection with Fasciola hepatica has been identified as an emerging disease, primarily in immigrants, refugees, and travelers. The laboratory test of choice for diagnosis of fascioliasis is detection of disease specific antibodies, most commonly uses excretory-secretory antigens for detection of IgG antibodies. Recently, recombinant proteins such as F. hepatica antigen (FhSAP2) have been used to detect IgG antibodies. The glutathione S-transferase (GST)-FhSAP2 recombinant antigen was used to develop Western blot (WB) and fluorescent bead-based (Luminex) assays to detect F. hepatica total IgG and IgG4 antibodies. The sensitivity and specificity of GST-FhSAP2 total IgG and IgG4 WB were similar at 94% and 98%, respectively. For the IgG Luminex assay, the sensitivity and specificity were 94% and 97%, and for the IgG4, the values were 100% and 99%, respectively. In conclusion, the GST-FhSAP2 antigen performs well in several assay formats and can be used for clinical diagnosis.

Clinical implementation and efficiency of kilovoltage image-guided radiation therapy.

This paper describes measurements of clinical efficiency and time requirements associated with image-guided radiation therapy (IGRT). In June 2004, the authors' institution installed an integrated kilovoltage (kV) imaging system attached to a medical linear accelerator for radiographic target localization. Over the past year, 242 patients have been localized with the kV radiographic imaging system for a total of 2,700 fractions. Data were analyzed by reviewing the time required for each patient's IGRT session, broken into both image acquisition and image analysis time. Average IGRT procedure time was reviewed pertaining to months, treatment sessions, disease sites, and radiation therapists. Results showed that the average IGRT procedure time was reduced from 450 to 237 seconds from June 2004 to June 2005. Further analysis revealed that each therapist showed improvement in reducing the IGRT procedure time from the first month of use to the month of June 2005. The routine use of IGRT may ultimately be performed within 3 to 4 minutes, with minimal disruption to the clinical treatment process.