Functional CT imaging of angiogenesis in rabbit VX2 soft-tissue tumour

Usefulness of intratumoral perfusion analysis for assessing biological features of non-functional pancreatic neuroendocrine neoplasm

PURPOSE

Here, we evaluated the usefulness of intratumoral perfusion analysis using preoperative contrast-enhanced CT (E-CT) to assess biological features of non-functional pancreatic neuroendocrine neoplasms (NF-PanNENs).

METHODS

We retrospectively studied 44 patients who underwent curative surgery for NF-PanNENs. We used preoperative E-CT with compartment model analysis to calculate the tumor perfusion parameters K1 (inflow rate constant), 1/k2 (mean transit time), and K1/k2 (distribution volume). We assessed the association between perfusion parameters and biological features of NF-PanNENs, including the WHO classification tumor histopathological grade and prognosis after surgery.

RESULTS

Patients in this study had a neuroendocrine tumor (NET) G1 (n = 32) or NET G2 (n = 12). Neither NET G3 or NEC tumors were observed. Among perfusion parameters, K1 was the most accurate predictor of the high-grade tumor (AUC: 0.726). K1-low (< 0.028 s-1) was significantly associated with large tumors (≥ 20 mm) (p = 0.022), high mitotic index (p = 0.017), high Ki-67 index (p = 0.004), and lymphatic invasion (p = 0.025). Synchronous extra-pancreatic metastasis, including lymph node metastasis or liver metastasis, more frequently developed in K1-low patients than in K1-high patients (29% vs 4%, p = 0.025). Disease-free survival of patients with a K1-low tumor was poorer than that of patients with a K1-high tumor (p = 0.005). Furthermore, no patient with a K1-high tumor developed recurrence after initial surgery.

CONCLUSION

The perfusion parameters obtained using E-CT were significantly associated with biological features and prognosis of NF-PanNENs.

In vivo tumour imaging employing regional delivery of novel gallium radiolabelled polymer composites

Background

Understanding the regional vascular delivery of particles to tumour sites is a prerequisite for developing new diagnostic and therapeutic composites for treatment of oncology patients. We describe a novel imageable ⁶⁷Ga-radiolabelled polymer composite that is biocompatible in an animal tumour model and can be used for preclinical imaging investigations of the transit of different sized particles through arterial networks of normal and tumour-bearing organs.

Results

Radiolabelling of polymer microspheres with ⁶⁷Ga was achieved using a simple mix and wash method, with tannic acid as an immobilising agent. Final in vitro binding yields after autoclaving averaged 94.7%. In vivo stability of the composite was demonstrated in New Zealand white rabbits by intravenous administration, and intrahepatic artery instillations were made in normal and VX2 tumour implanted rabbit livers. Stability of radiolabel was sufficient for rabbit lung and liver imaging over at least 3 hours and 1 hour respectively, with lung retention of radiolabel over 91%, and retention in both normal and VX2 implanted livers of over 95%. SPECT-CT imaging of anaesthetised animals and planar imaging of excised livers showed visible accumulation of radiolabel in tumours. Importantly, microsphere administration and complete liver dispersal was more easily achieved with 8 μm diameter MS than with 30 μm MS, and the smaller microspheres provided more distinct and localised tumour imaging.

Conclusion

This method of producing ⁶⁷Ga-radiolabelled polymer microspheres is suitable for SPECT-CT imaging of the regional vascular delivery of microspheres to tumour sites in animal models. Sharper distinction of model tumours from normal liver was obtained with smaller MS, and tumour resolution may be further improved by the use of ⁶⁸Ga instead of ⁶⁷Ga, to enable PET imaging.

Computed Tomography Perfusion Measurements in Renal Lesions Obtained by Bayesian Estimation, Advanced Singular-Value Decomposition Deconvolution, Maximum Slope, and Patlak Models: Intermodel Agreement and Diagnostic Accuracy of Tumor Classification

OBJECTIVES

The aims of this study were to evaluate the agreement of computed tomography (CT)-perfusion parameter values of the normal renal cortex and various renal tumors, which were obtained by different mathematical models, and to evaluate their diagnostic accuracy.

MATERIALS AND METHODS

Perfusion imaging was performed prospectively in 35 patients to analyze 144 regions of interest of the normal renal cortex and 144 regions of interest of renal tumors, including 21 clear-cell renal cell carcinomas (RCC), 6 papillary RCCs, 5 oncocytomas, 1 chromophobe RCC, 1 angiomyolipoma with minimal fat, and 1 tubulocystic RCC. Identical source data were postprocessed and analyzed on 2 commercial software applications with the following implemented mathematical models: maximum slope, Patlak plot, standard singular-value decomposition (SVD), block-circulant SVD, oscillation-limited block-circulant SVD, and Bayesian estimation technique. Results for blood flow (BF), blood volume (BV), and mean transit time (MTT) were recorded. Agreement and correlation between pairs of models and perfusion parameters were assessed. Diagnostic accuracy was evaluated by receiver operating characteristic (ROC) analysis.

RESULTS

Significant differences and poor agreement of BF, BV, and MTT values were noted for most of model comparisons in both the normal renal cortex and different renal tumors. The correlations between most model pairs and perfusion parameters ranged between good and perfect (Spearman ρ = 0.79-1.00), except for BV values obtained by Patlak method (ρ = 0.61-0.72). All mathematical models computed BF and BV values, which differed significantly between clear cell RCCs, papillary RCCs, and oncocytomas, which introduces them as useful diagnostic tests to differentiate between different histologic subgroups (areas under ROC curve, 0.83-0.99). The diagnostic accuracy to discriminate between clear-cell RCCs and the renal cortex was the lowest based on the Patlak plot model (area under ROC curve, 0.76); BF and BV values obtained by other algorithms did not differ significantly in their diagnostic accuracy.

CONCLUSIONS

Quantitative perfusion parameters obtained from different mathematical models cannot be used interchangeably. Based on BF and BV estimates, all models are a useful tool in the differential diagnosis of kidney tumors, with the Patlak plot model yielding a significantly lower diagnostic accuracy.

Establishment of metastatic liver carcinoma model by implanting AX7 cells into rabbit liver, and its histological findings

Background: Progression of metastatic liver carcinoma from any original cancer is aggressive and the prognosis is very poor. Therefore the new model that is easily approachable to study the propagation and prognosis of metastatic liver carcinoma is necessary. The aim of this study is to confirm the tumor formation and metastatic activity of anaplastic thyroid cancer and to support the research basis for the next generation cancer treatment that is to be developed, by carrying out additional experiments like cytokine stimulation. We investigated sequential findings of immunohistochemistry of rabbit hepatic malignancy induced by AX7 cells. Methods: 13 rabbits implanted with AX7 cells directly into liver parenchyme with laparotomy were investigated by histopathology examination, immunohistochemistry, which is useful for the evaluation of metastatic cancer angiogenesis. Growing tissue at the edge of the mass was collected and placed in the petri dish filled with saline. After removing necrotic and fibrous tissue, tumor tissue was cut into pieces, placed in saline, and extracted during the experiment. Results: Tumor growth and malignancy was confirmed on the 10th day after AX7 cells were implanted into liver. Positive for VEGF staining was found in the cytoplasm or cell membrane. The scores for VEGF stained cells were moderately positive (++) on day 10, strongly positive (+++) on day 44. Ki-67-positive hepatocytes reached at 65% on day 10, at 65.78% on day 14, at 66.4% on day 30, at 67.88% on day 44. Conclusion: AX7 cells implanted into liver can be used as a new rabbit metastatic liver carcinoma model and would become useful for human metastatic liver carcinoma studies. Future studies may facilitate the establishment of an effective systemic therapy for the metastatic liver cancer.

Quantitative analysis of thyroid tumors vascularity: A comparison between 3-D contrast-enhanced ultrasound and 3-D Power Doppler on benign and malignant thyroid nodules

PURPOSE

To perform a comparative quantitative analysis of Power Doppler ultrasound (PDUS) and Contrast-Enhancement ultrasound (CEUS) for the quantification of thyroid nodules vascularity patterns, with the goal of identifying biomarkers correlated with the malignancy of the nodule with both imaging techniques.

