Bingsheng Huang

Whole-Body PET/CT Scanning: Estimation of Radiation Dose and Cancer Risk

PURPOSEnTo estimate the radiation dose from whole-body fluorine 18 ((18)F)-fluorodeoxyglucose (FDG) positron emission tomographic (PET)/computed tomographic (CT) studies and to evaluate the induced cancer risk to U.S. and Hong Kong populations.nnnMATERIALS AND METHODSnFluorine 18-FDG PET/CT studies obtained by using a 64-detector CT unit and one of three CT protocols were evaluated. CT protocol A consisted of 120 kV; rotation time, 0.5 second; pitch, 0.984; 100-300 mA; and noise level, 20. CT protocol B was the same as A, except for a fixed tube current of 250 mA. CT protocol C consisted of 140 kV; rotation time, 0.5 second; pitch, 0.984; 150-350 mA; and noise level, 3.5. CT doses were measured in a humanoid phantom equipped with thermoluminescent dosimeters. Doses from (18)F-FDG PET scanning were estimated by multiplying the (18)F-FDG radioactivity (370 MBq) with dose coefficients. Effective doses were calculated according to International Commission on Radiological Protection publication 103. Lifetime attributable risk (LAR) of cancer incidence was estimated according to the National Academies Biological Effects of Ionizing Radiation VII Report.nnnRESULTSnEffective doses with protocols A, B, and C, respectively, were 13.45, 24.79, and 31.91 mSv for female patients and 13.65, 24.80, and 32.18 mSv for male patients. The LAR of cancer incidence associated with the dose was higher in the Hong Kong population than in the U.S. population. For 20-year-old U.S. women, LARs of cancer incidence were between 0.231% and 0.514%, and for 20-year-old U.S. men, LARs of cancer incidence were between 0.163% and 0.323%; LARs were 5.5%-20.9% higher for the Hong Kong population. The induced cancer risks decreased when age at exposure increased.nnnCONCLUSIONnWhole-body PET/CT scanning is accompanied by substantial radiation dose and cancer risk. Thus, examinations should be clinically justified, and measures should be taken to reduce the dose.

Radiation dose and cancer risk from pediatric CT examinations on 64-slice CT: a phantom study.

OBJECTIVEnTo measure the radiation dose from CT scans in an anthropomorphic phantom using a 64-slice MDCT, and to estimate the associated cancer risk.nnnMATERIALS AND METHODSnOrgan doses were measured with a 5-year-old phantom and thermoluminescent dosimeters. Four protocols; head CT, thorax CT, abdomen CT and pelvis CT were studied. Cancer risks, in the form of lifetime attributable risk (LAR) of cancer incidence, were estimated by linear extrapolation using the organ radiation doses and the LAR data.nnnRESULTSnThe effective doses for head, thorax, abdomen and pelvis CT, were 0.7mSv, 3.5mSv, 3.0mSv, 1.3mSv respectively. The organs with the highest dose were; for head CT, salivary gland (22.33mGy); for thorax CT, breast (7.89mGy); for abdomen CT, colon (6.62mGy); for pelvis CT, bladder (4.28mGy). The corresponding LARs for boys and girls were 0.015-0.053% and 0.034-0.155% respectively. The organs with highest LARs were; for head CT, thyroid gland (0.003% for boys, 0.015% for girls); for thorax CT, lung for boys (0.014%) and breast for girls (0.069%); for abdomen CT, colon for boys (0.017%) and lung for girls (0.016%); for pelvis CT, bladder for both boys and girls (0.008%).nnnCONCLUSIONnThe effective doses from these common pediatric CT examinations ranged from 0.7mSv to 3.5mSv and the associated lifetime cancer risks were found to be up to 0.16%, with some organs of higher radiosensitivity including breast, thyroid gland, colon and lungs.

