Blood flow–metabolic relationships are dependent on tumour size in non-small cell lung cancer: a study using quantitative contrast-enhanced computer tomography and positron emission tomography

Assessment of Correlation between Dual-Energy Ct (De-Ct)-Derived Iodine Concentration and Local Flourodeoxyglucose (Fdg) Uptake in Patients with Primary Non-Small-Cell Lung Cancer

(1) The current literature contains several studies investigating the correlation between dual-energy-derived iodine concentration (IC) and positron emission tomography (PET)-derived Flourodeoxyglucose (18F-FDG) uptake in patients with non-small-cell lung cancer (NSCLC). In previously published studies, either the entire tumor volume or a region of interest containing the maximum IC or 18F-FDG was assessed. However, the results have been inconsistent. The objective of this study was to correlate IC with FDG both within the entire volume and regional sub-volumes of primary tumors in patients with NSCLC. (2) In this retrospective study, a total of 22 patients with NSCLC who underwent both dual-energy CT (DE-CT) and 18F-FDG PET/CT were included. A region of interest (ROI) encircling the entire primary tumor was delineated, and a rigid registration of the DE-CT, iodine maps and FDG images was performed for the ROI. The correlation between tumor measurements and area-specific measurements of ICpeak and the peak standardized uptake value (SUVpeak) was found. Finally, a correlation between tumor volume and the distance between SUVpeak and ICpeak centroids was found. (3) For the entire tumor, moderate-to-strong correlations were found between SUVmax and ICmax (R = 0.62, p = 0.002), and metabolic tumor volume vs. total iodine content (R = 0.91, p < 0.001), respectively. For local tumor sub-volumes, a negative correlation was found between ICpeak and SUVpeak (R = −0.58, p = 0.0046). Furthermore, a strong correlation was found between the tumor volume and the distance in millimeters between SUVpeak and ICpeak centroids (R = 0.81, p < 0.0001). (4) In patients with NSCLC, high FDG uptakes and high DE-CT-derived iodine concentrations correlated on a whole-tumor level, but the peak areas were positioned at different locations within the tumor. 18F-FDG PET/CT and DE-CT provide complementary information and might represent different underlying patho-physiologies.

A comparison study of dual-energy spectral CT and 18F-FDG PET/CT in primary tumors and lymph nodes of lung cancer

PURPOSE

We aimed to investigate whether there is a correlation between dual-energy spectral computed tomography (DESCT) and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) parameters in primary tumor and metastatic lymph nodes in patients with newly diagnosed lung cancer.

METHODS

Primary tumor and metastatic lymph nodes of 68 patients diagnosed with lung cancer were evaluated retrospectively with 18F-FDG PET/CT and DESCT imaging. The histologic subtypes were adenocarcinoma (n=29), squamous cell carcinoma (SCC) (n=26), small cell lung cancer (SCLC) (n=11), and large cell neuroendocrine cancer (LCNEC) (n=2). In terms of PET parameters, SUVmax, SUVmean, SULmax, SULmean, SULpeak, and normalized SUL values were obtained for primary tumors and metastatic lymph nodes. In terms of DESCT parameters, maximum and mean iodine content (IC), normalized IC values, iodine enhancement (IE) and normalized IE values were calculated.

RESULTS

We found no correlation between DESCT and 18F-FDG PET/CT parameters in primary tumors and metastatic lymph nodes. In addition, no correlation was found in the analysis performed in any of the histologic subgroups. In patients with a primary tumor <3 cm, there was a moderate negative correlation between the parameters SUVmax-ICmax (r= -0.456, p = 0.043), SUVmean-ICmax (r= -0.464, p = 0.039) SULmean-ICmax (r= -0.497, p = 0.026), SUVmax-ICmean (r= -0.527, p = 0.020), SULmean-ICmean (r= -0.499, p = 0.025), and SULpeak-ICmean (r= -0.488, p = 0.029).

CONCLUSION

We consider that DESCT and 18F-FDG PET/CT indicate different characteristics of the tumors and should not supersede each other.

18F-FDG PET and DCE kinetic modeling and their correlations in primary NSCLC: first voxel-wise correlative analysis of human simultaneous [18F]FDG PET-MRI data

OBJECTIVES

To decipher the correlations between PET and DCE kinetic parameters in non-small-cell lung cancer (NSCLC), by using voxel-wise analysis of dynamic simultaneous [18F]FDG PET-MRI.

MATERIAL AND METHODS

Fourteen treatment-naïve patients with biopsy-proven NSCLC prospectively underwent a 1-h dynamic [18F]FDG thoracic PET-MRI scan including DCE. The PET and DCE data were normalized to their corresponding T1-weighted MR morphological space, and tumors were masked semi-automatically. Voxel-wise parametric maps of PET and DCE kinetic parameters were computed by fitting the dynamic PET and DCE tumor data to the Sokoloff and Extended Tofts models respectively, by using in-house developed procedures. Curve-fitting errors were assessed by computing the relative root mean square error (rRMSE) of the estimated PET and DCE signals at the voxel level. For each tumor, Spearman correlation coefficients (rs) between all the pairs of PET and DCE kinetic parameters were estimated on a voxel-wise basis, along with their respective bootstrapped 95% confidence intervals (n = 1000 iterations).

RESULTS

Curve-fitting metrics provided fit errors under 20% for almost 90% of the PET voxels (median rRMSE = 10.3, interquartile ranges IQR = 8.1; 14.3), whereas 73.3% of the DCE voxels showed fit errors under 45% (median rRMSE = 31.8%, IQR = 22.4; 46.6). The PET-PET, DCE-DCE, and PET-DCE voxel-wise correlations varied according to individual tumor behaviors. Beyond this wide variability, the PET-PET and DCE-DCE correlations were mainly high (absolute rs values > 0.7), whereas the PET-DCE correlations were mainly low to moderate (absolute rs values < 0.7). Half the tumors showed a hypometabolism with low perfused/vascularized profile, a hallmark of hypoxia, and tumor aggressiveness.

CONCLUSION

A dynamic "one-stop shop" procedure applied to NSCLC is technically feasible in clinical practice. PET and DCE kinetic parameters assessed simultaneously are not highly correlated in NSCLC, and these correlations showed a wide variability among tumors and patients. These results tend to suggest that PET and DCE kinetic parameters might provide complementary information. In the future, this might make PET-MRI a unique tool to characterize the individual tumor biological behavior in NSCLC.

The flow-metabolism ratio might predict treatment response and survival in patients with locally advanced esophageal squamous cell carcinoma

Background

Perfusion CT can offer functional information about tumor angiogenesis, and ¹⁸F-FDG PET/CT quantifies the glucose metabolic activity of tumors. This prospective study aims to investigate the value of biologically relevant imaging biomarkers for predicting treatment response and survival outcomes in patients with locally advanced esophageal squamous cell cancer (LA ESCC).

Methods

Twenty-seven patients with pathologically proven ESCC were included. All patients had undergone perfusion CT and ¹⁸F-FDG PET/CT using separate imaging systems before receiving definitive chemoradiotherapy (dCRT). The perfusion parameters included blood flow (BF), blood volume (BV), and time to peak (TTP), and the metabolic parameters included maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG). The flow-metabolism ratio (FMR) was defined as BF divided by SUVmax. Statistical methods used included Spearman’s rank correlation, Mann–Whitney U test or two-sample t test, receiver operating characteristic (ROC) curve analysis, the Kaplan–Meier method, and Cox proportional hazards models.

Results

The median overall survival (OS) and progression-free survival (PFS) were 18 and 11.6 months, respectively. FMR was significantly positively correlated with BF (r = 0.886, p < 0.001) and negatively correlated with SUVmax (r = − 0.547, p = 0.003) and TTP (r = − 0.462, p = 0.015) in the tumors. However, there was no significant correlation between perfusion and PET parameters. After dCRT, 14 patients (51.9%) were identified as responders, and another 13 were nonresponders. The BF and FMR of the responders were significantly higher than those of the nonresponders (42.05 ± 16.47 vs 27.48 ± 8.55, p = 0.007; 3.18 ± 1.15 vs 1.84 ± 0.65, p = 0.001). The ROC curves indicated that the FMR [area under the curve (AUC) = 0.846] was a better biomarker for predicting treatment response than BF (AUC = 0.802). Univariable Cox analysis revealed that of all imaging parameters, only the FMR was significantly correlated with overall survival (OS) (p = 0.015) and progression-free survival (PFS) (p = 0.017). Specifically, patients with a lower FMR had poorer survival. Multivariable analysis showed that after adjusting for age, clinical staging, and treatment response, the FMR remained an independent predictor of OS (p = 0.026) and PFS (p = 0.014).

