Baixuan Xu

Does the Novel Integrated PET/MRI Offer the Same Diagnostic Performance as PET/CT for Oncological Indications?

Background We compared PET/MRI with PET/CT in terms of lesion detection and quantitative measurement to verify the feasibility of the novel integrated imaging modality for oncological applications. Methodology/Principal Findings In total, 285 patients referred to our PET/CT center for oncological indications voluntarily participated in this same-day PET/CT and PET/MRI comparative study. PET/CT images were acquired and reconstructed following routine protocols, and then PET/MRI was performed at a mean time interval of 28±11 min (range 15–45 min). PET/MRI covered the body trunk with a sequence combination of transverse T1WI 3D-volumetric interpolated breath-hold, T2WI turbo spin echo with fat saturation, diffusion-weighted imaging with double b values (50 and 800 s/mm2), and simultaneous PET acquisition over 45 min/5 bed positions. The maximum standardized uptake value (SUVmax) was assessed by manually drawn regions of interest over fluorodeoxyglucose-positive lesions. Among 285 cases, 57 showed no abnormalities, and 368 lesions (278 malignant, 68 benign and 22 undetermined) were detected in 228 patients. When stand-alone modalities were evaluated, PET revealed 31 and 12 lesions missed by CT and MRI, respectively, and CT and MRI revealed 38 and 61 more lesions, respectively, than PET. Compared to CT, MRI detected 40 more lesions and missed 8. In the integrated mode, PET/CT correctly detected 6 lesions misdiagnosed by PET/MRI, but was false-negative in 30 cases that were detected by PET/MRI. The overall diagnosis did not differ between integrated PET/MRI and PET/CT. SUVmax for lesions were slightly higher from PET/MRI than PET/CT but correlated well (ρ = 0.85–0.91). Conclusions/Significance The novel integrated PET/MRI performed comparatively to PET/CT in lesion detection and quantitative measurements. PET from either scanner modality offered almost the same information despite differences in hardware. Further study is needed to explore features of integrated PET/MRI not addressed in this study.

SUVmax/THKmax as a Biomarker for Distinguishing Advanced Gastric Carcinoma from Primary Gastric Lymphoma

Background Gastric carcinoma and primary gastric lymphoma (PGL) are the two most common malignancies in stomach. The purpose of this study was to screen and validate a biomarker of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) for distinguishing advanced gastric carcinoma (AGC) from PGL for clinical applications. Methodology/Principal Findings We reviewed PET/CT scans collected from January 2008 to April 2012 of 69 AGC and 38 PGL (14 low-grade mucosa-associated lymphoid tissue [MALT], 24 non-MALT aggressive non-Hodgkin lymphoma [ANHL]) with a focus on FDG intensity (maximum standardized uptake value [SUVmax]) of primary lesions and its CT-detected abnormalities, including maximal gastrointestinal wall thickness (THKmax) and mucosal ulcerations. Gastric FDG uptake was found in 69 (100%) patients with AGC and 36 (95%, 12 MALT vs. 24 ANHL)with PGL. The presence of CT-detected abnormalities of AGC and PGL were 97% (67/69) and 89% (12 MALT vs. 22 ANHL), respectively. After controlling for THKmax, SUVmax was higher with ANHL than AGC (17.10±8.08 vs. 9.65±5.24, p<0.05) and MALT (6.20±3.60, p<0.05). THKmax did not differ among MALT, ANHL and AGC. Mucosal ulceration was more common with AGC (n = 9) than PGL (n = 2),but the difference was not statistically significant (p>0.05). Cross-validation analysis showed that for distinguishing ANHL from AGC, the classifier with SUVmax as a feature achieved a correct classification rate of 81% with thresholds 13.40±1.12 and the classifier with SUVmax/THKmax as a feature achieved a correct classification rate of 83% with thresholds 7.51±0.63. Conclusions/Significance SUVmax/THKmax may be as a promising biomarker of FDG-PET/CT for distinguishing ANHL from AGC. Structural CT abnormalities alone may not be reliable but can help with PET assessment of gastric malignancies. 18F-FDG PET/CT have potential for distinguishing AGC from PGL at the individual level.