Pediatric 64-MDCT Coronary Angiography With ECG-Modulated Tube Current: Radiation Dose and Cancer Risk

OBJECTIVEnThe purpose of our study was to measure the radiation dose from ECG-gated CT coronary angiography in children and to estimate the cancer risk associated with the radiation dose.nnnMATERIALS AND METHODSnOrgan doses were measured with a 5-year-old pediatric phantom and thermoluminescent dosimeters on a 64-MDCT scanner. Four retrospectively ECG-gated CT coronary angiography protocols with four simulated heart rates and the corresponding pitches were studied. The lifetime attributable risk of cancer incidence was estimated for children in the United States and Hong Kong according to the National Academies Biologic Effects of Ionizing Radiation VII report.nnnRESULTSnThe effective doses were 16.45, 12.17, 11.97, and 11.81 mSv for the four protocols, respectively. The corresponding lifetime attributable risks estimated for 5-year-old U.S. boys and girls were 0.14%-0.20% and 0.43%-0.60%, respectively, and for 5-year-old Hong Kong boys and girls were 0.22%-0.33% and 0.61%-0.85%. In relation to the total cancer incidence (baseline cancer incidence plus lifetime attributable risk), lifetime attributable risk from radiation exposure contributed up to 0.99% and 3.51% for Hong Kong boys and girls and up to 0.46% and 1.57% for U.S. boys and girls.nnnCONCLUSIONnOur results suggest that radiation dose and cancer risk of CT coronary angiography to pediatric patients are not negligible, more so in Hong Kong children than in U.S. children. Therefore, these examinations should be well justified clinically.

Nasopharyngeal Carcinoma: Investigation of Intratumoral Heterogeneity With FDG PET/CT

OBJECTIVEnThe purpose of this study was to quantitatively evaluate the role of intratumoral heterogeneity of (18)F-FDG uptake in characterizing nasopharyngeal carcinoma (NPC).nnnSUBJECTS AND METHODSnForty consecutively registered patients with newly diagnosed NPC underwent PET/CT. The heterogeneity factor, defined as the derivative of a volume threshold function, was computed for each tumor. The relations between heterogeneity factor and maximum standardized uptake value (SUV(max)), tumor volume, and TNM category were determined by two-tailed Spearman correlation. Factors that potentially affect outcome determined by disease-free survival were studied by Kaplan-Meier analysis with a log-rank test for univariate analysis and the Cox proportional hazard model for multivariate analysis.nnnRESULTSnThe heterogeneity factor ranged from -1.80 to -0.13 (mean, -0.40 [SD, 0.40]) and significantly correlated with SUV(max) (r = -0.372; p = 0.018), tumor volume (r = -0.983; p < 0.001), and T category (r = -0.457; p = 0.003) but not with N and M categories. There was a significant difference in heterogeneity factor between T1 and T2 tumors and T3 and T4 tumors (p = 0.012). The 2-year disease-free survival rate among the 38 patients was 67.4%. According to the results of Kaplan-Meier analysis with the log-rank test, heterogeneity factor and M category significantly affected disease-free survival. Patients with tumors that had a heterogeneity factor greater than -0.24 (less-heterogeneous group) (p = 0.0498) or M0 status (p < 0.001) had better disease-free survival rates. Multivariate analysis showed only M category to be an independent predictor of disease-free survival (p < 0.001).nnnCONCLUSIONnThe intratumoral heterogeneity of FDG uptake varies across NPC tumors, significantly correlates with tumor aggressiveness, and is predictive of patient outcome. These findings may be useful for characterizing NPC, predicting survival, and improving patient care.

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.

