Ayako Hino-Shishikura

Tumor hypoxia and microscopic diffusion capacity in brain tumors: A comparison of 62 Cu-Diacetyl-Bis (N4-Methylthiosemicarbazone) PET/CT and diffusion-weighted MR imaging

ObjectivesThe aim of this study was to clarify the relationship between tumor hypoxia and microscopic diffusion capacity in primary brain tumors using 62Cu-Diacetyl-Bis (N4-Methylthiosemicarbazone) (62Cu-ATSM) PET/CT and diffusion-weighted MR imaging (DWI).MethodsThis study was approved by the institutional human research committee and was HIPAA compliant, and informed consent was obtained from all patients. 62Cu-ATSM PET/CT and DWI were performed in a total of 40 primary brain tumors of 34 patients with low grade glioma (LGG, n = 13), glioblastoma (GBM, n = 20), and primary central nervous system lymphoma (PCNSL, n = 7). 62Cu-ATSM PET/CT parameters and apparent diffusion coefficient (ADC) obtained by DWI were compared.ResultsHigh intensity signals by 62Cu-ATSM PET/CT and DWI in patients with GBM and PCNSL, and low intensity signals in LGG patients were observed. An inverse correlation was found between maximum SUV (SUVmax) and minimum ADC (ADCmin) (r = −0.583, p < 0.0001), and between tumor/brain ratio (T/Bratio) and ADCmin for all tumors (r = −0.532, p < 0.0001). Both SUVmax and T/Bratio in GBM were higher than LGG (p < 0.0001 and p < 0.0001), and those in PCNSL were also higher than GBM (p = 0.033 and p = 0.044). The ADCmin was lower in GBM (p = 0.011) and PCNSL (p = 0.01) than in LGG, while no significant difference was found between GBM and PCNSL (p = 0.90).ConclusionTumor hypoxia assessed by 62Cu-ATSM PET/CT correlated with microscopic diffusion capacity obtained by DWI in brain tumors. Both 62Cu-ATSM PET/CT and DWI were considered feasible imaging methods for grading glioma. However, 62Cu-ATSM PET/CT provided additional diagnostic information to differentiate between GBM and PCNSL.

Biodistribution and radiation dosimetry of [18F]-5-fluorouracil

PURPOSE To estimate the radiation dose and biodistribution of (18)F-5-fluorouracil ([(18)F]-5-FU) from positron emission tomography/computed tomography (PET/CT) data, and to extrapolate mouse data to human data in order to evaluate cross-species consistency. METHODS Fifteen cancer patients (head and neck cancer (n=11), colon cancer (n=4)) were enrolled. Sequential PET/CT images were acquired for 2h after intravenous administration of [(18)F]-5-FU, and the percent of the injected dose delivered to each organ was derived. For comparison, [(18)F]-5-FU was administered to female BALB/cAJcl-nu/nu nude mice (n=19), and the percent of the injected dose delivered to mouse organs was extrapolated to the human model. Absorbed radiation dose was calculated using OLINDA/EXM 1.0 software. RESULTS In human subjects, high [(18)F]-5-FU uptake was seen in the liver, gallbladder and kidneys. The absorbed dose was highest in the gallbladder wall. In mice, the biodistribution of [(18)F]-5-FU corresponded to that of humans. Estimated absorbed radiation doses for all organs were moderately correlated, and doses to organs (except the gallbladder and urinary bladder) were significantly correlated between mice and humans. The mean effective [(18)F]-5-FU dose was higher in humans (0.0124mSv/MBq) than in mice (0.0058mSv/MBq). CONCLUSION Biodistribution and radiation dosimetry of [(18)F]-5-FU were compared between humans and mice: biodistribution in mice and humans was similar. Data from mice underestimated the effective dose in humans, suggesting that clinical measurements are needed for more detailed dose estimation in order to ensure radiation safety. The observed effective doses suggest the feasibility of [(18)F]-5-FU PET/CT for human studies.

Multimodal approach to detect osseous involvement in meningioma: additional value of (18)F-fluoride PET/CT for conventional imaging.

PURPOSE To compare the diagnostic performance of fluorine 18 ((18)F) fluoride positron emission tomography (PET)/computed tomography (CT) with that of conventional imaging (CT and magnetic resonance [MR] imaging) in evaluating the osseous involvement in meningioma. MATERIALS AND METHODS The study was approved by the ethics committee and institutional review board and was conducted according to the Declarations of Helsinki and Tokyo. Written informed consent was obtained from all patients. A retrospective comparative study between (18)F-fluoride PET/CT and conventional imaging was conducted to detect osseous involvement in patients with a verified diagnosis of meningioma. Osseous involvement was verified by using definitive surgery (including drilling or careful sampling of the skull in all patients). The diagnostic performance, determined by calculating the sensitivity, specificity, positive predictive value ( PPV positive predictive value ), negative predictive value ( NPV negative predictive value ), and accuracy, was assessed. RESULTS Data sets from a total of 78 patients with proven meningioma were compared. Osseous involvement was histopathologically confirmed in 25 patients (32%). The sensitivity, specificity, PPV positive predictive value , NPV negative predictive value , and accuracy were 92.0%, 86.8%, 76.7%, 95.8%, and 88.5% for (18)F-fluoride PET/CT and 64.0%, 83.0%, 64.0%, 83.0%, and 76.9% for conventional imaging, respectively. The receiver operating characteristic ( ROC receiver operating characteristic ) analysis revealed that the area under the ROC receiver operating characteristic curve ( Az area under the ROC curve ) value of (18)F-fluoride PET/CT was significantly greater than that of conventional imaging (0.965 ± 0.02 [standard error] vs 0.703 ± 0.066 [standard error], P < .0001). CONCLUSION An approach using (18)F-fluoride PET/CT improves preoperative detection of osseous involvement. In those without abnormal (18)F-fluoride uptake within the skull, the patient may proceed directly to conventional surgery. However, a positive finding of osseous involvement at (18)F-fluoride PET/CT should prompt confirmation by drilling or sampling of bone.

