Multimodal assessment of disease activity in glioblastoma : A single center experience.

BACKGROUND: Assessment of disease activity in glioblastoma (GBM) can be challenging due to several clinical and radiological pitfalls. Besides MRI, FET-PET and neurocognitive assessment (NA) are used in several neuro-oncological centers in order to improve the specificity of response assessment. We performed a retrospective study to investigate whether the assessment by RANO (Response Assessment in NeuroOncology) corresponds to FET-PET imaging and NA results. Moreover, the concordance of RANO with a final recommendation of an interdisciplinary neuro-oncological tumor board recommendation (TBR) was analyzed. METHODS: We enrolled 25 consecutive patients with newly diagnosed histologically confirmed GBM in a pilot study, accounting for 81 multimodal test results. All patients were selected after undergoing consecutive follow-up comprising MRI, FET-PET, and NA with a subsequent TBR. Results were analyzed for correlations between RANO, FET-PET and NA. An additional consistency analysis was performed to elucidate the impact of RANO on decision making. RESULTS: A highly statistically significant correlation was found between RANO and FET-PET and NA results (all P < 0.01); however, 26% of follow-up tests exhibited inconsistent results in multimodal assessment, among which RANO was only 48% in accordance with the final TBR. The concordance of NA and FET-PET with the final TBR was 67% and 86%, respectively. CONCLUSION: The RANO proved its value in the context of multimodal assessment of disease activity in GBM; however, because the implementation of multimodal assessment showed a considerably high percentage of inconsistent results, further studies are required to investigate the relationship between different assessment techniques, in addition to their overall significance to response rating.

Performance evaluation of the Biograph mCT Flow PET/CT system according to the NEMA NU2-2012 standard.

BACKGROUND: The purpose of the study is to evaluate the physical performance of a Biograph mCT Flow 64-4R PET/CT system (Siemens Healthcare, Germany) and to compare clinical image quality in step-and-shoot (SS) and continuous table motion (CTM) acquisitions. METHODS: The spatial resolution, sensitivity, count rate curves, and Image Quality (IQ) parameters following the National Electrical Manufactures Association (NEMA) NU2-2012 standard were evaluated. For resolution measurements, an (18)F point source inside a glass capillary tube was used. Sensitivity measurements were based on a 70-cm-long polyethylene tube, filled with 4.5 MBq of FDG. Scatter fraction and count rates were measured using a 70-cm-long polyethylene cylinder with a diameter of 20 cm and a line source (1.04 GBq of FDG) inserted axially into the cylinder 4.5 cm off-centered. A NEMA IQ phantom containing six spheres (10- to 37-mm diameter) was used for the evaluation of the image quality. First, a single-bed scan was acquired (NEMA standard), followed by a two-bed scan (4 min each) of the IQ phantom with the image plane containing the spheres centered in the overlap region of the two bed positions. In addition, a scan of the same region in CTM mode was performed with a table speed of 0.6 mm/s. Furthermore, two patient scans were performed in CTM and SS mode. Image contrasts and patient images were compared between SS and CTM acquisitions. RESULTS: Full Width Half Maximum (FWHM) of the spatial resolution ranged from 4.3 to 7.8 mm (radial distance 1 to 20 cm). The measured sensitivity was 9.6 kcps/MBq, both at the center of the FOV and 10 cm off-center. The measured noise equivalent count rate (NECR) peak was 185 kcps at 29.0 kBq/ml. The scatter fraction was 33.5 %. Image contrast recovery values (sphere-to-background of 8:1) were between 42 % (10-mm sphere) to 79 % (37-mm sphere). The background variability was between 2.1 and 5.3 % (SS) and between 2.4 and 6.9 % (CTM). No significant difference in image quality was observed between SS and CTM mode. CONCLUSIONS: The spatial resolution, sensitivity, scatter fraction, and count rates were in concordance with the published values for the predecessor system, the Biograph mCT. Contrast recovery values as well as image quality obtained in SS and CTM acquisition modes were similar.

Multiple window spatial registration error of a gamma camera: 133Ba point source as a replacement of the NEMA procedure.

BACKGROUND: The accuracy of multiple window spatial resolution characterises the performance of a gamma camera for dual isotope imaging. In the present study we investigate an alternative method to the standard NEMA procedure for measuring this performance parameter. METHODS: A long-lived 133Ba point source with gamma energies close to 67Ga and a single bore lead collimator were used to measure the multiple window spatial registration error. Calculation of the positions of the point source in the images used the NEMA algorithm. The results were validated against the values obtained by the standard NEMA procedure which uses a liquid 67Ga source with collimation. RESULTS: Of the source-collimator configurations under investigation an optimum collimator geometry, consisting of a 5 mm thick lead disk with a diameter of 46 mm and a 5 mm central bore, was selected. The multiple window spatial registration errors obtained by the 133Ba method showed excellent reproducibility (standard deviation < 0.07 mm). The values were compared with the results from the NEMA procedure obtained at the same locations and showed small differences with a correlation coefficient of 0.51 (p < 0.05). In addition, the 133Ba point source method proved to be much easier to use. A Bland-Altman analysis showed that the 133Ba and the 67Ga Method can be used interchangeably. CONCLUSION: The 133Ba point source method measures the multiple window spatial registration error with essentially the same accuracy as the NEMA-recommended procedure, but is easier and safer to use and has the potential to replace the current standard procedure.

An inter-laboratory comparison study of image quality of PET scanners using the NEMA NU 2-2001 procedure for assessment of image quality.

An inter-laboratory comparison study was conducted to assess the image quality of PET scanners in Austria. The survey included both dedicated PET scanners (D-PET, n = 8) and coincidence cameras (GC-PET, n = 7). Measurement of image quality was based on the NEMA (National Electrical Manufacturers Association) NU 2-2001 protocol and the IEC (International Electrotechnical Commission) body phantom. The latter contains six fillable spheres ranging in diameter from 37 mm down to 10 mm and a 'lung' insert. The two largest lesions L1-2 simulate cold lesions, the four smaller ones (L3-6) are filled with 18F and activity concentration ratios relative to background of 8:1 and 4:1, respectively. Acquisition and reconstruction in the study employed the participating institutes' standard oncological processing protocol. Calculation of contrast of the spheres was performed with a fully automated procedure. Contrast quality indices (CQIs) reflecting global performance were obtained by summing individual contrast values. Other image quality parameters calculated according to the NEMA protocol were background variability and relative error for correction of attenuation and scatter. Contrast values obtained were 61 +/- 16 and 37 +/- 14 for L1 (per cent contrast +/- SD for D-PET and GC-PET, respectively), 57 +/- 16 and 29 +/- 16 for L2, 46 +/- 10 and 26 +/- 6.3 for L3, 37 +/- 10 and 15 +/- 4.3 for L4, 26 +/- 11.5 and 6.1 +/- 2.5 for L5, 14 +/- 7.1 and 2.6 +/- 2.6 for L6, with D-PET systems consistently being superior to GC-PET systems. CQIs permitted ranking of the scanners, also demonstrating a clear distinction between D-PET and GC-PET systems. Background variability was largest for GC-PET systems; the relative error of attenuation and scatter correction was significantly correlated with image quality for D-PET systems only. The study demonstrated considerable differences in image quality not only between GC-PET and D-PET systems but also between individual D-PET systems with possible consequences for clinical interpretation of images and measurement of quantitative indices such as the standardized uptake value. The study provided valuable feedback to the participants as well as baseline data for improving interchangeability of PET images and of quantitative indices between different laboratories.