METHODS

We propose a novel method to reconstruct the vascular architecture from 3-D PDUS and CEUS images of thyroid nodules, and to automatically extract seven quantitative features related to the morphology and distribution of vascular network. Features include three tortuosity metrics, the number of vascular trees and branches, the vascular volume density, and the main spatial vascularity pattern. Feature extraction was performed on 20 thyroid lesions (ten benign and ten malignant), of which we acquired both PDUS and CEUS. MANOVA (multivariate analysis of variance) was used to differentiate benign and malignant lesions based on the most significant features.

RESULTS

The analysis of the extracted features showed a significant difference between the benign and malignant nodules for both PDUS and CEUS techniques for all the features. Furthermore, by using a linear classifier on the significant features identified by the MANOVA, benign nodules could be entirely separated from the malignant ones.

CONCLUSIONS

Our early results confirm the correlation between the morphology and distribution of blood vessels and the malignancy of the lesion, and also show (at least for the dataset used in this study) a considerable similarity in terms of findings of PDUS and CEUS imaging for thyroid nodules diagnosis and classification.

Perfusion CT - Can it resolve the pancreatic carcinoma versus mass forming chronic pancreatitis conundrum?

OBJECTIVES

To evaluate the utility of perfusion CT (PCT) in differentiating pancreatic adenocarcinoma from mass forming chronic pancreatitis (MFCP).

METHODS

In this ethically approved study, PCT was performed in 122 patients with pancreatic masses of which 42 patients had pancreatic adenocarcinoma and 13 had MFCP on histopathology. Perfusion parameters studied included blood flow (BF), blood volume (BV), permeability surface area product (PS), time to peak (TTP), peak enhancement intensity (PEI) and mean transit time (MTT). Twenty five controls with no pancreatic pathology were also studied.

RESULTS

Amongst the perfusion parameters BF and BV were found to be the most reliable for differentiating between adenocarcinoma and mass forming pancreatitis. Although they were reduced in both pancreatic adenocarcinoma (BF- 16.6 ± 13.1 ml/100 ml/min and BV- 5 ± 3.5 ml/100 ml) and MFCP (BF- 30.4 ± 8.7 ml/100 ml/min and BV- 8.9 ± 3.1 ml/100 ml) as compared to normal controls (BF- 94.1 ± 24 ml/100 ml/min and BV- 36 ± 10.7 ml/100 ml) but the extent of reduction was greater in pancreatic adenocarcinoma than in MFCP. Based on ROC analysis cut off values of 19.1 ml/100 ml/min for BF and 5 ml/100 ml for BV yielded optimal sensitivity and specificity for differentiating pancreatic adenocarcinoma from MFCP.

CONCLUSIONS

PCT may serve as an additional paradigm for differentiating pancreatic adenocarcinoma from mass forming chronic pancreatitis and a useful tool for detecting masses which are isodense on conventional CT.

Computed Tomography Perfusion of Prostate Cancer: Diagnostic Value of Quantitative Analysis

OBJECTIVE

The aim of the study was to assess the diagnostic value of computed tomography perfusion (CTp) of prostate in distinguishing between normal tissue and malignant lesion by using quantitative threshold values of CTp parameters.

MATERIALS AND METHODS

Sixty-one consecutive men with indication for radical prostatectomy were prospectively enrolled. All patients were intravenously injected with 80-mL bolus of nonionic iodinated contrast medium during cine-mode acquisition protocol. Perfusion data sets were analyzed by a dedicated software system and values for each of the 4 CTp parameters (blood volume, blood flow, mean transit time, and permeability surface-area product measurements) were recorded. Receiver operating characteristic curves were calculated to find which CTp parameter and which cutoff value might reveal the best diagnostic accuracy. Histopathology was used as reference standard.

RESULTS

Statistical correlation between radiological and pathological results was performed on 48 patients using 3456 segmented squares. Blood volume and permeability surface revealed the best diagnostic accuracy for differentiating between malignant and benign squares, with cutoff values of 6.1 and 16.5, respectively, and a sensitivity of 84.8% and 81.8%, respectively. All parameters showed also a high negative predictive value: 97.1% for blood volume and 95.4% for permeability surface.

CONCLUSIONS

Blood volume and permeability surface are the 2 CTp parameters with the highest diagnostic accuracy in differentiating between normal tissue and prostatic neoplasia. Due to the extremely high negative predictive value, they are particularly valuable in excluding the presence of cancer and thus resulting potentially useful in assessing cancer response to adjuvant therapy.

Contrast-Enhanced X-Ray Micro-Computed Tomography as a Versatile Method for Anatomical Studies of Adult Zebrafish

One attractive quality of zebrafish as a model organism for biological research is that transparency at early developmental stages allows the optical imaging of cellular and molecular events. However, this advantage cannot be applied to adult zebrafish. In this study, we explored the use of contrast-enhanced X-ray micro-computed tomography (microCT) on adult zebrafish in which the organism was stained with iodine, a simple and economical contrasting agent, after fixation. Tomographic reconstruction of the microCT data allowed the three-dimensional (3D) volumetric analyses of individual organs in adult zebrafish. Adipose tissues showed a higher affinity to iodine and were more strongly contrasted in microCT. As traditional histological techniques often involve dehydration steps that remove tissue lipids, iodine-contrasted microCT offers a convenient method for visualizing fat deposition in fish. Utilizing this advantage, we discovered a transient accumulation of lipids around the heart after ventricular amputation, suggesting a correlation between lipid distribution and heart regeneration. Taken together, microCT is a versatile technique that enables the 3D visualization of zebrafish organs, as well as other fish models, in their anatomical context. This simple method is a valuable new addition to the arsenal of techniques available to this model organism.

Evaluation of neovascularization with spectral computed tomography in a rabbit VX2 liver model: a comparison with real-time contrast-enhanced ultrasound and molecular biological findings

OBJECTIVE

To validate the feasibility of using the parameters of spectral CT and CT perfusion and the dynamic features of real-time contrast-enhanced ultrasound (CEUS) to evaluate the vascularization of VX2 hepatic tumours.

METHODS

Spectral CT imaging, CT perfusion and CEUS analysis were performed on rabbits implanted with VX2 hepatic tumours, 7 and 14 days after implantation. The perfusion parameters of CT, normalized iodine concentration (NIC) and dynamic features of CEUS were measured in the rim of the tumour (TR) and the normal liver region. The expression of vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) was also determined.

RESULTS

Increased perfusion parameters of CT were found in the TR. In addition, the NIC was elevated in TR during the arterial phase, and the peak intensity of the CEUS of the TR was reached significantly earlier than that on normal liver region. At 14 days, the perfusion parameters of CT (blood volume, permeability surface and hepatic arterial fraction) offered higher accuracy and stability in differentiating the TR from the normal liver region. Furthermore, CEUS was more accurate in diagnosing tumours <1.0 cm in diameter. In addition, VEGF and FGF2 expression was higher in the TR and were positively correlated with CT and CEUS parameters, except mean transit time, rise time, washout time and peak time.

CONCLUSION

Use of spectral CT with perfusion techniques, iodine-based material-decomposition analysis and dynamic CEUS changes may reflect the angiogenesis and haemodynamic information of hepatic tumours.

ADVANCES IN KNOWLEDGE

It is feasible to assess vascularization in hepatic cancer using CT or CEUS.

Glioma Angiogenesis and Perfusion Imaging: Understanding the Relationship between Tumor Blood Volume and Leakiness with Increasing Glioma Grade

BACKGROUND AND PURPOSE

The purpose of this study was to investigate imaging correlates to the changes occurring during angiogenesis in gliomas. This was accomplished through in vivo assessment of vascular parameters (relative CBV and permeability surface-area product) and their changing relationship with increasing glioma grade.

MATERIALS AND METHODS

Seventy-six patients with gliomas underwent preoperative perfusion CT and assessment of relative CBV and permeability surface-area product. Regression analyses were performed to assess the rate of change between relative CBV and permeability surface-area product and to test whether these differed for distinct glioma grades. The ratio of relative CBV to permeability surface-area product was also computed and compared among glioma grades by using analysis of variance methods.