Use of count-based image reconstruction to evaluate the variability and repeatability of measured standardised uptake values

Standardized uptake values (SUVs) are the most widely used quantitative imaging biomarkers in PET. It is important to evaluate the variability and repeatability of measured SUVs. Phantom studies seem to be essential for this purpose; however, repetitive phantom scanning is not recommended due to the decay of radioactivity. In this study, we performed count-based image reconstruction to avoid the influence of decay using two different PET/CT scanners. By adjusting the ratio of 18F-fluorodeoxyglucose solution to tap water, a NEMA IEC body phantom was set for SUVs of 4.0 inside six hot spheres. The PET data were obtained using two scanners (Aquiduo and Celesteion; Toshiba Medical Systems, Tochigi, Japan). We set the start time for image reconstruction when the total radioactivity in the phantom was 2.53 kBq/cc, and employed the counts of the first 2-min acquisition as the standard. To maintain the number of counts for each image, we set the acquisition time for image reconstruction depending on the decay of radioactivity. We obtained 50 images, and calculated the SUVmax and SUVpeak of all six spheres in each image. The average values of the SUVmax were used to calculate the recovery coefficients to compare those measured by the two different scanners. Bland-Altman analyses of the SUVs measured by the two scanners were also performed. The measured SUVs using the two scanners exhibited a 10–30% difference, and the standard deviation (SD) of the measured SUVs was between 0.1–0.2. The Celesteion always exhibited higher values than the Aquiduo. The smaller sphere exhibited a larger SD, and the SUVpeak had a smaller SD than the SUVmax. The Bland-Altman analyses showed poor agreement between the SUVs measured by the two scanners. The recovery coefficient curves obtained from the two scanners were considerably different. The Celesteion exhibited higher recovery coefficients than the Aquiduo, especially at approximately 20-mm-diameter. Additionally, the curves were lower than those calculated from the standard 30-min acquisition images. We propound count-based image reconstruction to evaluate the variability and repeatability of measured SUVs. These results are also applicable for the standardization and harmonization of SUVs in multi-institutional studies.

Clinical significance of subcutaneous fat and fascial involvement in juvenile dermatomyositis

Abstract Objectives: Subcutaneous involvement, including calcinosis and panniculitis, is a more common complication in juvenile dermatomyositis (JDM) than in adult dermatomyositis. Magnetic resonance imaging (MRI) is useful for evaluating disease distribution. We investigated the clinical significance of subcutaneous involvement in JDM. Methods: Thighs and hips in 18 newly diagnosed JDM patients were evaluated with fat-suppression MRI. Bilateral muscle, fascial and subcutaneous fat involvement were scored from 0 to 8 points according to the severity of distribution on MRI. Associations between clinical manifestations, serum muscle enzymes, and MRI scores were also evaluated. Results: Abnormal MRI findings in muscle, fascia and subcutaneous fat were observed in 18, 18, and 10 patients, respectively. Subcutaneous fat scores were significantly higher in early-diagnosed JDM patients (diagnosed less than 2 months from onset) than in late-diagnosed JDM patients (diagnosed later) (p = .025). Serum aldolase was elevated in all patients, although only eight demonstrated elevated serum creatine phosphokinase. Serum aldolase was significantly correlated with MRI scores for subcutaneous fat (p < .0001, ρ = .787) and fascia (p = .013 ρ = 0.574), but not muscle. Additionally, serum aldolase was significantly correlated with serum triglycerides (p = .009, ρ = 0.629). Conclusion: Subcutaneous fat involvement is a characteristic finding in early-diagnosed JDM and correlates with elevated serum aldolase.

Visual and Quantitative Assessment of a New Anisotropic Diffusion Filter (Statistical Transfer with Optimizing Noise and Edge Sensing) for Positron Emission Tomography

Post-filtering with a Gaussian filter is commonly used to reduce noise in positron emission tomography (PET) images. However, its non-selective smoothing obscures the edges of lesions or organs. We compared the performance of a newly developed anisotropic diffusion filter called “Statistical Transfer with Optimizing Noise and Edge Sensing” (STONES) with that of the Gaussian filter for small lesions on PET images. We selected seven PET/computed tomography (CT) image slices of the lungs from three patients with multiple lung metastases. For each slice, the lesion detection rates by two physicians (A and B) were compared for Gaussian- and STONES-filtered PET images. The maximum standardized uptake (SUVmax) values of the detected lesions were also compared for non-, Gaussian-, and STONES-filtered images. Physician A detected 19 lesions in the Gaussian-filtered images and 23 lesions in the STONES-filtered images, while Physician B detected 14 lesions in the Gaussian-filtered images and 19 lesions in the STONES-filtered images. SUVmax for the STONES-filtered images was significantly higher and closer to that of the non-filtered images compared to those for the Gaussian-filtered images. STONES improved the detection rate and increased SUVmax in comparison with Gaussian filter. Thus, it should be more advantageous for the detection of small lesions with PET.