Conclusions

The flow-metabolism mismatch demonstrated by a low FMR shows good potential in predicting chemoradiotherapy sensitivity and prognosis in ESCC.

Cavity Formation is a Prognostic Indicator for Pathologic Stage I Invasive Lung Adenocarcinoma of ≥3 cm in Size

Background

We investigated the correlation between cavity formation, prognosis, and tumor stage for pathologic stage I invasive lung adenocarcinomas (IADCs) ≤3 cm in size.

Material/Methods

2106 candidates with pathologic stage I IADC were identified from Shanghai Chest Hospital between 2009 and 2014. There were 227 patients who were diagnosed as having cavity formation and another 1879 patients who were not (the non-cavitary lung cancer group). Kaplan-Meier analysis curves were conducted to compare the overall survival (OS) and relapse-free survival (RFS) between these 2 groups. Cox proportional hazards regression was performed to discover the independent risk factors of OS and RFS. Receiver operating characteristic (ROC) curve was done to determine the cutoff value of cavity size for predicting prognosis. Furthermore, subgroup analysis was stratified by the size of tumor and the 8^th classification of T category.

Results

Compared with non-cavitary lung cancer group, patients with cavity formation were found to have a higher prevalence of male patients (P=0.015), older age patients (P=0.039), larger size tumors (P=0.004), and worse cancer relapse (P<0.001). Survival analysis found that patients with cavitary IADC had significantly shorter RFS than those with non-cavitary IADC (P=0.001). Further, subgroup analysis confirmed a significantly worse RFS in cavitary IADC group both in stage T1a (P=0.002) and T1b (P<0.001), but not for stage T1c (P=0.962) and T2a (P=0.364). Moreover, cavity formation was still less of a significant predictor of RFS in multivariable analysis (hazard ratio [HR] 1.810, 95% confidence level [CI] 1.229–2.665, P=0.003). The ROC curve showed that the best cutoff value of maximum diameter of the cavity for judging RFS was 5 mm (sensitivity: 0.500; specificity: 0.783). At the same time, multiple cavities were more likely to lead to recurrence (sensitivity: 0.605; specificity: 0.439).

Conclusions

Cavitary adenocarcinoma was a worse prognostic indicator compared with non-cavitary adenocarcinoma, especially for cavity >5 mm and multiple cavities. Thus, for stage T1a and T1b, cavitary and non-cavitary IADC should be considered separately.

Noninvasive assessment and quantification of tumor vascularization using [18F]FDG-PET/CT and CE-CT in a tumor model with modifiable angiogenesis-an animal experimental prospective cohort study

Background

This study investigated the noninvasive assessment of tumor vascularization with clinical F-18-fluorodeoxyglucose positron emission tomography/computed tomography and contrast-enhanced computed tomography ([18F]FDG-PET/CT and CE-CT) in experimental human xenograft tumors with modifiable vascularization and compared results to histology. Tumor xenografts with modifiable vascularization were established in 71 athymic nude rats by subcutaneous transplantation of human non-small-cell lung cancer (NSCLC) cells. Four different groups were transplanted with two different tumor cell lines (either A549 or H1299) alone or tumors co-transplanted with rat glomerular endothelial (RGE) cells, the latter to increase vascularization. Tumors were assessed noninvasively by [18F]FDG PET/CT and contrast-enhanced CT (CE-CT) using clinical scanners. This was followed by histological examinations evaluating tumor vasculature (CD-31 and intravascular fluorescent beads).

Results

In both tumor lines (A549 and H1299), co-transplantation of RGE cells resulted in faster growth rates [maximal tumor diameter of 20 mm after 22 (± 1.2) as compared to 45 (± 1.8) days, p < 0.001], higher microvessel density (MVD) determined histologically after CD-31 staining [171.4 (± 18.9) as compared to 110.8 (± 11) vessels per mm², p = 0.002], and higher perfusion as indicated by the number of beads [1.3 (± 0.1) as compared to 1.1 (± 0.04) beads per field of view, p = 0.001]. In [18F]FDG-PET/CT, co-transplanted tumors revealed significantly higher standardized uptake values [SUVmax, 2.8 (± 0.2) as compared to 1.1 (± 0.1), p < 0.001] and larger metabolic active volumes [2.4 (± 0.2) as compared to 0.4 (± 0.2) cm³, p < 0.001] than non-co-transplanted tumors. There were significant correlations for vascularization parameters derived from histology and [18F]FDG PET/CT [beads and SUVmax, r = 0.353, p = 0.005; CD-31 and SUVmax, r = 0.294, p = 0.036] as well as between CE-CT and [18F]FDG PET/CT [contrast enhancement and SUVmax, r = 0.63, p < 0.001; vital CT tumor volume and metabolic PET tumor volume, r = 0.919, p < 0.001].

Conclusions

In this study, a human xenograft tumor model with modifiable vascularization implementable for imaging, pharmacological, and radiation therapy studies was successfully established. Both [18F]FDG-PET/CT and CE-CT are capable to detect parameters closely connected to the degree of tumor vascularization, thus they can help to evaluate vascularization in tumors noninvasively. [18F]FDG-PET may be considered for characterization of tumors beyond pure glucose metabolism and have much greater contribution to diagnostics in oncology.

Photoacoustic microscopy: principles and biomedical applications

Photoacoustic microscopy (PAM) has become an increasingly popular technology for biomedical applications, providing anatomical, functional, and molecular information. In this concise review, we first introduce the basic principles and typical system designs of PAM, including optical-resolution PAM and acoustic-resolution PAM. The major imaging characteristics of PAM, i.e. spatial resolutions, penetration depth, and scanning approach are discussed in detail. Then, we introduce the major biomedical applications of PAM, including anatomical imaging across scales from cellular level to organismal level, label-free functional imaging using endogenous biomolecules, and molecular imaging using exogenous contrast agents. Lastly, we discuss the technical and engineering challenges of PAM in the translation to potential clinical impacts.

Use of patient outcome endpoints to identify the best functional CT imaging parameters in metastatic renal cell carcinoma patients

OBJECTIVE

To use the patient outcome endpoints overall survival and progression-free survival to evaluate functional parameters derived from dynamic contrast-enhanced CT.

METHODS

69 patients with metastatic renal cell carcinoma had dynamic contrast-enhanced CT scans at baseline and after 5 and 10 weeks of treatment. Blood volume, blood flow and standardized perfusion values were calculated using deconvolution (BV_deconv, BF_deconv and SPV_deconv), blood flow and standardized perfusion values using maximum slope (BF_max and SPV_max) and blood volume and permeability surface area product using the Patlak model (BV_patlak and PS). Histogram data for each were extracted and associated to patient outcomes. Correlations and agreements were also assessed.

RESULTS

The strongest associations were observed between patient outcome and medians and modes for BV_deconv, BV_patlak and BF_deconv at baseline and during the early ontreatment period (p < 0.05 for all). For the relative changes in median and mode between baseline and weeks 5 and 10, PS seemed to have opposite associations dependent on treatment. Interobserver correlations were excellent (r ≥ 0.9, p < 0.001) with good agreement for BF_deconv, BF_max, SPV_deconv and SPV_max and moderate to good (0.5 < r < 0.7, p < 0.001) for BV_deconv and BV_patlak. Medians had a better reproducibility than modes.

CONCLUSION

Patient outcome was used to identify the best functional imaging parameters in patients with metastatic renal cell carcinoma. Taking patient outcome and reproducibility into account, BV_deconv, BV_patlak and BF_deconv provide the most clinically meaningful information, whereas PS seems to be treatment dependent. Standardization of acquisition protocols and post-processing software is necessary for future clinical utilization. Advances in knowledge: Taking patient outcome and reproducibility into account, BV_deconv, BV_patlak and BF_deconv provide the most clinically meaningful information. PS seems to be treatment dependent.

Dynamic Contrast-Enhanced Perfusion Area-Detector CT: Preliminary Comparison of Diagnostic Performance for N Stage Assessment With FDG PET/CT in Non-Small Cell Lung Cancer

OBJECTIVE

The objective of our study was to directly compare the capability of dynamic first-pass contrast-enhanced (CE) perfusion area-detector CT (ADCT) and FDG PET/CT for differentiation of metastatic from nonmetastatic lymph nodes and assessment of N stage in patients with non-small cell lung carcinoma (NSCLC).

