The use of perfusion CT for the evaluation of therapy combining AZD2171 with gefitinib in cancer patients

Considerations for Imaging of Malignant Pleural Mesothelioma: A Consensus Statement from the International Mesothelioma Interest Group

Malignant pleural mesothelioma (MPM) is an aggressive primary malignancy of the pleura that presents unique radiologic challenges with regard to accurate and reproducible assessment of disease extent at staging and follow-up imaging. By optimizing and harmonizing technical approaches to imaging MPM, the best quality imaging can be achieved for individual patient care, clinical trials, and imaging research. This consensus statement represents agreement on harmonized, standard practices for routine multimodality imaging of MPM, including radiography, computed tomography, ¹⁸F-2-deoxy-D-glucose positron emission tomography, and magnetic resonance imaging, by an international panel of experts in the field of pleural imaging assembled by the International Mesothelioma Interest Group. In addition, modality-specific technical considerations and future directions are discussed. A bulleted summary of all technical recommendations is provided.

Appraisal of radiation dose with 64-slice computed tomography perfusion in lung cancer patients with special reference to SSDE: An initial experience in a tertiary care hospital

Context:

Computed tomography perfusion (CTP) is an important functional tool for lung cancer. It is expected to deliver high radiation dose, making its accurate estimation important. Size-specific dose estimate (SSDE) is a new dose metric, which includes the scanner output as well as the patient size.

Aims:

To determine radiation dose [CT dose index (CTDI_vol), dose length product (DLP), effective dose (ED), and SSDE] for CTP in lung cancer and the correlation of CTDI_vol, DLP, and SSDE with effective diameter and SSDE with weight, body mass index (BMI), and the scan length.

Settings and Design:

Cross-sectional study in the Department of Radio-diagnosis from October 2015 to March 2016.

Patients and Methods:

Due ethical approval and informed consent was taken. Thirty consecutive adult patients of lung cancer undergoing CTP study were included; various radiation dose parameters were determined and presented as mean ± SD.

Statistical Analysis Used:

Paired Student's t-test and Pearson correlation using Statistical Package for the Social Sciences, Version 16.

Results:

Mean radiation dose was CTDI_vol = 270.138 ± 1.627 mGy, DLP = 681 ± 53.496 mGy.cm, ED = 12.501 ± 0.923 mSv, SSDE = 388.90 ± 81.27 mGy. The CTDI_vol and DLP had significant positive correlation (r = 0.556, P = 0.000 and r = 0.522, P = 0.003, respectively) with effective diameter. SSDE had strong negative correlation (r = −0.997, P = 0.000) with effective diameter, significant negative correlation with the BMI (r = −0.889; P = 0.000) and weight (r = −0.910, P = 0.000) of patients. Scan length was not significantly correlated in SSDE (r = −0.012, P = 0.951).

Conclusions:

Smaller sized patients had greater SSDE.

Response Evaluation of Chemotherapy for Lung Cancer

Assessing response to therapy allows for prospective end point evaluation in clinical trials and serves as a guide to clinicians for making decisions. Recent prospective and randomized trials suggest the development of imaging techniques and introduction of new anti-cancer drugs. However, the revision of methods, or proposal of new methods to evaluate chemotherapeutic response, is not enough. This paper discusses the characteristics of the Response Evaluation Criteria In Solid Tumor (RECIST) version 1.1 suggested in 2009 and used widely by experts. It also contains information about possible dilemmas arising from the application of response assessment by the latest version of the response evaluation method, or recently introduced chemotherapeutic agents. Further data reveals the problems and limitations caused by applying the existing RECIST criteria to anti-cancer immune therapy, and the application of a new technique, immune related response criteria, for the response assessment of immune therapy. Lastly, the paper includes a newly developing response evaluation method and suggests its developmental direction.

Mathematical Models of Contrast Transport Kinetics for Cancer Diagnostic Imaging: A Review

Angiogenesis plays a fundamental role in cancer growth and the formation of metastasis. Novel cancer therapies aimed at inhibiting angiogenic processes and/or disrupting angiogenic tumor vasculature are currently being developed and clinically tested. The need for earlier and improved cancer diagnosis, and for early evaluation and monitoring of therapeutic response to angiogenic treatment, have led to the development of several imaging methods for in vivo noninvasive assessment of angiogenesis. The combination of dynamic contrast-enhanced imaging with mathematical modeling of the contrast agent kinetics enables quantitative assessment of the structural and functional changes in the microvasculature that are associated with tumor angiogenesis. In this paper, we review quantitative imaging of angiogenesis with dynamic contrast-enhanced magnetic resonance imaging, computed tomography, and ultrasound.

