title: Receiver operating characteristic (ROC) curve for classification of (18)F-NaF uptake on PET/CT.
abstract: OBJECTIVE
  To assess the cutoff values established by ROC curves to classify (18)F-NaF uptake as normal or malignant.
  
  
  METHODS
  PET/CT images were acquired 1 hour after administration of 185 MBq of (18)F-NaF. Volumes of interest (VOIs) were drawn on three regions of the skeleton as follows: proximal right humerus diaphysis (HD), proximal right femoral diaphysis (FD) and first vertebral body (VB1), in a total of 254 patients, totalling 762 VOIs. The uptake in the VOIs was classified as normal or malignant on the basis of the radiopharmaceutical distribution pattern and of the CT images. A total of 675 volumes were classified as normal and 52 were classified as malignant. Thirty-five VOIs classified as indeterminate or nonmalignant lesions were excluded from analysis. The standardized uptake value (SUV) measured on the VOIs were plotted on an ROC curve for each one of the three regions. The area under the ROC (AUC) as well as the best cutoff SUVs to classify the VOIs were calculated. The best cutoff values were established as the ones with higher result of the sum of sensitivity and specificity.
  
  
  RESULTS
  The AUCs were 0.933, 0.889 and 0.975 for UD, FD and VB1, respectively. The best SUV cutoffs were 9.0 (sensitivity: 73%; specificity: 99%), 8.4 (sensitivity: 79%; specificity: 94%) and 21.0 (sensitivity: 93%; specificity: 95%) for UD, FD and VB1, respectively.
  
  
  CONCLUSIONS
  The best cutoff value varies according to bone region of analysis and it is not possible to establish one value for the whole body.
authors.affiliation: Nuclear Physician, Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HC-FMUSP), São Paulo, SP, Brazil.
authors.forename: Agnes Araujo
authors.initials: AA
authors.lastname: Valadares
authors.affiliation: PhD, Physician Assistant, Service of Nuclear Medicine - Instituto do Câncer do Estado de São Paulo Octavio Frias de Oliveira (Icesp), São Paulo, SP Brazil.
authors.forename: Paulo Schiavom
authors.initials: PS
authors.lastname: Duarte
authors.affiliation: Physician Assistant, Service of Nuclear Medicine - Instituto do Câncer do Estado de São Paulo Octavio Frias de Oliveira (Icesp), São Paulo, SP Brazil.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Carvalho
authors.affiliation: PhD, Physician Assistant, Service of Nuclear Medicine - Instituto do Câncer do Estado de São Paulo Octavio Frias de Oliveira (Icesp), São Paulo, SP Brazil.
authors.forename: Carla Rachel
authors.initials: CR
authors.lastname: Ono
authors.affiliation: PhD, Physician Assistant, Service of Nuclear Medicine - Instituto do Câncer do Estado de São Paulo Octavio Frias de Oliveira (Icesp), São Paulo, SP Brazil.
authors.forename: George Barberio
authors.initials: GB
authors.lastname: Coura-Filho
authors.affiliation: PhD, Physician Assistant, Service of Nuclear Medicine - Instituto do Câncer do Estado de São Paulo Octavio Frias de Oliveira (Icesp), São Paulo, SP Brazil.
authors.forename: Heitor Naoki
authors.initials: HN
authors.lastname: Sado
authors.affiliation: Private Docent, Professor, Department of Radiology and Oncology - Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, SP Brazil.
authors.forename: Marcelo Tatit
authors.initials: MT
authors.lastname: Sapienza
authors.affiliation: Private Docent, Full Professor, Department of Radiology and Oncology - Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, SP Brazil.
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Buchpiguel
keywords: 18F-NaF PET/CT; Cutoff values; Malignant uptake; Normal uptake; ROC curve