Elaine Yuen Phin Lee

Relationship between intravoxel incoherent motion diffusion‐weighted MRI and dynamic contrast‐enhanced MRI in tissue perfusion of cervical cancers

To investigate the relationship between intravoxel incoherent motion (IVIM) diffusion‐weighted magnetic resonance imaging (MRI) and dynamic contrast‐enhanced MRI (DCE‐MRI) in cervical cancer perfusion.

Midtreatment 18F-FDG PET/CT Scan for Early Response Assessment of SMILE Therapy in Natural Killer/T-Cell Lymphoma: A Prospective Study from a Single Center

In a prospective study of newly diagnosed or relapsed histologically proven extranodal natural killer/T-cell lymphoma (ENKTL) patients, we aimed to determine the accuracy of midtreatment 18F-FDG PET for response assessment using both visual and quantitative analyses. Methods: Twenty-four patients (12 men, 12 women; median age, 50 y; age range, 16–83 y) were referred for pre-, mid- (after 2–3 cycles of SMILE [prednisolone, methotrexate, ifosfamide, L-asparaginase, etoposide] chemotherapy), and end-treatment PET/CT scans (n = 24, 24, and 17, respectively) using a standardized protocol. Sixty-five PET/CT scans were analyzed visually using the Deauville 5-point score (DS), and the lesion with the highest maximum standardized uptake value (SUVmax) was recorded. Survival curves were obtained using Kaplan–Meier analysis and compared using the log rank test, followed by multivariate analysis using the Cox proportional hazards model to assess the independent effects of International Prognostic Index (IPI) score (0–1 vs. 2–5), stage (stage I/II vs. stage III/IV), sex, DS (1–3 vs. 4–5), SUVmax, and change in SUVmax on overall survival (OS) and progression-free survival (PFS). The mean (±SD) follow-up period was 32 mo (±21 mo). Results: For 2-y OS, the following parameters were predictive: IPI score (P = 0.047), DS at mid- and end-treatment (P < 0.001), and SUVmax at mid- and end-treatment (P < 0.001 and 0.045, respectively). For 2-y PFS, the following parameters were predictive: sex (P = 0.006), stage (P = 0.034), IPI score (P = 0.038), DS at mid- and end-treatment (P < 0.001 and 0.001, respectively), and SUVmax at midtreatment (P = 0.001). Multivariate analysis showed DS on mid- and end-treatment scans to be the only significant independent predictor of both OS (P = 0.004 and 0.018, respectively) and PFS (P = 0.004 and 0.014, respectively). The 2-y estimate for OS and PFS was 81% and 62%, respectively, in patients with a DS of 1–3, compared with 17% in patients with a DS of 4–5 (P < 0.001 and 0.001, respectively). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the midtreatment DS for prediction of OS and PFS were 63%, 94%, 83%, 83%, and 83%, respectively. Conclusion: Midtreatment PET/CT is a valuable tool for early treatment response assessment in extranodal natural killer/T-cell lymphoma patients.

The value of 18F-FDG PET/contrast-enhanced CT in detection of tumor thrombus.

Purpose The differentiation between tumor and bland thromboses is important as the management differs. Retrospectively, we aim to evaluate the utility of FDG PET in detecting and differentiating tumor from bland thromboses and if FDG PET provides additional value to contrast-enhanced CT for tumor thrombus detection. Patients and Methods Twenty-four sites of venous thromboembolism, detected on PET/CT, were retrospectively reviewed. Classification of type of thrombosis was based on histology and radiological follow-up. We evaluated the presence of contrast-enhanced CT findings that were suggestive of tumor thrombosis; sign of invasion, neovascularity, and enhancement. Metabolic activity by means of SUVmax was measured by drawing ROI at the site of thrombosis. Mann-Whitney U test was used to compare the mean SUVmax between thromboses and internal references. We used ROC analysis to identify the optimal cutoff value of SUVmax for detection of tumor thrombosis. Results Twenty-four sites of venous thromboembolism were identified in 15 patients. All tumor thromboses demonstrated at least 1 positive sign on contrast-enhanced CT, whereas 33% of bland thromboses had the same finding. The difference between tumor and bland thrombus SUVmax was statistically significant (P < 0.005). On ROC analysis, a cutoff of SUVmax 2.25 (sensitivity, 78%; specificity, 100%) was suggested to differentiate tumor from bland thrombosis. Conclusion PET/CT is able to differentiate tumor from bland thrombosis, with an optimal cutoff value of SUVmax 2.25. The metabolic information increases the diagnostic accuracy of tumor thrombus and is a useful adjunct to the described features on contrast-enhanced CT.