Nasopharyngeal carcinoma: comparison of diffusion and perfusion characteristics between different tumour stages using intravoxel incoherent motion MR imaging

AbstractObjectiveTo explore intravoxel incoherent motion (IVIM) characteristics of nasopharyngeal carcinoma (NPC) and relationships with different tumour stages.MethodsWe prospectively recruited 80 patients with newly diagnosed undifferentiated NPC. Diffusion-weighted MR imaging was performed and IVIM parameters (D, pure diffusion; f, perfusion fraction; D*, pseudodiffusion coefficient) were calculated. Patients were stratified into low and high tumour stage groups based on American Joint Committee on Cancer (AJCC) and TNM staging for determination of the predictive powers of IVIM parameters using t test, multiple logistic regression and ROC curve analyses.ResultsD, f and D* were all statistically significantly lower in high-stage groups in AJCC, T and N staging. D, f and D* were all independent predictors of AJCC staging, f and D* were independent predictors of T staging, and D was an independent predictor of N staging. D was most powerful for AJCC and N staging, whereas f was most powerful for T staging. Optimal cut-off values (area under the curve, sensitivity, specificity, positive likelihood ratio, negative likelihood ratio) were as follows: AJCC stage, Du2009=u20090.782u2009×u200910−3xa0mm2/s (0.915, 93.3xa0%, 76.2xa0%, 3.92, 0.09); T staging, fu2009=u20090.133 (0.905, 80.5xa0%, 92.5xa0%, 10.73, 0.21); N staging, Du2009=u20090.761u2009×u200910−3xa0mm2/s (0.848, 87.5xa0%, 66.7xa0%, 2.62, 0.19). Multivariate analysis showed no diagnostic improvement.ConclusionNasopharyngeal carcinoma has distinctive intravoxel incoherent motion characteristics parameters in different tumour staging, potentially helping pretreatment staging.Key Points• Magnetic resonance imaging is increasingly used to assess nasopharyngeal carcinoma (NPC).n • NPC has distinctive diffusion/perfusion characteristics at different stages.n • Non-invasive MR imaging may help pretreatment staging prediction.n • Diffusion properties of NPC best correlate with AJCC and N staging.n • Perfusion properties of NPC best correlate with T staging.

Nasopharyngeal carcinoma: relationship between 18F-FDG PET-CT maximum standardized uptake value, metabolic tumour volume and total lesion glycolysis and TNM classification.

PurposeWe aimed to evaluate the relationships between primary tumour; maximum standardized uptake value (SUVmax), metabolic tumour volume (TV) and total lesion glycolysis (TLG) and tumour-node metastases (TNM) classification in nasopharyngeal carcinoma (NPC) patients. MethodsFluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography scans of 57 consecutive newly diagnosed NPC patients (age range, 15–80 years) were retrospectively reviewed. SUVmax, TV and TLG were recorded. Two-tailed Spearmans correlation was used to analyse the relationships between the metabolic parameters and the TNM staging system. ResultsPositive correlations were observed between SUVmax (P<0.001, R=0.516), TV (P<0.001, R=0.504) and TLG (P<0.001, R=0.620) and T-stage, and both TV and SUVmax were independent variables that significantly affected T-stage (P<0.001, adjusted R2=0.370). No other significant correlations were found between the metabolic parameters and TNM classification system. ConclusionThe metabolic parameters derived from fluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography were positively correlated with T-stage in primary NPC. Our findings may suggest a complementary role of these parameters to TNM staging in prognostication of NPC patients.

Dynamic contrast-enhanced magnetic resonance imaging for characterising nasopharyngeal carcinoma: comparison of semiquantitative and quantitative parameters and correlation with tumour stage

