18 F-FDG PET/CT allows the direct measurement of metabolic tumor burden in a variety of different malignancies. The aim of this study was to assess whether metabolic tumor volume (MTV) determined by 18 F-FDG PET/CT could be used in the prediction of progression-free and overall survival in multiple myeloma patients. Methods: Forty-seven patients (18 women, 29 men; mean age 6 SD, 63 6 11 y) with stage IIIA disease who had undergone whole-body 18 F-FDG PET/CT were retrospectively evaluated. Images underwent a 3-dimensional region-of-interest analysis including all focal lesions with a maximum standardized uptake value . 2.5. The MTV of each lesion was calculated using an automated contouring program based on the standardized uptake value and developed with a threshold of 40% of the maximum standardized uptake value. The total MTV of each patient was defined as the sum of metabolic volume of all focal lesions. Patients were treated and then subjected to a mean follow-up period of 24 mo. Results: In the 47 patients studied, MTV range was 1.3-316.3 mL, with a median of 23.7 mL. A direct, significant correlation was found between MTV and the percentage of diffuse infiltration of bone marrow by plasma cells (r 5 0.46, P 5 0.006), whereas hemoglobin levels were inversely correlated with MTV (r 5 20.56, P 5 0.0001). At follow-up, patients who developed progressive disease (n 5 18) showed a significantly higher MTV (74.7 6 19.3 vs. 29.8 6 5.1 mL, P 5 0.009) than patients without progressive disease (n 5 29). Furthermore, patients who died of myeloma (n 5 9) had a significantly higher MTV (123.2 6 30.6 vs. 28.9 6 4.2 mL, P 5 0.0001) than survivors (n 5 38). No differences in age, plasma cell infiltration, M protein, albumin, b2-microglobulin, performance status, International Staging System score, and presence or absence of a bone marrow transplant were found between groups. The MTV cutoff level was determined by receiver-operating-characteristic curve analysis, and the best discriminative value found for predicting progression-free and overall survival was 42.2 and 77.6 mL, respectively. By Kaplan-Meier analysis and log-rank testing, progression-free and overall survival at follow-up were significantly better in patients showing an MTV lower than the cutoff than in those having an MTV higher than the cutoff (x 2 5 3.9, P 5 0.04, and x 2 5 56.3, P , 0.0001, respectively). Conclusion: The direct measurement of tumor burden obtained by calculating MTV on 18 F-FDG PET/CT images may be used in the prediction of progression-free and overall survival in myeloma patients.

Image file format is often a confusing aspect for someone wishing to process medical images. This article presents a demystifying overview of the major file formats currently used in medical imaging: Analyze, Neuroimaging Informatics Technology Initiative (Nifti), Minc, and Digital Imaging and Communications in Medicine (Dicom). Concepts common to all file formats, such as pixel depth, photometric interpretation, metadata, and pixel data, are first presented. Then, the characteristics and strengths of the various formats are discussed. The review concludes with some predictive considerations about the future trends in medical image file formats.

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