Utility of FDG PET/CT in the Assessment of Myeloid Sarcoma

OBJECTIVE Myeloid sarcoma (MS) is a rare extramedullary manifestation of acute myeloid leukemia that often presents during remission or disease relapse. With awareness of this clinical entity and the appropriate clinical history, MS can be detected despite its nonspecific radiologic features. CONCLUSION This article highlights the utility of (18)F-FDG PET/CT, which has high sensitivity in detecting early MS and provides a systemic overview of tumor burden, and its potential role in monitoring of treatment response.

Correlation between tissue metabolism and cellularity assessed by standardized uptake value and apparent diffusion coefficient in peritoneal metastasis

To evaluate the correlation between standardized uptake value (SUV) (tissue metabolism) and apparent diffusion coefficient (ADC) (water diffusivity) in peritoneal metastases.

Metabolic phenotype of stage IV lung adenocarcinoma: relationship with epidermal growth factor receptor mutation.

Purpose Epidermal growth factor receptor (EGFR) mutation status is important in treatment stratification of stage IV lung adenocarcinoma. We evaluated the relationship between the SUVmax measured on PET/CT and EGFR mutations and the value of SUVmax in predicting EGFR mutations. Patients and Methods Seventy-one stage IV lung adenocarcinoma patients with verified EGFR mutations (48 EGFR mutant, 23 EGFR wild-type) having pretreatment PET/CT were retrospectively reviewed. SUVmax values of the primary tumors (n = 71), nodal (n = 246), and distant metastases (n = 618) were compared between EGFR-mutant and EGFR wild-type adenocarcinoma by Mann-Whitney U test. The receiver operating characteristics curve and logistic regression were performed for factors, SUVmax, age, sex, and smoking status. The significant predictors were assessed individually and in combination in discriminating EGFR mutation status. Statistical significance was assumed at P < 0.05 Results The metastases in EGFR-mutant adenocarcinoma had lower SUVmax than EGFR wild-type adenocarcinoma (nodal SUVmax 3.4 vs 5.5, distant metastasis SUVmax 3.4 vs 4.7, respectively; both P < 0.001). No statistical significant difference was observed in the primary tumors SUVmax between the 2 groups (SUVmax 7.4 vs 8.1, P = 0.311). A receiver operating characteristics–derived SUVmax less than or equal to 7.2 in metastasis could separate EGFR-mutant from EGFR wild-type adenocarcinoma (area under the curve, 0.71–0.74; P < 0.05). SUVmax was a significant independent predictor, and when combined with age, sex, and smoking status, it is highly predictive of EGFR mutation status (area under the curve, 0.90). Conclusions Low SUVmax in the metastasis favors the presence of EGFR mutations in stage IV lung adenocarcinoma, and SUVmax is an independent predictor of EGFR mutations.

Differentiation of aggressive and indolent subtypes of uterine sarcoma using maximum standardized uptake value

ObjectiveThe aim of the study was to elucidate the differential metabolic activities in aggressive and indolent subtypes of uterine sarcomas, which may aid in managing these heterogeneous tumours. MethodsWe retrospectively analysed the PET/computed tomography scans of consecutive patients (N=18) diagnosed with uterine sarcoma at our unit. The patients were divided into indolent (N=4) and aggressive (N=14) tumour groups, and the maximum standardized uptake values (SUVmax) of all lesions (n=134) were measured. The SUVmax of the lesions were compared between the two tumour groups using the Mann–Whitney U-test. We calculated the optimal cutoff value as determined by receiver operating characteristic analysis. A P-value less than 0.05 was considered statistically significant. ResultsThe mean SUVmax of aggressive (n=104) and indolent tumours (n=30) were significantly different (8.0±7.3 vs. 1.9±0.9 respectively; P<0.001). A cutoff of SUVmax greater than 4.0 was able to exclude indolent tumours, with 100% specificity and positive predictive value (sensitivity 72%, negative predictive value 50% and accuracy 78%; area under the curve 97%). By applying this same cutoff value on the most metabolic active lesion in each patient, we were able to correctly classify all but one patient into either the aggressive or indolent tumour group with 100% specificity and positive predictive value (sensitivity 93%, negative predictive value 80% and accuracy 94%). ConclusionAggressive and indolent uterine sarcoma subtypes have differential metabolic activities that can be used to classify them and this can aid in patient management for preoperative surgical planning and treatment stratification.