Perfusion CT imaging of treatment response in oncology

Perfusion CT was first described in the 1970s but has become accepted as a clinical technique in recent years. In oncological practice Perfusion CT allows the downstream effects of therapies on the tumour vasculature to be monitored. From the dynamic changes in tumour and vascular enhancement following intravenous iodinated contrast agent administration, qualitative and quantitative parameters may be derived that reflect tumour perfusion, blood volume, and microcirculatory changes with treatment. This review outlines the mechanisms of action of available therapies and state-of-the-art imaging practice.

Anti-angiogenic activity of VXM01, an oral T-cell vaccine against VEGF receptor 2, in patients with advanced pancreatic cancer: A randomized, placebo-controlled, phase 1 trial

VEGFR-2 is expressed on tumor vasculature and a target for anti-angiogenic intervention. VXM01 is a first in kind orally applied tumor vaccine based on live, attenuated Salmonella bacteria carrying an expression plasmid, encoding VEGFR-2. We here studied the safety, tolerability, T effector (Teff), T regulatory (Treg) and humoral responses to VEGFR2 and anti-angiogenic effects in advanced pancreatic cancer patients in a randomized, dose escalation phase I clinical trial. Results of the first 3 mo observation period are reported. Locally advanced or metastatic, pancreatic cancer patients were enrolled. In five escalating dose groups, 30 patients received VXM01 and 15 placebo on days 1, 3, 5, and 7. Treatment was well tolerated at all dose levels. No dose-limiting toxicities were observed. Salmonella excretion and salmonella-specific humoral immune responses occurred in the two highest dose groups. VEGFR2 specific Teff, but not Treg responses were overall increased in vaccinated patients. We furthermore observed a significant reduction of tumor perfusion after 38 d in vaccinated patients together with increased levels of serum biomarkers indicative of anti-angiogenic activity, VEGF-A, and collagen IV. Vaccine specific Teff responses significantly correlated with reductions of tumor perfusion and high levels of preexisting VEGFR2-specific Teff while those showing no antiangiogenic activity had low levels of preexisting VEGFR2 specific Teff, showed a transient early increase of VEGFR2-specific Treg and reduced levels of VEGFR2-specific Teff at later time points - pointing to the possibility that early anti-angiogenic activity might be based at least in part on specific reactivation of preexisting memory T cells.

Development of a dynamic quality assurance testing protocol for multisite clinical trial DCE-CT accreditation

PURPOSE

Credentialing can have an impact on whether or not a clinical trial produces useful quality data that is comparable between various institutions and scanners. With the recent increase of dynamic contrast enhanced-computed tomography (DCE-CT) usage as a companion biomarker in clinical trials, effective quality assurance, and control methods are required to ensure there is minimal deviation in the results between different scanners and protocols at various institutions. This paper attempts to address this problem by utilizing a dynamic flow imaging phantom to develop and evaluate a DCE-CT quality assurance (QA) protocol.

METHODS

A previously designed flow phantom, capable of producing predictable and reproducible time concentration curves from contrast injection was fully validated and then utilized to design a DCE-CT QA protocol. The QA protocol involved a set of quantitative metrics including injected and total mass error, as well as goodness of fit comparison to the known truth concentration curves. An additional region of interest (ROI) sensitivity analysis was also developed to provide additional details on intrascanner variability and determine appropriate ROI sizes for quantitative analysis. Both the QA protocol and ROI sensitivity analysis were utilized to test variations in DCE-CT results using different imaging parameters (tube voltage and current) as well as alternate reconstruction methods and imaging techniques. The developed QA protocol and ROI sensitivity analysis was then applied at three institutions that were part of clinical trial involving DCE-CT and results were compared.

RESULTS

The inherent specificity of robustness of the phantom was determined through calculation of the total intraday variability and determined to be less than 2.2±1.1% (total calculated output contrast mass error) with a goodness of fit (R2) of greater than 0.99±0.0035 (n=10). The DCE-CT QA protocol was capable of detecting significant deviations from the expected phantom result when scanning at low mAs and low kVp in terms of quantitative metrics (Injected Mass Error 15.4%), goodness of fit (R2) of 0.91, and ROI sensitivity (increase in minimum input function ROI radius by 146±86%). These tests also confirmed that the ASIR reconstruction process was beneficial in reducing noise without substantially increasing partial volume effects and that vendor specific modes (e.g., axial shuttle) did not significantly affect the phantom results. The phantom and QA protocol were finally able to quickly (<90 min) and successfully validate the DCE-CT imaging protocol utilized at the three separate institutions of a multicenter clinical trial; thereby enhancing the confidence in the patient data collected.