Combination of dynamic 11C-PIB PET and structural MRI improves diagnosis of Alzheimer’s disease

Structural magnetic resonance imaging (sMRI) is an established technique for measuring brain atrophy, and dynamic positron emission tomography with (11)C-Pittsburgh compound B ((11)C-PIB PET) has the potential to provide both perfusion and amyloid deposition information. It remains unclear, however, how to better combine perfusion, amyloid deposition and morphological information extracted from dynamic (11)C-PIB PET and sMRI with the goal of improving the diagnosis of Alzheimers disease (AD) and mild cognitive impairment (MCI). We adopted a linear sparse support vector machine to build classifiers for distinguishing AD and MCI subjects from cognitively normal (CN) subjects based on different combinations of regional measures extracted from imaging data, including perfusion and amyloid deposition information extracted from early and late frames of (11)C-PIB separately, and gray matter volumetric information extracted from sMRI data. The experimental results demonstrated that the classifier built upon the combination of imaging measures extracted from early and late frames of (11)C-PIB as well as sMRI achieved the highest classification accuracy in both classification studies of AD (100%) and MCI (85%), indicating that multimodality information could aid in the diagnosis of AD and MCI.

Establish New Formulas for the Calculation of Renal Depth in Both Children and Adults.

Objective This study was performed to develop a new formula to estimate the renal depth in both children and adults; then compare the new formula with previously published formulas. Methods Renal depth and total thickness (T, cm) of the body at the level of the kidneys were measured by CT in 113 children and 246 adults. Their sex, age, height (H, cm), and weight (W, kg) were recorded. Multiple stepwise linear regression analysis were conducted, using data from children and adults together. The 359 cases were divided into 2 random groups, of which, the first group was used to derive a regressive formula, and the second was used to verify the formula and compare the formula with previously published formulas in different groups. Results Multiple stepwise linear regression analysis showed that the important variable in estimating the depth of each kidney was the ratio of body weight (W, kg) to body height (H, cm) and the total thickness (T, cm) of the body at the level of the kidneys. The new formula was as follows: for right renal depth (cm) = 0.22 × T + 7.714 × W/H-0.331 (r = 0.95), and for left renal depth (cm) = 0.238 × T + 6.553 × W/H-0.618 (r = 0.95). It is better than the other four formulas in different groups, especially in children and W/H ⩽ 0.30 (in adults) groups. Conclusions We first introduced T into renal depth estimation formula and established the new formula. It has a better performance than the other four formulas in different groups. The new formula provided reliable and accurate renal depth and may contribute to improving the methods used to estimate renal function from radionuclide renography.

Correlation between long-term aspirin use and F-fluorodeoxyglucose uptake in colorectal cancer measured by PET/CT.

Purpose The aim of this study was to evaluate the relationship between long-term aspirin use with pretreatment 18 Fluorodeoxyglucose (FDG) uptake of primary lesions of Colorectal cancer (CRC) and evaluate their clinical significance. Materials and Methods We enrolled 84 patients with CRC who underwent 18F-FDG PET/CT scanning before surgery between 1st July 2008 and 1st March 2013 and followed up until 1st March 2014. Maximum standardized uptake value (SUVmax) of the primary tumor was measured by 18F-FDG PET/CT. The history of aspirin taken and other clinicopathogical factors were also obtained and their relationships were examined by Mann-Whitney or χ2 tests. Progression-free survival (PFS) was determined by standard Kaplan-Meier survival analysis. Cox proportional hazards regression was performed to determine whether history of aspirin taken, pretreatment SUVmax, age, gender, TNM stage, tumor sizes and differentiation influenced outcomes. Results CRC Patients with long-term history of aspirin use had lower SUVmax of primary lesions than control group (9.74±2.62 vs. 13.91±6.18) and showed a trend towards improved PFS after curative surgery. However, pretreatment of SUVmax showed no prognostic value in patients with CRC. Conclusions Long-term aspirin use is associated with lower pretreatment SUVmax of CRC and is a promising prognostic factor for predicting PFS in patients with CRC.