SUV as an adjunct in evaluating disease activity in idiopathic pulmonary fibrosis - a pilot study

ObjectiveWe hypothesize that the standardized uptake value (SUV) from PET/computed tomography (CT) can act as an adjunct to forced vital capacity (FVC) in evaluating disease status in idiopathic pulmonary fibrosis (IPF). MethodsEight consecutive male patients diagnosed with IPF were prospectively recruited to undergo full pulmonary function tests, high-resolution computed tomography of the thorax and PET/CT. The corrected mean SUV (rSUVmean) and corrected maximum SUV (rSUVmax) against the mediastinal blood pool were correlated with clinical parameters. Examinations were repeated 6 months later in six patients (2/8 patients had died) and changes were evaluated. Correlation was assessed by Spearman’s rank correlation, and statistical significance was considered when the P-value was less than 0.05. ResultsThe rSUVmean in IPF was negatively correlated with FVC (r=−0.6, P=0.024) and diffusing capacity for carbon monoxide (r=−0.7, P=0.010). The decline in FVC was associated with an increment in rSUVmax (r=−0.9, P=0.019), but no similar observation was made with total CT score (r=−0.1, P=0.787). ConclusionPulmonary metabolism, rSUVmean, contributes to the functional status of IPF patients, and changes in rSUVmax may serve as an adjunct surrogate marker to FVC in evaluating the disease status in IPF patients.

Assessment of Cervical Cancer with a Parameter-Free Intravoxel Incoherent Motion Imaging Algorithm

Objective To evaluate the feasibility of a parameter-free intravoxel incoherent motion (IVIM) approach in cervical cancer, to assess the optimal b-value threshold, and to preliminarily examine differences in the derived perfusion and diffusion parameters for different histological cancer types. Materials and Methods After Institutional Review Board approval, 19 female patients (mean age, 54 years; age range, 37–78 years) gave consent and were enrolled in this prospective magnetic resonance imaging study. Clinical staging and biopsy results were obtained. Echo-planar diffusion weighted sequences at 13 b-values were acquired at 3 tesla field strength. Single-sliced region-of-interest IVIM analysis with adaptive b-value thresholds was applied to each tumor, yielding the optimal fit and the optimal parameters for pseudodiffusion (D*), perfusion fraction (Fp) and diffusion coefficient (D). Monoexponential apparent diffusion coefficient (ADC) was calculated for comparison with D. Results Biopsy revealed squamous cell carcinoma in 10 patients and adenocarcinoma in 9. The b-value threshold (median [interquartile range]) depended on the histological type and was 35 (22.5–50) s/mm2 in squamous cell carcinoma and 150 (100–150) s/mm2 in adenocarcinoma (p < 0.05). Comparing squamous cell vs. adenocarcinoma, D* (45.1 [25.1–60.4] × 10−3 mm2/s vs. 12.4 [10.5–21.2] × 10−3 mm2/s) and Fp (7.5% [7.0–9.0%] vs. 9.9% [9.0–11.4%]) differed significantly between the subtypes (p < 0.02), whereas D did not (0.89 [0.75–0.94] × 10−3 mm2/s vs. 0.90 [0.82–0.97] × 10−3 mm2/s, p = 0.27). The residuals did not differ (0.74 [0.60–0.92] vs. 0.94 [0.67–1.01], p = 0.32). The ADC systematically underestimated the magnitude of diffusion restriction compared to D (p < 0.001). Conclusion The parameter-free IVIM approach is feasible in cervical cancer. The b-value threshold and perfusion-related parameters depend on the tumor histology type.

Beyond the lymph nodes: FDG-PET/CT in primary extranodal lymphoma

Extranodal lymphoma can be the primary presentation or secondary to systemic involvement of lymphoma. 2-(fluorine-18) fluoro-2-deoxy-d-glucose positron emission tomography with computer tomography (FDG-PET/CT) is useful in detecting extranodal sites during staging, treatment response assessment or recurrence detection in patients with lymphoma. In this article, we reviewed the imaging features and FDG avidity of primary extranodal lymphoma of various organs and systems on FDG-PET/CT, demonstrating the pearls and pitfalls of FDG-PET/CT in evaluating this disease entity and cross-referencing to other imaging modalities that aid in diagnosis and management.