CONCLUSIONS

A DCE QA protocol was developed that, in combination with a dynamic multimodality flow phantom, allows the intrascanner variability to be separated from other sources of variability such as the impact of injection protocol and ROI selection. This provides a valuable resource that can be utilized at various clinical trial institutions to test conformance with imaging protocols and accuracy requirements as well as ensure that the scanners are performing as expected for dynamic scans.

Functional imaging biomarkers for assessing response to treatment in liver and lung metastases

Management of patients with metastatic cancer and development of new treatments rely on imaging to provide non-invasive biomarkers of tumour response and progression. The widely used size-based criteria have increasingly become inadequate where early measures of response are required to avoid toxicity of ineffective treatments, as biological, physiologic, and molecular modifications in tumours occur before changes in gross tumour size. A multiparametric approach with the current range of imaging techniques allows functional aspects of tumours to be simultaneously interrogated. Appropriate use of these imaging techniques and their timing in relation to the treatment schedule, particularly in the context of clinical trials, is fundamental. There is a lack of consensus regarding which imaging parameters are most informative for a particular disease site and the best time to image so that, despite an increasing body of literature, open questions on these aspects remain. In addition, standardization of these new parameters is required. This review summarizes the published literature over the last decade on functional and molecular imaging techniques in assessing treatment response in liver and lung metastases.

Perfusion CT vascular parameters do not correlate with immunohistochemically derived microvessel density count in colorectal tumors

PURPOSE

To determine whether perfusion computed tomography (CT)-derived vascular parameters-namely, blood flow, mean transit time (MTT), volume transfer constant (K(trans)), permeability-surface area product (PS), extracellular extravascular space volume, and vascular volume-correlate with the immunohistologic markers of angiogenesis in colorectal tumors.

MATERIALS AND METHODS

This prospective study was approved by the Regional Ethics and Research and Development Committees. The perfusion CT protocol was incorporated in the staging CT after informed consent in 29 patients (14 men, 15 women; mean age, 70 years; age range, 55-94 years). The perfusion parameters were calculated over two regions of interest (ROIs), at the invasive and luminal site defined by two radiologists independently. Accurate representative data were captured manually by correcting for motion artifacts and were analyzed by using Matlab software. The vascular heterogeneity between ROIs was assessed by using the Wilcoxon signed rank test. Perfusion CT parameters were correlated with the microvessel density (MVD) count at both corresponding sites obtained by means of immunohistochemical staining of the selected histologic slide with factor VIII and CD105 antigens by using Spearmen rank coefficient.

RESULTS

There was no statistically significant difference found between perfusion CT vascular parameters at the two ROIs by either of the radiologists. The Pearson coefficient for blood flow, MTT, K(trans), and PS at the two ROIs demonstrated good to moderate interobserver variability (for the two ROIs, 0.46 and 0.44; 0.67 and 0.64; 0.41 and 0.72; and 0.86 and 0.56, respectively). None of these parameters correlated with MVD count at the invasive or the luminal site for either of the two antigens.

CONCLUSION

Perfusion CT measurements may measure vascularity of colorectal tumors, however, correlation with MVD, which is a morphologic measure, appears inappropriate. © RSNA, 2013.

A Phase 1 dose-finding and pharmacodynamic study of rapamycin in combination with bevacizumab in patients with unresectable hepatocellular carcinoma

BACKGROUND & AIMS

Preclinical studies have demonstrated the additive effect of rapamycin with bevacizumab for hepatocellular carcinoma treatment. We conducted a Phase 1 study to evaluate the safety and pharmacokinetics of the combination in patients with hepatocellular carcinoma.

METHODS

Adult participants with advanced hepatocellular carcinoma received intravenous bevacizumab (5mg/kg every 14 days) and oral rapamycin (1-6 mg/day; 3+3 dose escalation design). Computed tomography assessed tumour response and treatment safety. Pharmacokinetics assessment established rapamycin blood concentrations pre- and post-dose. Dynamic contrast-enhanced computed tomography analysed the tumour region for blood flow, permeability surface area product, fractional intravascular blood volume and extracellular-extravascular volume.