RESULTS

The rate of change in relative CBV with respect to permeability surface-area product was highest for grade II gliomas followed by grade III and then grade IV (1.64 versus 0.91 versus 0.27, respectively). The difference in the rate of change was significant between grade III and IV (P = .003) and showed a trend for grades II and IV (P = .098). Relative CBV/permeability surface-area product ratios were the highest for grade II and lowest for grade IV. The pair-wise difference among all 3 groups was significant (P < .001).

CONCLUSIONS

There is an increase in relative CBV more than permeability surface-area product in lower grade gliomas, whereas in grade III and especially grade IV gliomas, permeability surface-area product increases much more than relative CBV. The rate of change of relative CBV with respect to permeability surface-area product and relative CBV/permeability surface-area product ratio can serve as an imaging correlate to changes occurring at the tumor microvasculature level.

Dynamic contrast-enhanced MRI and CT provide comparable measurement of blood-brain barrier permeability in a rodent stroke model

In the current management of acute ischemic stroke (AIS), clinical criteria are used to estimate the risk of hemorrhagic transformation (HT), which is a devastating early complication. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and computed tomography (DCE-CT) may serve as physiologically-based decision making tools to more reliably assess the risk of HT. Before these tools can be properly validated, the comparability of the blood-brain barrier (BBB) permeability measurements they generate should be assessed. Sixteen rats were subjected to a transient middle cerebral artery occlusion before successively undergoing DCE-CT and DCE-MRI at 24-hours. BBB permeability (K(trans)) values were generated from both modalities. A correlation of R=0.677 was found (p<0.01) and the resulting relationship was [DCE-CT=(0.610*DCE-MRI)+4.140]. A variance components analysis found the intra-rat coefficient of variation to be 0.384 and 0.258 for K(trans) values from DCE-MRI and DCE-CT respectively. Permeability measures from DCE-CT were 22% higher than those from DCE-MRI. The results of this study demonstrate for the first time comparability between DCE-CT and DCE-MRI in the assessment of AIS. These results may provide a foundation for future clinical trials making combined use of these modalities.

Perfusion CT estimates photosensitizer uptake and biodistribution in a rabbit orthotopic pancreatic cancer model: a pilot study

RATIONALE AND OBJECTIVES

It was hypothesized that perfusion computed tomography (CT), blood flow (BF), blood volume (BV), and vascular permeability surface area (PS) product parameters would be predictive of therapeutic anticancer agent uptake in pancreatic cancer, facilitating image-guided interpretation of human treatments. The hypothesis was tested in an orthotopic rabbit model of pancreatic cancer, by establishing the model, imaging with endoscopic ultrasound (EUS) and contrast CT, and spatially comparing the perfusion maps to the ex vivo uptake values of the injected photosensitizer, verteporfin.

MATERIALS AND METHODS

Nine New Zealand white rabbits underwent direct pancreas implantation of VX2 tumors, and CT perfusion or EUS was performed 10 days postimplantation. Verteporfin was injected during CT imaging, and the tissue was removed 1 hour postinjection for frozen tissue fluorescence scanning. Region-of-interest comparisons of CT data with ex vivo fluorescence and histopathologic staining were performed.

RESULTS

Dynamic contrast-enhanced CT showed enhanced BF, BV, and PS in the tumor rim and decreased BF, BV, and PS in the tumor core. Significant correlations were found between ex vivo verteporfin concentration and each of BF, BV, and PS.

CONCLUSIONS

The efficacy of verteporfin delivery in tumors is estimated by perfusion CT, providing a noninvasive method of mapping photosensitizer dose.

Thermochemical ablation therapy of VX2 tumor using a permeable oil-packed liquid alkali metal

Objective

Alkali metal appears to be a promising tool in thermochemical ablation, but, it requires additional data on safety is required. The objective of this study was to explore the effectiveness of permeable oil-packed liquid alkali metal in the thermochemical ablation of tumors.

Methods

Permeable oil-packed sodium–potassium (NaK) was prepared using ultrasonic mixing of different ratios of metal to oil. The thermal effect of the mixture during ablation of muscle tissue ex vivo was evaluated using the Fluke Ti400 Thermal Imager. The thermochemical effect of the NaK-oil mixture on VX2 tumors was evaluated by performing perfusion CT scans both before and after treatment in 10 VX2 rabbit model tumors. VX2 tumors were harvested from two rabbits immediately after treatment to assess their viability using trypan blue and hematoxylin and eosin (H.E.) staining.

Results

The injection of the NaK–oil mixture resulted in significantly higher heat in the ablation areas. The permeable oil controlled the rate of heat released during the NaK reaction with water in the living tissue. Perfusion computed tomography and its parameter map confirmed that the NaK–oil mixture had curative effects on VX2 tumors. Both trypan blue and H.E. staining showed partial necrosis of the VX2 tumors.

Conclusions

The NaK–oil mixture may be used successfully to ablate tumor tissue in vivo. With reference to the controlled thermal and chemical lethal injury to tumors, using a liquid alkali in ablation is potentially an effective and safe method to treat malignant tumors.

The evaluation of anti-angiogenic effects of Endostar on rabbit VX2 portal vein tumor thrombus using perfusion MSCT

BACKGROUND

There were many treatments for hepatocellular carcinoma with portal vein tumor thrombus (PVTT), in which targeted anti-angiogenic drug therapy is becoming a popular research topic. However, an objective and non-invasive method that can evaluate the treatment effects is still lacking.

METHODS

Eighteen New Zealand white rabbits implanted with VX2 tumor thrombus in portal vein were randomly assigned into 3 groups: Endostar, saline, or control, six in each group. Multi-slice CT (MSCT) perfusion scanning was performed to measure the differences in blood flow (TBF), tissue blood volume (TBV), and capillary permeability time the surface (PS) before and after Endostar treatment, between Endostar and saline treatment. Two weeks after treatment, both Endostar and saline groups underwent CT perfusion scan. The rabbits then were sacrificed by air embolism, and specimens of tumor thrombosis were collected. Immunohistochemistry assay was also performed to compare the expression of vascular endothelial growth factor (VEGF) in PVTT after Endostar, saline and placebo treatment.

RESULTS

In Endostar group, PVTT CT perfusion parameters (TBF, TBV, PS) significantly decreased after the treatment (p <0.05). Post-treatment PVTT CT perfusion parameters (TBF, TBV, PS) were significantly lower in Endostar group than in Saline group (p <0.05). VEGF is mainly expressed in cytoplasma. After Endostar treatment, the expression of VEGF in PVTT was markedly reduced. There was also significant difference on post-treatment VEGF protein expression measured by Immunohistochemistry assay between Endostar group and control group (p <0.05). Post-treatment PVTT CT perfusion parameters (TBF, TBV, PS) were positively correlated with VEGF protein expression in all 3 groups (rs > 0, p <0.05).

CONCLUSIONS

Multi-slice CT perfusion imaging can evaluate the anti-angiogenic effects of Endostar for the VX2 tumor thrombus in portal vein, and provide quantitative functional information.

Comparing CT perfusion with oxygen partial pressure in a rabbit VX2 soft-tissue tumor model

The aim of this study was to evaluate the oxygen partial pressure of the rabbit model of the VX2 tumor using a 64-slice perfusion CT and to compare the results with that obtained using the oxygen microelectrode method. Perfusion CT was performed for 45 successfully constructed rabbit models of a VX2 brain tumor. The perfusion values of the brain tumor region of interest, the blood volume (BV), the time to peak (TTP) and the peak enhancement intensity (PEI) were measured. The results were compared with the partial pressure of oxygen (PO2) of that region of interest obtained using the oxygen microelectrode method. The perfusion values of the brain tumor region of interest in 45 successfully constructed rabbit models of a VX2 brain tumor ranged from 1.3-127.0 (average, 21.1 ± 26.7 ml/min/ml); BV ranged from 1.2-53.5 ml/100g (average, 22.2 ± 13.7 ml/100g); PEI ranged from 8.7-124.6 HU (average, 43.5 ± 28.7 HU); and TTP ranged from 8.2-62.3 s (average, 38.8 ± 14.8 s). The PO2 in the corresponding region ranged from 0.14-47 mmHg (average, 16 ± 14.8 mmHg). The perfusion CT positively correlated with the tumor PO2, which can be used for evaluating the tumor hypoxia in clinical practice.