SUBJECTS AND METHODS

Seventy-seven consecutive patients, 45 men (mean age ± SD, 70.4 ± 5.9 years) and 32 women (71.2 ± 7.7 years), underwent dynamic first-pass CE-perfusion ADCT at two or three different positions for covering the entire thorax, FDG PET/CT, surgical treatment, and pathologic examination. From all ADCT data for each of the subjects, a whole-chest perfusion map was computationally generated using the dual- and single-input maximum slope and Patlak plot methods. For quantitative N stage assessment, perfusion parameters and the maximum standardized uptake value (SUV_max) for each lymph node were determined by measuring the relevant ROI. ROC curve analyses were performed for comparing the diagnostic capability of each of the methods on a per-node basis. N stages evaluated by each of the indexes were then statistically compared with the final pathologic diagnosis by means of chi-square and kappa statistics.

RESULTS

The area under the ROC curve (A_z) values of systemic arterial perfusion (A_z = 0.89), permeability surface (A_z = 0.78), and SUV_max (A_z = 0.85) were significantly larger than the A_z values of total perfusion (A_z = 0.70, p < 0.05) and distribution volume (A_z = 0.55, p < 0.05). For each of the threshold values, agreement for systemic arterial perfusion calculated using the dual-input maximum slope model was substantial (κ = 0.70, p < 0.0001), and agreement for SUV_max was moderate (κ = 0.60, p < 0.0001).

CONCLUSION

Dynamic first-pass CE-perfusion ADCT is as useful as FDG PET/CT for the differentiation of metastatic from nonmetastatic lymph nodes and assessment of N stage in patients with NSCLC.

Assessing Tumor Response to Treatment in Patients with Lung Cancer Using Dynamic Contrast-Enhanced CT

The aim of this study was to provide an overview of the literature available on dynamic contrast-enhanced computed tomography (DCE-CT) as a tool to evaluate treatment response in patients with lung cancer. This systematic review was compiled according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Only original research articles concerning treatment response in patients with lung cancer assessed with DCE-CT were included. To assess the validity of each study we implemented Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2). The initial search yielded 651 publications, and 16 articles were included in this study. The articles were divided into groups of treatment. In studies where patients were treated with systemic chemotherapy with or without anti-angiogenic drugs, four out of the seven studies found a significant decrease in permeability after treatment. Four out of five studies that measured blood flow post anti-angiogenic treatments found that blood flow was significantly decreased. DCE-CT may be a useful tool in assessing treatment response in patients with lung cancer. It seems that particularly permeability and blood flow are important perfusion values for predicting treatment outcome. However, the heterogeneity in scan protocols, scan parameters, and time between scans makes it difficult to compare the included studies.

βIII-Tubulin alters glucose metabolism and stress response signaling to promote cell survival and proliferation in glucose-starved non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) survival rates are dismal and high βIII-tubulin expression is associated with chemotherapy drug resistance and tumor aggressiveness in this disease. Mounting evidence supports a role for βIII-tubulin in promoting cell survival in the harsh tumor microenvironment, which is characterized by poor nutrient supply. This study aimed to investigate the role of βIII-tubulin in glucose stress response signaling and the survival and proliferation of NSCLC cells. This study revealed that βIII-tubulin regulates cellular metabolism and glucose stress response signaling in NSCLC cells to promote cell survival and proliferation in glucose starvation. βIII-Tubulin decreases the reliance of cells on glycolytic metabolism, priming them to cope with variable nutrient supply present within the tumor microenvironment. βIII-Tubulin protects cells from endoplasmic reticulum (ER) stress and reduces both basal and glucose starvation-induced autophagy to maintain cell survival and proliferation. βIII-Tubulin enables rapid Akt activation in response to glucose starvation and co-immunoprecipitates with the master regulator of the ER stress response GRP78. Furthermore, suppression of βIII-tubulin delays the association of GRP78 with Akt in response to glucose starvation with the potential to influence Akt activation and ER homeostasis under these conditions. Together these results identify that βIII-tubulin regulates glucose metabolism and alters glucose starvation stress signaling to promote cell proliferation and survival in NSCLC cells. This elucidates a hitherto unknown role for this microtubule protein and provides insight into correlations between high βIII-tubulin expression and poor patient outcome in this disease.

Increased 18F-FDG Uptake on PET/CT is Associated With Poor Arterial and Portal Perfusion on Multiphase CT

PURPOSE

To correlate 18F-FDG uptake on PET/CT with patterns of arterial and portal perfusion on multi-detector CT (MDCT) in patients with hepatocellular carcinoma (HCC) and to assess the value of variables from PET/CT and MDCT in predicting histological grades and overall survival.

METHODS

We retrospectively analyzed MDCT and PET/CT of 66 patients with HCC who underwent surgical treatment. Tumor peak standard uptake value (SUV) was divided by the mean liver SUV (T/LSUV). The mean tumor Hounsfield unit (HU) to mean liver HU was calculated for arterial (T/LHU-A) and portal phases (T/LHU-P). All patients were divided into three groups: I, T/LHU-A ≤l and T/LHU-P <1; II, T/LHU-A >1 and T/LHU-P <1; and III, T/LHU-A >1 and T/LHU-P ≥1. The relationships between the CT perfusion groups and T/LSUV were assessed. Multivariate logistic regression analyses were performed using clinical and imaging parameters for predicting histological grade. Overall survival curves stratified by T/LSUV and CT perfusion groups were estimated using the Kaplan-Meier method.

RESULTS

Statistically significant differences in T/LSUV were noted between groups I and II (2.29 [range 1.74-3.60] vs. 1.20 [range 1.07-1.58], P < 0.001) and groups I and III (2.29 [range 1.74-3.60] vs. 1.30 [range 1.07-1.43], P < 0.001). In multivariate analysis, a T/LSUV cutoff of >1.46 was the only independent predictor of tumor grade, with an odds ratio of 8.462 (95% confidence interval 1.799-39.803). Kaplan-Meier curves showed significant differences in OS according to T/LSUV >1.62, group I perfusion pattern, and T/LSUV >1.62 plus group I perfusion pattern (P = 0.04, P = 0.021, and P = 0.002, respectively).

CONCLUSION

18F-FDG PET/CT is not commonly used for detecting HCC due to its limited sensitivity. We found that increased 18F-FDG uptake is associated with decreased arterial and portal perfusion on MDCT. This can be used to preselect patients who would benefit the most from PET/CT. Meanwhile, 18F-FDG uptake remained as the only independent predictor of histological grade, and higher 18F-FDG uptake and lower perfusion pattern on MDCT were significantly related to shorter OS.

Modeling of Tracer Transport Delays for Improved Quantification of Regional Pulmonary ¹⁸F-FDG Kinetics, Vascular Transit Times, and Perfusion

¹⁸F-FDG-PET is increasingly used to assess pulmonary inflammatory cell activity. However, current models of pulmonary ¹⁸F-FDG kinetics do not account for delays in ¹⁸F-FDG transport between the plasma sampling site and the lungs. We developed a three-compartment model of ¹⁸F-FDG kinetics that includes a delay between the right heart and the local capillary blood pool, and used this model to estimate regional pulmonary perfusion. We acquired dynamic ¹⁸F-FDG scans in 12 mechanically ventilated sheep divided into control and lung injury groups (n = 6 each). The model was fit to tracer kinetics in three isogravitational regions-of-interest to estimate regional lung transport delays and regional perfusion. ¹³NN bolus infusion scans were acquired during a period of apnea to measure regional perfusion using an established reference method. The delayed input function model improved description of ¹⁸F-FDG kinetics (lower Akaike Information Criterion) in 98% of studied regions. Local transport delays ranged from 2.0 to 13.6 s, averaging 6.4 ± 2.9 s, and were highest in non-dependent regions. Estimates of regional perfusion derived from model parameters were highly correlated with perfusion measurements based on ¹³NN-PET (R² = 0.92, p < 0.001). By incorporating local vascular transports delays, this model of pulmonary ¹⁸F-FDG kinetics allows for simultaneous assessment of regional lung perfusion, transit times, and inflammation.

Differentiation of lung cancers from inflammatory masses with dual-energy spectral CT imaging

RATIONALE AND OBJECTIVES

To investigate the value of dual-energy spectral computed tomography (DESCT) in the quantitative differentiation between pulmonary malignant masses and inflammatory masses.

MATERIALS AND METHODS

This study was an institutional review board-approved study, and written informed consent was obtained from all patients. Sixty patients with 35 lung cancers and 25 inflammatory masses underwent DESCT scan during arterial phase (AP) and venous phase (VP). CT numbers of net enhancement in 70 keV monochromatic images in central and peripheral regions of masses and their differences (dCT) were measured. Iodine concentrations in the two regions were measured and normalized to the aorta as normalized iodine concentrations (NICs). The slopes of spectral attenuation curves (λHU) in the two regions were also calculated. The two-sample t test was used to compare quantitative parameters. Receiver operating characteristic (ROC) curves were generated to calculate sensitivity and specificity.