AbstractObjectivesTo evaluate dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for characterising nasopharyngeal carcinoma (NPC).MethodsForty-five newly diagnosed NPC patients were recruited. The initial enhancement rate (ER), contrast transfer rate (kep), elimination rate (kel), maximal enhancement (MaxEn) and initial area under the curve (iAUC) were calculated from semiquantitative analysis. The Ktrans (volume transfer constant), ve (volume fraction) and kep were calculated from quantitative analysis. Student’s t-test was used to evaluate the differences among tumour stages. Pearson’s correlation between the two sets of kep was performed.ResultsComparing tumours of T1/2 stage (nu2009=u200918) and T3/4 stage (nu2009=u200927), MaxEn (Pu2009=u20090.030) and iAUC (Pu2009=u20090.039) were both significantly different; however, the iAUC was the only independent variable with 69.6xa0% sensitivity and 76.5xa0% specificity respectively; ve was also significantly different (Pu2009=u20090.010) with 69.6xa0% sensitivity and 70.6xa0% specificity respectively. No significant difference was found among N stages. The two sets of keps were highly correlated (ru2009=u20090.809, Pu2009<u20090.001). Forty-three patients had chemoradiation, one palliative chemotherapy and one radiotherapy only. In the four patients with poor outcome, kel,ER, MaxEn and iAUC tended to be higher.ConclusionsNeovasculature in higher T stage NPC exhibits some parameters of increased permeability and perfusion. Thus, DCE-MRI may be helpful as an adjunctive technique in evaluating NPC.Key Points• The correct assessment of nasopharyngeal carcinoma (NPC) is important for planning treatment.n • Neovasculature in higher T stage NPC exhibits increased permeability and perfusion.n • Correlation between quantitative and semi-quantitative analysis validates the robustness of DCE-MRI.n • DCE-MRI may be helpful as an adjunctive parameter in evaluating NPC.

Prognostic Impact of Standardized Uptake Value of F-18 Fdg Pet/ct in Nasopharyngeal Carcinoma

Purpose: We evaluated the use of metabolic parameters of F-18 fluorodeoxyglucose positron emission tomography (FDG PET) for the assessment of the primary tumor and nodal metastasis in predicting survival in nasopharyngeal carcinoma (NPC) patients. Materials and Methods: The F-18 FDG PET/CT (computed tomography) scans of 46 consecutive newly diagnosed NPC patients were retrospectively reviewed. Maximal standardized uptake value (SUVmax) corrected for lean body mass of primary tumor (pSUVmax) and highest SUVmax of cervical lymph nodes (nSUVmax) were recorded. The association of FDG uptake and 2-year disease-free survival (DFS) was examined. Results: Significantly better DFS was found in patients with pSUVmax <7.5 and nSUVmax <6.5 (P = 0.042 and P = 0.019, respectively). In multivariate analysis, both pSUVmax and nSUVmax were significant independent predictors of DFS. Conclusions: The SUVmax of the primary tumor and nodal metastasis are useful parameters for predicting DFS in NPC patients.

Dynamic PET-CT studies for characterizing nasopharyngeal carcinoma metabolism: comparison of analytical methods

ObjectivesTo investigate the optimal PET protocol and analytical method to characterize the glucose metabolism in nasopharyngeal carcinoma (NPC). MethodsNewly diagnosed NPC patients were recruited and a dynamic PET-CT scan was performed. The optimized threshold to derive the arterial input function (AIF) was studied. Two-tissue compartmental kinetic modeling using three, four, and five parameters, Patlak graphical analysis, and time sensitivity (S-factor) analysis were performed. The best compartmental model was determined in terms of goodness of fit, and correlated with Ki from Patlak graphical analysis and the S-factor. The methods with R>0.9 and P<0.05 were considered acceptable. The protocols using two static scans with its retention index (RI=(SUV2/SUV1−1)×100%, where SUV is the standardized uptake value) were also studied and compared with S-factor analysis. ResultsThe best threshold of 0.6 was determined and used to derive AIF. The kinetic model with five parameters yields the best statistical results, but the model with k4=0 was used as the gold standard. All Ki values and some S-factors from data between various intervals (10–30, 10–45, 15–30, 15–45, 20–30, and 20–45 min) fulfilled the criteria. The RIs calculated from the S-factor were highly correlated to RI derived from simple two-point static scans at 10 and 30 min (R=0.9, P<0.0001). ConclusionThe Patlak graphical analyses and even a 20-min-interval S-factor analysis or simple two-point static scans were shown to be sufficient to characterize NPC metabolism, confirming the clinical feasibility of applying a short dynamic with image-derived AIF or simple two-point static PET scans for studying NPC.