BackgroundEvaluation of changes in tumor size from images acquired by ultrasound (US), computed tomography (CT) or magnetic resonance imaging (MRI) is a common measure of cancer chemotherapy efficacy. Tumor size measurement based on either the World Health Organization (WHO) criteria or the Response Evaluation Criteria in Solid Tumors (RECIST) is the only imaging biomarker for anti-cancer drug testing presently approved by the United States Food and Drug Administration (FDA). The aim of this paper was to design and test a quality assurance phantom with the capability of monitoring tumor size changes with multiple preclinical imaging scanners (US, CT and MRI) in order to facilitate preclinical anti-cancer drug testing.MethodsThree phantoms (Gammex/UTHSCSA Mark 1, Gammex/UTHSCSA Mark 2 and UTHSCSA multimodality tumor measurement phantom) containing tumor-simulating test objects were designed and constructed. All three phantoms were scanned in US, CT and MRI devices. The size of test objects in the phantoms was measured from the US, CT and MRI images. RECIST, WHO and volume analyses were performed.ResultsThe smaller phantom size, simplified design and better test object CT contrast of the UTHSCSA multimodality tumor measurement phantom allowed scanning of the phantom in preclinical US, CT and MRI scanners compared with only limited preclinical scanning capability of Mark 1 and Mark 2 phantoms. For all imaging modalities, RECIST and WHO errors were reduced for UTHSCSA multimodality tumor measurement phantom (≤1.69 ± 0.33%) compared with both Mark 1 (≤ -7.56 ± 6.52%) and Mark 2 (≤ 5.66 ± 1.41%) phantoms. For the UTHSCSA multimodality tumor measurement phantom, measured tumor volumes were highly correlated with NIST traceable design volumes for US (R2 = 1.000, p < 0.0001), CT (R2 = 0.9999, p < 0.0001) and MRI (R2 = 0.9998, p < 0.0001).ConclusionsThe UTHSCSA multimodality tumor measurement phantom described in this study can potentially be a useful quality assurance tool for verifying radiologic assessment of tumor size change during preclinical anti-cancer therapy testing with multiple imaging modalities.

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Purpose: A prototype quality control (QC) phantom and analysis process has been designed specifically to monitor dual‐energy CT and address the current lack of quantitative oversight of the spectral capabilities of these scanners. Methods: A prototype solid water phantom was designed with multiple material inserts, and to support both head and body protocols. Inserts included tissue equivalent and material rods (iodine, iron, calcium) at various concentrations. The oval body phantom, measuring 30cm×40cm×15cm, was scanned using four dual‐energy protocols with CTDIvol ranges of 19.6–62mGy (0.516 pitch) and 10.3–32.5mGy (0.984 pitch), and rotation times ranging from 0.5‐1sec. The circular head phantom, measuring 22cm in diameter by 15cm, was scanned using three dual‐energy protocols with CTDIvol ranges of 67–132.6mGy (0.531 pitch) and 36.7–72.7mGy (0.969 pitch), and rotation times ranging from 0.5–0.9sec. All images were reconstructed at 50, 70, 110 and 140 keV, and using a water‐iodine material basis pair. The images were evaluated for iodine quantification accuracy and stability of monoenergetic reconstructions. The phantom was scanned twice on ten GE 750HD CT scanners to evaluate inter‐scanner agreement, as well as ten times on a single scanner over a oneweek period to evaluate intra‐scanner repeatability. Results: Preliminary analysis revealed consistent (inter‐ and intra‐scanner) iodine quantification accuracy within 10% was only achieved for protocols in the upper half of dose levels assessed when grouped by pitch. Although all scanners undergo rigorous daily single‐energy QC, iodine quantification accuracy from one scanner unexpectedly deviated from the other nine substantially. In general, inter‐scanner agreement and intra‐scanner repeatability varied with dose, rotation time and reconstructed keV. Conclusion: Preliminary results indicate the need for a dual‐energy QC process to ensure inter‐scanner agreement and intra‐scanner repeatability. In particular, iodine quantification accuracy within 10% may not be achievable using lower dose techniques. Future plans include longer term dual‐energy CT QC data collection. In‐kind financial support was provided by GE Healthcare.

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Purpose: There are growing expectations that imaging biomarkers can speed preclinical testing of anti‐tumor drugs in rodent models. The only presently accepted imaging biomarker by the US Food and Drug Administration (FDA) is tumor size measurement based on WHO or RECIST criteria. Standardized Tumor Response QA procedures are needed to allow accurate tumor size measurements in rodent models coming from multiple devices and laboratories. This project tests the hypothesis that development and testing of new anti‐tumor drugs with imaging biomarkers can be facilitated and speeded by the development of effective QA procedures for preclinical drug testing in rodent tumor models. Methods and Materials: A multi‐modality Rodent Tumor Response (RTR) QA procedure was constructed using two sets of measurements on a special purpose calibration phantom: A. Tumor Diameter — low contrast spheres with 2, 4, 7, 10 and 14mm diameters, B. Tumor Volume — five low contrast spheres ranging 4.2 to 1436.8 mm3. Repeated images (n = 3) were obtained with 10 and 35 MHz ultrasound scanners, animal cone beam μ‐CT and a 7T MR animal imager to develop “RTR‐QA Standardized Measurement Protocols” for each device. The capacity of RTR‐QA methods to standardize tumor drug response measurements was validated using measurements of Head and Neck rat tumor models (SCC‐4) ranging in tumor size from 2, 4, 7, 10, 14mm (three rats per group). Results of Standardized RTR‐QA were compared against gold standard measurements of NIST referenced mass and size of surgically extracted tumors. Statistical comparisons of WHO and RECIST data precision and accuracy were made. Results: Tumor size measurements in rat tumor models using Standardized RTR‐QA procedures showed more accurate results. Conclusions: We conclude that accurate measurements of tumor response from multiple laboratories/instruments are possible using imaging size biomarkers with Standardized RTR‐QA RECIST and WHO procedures.