RESULTS

CT numbers of net enhancement and NICs in central regions, and λHU values both in the central and peripheral region of lung cancers were significantly lower than those of inflammatory masses during AP and VP. On the other hand, the dCT values of lung cancers were higher than that of inflammatory masses. NIC value in the central regions in VP had the highest sensitivity (86%) and specificity (100%) in differentiating malignant masses from inflammatory masses.

CONCLUSIONS

DESCT imaging with quantitative parameters such as CT numbers of 70 keV monochromatic images, NIC, and λHU may be a new method for differentiating lung cancers from inflammatory masses.

Feasibility of quantitative parameters of dynamically enhanced patterns of spiral computed tomography scanning integrated into tumour progression before targeted treatment of non-small cell lung cancer

INTRODUCTION

The relationship between quantitative parameters of contrast-enhanced computed tomography (CT) and non-small cell lung cancer (NSCLC) progression remains controversial. We aimed to explore the usefulness of contrast-enhanced spiral CT scanning for confirming the time of tumour progression before targeted treatment of NSCLC.

METHODS

Contrast-enhanced spiral CT scanning was performed on 33 NSCLC patients with a biopsy-proven diagnosis of NSCLC. All the patients were divided into three groups according to times of tumour progression (<6 weeks, 6-20 weeks, and >20 weeks). The perfusion CT data were used to calculate quantitative parameters, including enhanced peak values, peak time of tumour enhancement, ratio of tumour mass and enhanced aorta peak value and perfusion value of blood flow. Variance analysis was used for statistical analysis among the three groups using SAS 9.13 statistical software.

RESULTS

Tumour perfusion values among the three group with different stage of TTP were significantly different from each other with P = 0.0129 (<6 weeks, perfusion value = 0.35 ± 0.15 mL/(min × mL); 6-20 weeks, perfusion value = 0.41 ± 0.086 mL/(min × mL); > 20 weeks, perfusion value = 0.47 ± 0.087 mL/(min × mL)). However, no significant differences were found in other parameters (enhanced peak values, peak time of tumour enhancement, ratios of tumour mass, and enhanced aorta peak value) among three groups (P > 0.05).

CONCLUSION

The NSCLC patients with high perfusion value before targeted therapy are more sensitive to targeted therapy, and further experiments with larger sample size are needed.

Effects of guided random sampling of TCCs on blood flow values in CT perfusion studies of lung tumors

RATIONALE AND OBJECTIVES

Tissue perfusion is commonly used to evaluate lung tumor lesions through dynamic contrast-enhanced computed tomography (DCE-CT). The aim of this study was to improve the reliability of the blood flow (BF) maps by means of a guided sampling of the tissue time-concentration curves (TCCs).

MATERIALS AND METHODS

Fourteen selected CT perfusion (CTp) examinations from different patients with lung lesions were considered, according to different degrees of motion compensation. For each examination, two regions of interest (ROIs) referring to the target lesion and the arterial input were manually segmented. To obtain the perfusion parameters, we computed the maximum slope of the Hill equation, describing the pharmacokinetics of the contrast agent, and the TCC was fitted for each voxel. A guided iterative approach based on the Random Sample Consensus method was used to detect and exclude samples arising from motion artifacts through the assessment of the confidence level of each single temporal sample of the TCC compared to the model. Removing these samples permits to refine the model fitting, thus exploiting more reliable data. Goodness-of-fit measures of the fitted TCCs to the original data (eg, root mean square error and correlation distance) were used to assess the reliability of the BF values, so as to preserve the functional structure of the resulting perfusion map. We devised a quantitative index, the local coefficient of variation (lCV), to measure the spatial coherence of perfusion maps, from local to regional and global resolution. The effectiveness of the algorithm was tested under three different degrees of motion yielded by as many alignment procedures.

RESULTS

At pixel level, the proposed approach improved the reliability of BF values, quantitatively assessed through the correlation index. At ROI level, a comparative analysis emphasized how our approach "replaced" the noisy pixels, providing smoother parametric maps while preserving the main functional structure. Moreover, the implemented algorithm provides a more meaningful effect in correspondence of a higher motion degree. This was confirmed both quantitatively, using the lCV, and qualitatively, through visual inspection by expert radiologists.

CONCLUSIONS

Perfusion maps achieved with the proposed approach can now be used as a valid tool supporting radiologists in DCE-CTp studies. This represents a step forward to clinical utilization of these studies for staging, prognosis, and monitoring values of therapeutic regimens.

Multiparametric monitoring of early response to antiangiogenic therapy: a sequential perfusion CT and PET/CT study in a rabbit VX2 tumor model

OBJECTIVES

To perform dual analysis of tumor perfusion and glucose metabolism using perfusion CT and FDG-PET/CT for the purpose of monitoring the early response to bevacizumab therapy in rabbit VX2 tumor models and to assess added value of FDG-PET to perfusion CT.

METHODS

Twenty-four VX2 carcinoma tumors implanted in bilateral back muscles of 12 rabbits were evaluated. Serial concurrent perfusion CT and FDG-PET/CT were performed before and 3, 7, and 14 days after bevacizumab therapy (treatment group) or saline infusion (control group). Perfusion CT was analyzed to calculate blood flow (BF), blood volume (BV), and permeability surface area product (PS); FDG-PET was analyzed to calculate SUVmax, SUVmean, total lesion glycolysis (TLG), entropy, and homogeneity. The flow-metabolic ratio (FMR) was also calculated and immunohistochemical analysis of microvessel density (MVD) was performed.

RESULTS

On day 14, BF and BV in the treatment group were significantly lower than in the control group. There were no significant differences in all FDG-PET-derived parameters between both groups. In the treatment group, FMR prominently decreased after therapy and was positively correlated with MVD.

CONCLUSIONS

In VX2 tumors, FMR could provide further insight into the early antiangiogenic effect reflecting a mismatch in intratumor blood flow and metabolism.

Correlation of intra-tumor 18F-FDG uptake heterogeneity indices with perfusion CT derived parameters in colorectal cancer

METHODS

Thirty patients with proven colorectal cancer prospectively underwent integrated 18F-FDG PET/DCE-CT to assess the metabolic-flow phenotype. Both CT blood flow parametric maps and PET images were analyzed. Correlations between PET heterogeneity and perfusion CT were assessed by Spearman's rank correlation analysis.

RESULTS

Blood flow visualization provided by DCE-CT images was significantly correlated with 18F-FDG PET metabolically active tumor volume as well as with uptake heterogeneity for patients with stage III/IV tumors (|ρ|:0.66 to 0.78; p-value<0.02).

CONCLUSION

The positive correlation found with tumor blood flow indicates that intra-tumor heterogeneity of 18F-FDG PET accumulation reflects to some extent tracer distribution and consequently indicates that 18F-FDG PET intra-tumor heterogeneity may be associated with physiological processes such as tumor vascularization.

Dual-phase dual-energy CT in patients with lung cancer: assessment of the additional value of iodine quantification in lymph node therapy response

OBJECTIVES

To investigate the potential contribution of iodine uptake calculation from dual-phase dual-energy CT (DE-CT) for lymph node staging and therapy response monitoring in lung cancer patients.

METHODS

Retrospective analysis of 27 patients with non-small cell lung carcinoma (NSCLC), who underwent dual-phase DE-CT before and after chemotherapy, was performed. Iodine uptake (mg/mL) and total iodine uptake (mg) were calculated using prototype software in the early (arterial) and late (venous) post-contrast circulatory phase in 110 mediastinal lymph nodes. The arterial enhancement fraction (AEF) was calculated and compared with lymph node size and response to chemotherapy.

RESULTS

A significant difference of AEF was observed between enlarged (90.4%; 32.3-238.5%) and non-enlarged (72.7%; -37.5-237.5%) lymph nodes (p = 0.044) before treatment onset. A significantly different change of AEF in responding (decrease of 26.3%; p = 0.022) and non-responding (increase of 43.0%; p = 0.031) lymph nodes was demonstrated. A higher value of AEF before treatment was observed in lymph nodes with subsequent favourable response (88.6% vs. 77.7%; p = 0.122), but this difference did not reach statistical significance.

CONCLUSIONS

The dual-phase DE-CT examination with quantification of ratio of early and late post-contrast iodine uptake is a feasible and promising method for the functional evaluation of mediastinal lymph nodes including therapy response assessment.