Measurements of tumor vascular leakiness using DCE in brain tumors: clinical applications

Various imaging techniques have been employed to evaluate blood-brain-barrier leakiness in brain tumors, as higher tumor vascular leakiness is known to be associated with higher grade and malignant potential of the tumor, and hence can help provide additional diagnostic and prognostic information. These imaging techniques range from routine post-contrast T1 -weighted images that highlight degree of contrast enhancement to absolute measurement of quantitative metrics of vascular leakiness employing complex pharmacokinetic modeling. The purpose of this article is to discuss the clinical applications of available imaging techniques, and in particular dynamic contrast-enhanced T1 -weighted MR imaging (DCE-MRI), to evaluate tumor vascular leakiness.

Preliminary study of CT in combination with MRI perfusion imaging to assess hemodynamic changes during angiogenesis in a rabbit model of lung cancer

Background

This study used CT (computed tomography) and magnetic resonance imaging (MRI) to identify correlations between perfusion parameters for squamous cell lung carcinoma and tumor angiogenesis in a rabbit model of VX2 lung cancer.

Methods

VX2 tumors were implanted in the lungs of 35 New Zealand White rabbits. CT and MRI perfusion scanning were performed on days 14, 17, 21, 25, and 28 after tumor implantation. CT perfusion parameters were perfusion, peak enhanced increment, transit time peak, and blood volume, and MRI perfusion parameters were wash in rate, wash out rate, maximum enhancement rate, and transit time peak. CT and MRI perfusion parameters were obtained at the tumor rim, in the tumor tissue, and in the muscle tissue surrounding the tumor.

Results

On CT perfusion imaging, t values for perfusion, peak enhanced increment, and blood volume (tumor rim versus muscle) were 16.31, 11.79, and 5.21, respectively (P < 0.01); t values for perfusion, peak enhanced increment, and blood volume (tumor versus muscle) were 9.87, 4.09, and 5.35, respectively (P < 0.01); and t values for transit time peak were 1.52 (tumor rim versus muscle) and 1.29 (tumor versus muscle), respectively (P > 0.05). On MRI perfusion imaging, t values for wash in rate, wash out rate, and maximum enhancement rate (tumor rim versus muscle) were 18.14, 8.79, and 6.02, respectively (P < 0.01); t values for muscle wash in rate, wash out rate, and maximum enhancement rate (tumor versus muscle) were 9.45, 8.23, and 4.21, respectively (P < 0.01); and t values for transit time peak were 1.21 (tumor rim versus muscle) and 1.05 (tumor versus muscle), respectively (P > 0.05).

Conclusion

A combination of CT and MRI perfusion imaging demonstrated hemodynamic changes in a rabbit model of VX2 lung cancer, and provides a theoretical foundation for treatment of human squamous cell lung carcinoma.

Enhanced drug delivery in rabbit VX2 tumours using thermosensitive liposomes and MRI-controlled focused ultrasound hyperthermia

PURPOSE

The efficacy of anticancer drugs in solid tumours is impaired by their inability to reach all cancer cells in sufficient concentration to cause cytotoxicity. Hyperthermia-triggered release of drugs from thermosensitive liposomes can increase tumour drug concentration, but tumour-specific drug delivery requires precise temperature control, and effects on microregional distribution of anticancer drugs in tumours are unknown. Here we evaluate thermally triggered release of doxorubicin in a rabbit tumour model by comparing free versus thermosensitive liposomal doxorubicin administered systemically during magnetic resonance imaging (MRI)-controlled focused ultrasound hyperthermia.

MATERIALS AND METHODS

Twelve rabbits with a transplanted VX2 tumour in each thigh had a 10 mm diameter region in one tumour heated to 43°C using focused ultrasound with temperature control by MRI thermometry. Delivery of doxorubicin to tumours and normal tissues was quantified by fluorescence in tissue homogenates, and by fluorescence microscopy.

RESULTS

Using thermosensitive liposomal doxorubicin (2.5 mg/kg), doxorubicin concentrations in heated tumours were 26.7 times higher than in unheated tumours (n = 7, p = 0.017, two-sided Wilcoxon signed-rank test). There was no significant enhancement with free doxorubicin in heated versus unheated tumours (n = 3, p = 0.5). With thermosensitive liposomes (8.3 mg/kg), fluorescence microscopy demonstrated increased doxorubicin fluorescence in heated versus unheated tumours, co-localised with nuclear staining throughout the tumour.

CONCLUSIONS

Localised image-guided delivery of high concentrations of doxorubicin to cancer cells was achieved non-invasively in implanted tumours with temperature-sensitive drug carriers and a preclinical MRI-controlled focused ultrasound hyperthermia system.

Correlation of CT perfusion images with VEGF expression in solitary brain metastases

OBJECTIVES

To obtain permeability surface (PS) values using multi-slice helical CT perfusion imaging and to evaluate the spatial distribution correlation between PS values and vascular endothelial growth factor (VEGF) expression in solitary brain metastases.

METHODS

Imaging was performed on 21 patients, PS values being calculated from the central, border and peripheral parts of tumours. VEGF expression was determined by immunohistochemical staining.

RESULTS

Rim enhancement was found in 16 cases, the border of the tumour featuring PS elevation with high VEGF expression in 13 cases. In the 5 cases with nodular enhancement, the border and the central part had high permeability and VEGF expression was high in all cases, the correlation being significant (P<0.01) .

CONCLUSION

VEGF expression in brain metastases positively correlates with PS values from CT perfusion imaging, so that the latter can be used in the surveillance of angiogenic activity in brain metastases.

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.

Longitudinal in vivo monitoring of rodent glioma models through thinned skull using laser speckle contrast imaging

Laser speckle contrast imaging (LSCI) is a contrast agent free imaging technique suited for longitudinal assessment of vascular remodeling that accompanies brain tumor growth. We report the use of LSCI to monitor vascular changes in a rodent glioma model. Ten rats are inoculated with 9L gliosarcoma cells, and the angiogenic response is monitored five times over two weeks through a thinned skull imaging window. We are able to visualize neovascularization and measure the number of vessels per unit area to assess quantitatively the microvessel density (MVD). Spatial spread of MVD reveals regions of high MVD that may correspond to tumor location. Whole-field average MVD values increase with time in the tumor group but are fairly stable in the control groups. Statistical analysis shows significant differences in MVD values between the tumor group and both saline-receiving and unperturbed control groups over the two-week period (p<0.05). In conclusion, LSCI is suitable for investigation of tumor angiogenesis in rodent models. In addition, the statistical difference (p<0.02) between MVD values of the tumor (24.40 ± 1.41) and control groups (15.40 ± 1.60) on the 14th day after inoculation suggests a potential use of LSCI in the clinic in distinguishing tumor environments from normal vasculature.

Quantification of variability in breath-hold perfusion CT of hepatocellular carcinoma: a step toward clinical use

PURPOSE

To assess the variability of breath-hold perfusion computed tomography (CT) parameters and to investigate whether these measurements are affected by a commercial software upgrade in patients with hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Written informed consent was obtained from all participants in this institutional ethics committee-approved study. Perfusion CT examinations in HCC patients were prospectively analyzed by three readers. Two readers repeated their analysis after an interval of at least 4 weeks. Inter- and intraobserver agreement, as well as intersoftware agreement, were assessed with intraclass correlation coefficients (ICCs) and Bland-Altman limits of agreement (LoA), with adjustment for correlation between repeated measures.