RESULTS

Twenty-four participants were treated. There were two dose limiting toxicities with rapamycin 5mg: grade 3 thrombocytopenia and grade 3 mucositis. The maximally tolerated dose of rapamycin was 4 mg. Adverse events (grade 1-2) included hyperglycaemia (83%), thrombocytopenia (75%), fatigue (46%), mucositis (46%), anorexia (42%), diarrhoea (33%) and proteinuria (12.5%). Of 20 evaluable participants, one reached complete response that lasted 4.5 months, two reached partial response, 14 reached stable disease and three had progressive disease. Median overall survival was 9.4 months; progression-free survival was 5.5 months. Dose level and steady state area under the concentration time curve for hour zero to infinity of rapamycin correlated inversely with blood flow rate and change in permeability-surface area. After 22 days of treatment, there were significant reductions from baseline in blood flow rate, permeability-surface area and fractional intracellular blood volume.

CONCLUSIONS

The recommended Phase 2 dose of rapamycin is 4 mg in combination with bevacizumab. Evidence of anti-vascular activity was observed together with promising clinical activity.

Effectiveness of a breath-hold monitoring system in improving the reproducibility of different breath-hold positions in multiphasic CT imaging

This study tests whether the utilization of an electronic breath-hold monitoring device improves breath-hold reproducibility during computed tomographic (CT) scanning. Two cohorts of 40 patients underwent dual-phase abdominal CT scans, either with a breath-hold monitoring device or with the standard breath-holding technique. Two blinded readers measured the differences in diaphragmatic position between phases. There was no statistical difference in diaphragmatic position (P=.14) between the monitored (8.5±11.5 mm) and control (5.6±5.2 mm) cohorts. Ten percent of patients from the monitored cohort had greater than 20 mm of deviation, versus 0%-2.5% for the control cohort. Reproduction of breath-holding position remains challenging, even with a monitoring system.

Operable non-small cell lung cancer: correlation of volumetric helical dynamic contrast-enhanced CT parameters with immunohistochemical markers of tumor hypoxia

PURPOSE

To assess the relationship between helical dynamic contrast material-enhanced (DCE) computed tomographic (CT) parameters and immunohistochemical markers of hypoxia in patients with operable non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

After institutional review board approval was obtained, 20 prospective patients who were suspected of having NSCLC underwent whole-tumor DCE CT with kinetic modeling (Patlak analysis) 24 hours before scheduled surgery. Flow-extraction product (in milliliters per 100 milliliters per minute) and blood volume (in milliliters per 100 milliliters) were derived. After surgery, matched whole-tumor sections were stained for exogenous and endogenous markers of hypoxia (pimonidazole infused intravenously 24 hours before surgery, immediately after DCE CT; glucose transporter protein). Correlation between DCE CT parameters and immunohistochemical markers was assessed by using the Spearman rank correlation. DCE CT parameters and immunohistochemical markers were also compared according to pathologic subtype, grade, stage, and nodal status by using the Mann-Whitney test. P values less than .05 indicated a statistically significant difference.

RESULT

Fourteen patients with confirmed primary NSCLC underwent resection. There were negative correlations between blood volume and pimonidazole staining (r = -0.48, P = .004), and between flow-extraction product and glucose transporter protein expression (r = -0.50, P = .002). Flow-extraction product was significantly higher in adenocarcinomas than in squamous cell tumors (17.73 vs 11.46; P = .043). Glucose transporter protein expression was significantly lower for adenocarcinomas than for squamous tumors (14.07 vs 33.03; P < .001) and in node negative than in node positive tumors (15.63 vs 23.85; P = .005).

CONCLUSION

Blood volume and flow-extraction product derived at DCE CT correlated negatively with pimonidazole and glucose transporter protein expression, indicating the potential of these CT parameters as imaging biomarkers of hypoxia.

Comparison of free breathing versus breath-hold in perfusion imaging using dynamic volume CT

Objectives

To compare two scanning protocols (free breathing versus breath-hold) for perfusion imaging using dynamic volume computed tomography (CT) and to evaluate their effects on image registration.

Material and methods

Forty patients underwent dynamic volume CT for pancreatic perfusion analysis and were randomly assigned to either a shallow-breathing (I) or breath-hold (II) group. Both dynamic CT protocols consisted of 17 low-dose volumetric scans. Rigid image registration was performed by using the volume with highest aortic attenuation as reference. All other volumes were visually matched with the pancreatic lesion serving as the volumetric region of interest. The overall demand for post-processing per patient was calculated as the median of three-dimensional vector lengths of all volumes in relation to the relative patient origin. The number of volumes not requiring registration was recorded per group.