KEY POINTS

• Dual-phase DE-CT is beneficial for mediastinal lymph node assessment in NSCLC. • Arterial to venous iodine uptake ratio was higher in enlarged lymph nodes. • Change of arterial enhancement fraction correlated to therapy response.

Integrated ¹⁸F-FDG PET/perfusion CT for the monitoring of neoadjuvant chemoradiotherapy in rectal carcinoma: correlation with histopathology

PURPOSE

The aim of this study was to prospectively monitor changes in the flow-metabolic phenotype (ΔFMP) of rectal carcinoma (RC) after neoadjuvant chemoradiotherapy (CRT) and to evaluate whether ΔFMP of RC correlate with histopathological prognostic factors including response to CRT.

METHODS

Sixteen patients with RC (12 men, mean age 60.7 ± 12.8 years) underwent integrated (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/perfusion CT (PET/PCT), followed by neoadjuvant CRT and surgery. In 13 patients, PET/PCT was repeated after CRT. Perfusion [blood flow (BF), blood volume (BV), mean transit time (MTT)] and metabolic [maximum and mean standardized uptake values (SUVmax, SUVmean)] parameters as well as the FMP (BF × SUVmax) were determined before and after CRT by two independent readers and correlated to histopathological prognostic factors of RC (microvessel density, necrosis index, regression index, vascular invasion) derived from resected specimens. The diagnostic performance of ΔFMP for prediction of treatment response was determined.

RESULTS

FMP significantly decreased after CRT (p < 0.001), exploiting higher changes after CRT as compared to changes of perfusion and metabolic parameters alone. Before CRT, no significant correlations were found between integrated PET/PCT and any of the histopathological parameters (all p > 0.05). After CRT, BV and SUVmax correlated positively with the necrosis index (r = 0.67/0.70), SUVmax with the invasion of blood vessels (r = 0.62) and ΔFMP with the regression index (r = 0.88; all p < 0.05). ΔFMP showed high accuracy for prediction of histopathological response to CRT (AUC 0.955, 95 % confidence interval 0.833-1.000, p < 0.01) using a cut-off value of -75%.

CONCLUSION

In RC, ΔFMP derived from integrated (18)F-FDG PET/PCT is useful for monitoring the effects of neoadjuvant CRT and allows prediction of histopathological response to CRT.

Tumor vascularity and glucose metabolism correlated in adenocarcinoma, but not in squamous cell carcinoma of the lung

Background/Objectives

To prospectively examine the relation between tumor vascularity and glucose metabolism in adenocarcinoma (AC) and squamous cell carcinoma(SCC) of the lung by using positron emission tomography/computed tomography (PET/CT) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI).

Materials and Methods

Forty-one consecutive patients with histologically confirmed untreated NSCLC underwent routine diagnostic work-up, including DCE-MRI and PET/CT. PET/CT images were used to derive glucose metabolism (SUVmax and SUVmean), and DCE-MRI images were used to derive tumor vascularity (Ktrans, Kep, Ve and iAUC). Any differences in the DCE-MRI and PET/CT estimations between the NSCLC subtypes were determined by the Wilcoxon rank sum test. Spearman’s rank correlation coefficients were calculated between the DCE-MRI parameter values and the SUV.

Results

SUVmean and SUVmax in AC were significantly lower than in SCC, but Ktrans and Ve in AC were significantly higher than in SCC. Significant correlations between SUV and DCE-MRI parameters were observed for SUVmax and Ve (ρ = −0.357, P = 0.022), SUVmean and Ktrans (ρ = −0.341, P = 0.029), and SUVmean and iAUC (ρ = −0.374, P = 0.016 ) in total; for SUVmax and iAUC (ρ = −0.420, P = 0.037), SUVmean and Ktrans (ρ = −0.411, P = 0.041), SUVmean and Kep (ρ = −0.045, P = 0.026), and SUVmean and iAUC (ρ = −0.512, P = 0.009) in AC; However, for neither in SCC.

Conclusion

AC and SCC showed different patterns in both tumor vascularity and glucose metabolism. Tumor vascularity and glucose metabolism negatively correlated in AC, but not in SCC. These differences may underlie the heterogeneity in clinical aspect of NSCLC subtypes and have implications for their imaging profiling and monitor the treatment response.

Multiparametric PET/CT-perfusion does not add significant additional information for initial staging in lung cancer compared with standard PET/CT

BACKGROUND

The purpose of this study was to assess the relationship of CT-perfusion (CTP), 18F-FDG-PET/CT and histological parameters, and the possible added value of CTP to FDG-PET/CT in the initial staging of lung cancer.

METHODS

Fifty-four consecutive patients (median age 65 years, 15 females, 39 males) with suspected lung cancer were evaluated prospectively by CT-perfusion scan and 18F-FDG-PET/CT scan. Overall, 46 tumors were identified. CTP parameters blood flow (BF), blood volume (BV), and mean transit time (MTT) of the tumor tissue were calculated. Intratumoral microvessel density (MVD) was assessed quantitatively. Differences in CTP parameters concerning tumor type, location, PET positivity of lymph nodes, TNM status, and UICC stage were analyzed. Spearman correlation analyses between CTP and 18F-FDG-PET/CT parameters (SUVmax, SUVmean, PETvol, and TLG), MVD, tumor size, and tumor stage were performed.

RESULTS

The mean BF (mL/100 mL min-1), BV (mL/100 mL), and MTT (s) was 35.5, 8.4, and 14.2, respectively. The BF and BV were lower in tumors with PET-positive lymph nodes (p = 0.02). However, the CTP values were not significantly different among the N stages. The CTP values were not different, depending on tumor size and location. No significant correlation was found between CTP parameters and MVD.

CONCLUSIONS

Overall, the CTP information showed only little additional information for the initial staging compared with standard FDG-PET/CT. Low perfusion in lung tumors might possibly be associated with metabolically active regional lymph nodes. Apart from that, both CTP and 18F-FDG-PET/CT parameter sets may reflect different pathophysiological mechanisms in lung cancer.

Functional imaging in lung cancer

Lung cancer represents an increasingly frequent cancer diagnosis worldwide. An increasing awareness on smoking cessation as an important mean to reduce lung cancer incidence and mortality, an increasing number of therapy options and a steady focus on early diagnosis and adequate staging have resulted in a modestly improved survival. For early diagnosis and precise staging, imaging, especially positron emission tomography combined with CT (PET/CT), plays an important role. Other functional imaging modalities such as dynamic contrast-enhanced CT (DCE-CT) and diffusion-weighted MR imaging (DW-MRI) have demonstrated promising results within this field. The purpose of this review is to provide the reader with a brief and balanced introduction to these three functional imaging modalities and their current or potential application in the care of patients with lung cancer.

Characterization of tumor heterogeneity using dynamic contrast enhanced CT and FDG-PET in non-small cell lung cancer

PURPOSE

Dynamic contrast-enhanced CT (DCE-CT) quantifies vasculature properties of tumors, whereas static FDG-PET/CT defines metabolic activity. Both imaging modalities are capable of showing intra-tumor heterogeneity. We investigated differences in vasculature properties within primary non-small cell lung cancer (NSCLC) tumors measured by DCE-CT and metabolic activity from FDG-PET/CT.

METHODS

Thirty three NSCLC patients were analyzed prior to treatment. FDG-PET/CT and DCE-CT were co-registered. The tumor was delineated and metabolic activity was segmented on the FDG-PET/CT in two regions: low (<50% maximum SUV) and high (≥50% maximum SUV) metabolic uptake. Blood flow, blood volume and permeability were calculated using a maximum slope, deconvolution algorithm and a Patlak model. Correlations were assessed between perfusion parameters for the regions of interest.

RESULTS

DCE-CT provided additional information on vasculature and tumor heterogeneity that was not correlated to metabolic tumor activity. There was no significant difference between low and high metabolic active regions for any of the DCE-CT parameters. Furthermore, only moderate correlations between maximum SUV and DCE-CT parameters were observed.

CONCLUSIONS

No direct correlation was observed between FDG-uptake and parameters extracted from DCE-CT. DCE-CT may provide complementary information to the characterization of primary NSCLC tumors over FDG-PET/CT imaging.

Does volume perfusion computed tomography enable differentiation of metastatic and non-metastatic mediastinal lymph nodes in lung cancer patients? A feasibility study

OBJECTIVES

To compare the perfusion characteristics of mediastinal lymph node metastases with those of non-metastatic nodes in patients with newly diagnosed lung cancer using volume perfusion computed tomography (VPCT).