RESULTS

Ninety-three breath-hold perfusion CT examinations were included from 23 HCC patients. The ICC between readers was very high (>0.91) for blood flow (BF), high (>0.84) for blood volume (BV), and lower (>0.30 and >0.39) for mean transit time (MTT) and permeability surface area product (PS), respectively, while ICC between readings was high (>0.80) for BF and BV, good (>0.75) for PS, and lower (>0.38) for MTT, irrespective of software version. By using the current software, the clinically relevant percentage of LoA between readers for BF were -33%; for BV, -39%; for MTT, 55%; and for PS, -93%. Between readings by the most expert reader, the clinically relevant LoA were -35% for BF,-43% for BV, 33% for MTT, and -79% for PS. BF, BV, and PS values were significantly higher and MTT values were significantly lower (P<.01) with the current software version relative to the previous version.

CONCLUSION

With the current CT perfusion software, only decreases between scans of HCC lesions of more than 35% for BF and 43% for BV, or an increase of more than 55% for MTT, could be considered beyond the analysis variability. The perfusion parameters obtained with the current and previous software versions were not exchangeable. The results of this study are specific for breath-hold perfusion CT of HCC and may not apply to different acquisition protocols and tumors.

Perfusion computed tomography assessments of peri-enhancing brain tissue in high-grade gliomas

PURPOSE

This study was undertaken to identify tumoural infiltration of peri-enhancing brain tissue in patients with glioblastoma by means of perfusion computed tomography (PCT) parameters, cerebral blood volume (CBV) and permeability surface (PS).

MATERIALS AND METHODS

Eight patients with surgically treated glioblastoma who were eligible for radiotherapy and nine patients with brain metastases from lung and breast cancer underwent CT before and after injection of contrast medium. CBV and PS were calculated in the contrast-enhancing lesion area, in the area of perilesional oedema and in the normal-appearing white matter (NAWM), normalised to contralateral symmetrical areas.

RESULTS

No significant differences were found for normalised CBV (nCBV) and nPS in NAWM regions between metastasis and glioma. Significant differences in nPS (p<0.005) were found between the typically vasogenic oedema surrounding the metastases and signal alteration surrounding the glial neoplasm. On the contrary, no significant differences were detected in the same areas for nCBV.

CONCLUSIONS

PCT can analyse the histopathological substrate underlying the hypodense peritumoural halo and differentiate between vasogenic oedema and neoplastic infiltration on the basis of the PS parameter. In our study, PS was more informative than CBV. These findings can be used to integrate plans for radiation therapy and/or surgery.

Reproducibility and comparison of DCE-MRI and DCE-CT perfusion parameters in a rat tumor model

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and computed tomography (DCE-CT) provide independent measures of biomarkers related to tumor perfusion. We compared the reproducibilities and absolute values of DCE-MRI and DCE-CT biomarkers in the same tumors in an animal model, to investigate the physiologic validity of both approaches. DCE-MRI and DCE-CT were each performed sequentially on three consecutive days in each of twelve rats bearing C6 glioma xenografts. DCE-MRI yielded endothelial transfer constant (K(trans)), extracellular, extravascular space volume fraction (v(e)), and contrast agent reflux rate constant (k(ep)); and DCE-CT, blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability-surface area product (PS) using Tofts and deconvolution physiological models, with 6.6 and 0.4 seconds temporal resolutions, respectively. Variability in DCE-CT and DCE-MRI were evaluated by variance components analysis. Intra-rat coefficients of variation for DCE-CT parameters BF, BV, MTT and PS were 25%, 22%, 18% and 23%; and for DCE-MRI parameters K(trans), k(ep) and v(e) were 23%, 16% and 20%, respectively. Mean (±SD) BF, BV, MTT and PS were: 44.6 (±13.7) ml min(-1) 100 g(-1), 5.7 (±1.5) ml 100 g(-1), 10.8 (±2.3) seconds, and 14.6 (±4.7) ml min(-1) 100 g(-1), respectively. Mean (±SD) K(trans), k(ep) and v(e) were: 0.21 (±0.05) min(-1), 0.68 (±0.14) min(-1), and 0.29 (±0.06), respectively. Permeability estimates from DCE-MRI (K(trans)) were 44% higher than from DCE-CT (PS), despite application of appropriate corrections. DCE-MRI and DCE-CT biomarkers of tumor perfusion have similar reproducibilities suggesting that they may have comparable utility, but their derived parameter values are not equivalent.

Current status and guidelines for the assessment of tumour vascular support with dynamic contrast-enhanced computed tomography

Dynamic contrast-enhanced computed tomography (DCE-CT) assesses the vascular support of tumours through analysis of temporal changes in attenuation in blood vessels and tissues during a rapid series of images acquired with intravenous administration of iodinated contrast material. Commercial software for DCE-CT analysis allows pixel-by-pixel calculation of a range of validated physiological parameters and depiction as parametric maps. Clinical studies support the use of DCE-CT parameters as surrogates for physiological and molecular processes underlying tumour angiogenesis. DCE-CT has been used to provide biomarkers of drug action in early phase trials for the treatment of a range of cancers. DCE-CT can be appended to current imaging assessments of tumour response with the benefits of wide availability and low cost. This paper sets out guidelines for the use of DCE-CT in assessing tumour vascular support that were developed using a Delphi process. Recommendations encompass CT system requirements and quality assurance, radiation dosimetry, patient preparation, administration of contrast material, CT acquisition parameters, terminology and units, data processing and reporting. DCE-CT has reached technical maturity for use in therapeutic trials in oncology. The development of these consensus guidelines may promote broader application of DCE-CT for the evaluation of tumour vascularity. Key Points • DCE-CT can robustly assess tumour vascular support • DCE-CT has reached technical maturity for use in therapeutic trials in oncology • This paper presents consensus guidelines for using DCE-CT in assessing tumour vascularity.

Tracer kinetic modelling in MRI: estimating perfusion and capillary permeability

The tracer-kinetic models developed in the early 1990s for dynamic contrast-enhanced MRI (DCE-MRI) have since become a standard in numerous applications. At the same time, the development of MRI hardware has led to increases in image quality and temporal resolution that reveal the limitations of the early models. This in turn has stimulated an interest in the development and application of a second generation of modelling approaches. They are designed to overcome these limitations and produce additional and more accurate information on tissue status. In particular, models of the second generation enable separate estimates of perfusion and capillary permeability rather than a single parameter K(trans) that represents a combination of the two. A variety of such models has been proposed in the literature, and development in the field has been constrained by a lack of transparency regarding terminology, notations and physiological assumptions. In this review, we provide an overview of these models in a manner that is both physically intuitive and mathematically rigourous. All are derived from common first principles, using concepts and notations from general tracer-kinetic theory. Explicit links to their historical origins are included to allow for a transfer of experience obtained in other fields (PET, SPECT, CT). A classification is presented that reveals the links between all models, and with the models of the first generation. Detailed formulae for all solutions are provided to facilitate implementation. Our aim is to encourage the application of these tools to DCE-MRI by offering researchers a clearer understanding of their assumptions and requirements.

Dynamic contrast-enhanced micro-CT on mice with mammary carcinoma for the assessment of antiangiogenic therapy response

OBJECTIVE

To evaluate the potential of in vivo dynamic contrast-enhanced micro-computed tomography (DCE micro-CT) for the assessment of antiangiogenic drug therapy response of mice with mammary carcinoma.

METHODS

20 female mice with implanted MCF7 tumours were split into control group and therapy group treated with a known effective antiangiogenic drug. All mice underwent DCE micro-CT for the 3D analysis of functional parameters (relative blood volume [rBV], vascular permeability [K], area under the time-enhancement curve [AUC]) and morphology. All parameters were determined for total, peripheral and central tumour volumes of interest (VOIs). Immunohistochemistry was performed to characterise tumour vascularisation. 3D dose distributions were determined.

RESULTS

The mean AUCs were significantly lower in therapy with P values of 0.012, 0.007 and 0.023 for total, peripheral and central tumour VOIs. K and rBV showed significant differences for the peripheral (P(per)(K) = 0.032, P(per) (rBV) = 0.029), but not for the total and central tumour VOIs (P(total)(K) = 0.108, P(central)(K) = 0.246, P(total) (rBV) = 0.093, P(central) (rBV) = 0.136). Mean tumour volume was significantly smaller in therapy (P (in vivo) = 0.001, P (ex vivo) = 0.005). Histology revealed greater vascularisation in the controls and central tumour necrosis. Doses ranged from 150 to 300 mGy.