Standardized uptake value based evaluation of lymphoma by FDG and FLT PET/CT

Although 18F‐FDG PET/CT imaging is the conventional method for evaluating lymphoma, PET/CT imaging with radiopharmaceuticals other than FDG is being investigated. We evaluated the utility of different standardized uptake value (SUV) measurements in 18F‐FLT PET/CT scans compared with PET/CT scans performed with FDG. Two scans, each using one of the radiopharmaceuticals, were performed on each of 114 patients with histologically proven lymphoma. Maximum and mean SUV (SUVmax) and (SUVmean) of all visualized lesions, with backgrounds of mediastinal blood pool, liver, spleen and vertebra were calculated. The ratios of the SUVs of the lesions to those of each reference region were statistically analyzed. Using receiver operating characteristic curves, we analyzed the differences in uptake of the two agents in aggressive and indolent B‐cell non‐Hodgkin lymphoma. We found that the SUVmax measurements of FDG were significantly different between aggressive and indolent B‐cell non‐Hodgkin lymphoma. The receiver operating characteristic curve of SUVmax of tumour/liver for FDG studies resulted in the most area under the curve. The SUVmax of the tumour/mediastinum ratio for FLT studies resulted in the most area under the curve (0.781). There was no significant correlation between FDG and FLT uptake in most types of lymphoma we studied. Further studies of the characteristics of 18F‐FLT should employ the tumour/mediastinum SUVmax ratio for accurate uptake measurement. Copyright

Evaluation of 18F-FDG and 18F-FLT for monitoring therapeutic responses of colorectal cancer cells to radiotherapy

In order to compare the efficacy of (18)F-fluorothymidine (FLT) and (18)F-fluorodeoxyglucose (FDG) for monitoring early responses to irradiation, two human colorectal cancer (CRC) cell lines SW480 and SW620, which were derived from the primary lesions and the metastatic lymph node, underwent X-ray irradiation of 0, 10, or 20 Gy and were examined at 0, 24 and 72 h After irradiation, reduced proliferation of both SW480 and SW620 cells was observed in a dose-dependent manner (P<0.001), G0-G1 arrest was also noted in both cell types after 72 h in the 20 Gy group (P<0.001). Although increased apoptosis was observed in both cell lines after irradiation (P<0.001), a greater percentage of SW480 cells underwent apoptosis in response to irradiation than SW620 cells. Increased Hsp27 and decreased integrin β3, Ki67 and VEGFR2 expression was observed over time via immunocytochemistry and Western blot analysis (P<0.001), however, no significant changes were noted in response to irradiation. Finally, reduced uptake of (18)F-FLT by SW480 or SW620 cells was observed at 24-h post-irradiation, however, reduced (18)F-FDG uptake was only observed after 72 h. Therefore, we conclude that (18)F-FLT is a more suitable positron emission tomography (PET) tracer for monitoring early responses to irradiation in primary and metastatic lymph node CRC cells.

The Influence of Interpreters’ Professional Background and Experience on the Interpretation of Multimodality Imaging of Pulmonary Lesions Using 18F-3′-Deoxy-Fluorothymidine and 18F-Fluorodeoxyglucose PET/CT