MATERIALS AND METHODS

Between January 2010 and October 2011, 101 patients with histologically confirmed, untreated lung cancer received a 40-s VPCT of the tumor bulk; 32/101 patients had evident hilar/mediastinal metastatic disease and 17/101 patients had proven non-metastasized lymph nodes within the VPCT scan range. Validation or exclusion of metastatic node involvement was proven by mediastinoscopy, biopsy, positron emission tomography imaging and/or unequivocal volume dynamics on follow-up computed tomography. A total of 45 metastases and 23 non-metastatic lymph nodes were found within the scan range and subsequently evaluated. Blood flow (BF), blood volume (BV) and K(trans) were determined. Tumor volume was recorded as whole tumor volume.

RESULTS

In a comparison between metastatic and non-metastatic lymph nodes, we controlled for age, lymph node volume, lung tumor volume, lung tumor location, and histologic type effects and found no significant differences with respect to BF, BV, K(trans) or heterogeneity in nodal perfusion (P > 0.05, respectively), even after adjusting lymph node perfusion values to the perfusion parameters of the primary tumor (P > 0.05, respectively). Metastatic lymph node volume had a significant increasing effect on perfusion heterogeneity (P < 0.05, respectively) and BV in the primary was a highly significant factor for BV in metastatic disease (P < 0.001).

CONCLUSION

Perfusion characteristics of mediastinal metastatic and non-metastatic lymph nodes in untreated lung cancer show considerable overlap, so that a reliable differentiation via VPCT is not possible.

Low tumor blood flow assessed with perfusion CT correlates with lymphatic involvement in patients with stage T1b non-small cell lung cancer

BACKGROUND

To investigate the correlation of computed tomography (CT) perfusion parameters and lymphatic involvement in patients with stage T1b non-small cell lung cancer (NSCLC).

METHODS

Forty-six patients (30 men and 16 women; age range, 36-73 years; mean age, 57 years), with stage T1b non-small cell lung cancer, underwent perfusion CT before surgery. The correlations between CT perfusion parameters (blood flow, blood volume, peak enhancement intensity), tumor angiogenesis (microvessel density and maturity of microvessels of surgical specimens) and lymphatic involvement were retrospectively investigated. Receiver operator curve (ROC) analysis was used to identify the parameter threshold at which tumors had or did not have lymph node metastasis, and the corresponding sensitivity and specificity were calculated.

RESULTS

A significant tendency for tumors with low blood flow and high density of immature microvessels to show lymphatic involvement was found (all P < 0.001). High correlation (r =-0.769, P < 0.001) was observed between tumor blood flow and immature microvessels. The area under ROC curves (AUC) for blood flow to detect lymph node metastasis was 0.866 (95% confidence interval, 0.766-0.966). For blood flow, the sensitivity, specificity, and accuracy of predicting lymph node metastasis were 88.9, 64.3, and 73.9% respectively, if the cutoff point was set at 43.05 mL/100 g/minute.

CONCLUSIONS

Blood flow may be useful to predict lymphatic involvement before surgery in stage T1b NSCLC.

Non-small cell lung cancer evaluated with quantitative contrast-enhanced CT and PET-CT: net enhancement and standardized uptake values are related to tumour size and histology

Background

Personalized cancer therapy remains a challenge. In this context, we attempted to identify correlations between tumour angiogenesis, tumour metabolism and tumour cell type. To this aim, we used single=phase multidetector computed tomography (MDCT) and hybrid positron emission tomography-computed tomography (PET/CT) to determine whether net enhancement and standardized uptake value (SUVmax) were correlated with tumour size and cytology in patients affected by non-small cell lung cancer (NSCLC).

Material/Methods

Our study included 38 patients (30 men, 8 women, mean age 70) with a NSCLC measuring between 3 cm and 7 cm, using a 16-slice multidetector CT (Brilliance Philips) and with PET-CT (Biograph 16 Siemens Medical Solutions). The following lesion parameters were evaluated: maximum diameter, medium density before contrast injection (CT_pre), medium density after contrast injection (CT_{post average}), density in the most enhanced part of the lesion after contrast (CT_{post max}), net enhancement, SUVmax, age, and cytology. Correlation coefficient and p-value were computed for each pair of variables. In addition, correlations were computed for each pair of variables, and for all combinations of tumour types. We focused on subsets of data with more than 10 observations, and with correlation r>0.500 and p<0.05.

Results

A weak correlation (r=0.32; p=0.048) was found between SUVmax and tumour size; the correlation was stronger for masses larger than 31 mm (r=0.4515; p=0.0268). No other correlations were found among the variables examined.

Conclusions

Our data may have prognostic significance, and could lead to more appropriate surgical treatment and better treatment outcome.

Quantitative p retreatment VOI analysis of liver metastases. (99m)Tc-MAA SPECT/CT and FDG PET/CT in relation with treatment response to SIRT

Using quantitive VOI analysis, the percentage (99m)Tc-MAA uptake and SUVmax and mean values of liver metastases obtained prior to SIRT were related to treatment response using both a lesion-based and clinical dichotomous approach. Based on the VOI % of (99m)Tc-MAA activity, the estimated (90)Y-microspheres activity/cc (MBq/cc) was calculated from the effective dose injected. Baseline VOI FDG PET SUVmean and max values and estimated MBq/cc values were related to treatment response using a lesion-based approach (% change in SUVmean ≥  50%) and a clinical dichotomous approach. Fifteen treatment sessions were analyzed (13 patients). Using the lesion-based approach (12 treatment sessions) 40 lesions responded and 37 did not. SUVmax and mean values proved significantly different between non-responding and responding lesions; 18.6 (SD 10.8) versus 13.5 (SD 8.4 ) for SUVmax (p = 0.02) and 11.4 (SD 3.8) versus 6.3 (SD 4.5) for SUVmean (p = 0.002). Using the clinical dichotomous approach (15 treatment sessions / 11 responding), 91 lesions were analyzed; 57 responded. VOI volumes and estimated (90)Y-loaded glass microspheres activity (MBq/cc) did not differ between responders and non responders; 24 cc (SD 27) versus 21 cc (SD 21 cc) (p = 0.4) and 1.95 MBq/cc (SD 1.1 MBq/cc) versus 1.90 MB/cc (SD 2.7 MBq/cc) (p = 0.92). On the contrary, SUVmax and mean values proved significantly different between responders and non-responders; 23.7 (SD 9.8) versus 9.4 (SD 3.8 ) for SUVmax (p = 0.0001) and 13.1 (SD 8.1) versus 4.9 (SD 1.4) for SUVmean.

CONCLUSION

These findings suggest that in patients presenting with high baseline SUVmax and mean values, the administration of higher activities or alternatively, other potentially more useful treatment options might be considered.

Integrated (18)F-FDG PET/CT and perfusion CT of primary colorectal cancer: effect of inter- and intraobserver agreement on metabolic-vascular parameters

OBJECTIVE

The purpose of this article is to assess the effect of observers on combined metabolic-vascular parameters in colorectal cancer.

SUBJECTS AND METHODS

Twenty-five prospective patients (12 men and 13 women; mean age, 66.9 years) with proven primary colorectal adenocarcinoma underwent integrated (18)F-FDG PET/perfusion CT to assess tumor metabolism (mean and maximum standardized uptake value [SUV(mean) and SUV(max), respectively]) and vascularization (blood flow [BF], blood volume [BV], permeability surface-area product, and standardized perfusion value). Intra- and interobserver agreement for PET, perfusion CT, and combined metabolic-flow parameters were determined by Bland-Altman statistics and intraclass correlation coefficients (ICCs).

RESULTS

The mean tumor size was 3.8 ± 1.6 cm; there were five stage IA/B, six stage IIA/B, eight stage IIIA/B, and six stage IV tumors. Intra- and interobserver agreement for individual parameters was fair to good, with mean differences between observers of -0.74 for SUV(max), -0.16 for SUV(mean), 9.72 for BF, 0.15 for BV, -0.76 for permeability surface-area product, and 0.09 for standardized perfusion value. ICCs were 0.44-0.99 and 0.38-0.89 for intra- and interobserver agreement, respectively. Interobserver agreement was variable for combined metabolic-flow parameters but better for metabolic-flow difference than for metabolic-flow ratio: ICCs were 0.69-0.88 for the metabolic-flow difference and 0.44-0.94 for the metabolic-flow ratio.

CONCLUSION

Combined parameters to assess the metabolic-flow relationship are influenced by observer variation. Intra- and interobserver agreement are better for the metabolic-flow differences than for the ratios, suggesting that metabolic-flow differences may be a more robust parameter for clinical practice.