CONCLUSIONS

This study indicates the great potential of DCE micro-CT for early in vivo assessment of antiangiogenic drug therapy response.

KEY POINTS

Dynamic contrast enhanced micro-CT (computed tomography) is a new experimental laboratory technique. DCE micro-CT allows early in vivo assessment of antiangiogenic drug therapy response. Pharmaceutical drugs can be tested before translation to clinical practice. Both morphological and functional parameters can be obtained using DCE micro-CT. Antiangiogenic effects can be visualised with DCE micro-CT.

Reproducibility of CT perfusion parameters in liver tumors and normal liver

PURPOSE

To assess the reproducibility of computed tomographic (CT) perfusion measurements in liver tumors and normal liver and effects of motion and data acquisition time on parameters.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained for this prospective study. The study complied with HIPAA regulations. Two CT perfusion scans were obtained 2-7 days apart in seven patients with liver tumors with two scanning phases (phase 1: 30-second breath-hold cine; phase 2: six intermittent free-breathing cines) spanning 135 seconds. Blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability-surface area product (PS) for tumors and normal liver were calculated from phase 1 with and without rigid registration and, for combined phases 1 and 2, with manually and rigid-registered phase 2 images, by using deconvolution modeling. Variability was assessed with within-patient coefficients of variation (CVs) and Bland-Altman analyses.

RESULTS

For tumors, BF, BV, MTT, and PS values and reproducibility varied by analytical method, the former by up to 11%, 23%, 21%, and 138%, respectively. Median PS values doubled with the addition of phase 2 data to phase 1 data. The best overall reproducibility was obtained with rigidly registered phase 1 and phase 2 images, with within-patient CVs for BF, BV, MTT, and PS of 11.2%, 14.4%, 5.5% and 12.1%, respectively. Normal liver evaluations were similar, except with marginally lower variability.

CONCLUSION

Absolute values and reproducibility of CT perfusion parameters were markedly influenced by motion and data acquisition time. PS, in particular, probably requires data acquisition beyond a single breath hold, for which motion-correction techniques are likely necessary.

Perfusion CT evaluation in experimentally induced testicular torsion

INTRODUCTION

In this study, we define the characteristics of perfusion computed tomography (CT) in an experimental model of testicular torsion.

METHODS

Twenty male Sprague-Dawley rats were included for the study. Torsion was applied to 10 rats and perfusion CT was performed in the first hour to evaluate the following perfusion parameters: blood flow (BF), blood volume (BV) and time to peak (TTP) values. Detorsion was done for the same rats, and perfusion CT was repeated 2 hours later to evaluate reperfusion. Ten rats were left as part of the control group.

RESULTS

There is significant statistical correlation between the BF and BV values in the torsion and control groups (p = 0.001 and p = 0.001, respectively). There is no statistical correlation of the TTP parameters between the groups. No correlation was found between torsion and detorsion perfusion parameters.

CONCLUSION

Perfusion CT can demonstrate the testicular perfusion insult in an experimental model of torsion. Perfusion CT may be an alternative method for diagnosis of torsion in indeterminate cases. Following detorsion an interval of 2 hours is not sufficient for demonstrating luxury perfusion of the testis.

Perfusion CT assessment of tissue hemodynamics following hepatic arterial infusion of increasing doses of angiotensin II in a rabbit liver tumor model

PURPOSE

To investigate the effects of increasing doses of angiotensin II on hepatic hemodynamics in the normal rabbit liver and in hepatic VX2 tumors by using dynamic contrast material-enhanced perfusion computed tomography (CT).

MATERIALS AND METHODS

This study was approved by the institutional animal care and use committee. Solitary hepatic VX2 tumors were implanted into 12 rabbits. In each animal, perfusion CT of the liver was performed before (at baseline) and after hepatic arterial infusion of varying doses (0.1-50.0 μg/mL) of angiotensin II. Images were acquired continuously for 80 seconds after the start of the intravenous contrast material administration. Blood flow (BF), blood volume (BV), mean transit time (MTT), and capillary permeability-surface area product were calculated for the tumor and the adjacent and distant normal liver tissue. Generalized linear mixed models were used to estimate the effects of angiotensin II dose on outcome measures.

RESULTS

Angiotensin II infusion increased contrast enhancement of the tumor and distal liver vessels. Tumor BF increased in a dose-dependent manner after administration of 0.5-25.0 μg/mL angiotensin II, but only the 2.5 μg/mL dose induced a significant increase in tumor BF compared with BF in the adjacent (68.0 vs 26.3 mL/min/100 g, P < .0001) and distant (68.0 vs 28.3 mL/min/100 g, P = .02) normal liver tissue. Tumor BV varied with angiotensin II dose but was greater than the BV of the adjacent and distant liver tissue at only the 2.5 μg/mL (4.8 vs 3.5 mL/100 g for adjacent liver [P < .0001], 4.8 vs 3.3 mL/100 g for distant liver [P = .0006]) and 10.0 μg/mL (4.9 vs 4.4 mL/100 g for adjacent liver [P = .007], 4.9 vs 4.3 mL/100 g for distant liver [P = .04]) doses. Tumor MTT was significantly shorter than the adjacent liver tissue MTT at angiotensin II doses of 2.5 μg/mL (9.7 vs 15.8 sec, P = .001) and 10.0 μg/mL (5.1 vs 13.2 sec, P = .007) and significantly shorter than the distant liver tissue MTT at 2.5 μg/mL only (9.7 vs 15.3 sec, P = .0006). The capillary permeability-surface area product for the tumor was higher than that for the adjacent liver tissue at the 2.5 μg/mL angiotensin II dose only (11.5 vs 8.1 mL/min/100 g, P = .01).

CONCLUSION

Perfusion CT enables a mechanistic understanding of angiotensin II infusion in the liver and derivation of the optimal effective dose. The 2.5 μg/mL angiotensin II dose increases perfusion in hepatic VX2 tumors versus that in adjacent and distant normal liver tissue primarily by constricting normal distal liver vessels and in turn increasing tumor BF and BV.

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.

The evaluation of anti-angiogenic treatment effects for implanted rabbit VX2 breast tumors using functional multi-slice spiral computed tomography (f-MSCT)

OBJECTIVE

Investigate the benefit of functional multi-slice spiral computed tomography (f-MSCT) perfusion imaging in the non-invasive assessment of targeted anti-angiogenesis therapy on an implanted rabbit VX2 breast tumor model.

METHOD

69 female pure New Zealand white rabbits were randomly assigned to one of the 4 groups and received treatment accordingly: control (saline), Endostar, neoadjuvant chemotherapy (Cyclophosphamide, Epirubicin and 5-Fluorouracil, CEF), combination therapy (Endostar and CEF). After 2 weeks of treatment, f-MSCT perfusion scannings were performed for all rabbits and information about blood flow (BF), blood volume (BV), mean transit time (MTT) and surface permeability (SP) was collected. After perfusion imaging, tumor tissues were sampled for immunohistochemistry and the Western blot test of VEGF protein expression.

RESULTS

(1) The VEGF expression level, measured by immunohistochemistry and Western blot, decreased by treatment group (control > Endostar > CEF > combination therapy). The same was true for the mean BF, BV, MTT and PS, which decreased from the control group to the combination therapy group gradually. The mean MTT level increased in reverse order from the control to the combination therapy group. The difference between any 2 groups on these measures was statistically significant (P < 0.05). (2) There was moderate positive correlation between VEGF expression and BE, BV, or PS level (P < 0.05) and a negative correlation between VEGF expression and MTT level for all 4 groups (P < 0.05).

CONCLUSION

Therefore, f-MSCT can be used as a non-invasive approach to evaluate the effect of anti-angiogenic therapy for implanted rabbit VX2 breast tumors.

CT color mapping of the arterial enhancement fraction of VX2 carcinoma implanted in rabbit liver: comparison with perfusion CT

OBJECTIVE

The purpose of this study was to compare the arterial enhancement fraction (AEF) calculated at multiphasic liver CT with the hepatic perfusion index (HPI) measured with cine mode perfusion CT.

