title: A new method for apparent diffusion coefficient measurement using sequential (18)F-FDG PET and MRI: correlation with histological grade of invasive ductal carcinoma of the breast.
abstract: OBJECTIVE
  The aim of this study was to measure the apparent diffusion coefficient (ADC) value at the region with the highest FDG uptake using sequential (18)F-FDG PET and MRI, and to correlate it with the histological grade of invasive ductal carcinoma (IDC) of the breast.
  
  
  METHODS
  A retrospective study was conducted on 75 untreated patients with IDC. First, a PET/CT scan and subsequent breast MRI were done and the SUVmax of the each breast tumor was recorded. Then, a PET image and ADC map were co-registered. On the axial slice containing the pixel with SUVmax, we drew multiple circular ROIs within the tumor and measured the mean ADC value of each ROI. The average (ADC-mean) and minimum (ADC-min) of the mean ADC values for all ROIs within the tumor were calculated, respectively. Then, a circular ROI was placed at the corresponding location to the pixel with the highest SUV and the mean ADC value of the ROI was denoted as ADC-PET. We compared the averages of the ADC parameters and assessed the correlations among SUVmax and ADC parameters. ROC curve and logistic regression analyses were performed to assess the utility of ADC and SUVmax for detecting histological grade 3.
  
  
  RESULTS
  ADC-min was significantly lower than the ADC-mean or ADC-PET. All of the ADC parameters showed a negative correlation with SUVmax. The area under the ROC curve for identifying histological grade 3 using ADC-PET, ADC-min, ADC-mean and SUVmax was 0.684, 0.660, 0.633 and 0.639, respectively. By multivariate analysis, ADC-PET was a significant, independent predictor of histological grade 3 (p = 0.004).
  
  
  CONCLUSIONS
  We estimated the ADC value at the breast tumor region with the highest FDG uptake using sequential (18)F-FDG PET and MRI. This new ADC parameter distinguished high-grade IDC, supporting the feasibility of the combined PET-MRI system in patients with breast cancer.
authors.affiliation: Department of Nuclear Medicine, Korea Cancer Center Hospital, Korea Institute of Radiological and Medical Sciences (KIRAMS), 75 Nowongil, Nowon Gu, Seoul, 139-706, Republic of Korea.
authors.forename: Byung Hyun
authors.initials: BH
authors.lastname: Byun
authors.forename: Woo Chul
authors.initials: WC
authors.lastname: Noh
authors.forename: Ilhan
authors.initials: I
authors.lastname: Lim
authors.forename: Seung Sook
authors.initials: SS
authors.lastname: Lee
authors.forename: A Ra
authors.initials: AR
authors.lastname: Cho
authors.forename: Ji Ae
authors.initials: JA
authors.lastname: Park
authors.forename: Kyeong Min
authors.initials: KM
authors.lastname: Kim
authors.forename: Hyun-Ah
authors.initials: HA
authors.lastname: Kim
authors.forename: Eun-Kyu
authors.initials: EK
authors.lastname: Kim
authors.forename: Byung Il
authors.initials: BI
authors.lastname: Kim
authors.forename: Chang Woon
authors.initials: CW
authors.lastname: Choi
authors.forename: Sang Moo
authors.initials: SM
authors.lastname: Lim
mesh_terms: D000328:Adult; D001692:Biological Transport; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D004058:Diffusion; D005240:Feasibility Studies; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D008279:Magnetic Resonance Imaging; D064847:Multimodal Imaging / Q000379:methods*; D060787:Neoplasm Grading; D009361:Neoplasm Invasiveness; D015588:Observer Variation; D049268:Positron-Emission Tomography; D013997:Time Factors; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18