Feasibility of perfusion CT technique integrated into conventional 18FDG/PET-CT studies in lung cancer patients: clinical staging and functional information in a single study

PURPOSE

To assess the additional functional vascular information and the relationship between perfusion measurements and glucose metabolism (SUVmax) obtained by including a perfusion CT study in a whole-body contrast-enhanced PET/CT protocol in primary lung cancer lesions.

METHODS

Enrolled in this prospective study were 34 consecutive patients with a biopsy-proven diagnosis of lung cancer who were referred for contrast-enhanced PET/CT staging. This prospective study was approved by our institutional review board, and informed consent was obtained from all patients. Perfusion CT was performed with the following parameters: 80 kV, 200 mAs, 30 scans during intravenous injection of 50 ml contrast agent, flow rate 5 ml/s. Another bolus of contrast medium (3.5 ml/s, 80 ml, 60-s delay) was administered to ensure a full diagnostic contrast-enhanced CT scan for clinical staging. The perfusion CT data were used to calculate a range of tumour vascularity parameters (blood flow, blood volume and mean transit time), and tumour FDG uptake (SUVmax) was used as a metabolic indicator. Quantitative and functional parameters were compared and in relation to location, histology and tumour size. The nonparametric Kruskal-Wallis rank sum test was used for statistical analysis.

RESULTS

A cut-off value of 3 cm was used according to the TNM classification to discriminate between T1 and T2 tumours (i.e. T1b vs. T2a). There were significant perfusion differences (lower blood volumes and higher mean transit time) between tumours with diameter >30 mm and tumours with diameter <30 mm (p < 0.05; blood volume 5.6 vs. 7.1 ml/100 g, mean transit time 8.6 vs. 3.9 s, respectively). Also there was a trend for blood flow to be lower in larger lesions (p < 0.053; blood flow 153.1 vs. 98.3 ml/100 g tissue/min). Significant inverse correlations (linear regression) were found between blood volume and SUVmax in tumours with diameter >30 mm in diameter.

CONCLUSION

Perfusion CT combined with PET/CT is feasible technique that may provide additional functional information about vascularity and tumour aggressiveness as a result of lower perfusion and higher metabolism shown by larger lesions.

Can combined 18F-FDG-PET and dynamic contrast-enhanced MRI predict behavior of desmoid tumors in patients with familial adenomatous polyposis?

BACKGROUND

Desmoid tumors associated with familial adenomatous polyposis show variable behavior; about 10% grow relentlessly, resulting in severe morbidity or mortality. Investigations that could identify the minority of desmoid tumors that behave aggressively would allow these tumors to be treated early and spare the majority of patients who have more benign disease from unnecessary intervention.

OBJECTIVE

The aim of this study was to investigate whether imaging the tumor metabolic-vascular phenotype by modern methods predicts growth.

DESIGN

This is a prospective case series study.

SETTINGS

The study was conducted at a tertiary center specializing in familial adenomatous polyposis and desmoid disease.

PATIENTS

Nine patients with familial adenomatous polyposis (4 male, mean age 39 years) with desmoid tumor underwent 18F-FDG-PET and dynamic contrast-enhanced MRI. Standard MRI was repeated a year later to assess tumor growth.

MAIN OUTCOME MEASURES

The primary outcome measured was the correlation between 18F-FDG-PET and dynamic contrast-enhanced MRI parameters and subsequent desmoid growth.

RESULTS

Failed intravenous access precluded dynamic contrast-enhanced MRI in 1 female patient. Thirteen desmoid tumors (4 intra-abdominal, 2 extra-abdominal, 7 abdominal wall; mean area, 68 cm) were analyzed in the remaining 8 patients. Two patients died before follow-up MRI. Five tumors decreased in size, 3 increased in size, and 3 remained stable after a year. Significant correlation (Spearman rank correlation, significance at 5%) existed between maximum standardized uptake value and k(ep) (r = -0.56, p = 0.04), but not with other vascular parameters (K(trans) (r = -0.47, p = 0.09); v(e) (r = -0.11, p = 0.72); integrated area under the gadolinium-time curve at 60 seconds (r = -0.47, p = 0.10)). There was no significant difference in the maximum standardized uptake value or dynamic contrast-enhanced MRI parameters (K(trans), v(e), k(ep), integrated area under the gadolinium-time curve at 60 seconds) between the tumors that grew or decreased in size or between the tumor sites. However, vascular metabolic ratio (maximum standardized uptake value/K(trans)) was significantly different for tumor site (p = 0.001) and size (p = 0.001, 1-way ANOVA).

LIMITATIONS

This investigation is limited because of its exploratory nature and small patient numbers.

CONCLUSIONS

Although not predictive for tumor behavior, some correlations existed between dynamic contrast-enhanced MRI and 18F-FDG-PET parameters. Vascular metabolic ratio may provide further information on tumor behavior; however, this needs to be evaluated with further larger studies.

Multiparametric PET/CT in oncology

The standardized uptake value (SUV) and other measurements of tumour uptake of fluorodeoxyglucose (FDG) on positron emission tomography (PET) can potentially be supplemented by additional imaging parameters derived either from the PET images or from the computed tomography (CT) component of integrated PET/CT examinations including tumour size, CT attenuation, texture (reflecting tumour heterogeneity) and blood flow. This article illustrates the emerging benefits of such a multiparametric approach. Example benefits include greater diagnostic accuracy in characterization of adrenal masses achieved by using both the SUV and measured CT attenuation. Tumour size combined with the SUV can potentially improve the prognostic information available from PET/CT in oesophageal and lung cancer. However, greater improvements may be realized through using CT measurements of texture instead of size. Studies in breast and lung cancer suggest that combined PET/CT measurements of glucose metabolism and blood flow provide correlates for tumour proliferation and angiogenesis, respectively. These combined measurements can be utilized to determine vascular-metabolic phenotypes, which vary with tumour type. Uncoupling of blood flow and metabolism suggests a poor prognosis for larger more advanced tumours, high-grade lesions and tumours responding poorly to treatment. Vascular-metabolic imaging also has the potential to subclassify tumour response to treatment. The additional biomarkers described can be readily incorporated in existing FDG-PET examinations thereby improving the ability of PET/CT to depict tumour biology, characterize potentially malignant lesions, and assess prognosis and therapeutic response.

Limited value of ⁹⁹mTc depreotide single photon emission CT compared with CT for the evaluation of pulmonary lesions

OBJECTIVES

A contrast-enhanced multidetector CT (MDCT) scan is the first choice examination when evaluating patients with suspected lung cancer. However, while the clinical focus is on CT, research focus is on molecular biological methods whereby radiolabelled pharmaceuticals are injected into participants and target malignant lung tumours. We examined whether a contrast-enhanced MDCT scan supplied with an additional non-contrast enhanced high-resolution CT scan, or a newer but more expensive (99m)Tc depreotide single photon emission CT (SPECT) scan, was the better first-choice examination for the work-up of pulmonary lesions. Furthermore, we examined whether a (99m)Tc depreotide SPECT scan was an appropriate second-choice examination for patients with indeterminate lesions.

METHODS

140 participants were included in the analysis. CT images were given a malignancy potential rating of 1, 2 or 3 with higher rating being indicative of disease. (99m)Tc depreotide SPECT images were graded either positive or negative. Histopathology and CT follow-up were used as reference standard. Sensitivity, specificity and diagnostic accuracy were calculated.

RESULTS

Overall sensitivity, specificity and diagnostic accuracy of CT were 97%, 30% and 84%, respectively. Overall sensitivity, specificity and diagnostic accuracy of (99m)Tc depreotide SPECT were 94%, 58% and 76%, respectively. For indeterminate lesions sensitivity, specificity and diagnostic accuracy of (99m)Tc depreotide SPECT were 71%, 68% and 69%, respectively.

CONCLUSION

Both CT and (99m)Tc depreotide SPECT made valuable contributions to the evaluation of pulmonary lesions. (99m)Tc depreotide SPECT results were not superior to CT results and did not contribute further to the diagnostic work-up. Regarding indeterminate lesions,( 99m)Tc depreotide SPECT sensitivity was too low.

The flow-metabolic phenotype of primary colorectal cancer: assessment by integrated 18F-FDG PET/perfusion CT with histopathologic correlation

The aim of this study was to assess the in vivo flow-metabolic phenotype in primary colorectal cancer with integrated (18)F-FDG PET/perfusion CT and its relationship to gold standard histopathologic assessment of angiogenesis and hypoxia.

METHODS

45 patients (26 male and 19 female; mean age, 67.6 y) with primary colorectal cancer underwent integrated (18)F-FDG PET/perfusion CT, deriving tumor glucose metabolism (maximum standardized uptake value) and regional blood flow. From this cohort, 35 underwent surgery subsequently, without intervening neoadjuvant treatment, allowing histopathologic correlation with tumor stage, CD105 microvessel density, vascular endothelial growth factor (VEGF), glucose transporter protein 1 (Glut-1), and hypoxia-inducible factor 1 expression.