MATERIALS AND METHODS

Cine mode perfusion CT was performed after VX2 tumor implantation in the livers of 10 rabbits. HPI and its color map were obtained with a computer application. With raw data from cine mode perfusion CT, images were extracted in the unenhanced, arterial, and portal venous phases to simulate multiphasic liver CT. On the basis of simulated multiphasic CT images, the AEF color map was obtained with prototype software. HPI and AEF were compared for the same regions of interest in the liver parenchyma, whole liver tumor, and viable tumor portion.

RESULTS

In the liver parenchyma, the mean HPI was 23.3% ± 2.6% (SD) and the AEF 24.4% ± 2.8%; in whole liver tumor, 73.4% ± 9.5% and 78.4% ± 10.5%; and in the viable tumor portion, 78.0% ± 7.7% and 78.3% ± 7.5%. The differences were not statistically significant (p > 0.05, Wilcoxon's signed rank test). Measurement agreement between the two parameters was moderate (Bland-Altman 95% limits of agreement, -14.9% and 19.2%), but there was a strong positive correlation between AEF and HPI (within-subject r = 0.91, p < 0.001). Functional maps of HPI and AEF correlated with the histologic findings.

CONCLUSION

AEF calculated from simulated multiphasic liver CT images correlates strongly with HPI obtained at cine mode perfusion CT. Further study of the AEF is warranted to explore its value in providing hepatic perfusion information without additional radiation exposure.

A general dual-bolus approach for quantitative DCE-MRI

PURPOSE

To present a dual-bolus technique for quantitative dynamic contrast-enhanced MRI (DCE-MRI) and show that it can give an arterial input function (AIF) measurement equivalent to that from a single-bolus protocol.

METHODS

Five rabbits were imaged using a dual-bolus technique applicable for high-resolution DCE-MRI, incorporating a time resolved imaging of contrast kinetics (TRICKS) sequence for rapid temporal sampling. AIFs were measured from both the low-dose prebolus and the high-dose main bolus in the abdominal aorta. In one animal, TRICKS and fast spoiled gradient echo (FSPGR) acquisitions were compared.

RESULTS

The scaled prebolus AIF was shown to match the main bolus AIF, with 95% confidence intervals overlapping for fits of gamma-variate functions to the first pass and linear fits to the washout phase, with the exception of one case. The AIFs measured using TRICKS and FSPGR were shown to be equivalent in one animal.

CONCLUSION

The proposed technique can capture even the rapid circulation kinetics in the rabbit aorta, and the scaled prebolus AIF is equivalent to the AIF from a high-dose injection. This allows separate measurements of the AIF and tissue uptake curves, meaning that each curve can then be acquired using a protocol tailored to its specific requirements.

Perfusion CT imaging of brain tumors: an overview

Perfusion imaging of brain tumors has been performed by using various tracer and nontracer modalities and can provide additional physiologic and hemodynamic information, which is not available with routine morphologic imaging. Tumor vascular perfusion parameters obtained by using CT or MR perfusion have been used for tumor grading, prognosis, and treatment response in addition to differentiating treatment/radiation effects and non-neoplastic lesions from neoplasms. This article is an overview of the utility of PCT for assessment of brain tumors and describes the technique, its advantages, and limitations.

Increased blood-brain barrier permeability on perfusion CT might predict malignant middle cerebral artery infarction

BACKGROUND AND PURPOSE

Perfusion CT has been used to assess the extent of blood-brain barrier breakdown. The purpose of this study was to determine the predictive value of blood-brain barrier permeability measured using perfusion CT for development of malignant middle cerebral artery infarction requiring hemicraniectomy (HC).

METHODS

We retrospectively identified patients from our stroke registry who had middle cerebral artery infarction and were evaluated with admission perfusion CT. Blood-brain barrier permeability and cerebral blood volume maps were generated and infarct volumes calculated. Clinical and radiographic characteristics were compared between those who underwent HC versus those who did not undergo HC.

RESULTS

One hundred twenty-two patients (12 HC, 110 no HC) were identified. Twelve patients who underwent HC had developed edema, midline shift, or infarct expansion. Infarct permeability area, infarct cerebral blood volume area, and infarct volumes were significantly different (P < 0.018, P < 0.0211, P < 0.0001, P < 0.0014) between HC and no HC groups. Age (P = 0.03) and admission National Institutes of Health Stroke Scale (P = 0.0029) were found to be independent predictors for HC. Using logistic regression modeling, there was an association between increased infarct permeability area and HC. The OR for HC based on a 5-, 10-, 15-, or 20-cm² increase in infarct permeability area were 1.179, 1.390, 1.638, or 1.932, respectively (95% CI, 1.035 to 1.343, 1.071 to 1.804, 1.108 to 2.423, 1.146 to 3.255, respectively).

CONCLUSIONS

Increased infarct permeability area is associated with an increased likelihood for undergoing HC. Because early HC for malignant middle cerebral artery infarction has been associated with better outcomes, the infarct permeability area on admission perfusion CT might be a useful tool to predict malignant middle cerebral artery infarction and need for HC.

Morphological and functional MDCT: problem-solving tool and surrogate biomarker for hepatic disease clinical care and drug discovery in the era of personalized medicine

This article explains the significant role of morphological and functional multidetector computer tomography (MDCT) in combination with imaging postprocessing algorithms served as a problem-solving tool and noninvasive surrogate biomarker to effectively improve hepatic diseases characterization, detection, tumor staging and prognosis, therapy response assessment, and novel drug discovery programs, partial liver resection and transplantation, and MDCT-guided interventions in the era of personalized medicine. State-of-the-art MDCT depicts and quantifies hepatic disease over conventional CT for not only depicting lesion location, size, and extent but also detecting changes in tumor biologic behavior caused by therapy or tumor progression before morphologic changes. Color-encoded parameter display provides important functional information on blood flow, permeability, leakage space, and blood volume. Together with other relevant biomarkers and genomics, the imaging modality is being developed and validated as a biomarker to early response to novel, targeted anti-VEGF(R)/PDGFR or antivascular/angiogenesis agents as its parameters correlate with immunohistochemical surrogates of tumor angiogenesis and molecular features of malignancies. MDCT holds incremental value to World Health Organization response criteria and Response Evaluation Criteria in Solid Tumors in liver disease management. MDCT volumetric measurement of future remnant liver is the most important factor influencing the outcome of patients who underwent partial liver resection and transplantation. MDCT-guided interventional methods deliver personalized therapies locally in the human body. MDCT will hold more scientific impact when it is fused with other imaging probes to yield comprehensive information regarding changes in liver disease at different levels (anatomic, metabolic, molecular, histologic, and other levels).

Temporal resolution and SNR requirements for accurate DCE-MRI data analysis using the AATH model

Dynamic contrast-enhanced MRI has been used in conjunction with tracer kinetics modeling in a wide range of tissues for treatment monitoring, oncology drug development, and investigation of disease processes. Accurate measurement of model parameters relies on acquiring data with high temporal resolution and low noise, particularly for models with large numbers of free parameters, such as the adiabatic approximation to the tissue homogeneity model for separate measurements of blood flow and vessel permeability. In this simulation study, accuracy of the adiabatic approximation to the tissue homogeneity model was investigated, examining the effects of temporal resolution, noise levels, and error in the measured arterial input function. A temporal resolution of 1.5 s and high SNR (noise sd = 0.05) were found to ensure minimal bias (<5%) in all four model parameters (extraction fraction, blood flow, mean transit time, and extravascular extracellular volume), and the sampling interval can be relaxed to 6 s, if the transit time need not be measured accurately (bias becomes >10%). A 10% error in the measured height of the arterial input function first pass peak resulted in an error of at most 10% in each model parameter.