Results

Registration mismatch for groups I and II was 2.61 mm (SD, 1.57) and 4.95 mm (SD, 2.71), respectively (P < 0.005). Twenty-eight volumes in group I (8.2%) and 47 volumes in group II (14.1%) did not require manual registration (P = 0.014).

Conclusion

Shallow breathing during dynamic volume CT scanning reduces the overall demand for motion correction and thus may be beneficial in perfusion imaging of the pancreas

Main Messages

• Shallow breathing during perfusion CT scanning reduces the overall demand for motion correction.

• Shallow breathing may be beneficial in perfusion imaging of the pancreas.

• Image registration is crucial for CT perfusion imaging.

Computed tomography perfusion imaging for therapeutic assessment: has it come of age as a biomarker in oncology?

With the emergence of novel targeted therapies, imaging techniques that assess tumor vascular support have gained credence for response assessment alongside standard response criteria. Computed tomography (CT) perfusion techniques that quantify regional tumor blood flow, blood volume, flow-extraction product, and permeability-surface area product through standard kinetic models are attractive, but the level of evidence for CT perfusion to be a truly mature biomarker remains insufficient. Studies to date have not been powered to assess this. Future studies that include good quality prospective validation correlating perfusion CT to outcome end points in the trial setting are needed to take CT perfusion forward as a biomarker in oncology.

CTA combined with CT perfusion for assessing the efficacy of anti-angiogenic therapy in rabbit VX2 tumors

RATIONALE AND OBJECTIVES

The aim of this study was to validate the feasibility of assessing the efficacy of antiangiogenic therapy on VX2 tumors using three-dimensional computed tomographic (CT) angiography (CTA) combined with CT perfusion.

MATERIALS AND METHODS

Forty rabbits with VX2 tumors were randomly assigned to four groups according to different doses of antiangiogenic drug, which were administered intraperitoneally daily for 14 days. In each group, 10 animals were scanned using three-dimensional CTA and CT perfusion on days 1 and 2 after the latest administration of the drug. Tumor masses were sectioned, stained by immunohistochemistry, and processed for correlation between CT imaging and histology.

RESULTS

The numbers of new tumor vessels from CTA were significantly different among the four groups (P < .001). As the dose of the drug increased, blood flow and blood volume on CT perfusion increased linearly, but the mean transit time and permeability surface-area product decreased linearly (P < .001). Immunohistochemical analyses showed that microvascular density decreased, while both luminal vascular number and mature vessel number increased linearly as the drug dose increased (P < .001). CT manifestations were correlated well with histologic findings (P < .05).

CONCLUSIONS

It is feasible to assess the efficacy of antiangiogenic therapy on VX2 tumors using three-dimensional CTA combined with CT perfusion. Three-dimensional CTA can display the morphologic changes of tumor vessels, while CT perfusion can predict the functional changes of tumor vessels after antiangiogenic therapy.

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.

Neuroendocrine tumor liver metastases: use of dynamic contrast-enhanced MR imaging to monitor and predict radiolabeled octreotide therapy response

PURPOSE

To evaluate dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging for monitoring and assessing treatment response in patients with neuroendocrine liver metastases treated using yttrium 90 ((90)Y)-labeled octreotide ((90)Y-DOTATOC).

MATERIALS AND METHODS

The study was approved by the local research and ethics committee and patient informed consent was obtained. Twenty patients with liver metastases from neuroendocrine tumors underwent T1-weighted DCE MR imaging of the liver before and at 2 months after intravenous (90)Y-DOTATOC treatment. Regions of interest were drawn around target lesions, as well as along liver outlines for each patient. A dual-input single-compartment model was used to compute parameters including fractional distribution volume and the arterial flow fraction. Pre- and posttreatment values were compared using Wilcoxon signed rank test. Treatment response was defined as showing a greater than 50% reduction in the nadir chromogranin A level within the 1st year after treatment. Pretreatment values of responders and nonresponders were compared using the Mann-Whitney test. A two-tailed P value of .008 or less, which accounts for multiple testing, was considered to indicate a significant difference.

RESULTS

In responders, tumor and whole liver distribution volume significantly increased after treatment (median tumor distribution volume, 0.182 vs 0.244; median whole liver distribution volume, 0.175 vs 0.207; P = .008). The pretreatment whole liver distribution volume was significantly lower in responders (median, 0.175 vs 0.248; P = .003), while pretreatment tumor arterial flow fraction was significantly higher in responders (median, 1.000 vs 0.7 ± 1, P = .006).