Objective Based on the results of a recently accomplished multicenter clinical trial for the incremental value of a dual-tracer (18F-FDG and 18F-FLT), dual-modality (PET and CT) imaging in the differential diagnosis of pulmonary lesions, we investigate some issues that might affect the image interpretation and result reporting. Methods The images were read in two separate sessions. Firstly the images were read and reported by physician(s) of the imaging center on completion of each PET/CT scanning. By the end of MCCT, all images collected during the trial were re-read by a collective of readers in an isolated, blinded, and independent way. Results One hundred sixty two patients successfully passed the data verification and entered into the final analysis. The primary reporting result showed adding 18F-FDG image information did not change the clinical performance much in sensitivity, specifity and accuracy, but the ratio between SUVFLT and SUVFDG did help the differentiation efficacy among the three subgroups of patients. The collective reviewing result showed the diagnostic achievement varied with reading strategies. ANOVA indicated significant differences among 18F-FDG, 18F- FLT in SUV (F = 14.239, p = 0.004). CT had almost the same diagnostic performance as 18F-FLT. When the 18F-FDG, 18F- FLT and CT images read in pair, both diagnostic sensitivity and specificity improved. The best diagnostic figures were obtained in full-modality strategy, when dual-tracer PET worked in combination with CT. Conclusions With certain experience and training both radiologists and nuclear physicians are qualified to read and to achieve the similar diagnostic accuracy in PET/CT study. Making full use of modality combination and selecting right criteria seems more practical than professional back ground and personal experience in the new hybrid imaging technology, at least when novel tracer or application is concerned.

Brain Network Alterations in Alzheimer’s Disease Identified by Early-Phase PIB-PET

The aim of this study was to identify the brain networks from early-phase 11C-PIB (perfusion PIB, pPIB) data and to compare the brain networks of patients with differentiating Alzheimers disease (AD) with cognitively normal subjects (CN) and of mild cognitively impaired patients (MCI) with CN. Forty participants (14 CN, 12 MCI, and 14 AD) underwent 11C-PIB and 18F-FDG PET/CT scans. Parallel independent component analysis (pICA) was used to identify correlated brain networks from the 11C-pPIB and 18F-FDG data, and a two-sample t-test was used to evaluate group differences in the corrected brain networks between AD and CN, and between MCI and CN. Our study identified a brain network of perfusion (early-phase 11C-PIB) that highly correlated with a glucose metabolism (18F-FDG) brain network and colocalized with the default mode network (DMN) in an AD-specific neurodegenerative cohort. Particularly, decreased 18F-FDG uptake correlated with a decreased regional cerebral blood flow in the frontal, parietal, and temporal regions of the DMN. The group comparisons revealed similar spatial patterns of the brain networks derived from the 11C-pPIB and 18F-FDG data. Our findings indicate that 11C-pPIB derived from the early-phase 11C-PIB could provide complementary information for 18F-FDG examination in AD.

Suite PET/CT neuroimaging for the diagnosis of Parkinson’s disease: statistical parametric mapping analysis

Objectives The aim of this study was to investigate the topographical distribution of dopamine transporter (DAT), dopamine D2 receptor, and glucose metabolism in Parkinson’s disease (PD) using PET/computed tomography (CT) scanning and statistical parametric mapping (SPM) analysis. Participants and methods Seventy-four patients (58 PD patients and 16 normal controls) underwent DAT, D2 receptor, and glucose brain PET/CT scans using 11C-methyl-N-2-&bgr;-carbomethoxy-3-&bgr;-(4-fluorophenyl) tropane (11C-&bgr;-CFT), 11C-raclopride (11C-RAC), and fluorine-18-fluorodeoxyglucose (18F-FDG) radiotracers for the respective scans. All three PET/CT procedures were performed in each participant. The uptake patterns were analyzed using SPM software. Results Striatal DAT binding was lower in PD patients than in controls, whereas D2 receptor binding did not differ between PD patients and controls. D2 receptor binding was increased in the putamen in only the 12 drug-naive patients. Glucose uptake was also slightly lower in the cingulate gyrus of PD patients than in the controls. Conclusion Suite PET/CT scans using the ligands 11C-&bgr;-CFT, 11C-RAC, and 18F-FDG PET/CT are valuable for diagnosing PD. SPM-based analysis of static PET/CT scan data is potentially of great clinical use.