Experimental Study on Angiogenesis in a Rabbit VX2 Early Liver Tumour by Perfusion Computed Tomography

Ten rabbits implanted with VX2 liver tumours were investigated by perfusion computed tomography (PCT) imaging 1 week (early) and 2 weeks (late) after tumour induction; 10 other rabbits were non-implanted controls. Time–density curves, perfusion parametric maps and perfusion parameters were obtained for tumour rim and normal tissue surrounding the tumour, and for liver tissue from the controls. In addition, microvessel density (MVD) and vascular endothelial growth factor (VEGF) were studied by immunohistochemistry 2 weeks after tumour implantation. A deconvolution mathematical model was used to calculate hepatic blood flow (HBF), hepatic blood volume (HBV), mean transit time (MTT), capillary vessel surface permeability (PS) and hepatic arterial index (HAI). At the tumour rim on the early PCT scan, MTT was significantly lower whereas HBF, HBV, HAI and PS were significantly higher than in surrounding normal tissue. There were no significant changes in perfusion parameters on the late PCT scan compared with the early scan. Significant linear correlations of MVD and VEGF were found with HBF, PS and HAI, but not with HBV or MTT. It is concluded that PCT imaging is useful for the evaluation of tumour angiogenesis and for the early detection of liver tumours.

Does computed tomography or positron emission tomography/computed tomography contribute to detection of small focal cancers in the prostate?

Prostate cancer is considered to be a multifocal tumor in the majority of patients. Based on histologic data after prostatectomy, there is a growing insight that a considerable number of men who receive a diagnosis in the contemporary setting of prostate-specific antigen screening have unilateral or unifocal disease. With this, the current concept of whole-gland therapy has come into discussion. The need for improvement of intraprostatic tumor characterization is clear. Molecular imaging is one of the areas of research on this aspect. The clinical indications for positron emission tomography (PET)/CT have increased rapidly in the field of oncology and are largely based on fluorodeoxyglucose (FDG) PET. Both conventional CT and FDG PET, however, cannot detect prostate cancer foci <5 mm within the prostate. Dynamic contrast-enhanced CT involves imaging a region of interest rapidly (usually <10 seconds between images) during a bolus intravenous injection of a contrast agent. Through analysis of the contrast enhancement time curves, it is possible to distinguish tissues with different microvascular properties such as cancer. The technologic aspects of both imaging techniques and the clinical results of 11C-choline PET/CT for intraprostatic tumor characterization are discussed. Based on preliminary studies, dynamic contrast-enhanced (DCE)-CT may be a useful tool for localization of prostate tumors and, perhaps more importantly, quantification of therapeutic response in prostate cancer. Validation work is necessary, however, to define its accuracy and role in therapeutic paradigms such as focal therapies, particularly given the current accuracy of MRI. In the future, combining DCE-CT with CT or (11)C-choline PET/CT may be an alternative to MRI, offering a combination of quantitative parameters that may correlate to tumor prognosis as well as cancer localization for focal therapy.

CT perfusion in solid-body tumours. Part I: Technical issues

Functional imaging is becoming increasingly important in both research and clinical diagnostic radiology. Perfusion computed tomography (CTP) is a readily available and widely used tool that allows an objective measurement of tissue perfusion through the mathematical analysis of data obtained from repeated scans performed after administration of contrast agent. Recently, CTP has been increasingly used in the oncological field, being studied as a potential marker of neoplastic angiogenesis, which is one of the main targets of new tumour therapies. The aim of this paper was to provide the theoretical background and practical guidance for accurately performing CTP and interpreting results of examinations in solid-body tumours. CTP could be a valid tool for functional imaging of tumours if the acquisition technique is robust, if image and data analysis is accurate and if interpretation of results is adequately inserted within a clinical context.

Role of computed tomography perfusion in the evaluation of pancreatic necrosis and pancreatitis after endoscopic ultrasound-guided ablation of the pancreas in a porcine model

OBJECTIVES

To evaluate the role of computed tomography (CT) perfusion in detection of pancreatic necrosis and pancreatitis after endoscopic ultrasound-guided ethanol ablation of porcine pancreas and to correlate the evaluation with histopathology.

METHODS

Under endoscopic ultrasound guidance, 0.9% saline (control) and ethanol at 60%, 80%, and 100% concentrations were injected into the pancreatic tails of 4 pigs. On day 4, dynamic perfusion CT of the pancreas was performed. Perfusion analysis and evaluation of enhancement characteristics were done and correlated with histopathology.

RESULTS

Ethanol injections at 80% and 100% concentrations resulted in focal necrosis surrounded by focal pancreatitis, whereas 60% ethanol injection caused severe focal pancreatitis with microscopic necrosis. The necrotic area revealed reduced blood flow, blood volume, permeability-surface area product, and increased mean transit time compared with pancreatitis and normal tissue (P < or = 0.001). In the control pig, no pancreatitis or necrosis was observed on perfusion images and histopathology.

CONCLUSIONS

Pancreatic necrosis and pancreatitis after ethanol injection reduced the tissue perfusion on CT in comparison to normal tissue, with the changes being more substantial in necrosis than pancreatitis. These findings have possible implications in the accurate detection of pancreatic necrosis in patients with severe pancreatitis.

Quantitative helical dynamic contrast enhanced computed tomography assessment of the spatial variation in whole tumour blood volume with radiotherapy in lung cancer

We aim to assess the spatial distribution of blood volume (BV) in whole lung tumours in patients undergoing radiotherapy using helical dynamic contrast enhanced computed tomography (DCE-CT), and to determine whether conventional single level, or whole tumour measurements is more representative of the vascular effects of radiotherapy. Following ethical approval and informed consent, 15 patients with histologically proven non-small cell lung cancer underwent paired helical DCE-CT studies at baseline to assess repeatability, and after two fractions of radiotherapy (9 Gy total dose). Tumour BV was calculated for individual contiguous 10mm axial slices, and for the entire tumour volume on a pixel-per-pixel basis. Baseline tumour BV was heterogeneous varying by 15.33%+/-17.11 between adjacent 10mm axial slices. Within subject coefficient of variation was 36.72% with conventional single tumour level evaluation, and 13.62% with whole tumour measurements. Following radiotherapy, one patient had an increase in BV greater than baseline variation (derived from the 95% limits of change) using single level evaluation; in contrast, seven patients had an increase in BV when the whole tumour was assessed. As a group, following radiotherapy, mean BV increased by 17.27% (paired t-test, p=0.20) with single level evaluation and 19.26% (p=0.049) with whole tumour assessment. Tumour BV measured using DCE-CT is spatially heterogeneous. Given the slice-by-slice variation in blood volume, our results demonstrate that whole tumour DCE-CT measurements are more repeatable, and may be a better predictor of vascular changes following therapy, compared to conventional single tumour level evaluations.

Pancreatic adenocarcinoma: dynamic 64-slice helical CT with perfusion imaging

BACKGROUND

Perfusion CT is able to outline blood perfusion changes in a tissue. Thus, in lesions of the tissues of the pancreas, this offers to increase the accuracy of CT diagnosis. In this study, our aim was to explore the perfusion characteristics of normal pancreas and pancreatic adenocarcinoma.

METHODS

Dynamic 64-slice helical CT was conducted in 36 patients with non-pancreatic disease and in 40 patients with histopathologically proven pancreatic adenocarcinoma. Perfusion parameters including blood flow (BF), blood volume (BV), and permeability surface area product (PS) were recorded.

RESULTS

There was no significant difference noted between the distribution of BF, BV, and PS values in different regions of the pancreas, namely the head, neck, body, and tail (P > 0.05). The BF, BV, and PS of normal pancreas were recorded as 135.24 +/- 48.36 ml min(-1) 100 g(-1), 200.55 +/- 54.96 ml 100 g(-1), and 49.75 +/- 24.27 ml min(-1) 100 g(-1), respectively. BF, BV, and PS values of the tumor tissue of pancreatic adenocarcinoma decreased significantly compared to normal pancreas (P < 0.05).

CONCLUSIONS

Normal pancreas appears homogenous on perfusion CT. A significant decrease of BF, BV, and PS was observed in pancreatic adenocarcinoma. Dynamic 64-slice helical CT with perfusion imaging should be considered a potential modality to increase the accuracy of CT diagnosis for pancreatic adenocarcinoma.