RESULTS

The flow-metabolic ratio was significantly lower for tumors with higher VEGF (3.65 vs. 5.98; P = 0.01) or hypoxia-inducible factor 1 expression (3.63 vs. 5.48; P = 0.04) versus tumors with lower expression. There were significant negative correlations between the tumor flow-metabolic ratio and VEGF expression (r = -0.55, P = 0.0008), indicating that tumors with low blood flow but higher metabolism were associated with higher VEGF expression. Flow and metabolism were coupled in higher-stage (stage III/IV) tumors but not lower-stage tumors (stage I/II) (r = 0.47, P = 0.03, vs. r = 0.09, P = 0.65, respectively.

CONCLUSION

Tumors with a low-flow-high-metabolism phenotype demonstrated higher VEGF expression and may reflect a more angiogenic phenotype.

Multifunctional profiling of non-small cell lung cancer using 18F-FDG PET/CT and volume perfusion CT

The aim of this study was to investigate correlations between glucose metabolism registered by (18)F-FDG PET/CT and tumor perfusion quantified by volume perfusion CT and immunohistochemical markers Ki67 and microvessel density (MVD) in patients with non-small cell lung cancer (NSCLC).

METHODS

Between February 2010 and April 2011, 24 consecutive patients (21 women, 3 men; mean age ± SD, 67.6 ± 6.8 y; age range, 55.6-81.3 y) with histologically proven NSCLC (14 adenocarcinoma, 9 squamous cell lung carcinoma [SCC], and 1 mixed adenocarcinoma and SCC) underwent (18)F-FDG PET/CT and additional volume perfusion CT. Maximum standardized uptake value (SUV(max)), mean SUV, and the metabolic tumor volume were used for (18)F-FDG uptake quantification. Blood flow (BF), blood volume (BV), flow extraction product (K(trans)), and standardized perfusion value (SPV) were determined as CT perfusion parameters. Both perfusion parameters and (18)F-FDG uptake values were subsequently related to the histologic subtypes, proliferation marker Ki67, MVD according to CD34 staining, and total tumor volume.

RESULTS

Mean SUV, SUV(max), and the metabolic tumor volume (mL) were 5.8, 8.7, and 32.3, respectively, in adenocarcinoma and 8.5, 12.9, and 16.8, respectively, in SCC. Mean BF (mL/100 mL/min), mean BV (mL/100 mL), and K(trans) (mL/100 mL/min) were 35.4, 7.3, and 27.8, respectively, in adenocarcinoma and 35.5, 10.0, and 27.8, respectively, in SCC. Moderate correlations were found between the (18)F-FDG PET/CT parameters and Ki67 as well as between CT perfusion parameters and MVD but not vice versa. For all tumors, the following correlations were found: between SUV(max) and Ki67, r = 0.762 (P = 0.017); between SUV(max) and MVD, r = -0.237 (P = 0.359); between mean BF and Ki67, r = -0.127 (P = 0.626); and between mean BF and MVD, r = 0.467 (P = 0.059). Interestingly, correlations between the BF-metabolic relationship and total tumor volume were higher in SCC (r = 0.762, P = 0.017) than in adenocarcinoma (r = -0.0791, P = 0.788).

CONCLUSION

(18)F-FDG uptake correlates with Ki67, whereas BF, BV, and K(trans) correlate with MVD. Therefore, (18)F-FDG uptake and perfusion parameters provide complementary functional information. An improved tumor profiling will be beneficial for both prognosis and therapy response evaluation in these tumors.

Investigating tumor perfusion and metabolism using multiple hyperpolarized (13)C compounds: HP001, pyruvate and urea

The metabolically inactive hyperpolarized agents HP001 (bis-1,1-(hydroxymethyl)-[1-(13)C]cyclopropane-d(8)) and urea enable a new type of perfusion magnetic resonance imaging based on a direct signal source that is background-free. The addition of perfusion information to metabolic information obtained by spectroscopic imaging of hyperpolarized [1-(13)C]pyruvate would be of great value in exploring the relationship between perfusion and metabolism in cancer. In preclinical normal murine and cancer model studies, we performed both dynamic multislice imaging of the specialized hyperpolarized perfusion compound HP001 (T(1)=95 s ex vivo, 32 s in vivo at 3 T) using a pulse sequence with balanced steady-state free precession and ramped flip angle over time for efficient utilization of the hyperpolarized magnetization and three-dimensional echo-planar spectroscopic imaging of urea copolarized with [1-(13)C]pyruvate, with compressed sensing for resolution enhancement. For the dynamic data, peak signal maps and blood flow maps derived from perfusion modeling were generated. The spatial heterogeneity of perfusion was increased 2.9-fold in tumor tissues (P=.05), and slower washout was observed in the dynamic data. The results of separate dynamic HP001 imaging and copolarized pyruvate/urea imaging were compared. A strong and significant correlation (R=0.73, P=.02) detected between the urea and HP001 data confirmed the value of copolarizing urea with pyruvate for simultaneous assessment of perfusion and metabolism.

FDG PET/CT early dynamic blood flow and late standardized uptake value determination in hepatocellular carcinoma

PURPOSE

To prospectively determine whether fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) early dynamic blood flow estimates could be used to discriminate hepatocellular carcinoma (HCC) from background liver and to characterize HCC in patients with and those without angioinvasion; and to evaluate the association between blood flow measures at FDG PET/CT with metabolism in HCCs.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained for this prospective study. Twenty-one consecutive patients (mean age, 65 years) with 30 established HCCs (mean size, 5.5 cm; seven lesions in five patients with angioinvasion) underwent a blood flow study with an FDG dynamic scan divided into 18 sequences of 5 seconds each and a standard PET/CT scan. On the dynamic study, three independent operators obtained volumes of interest (VOIs) for which three blood flow estimates were calculated (hepatic perfusion index [HPI], time to peak [TTP], and peak intensity [PI]). On the late study, a VOI was placed on the fused scan for each HCC, and maximum standardized uptake value (SUV(max)) was obtained. By using a mixed-effects model analysis, comparison of blood flow estimates between HCC with and that without angioinvasion and background liver was performed. The association between blood flow estimates and SUV(max) was also assessed.

RESULTS

HPI and TTP showed better performance than did SUV(max) for discriminating HCC and background liver (areas under receiver operating characteristic curve: 0.96, 0.95, and 0.83, respectively; P < .05). HPI was higher in HCC in patients with angioinvasion (0.91 ± 0.15 [standard deviation]) than in those without angioinvasion (0.80 ± 0.18; P = .03). There was no difference in SUV(max) between HCC in patients with and those without angioinvasion (7.8 ± 2.9 vs 6.3 ± 3.4; P = .85). No clear association was found between HPI, PI, or TTP and SUV(max) (P = .49, .77, and .91, respectively).

CONCLUSION

Early dynamic blood flow FDG PET/CT may be used to help discriminate and characterize HCC tumors.

Demonstrating Intertumoural Differences in Vascular-Metabolic Phenotype with Dynamic Contrast-Enhanced CT-PET

Purpose. To assess whether the differences in vascular-metabolic relationships between lymphoma masses and colorectal liver metastases predicted from previous histopathological studies can be demonstrated by dynamic contrast-enhanced CT (DCE-CT) combined with fluorodeoxyglucose positron emission tomography (FDG-PET). Methods. DCE-CT and FDG-PET studies were drawn from an imaging archive for patients with either lymphoma masses (n = 11) or hepatic metastases from colorectal cancer (CRM: n = 12). Tumour vascularity was assessed using DCE-CT measurements of perfusion. Tumour glucose metabolism was expressed as the mean FDG Standardised Uptake Value (SUV_FDG). The relationship between metabolism and vascularity in each group was assessed from SUV_FDG /perfusion ratios and Pearson correlation coefficients. Results. An SUV_FDG threshold of 3.0 was used to designate lymphoma masses as active (AL, n = 6) or inactive lymphoma (IL, n = 5). Tumour perfusion was significantly higher in AL (0.65 mL/min/mL) than CRM (0.37 mL/min/mL: P = .031) despite similar SUV_FDG (5.05 and 5.33, resp.). AL demonstrated higher perfusion values than IL (0.24 mL/min/mL: P = .006). SUV_FDG/perfusion was significantly higher in CRM (15.3 min) than IL (4.2 min, P < .01). There was no correlation between SUV_FDG and perfusion for any patient group.