CONCLUSION

DCE MR imaging may be used to monitor the effects of peptide receptor radiolabeled targeted therapy in patients with neuroendocrine tumors liver metastases; a lower pretreatment distribution volume and high arterial flow fraction was associated with a better response to treatment.

Imaging evaluation of therapeutic response in patients with pancreatic cancer: recent advances

Chemoradiotherapy is the primary choice of non-surgical treatment of advanced pancreatic cancer, and diagnostic imaging plays an important role in objectively assessing early therapeutic response. This article systematically reviews the criteria for evaluation of therapeutic response in solid tumors and their application in pancreatic cancer, highlighting some key contents in imaging evaluation of therapeutic response in patients with pancreatic cancer.

Hepatic perfusion imaging: concepts and application

Hepatic perfusion imaging with magnetic resonance (MR) imaging is an emerging technique for quantitative assessment of diffuse hepatic disease and hepatic lesion blood flow. The principal method that has been used is based on T1 dynamic contrast-enhanced MR imaging. Perfusion imaging shows promise in the assessment of tumor therapy response, staging of liver fibrosis, and evaluation of hepatocellular carcinoma. The future standardization of imaging protocols and MR imaging pulse sequences will allow for broader clinical applications.

Estimation of intra-operator variability in perfusion parameter measurements using DCE-US

AIM: To investigate intra-operator variability of semi-quantitative perfusion parameters using dynamic contrast-enhanced ultrasonography (DCE-US), following bolus injections of SonoVue^®.

METHODS: The in vitro experiments were conducted using three in-house sets up based on pumping a fluid through a phantom placed in a water tank. In the in vivo experiments, B16F10 melanoma cells were xenografted to five nude mice. Both in vitro and in vivo, images were acquired following bolus injections of the ultrasound contrast agent SonoVue^® (Bracco, Milan, Italy) and using a Toshiba Aplio^® ultrasound scanner connected to a 2.9-5.8 MHz linear transducer (PZT, PLT 604AT probe) (Toshiba, Japan) allowing harmonic imaging (“Vascular Recognition Imaging”) involving linear raw data. A mathematical model based on the dye-dilution theory was developed by the Gustave Roussy Institute, Villejuif, France and used to evaluate seven perfusion parameters from time-intensity curves. Intra-operator variability analyses were based on determining perfusion parameter coefficients of variation (CV).

RESULTS: In vitro, different volumes of SonoVue^® were tested with the three phantoms: intra-operator variability was found to range from 2.33% to 23.72%. In vivo, experiments were performed on tumor tissues and perfusion parameters exhibited values ranging from 1.48% to 29.97%. In addition, the area under the curve (AUC) and the area under the wash-out (AUWO) were two of the parameters of great interest since throughout in vitro and in vivo experiments their variability was lower than 15.79%.

CONCLUSION: AUC and AUWO appear to be the most reliable parameters for assessing tumor perfusion using DCE-US as they exhibited the lowest CV values.

Protocol modifications for CT perfusion (CTp) examinations of abdomen-pelvic tumors: impact on radiation dose and data processing time

PURPOSE

To evaluate the effect of CT perfusion (CTp) protocol modifications on quantitative perfusion parameters, radiation dose and data processing time.

MATERIALS & METHODS

CTp datasets of 30 patients (21M:9F) with rectal (n = 24) or retroperitoneal (n = 6) tumours were studied. Standard CTp protocol included 50 sec cine-phase (0.5 sec/rotation) and delayed-phase after 70 ml contrast bolus at 5-7 ml/sec. CTp-data was sub-sampled to generate modified datasets (n = 105) with cine-phase(n = 15) alone, varying cine-phase duration (20-40 sec, n = 45) and varying temporal sampling-interval (1-3 sec, n = 45). The estimated CTp parameters (BF,BV,MTT&PS) and radiation dose of standard CTp served as reference for comparison.

RESULTS

CTp with 50 sec cine-phase showed moderate to high correlation with standard CTp for BF&MTT (r = 0.96&0.85) and low correlation for BV (0.75, p = 0.04). Limiting cine-phase duration to 30 sec demonstrated comparable results for BF&MTT, while considerable variation in CTp values existed at 20 sec. There was moderate-to-high correlation of CTp parameters with sampling interval of 1&2 sec (r = 0.83-0.97, p > 0.05), while at 3 sec only BF showed high correlation (r = 0.96, p = 0.05). Increasing sampling interval (47-60%) and reducing cine-phase duration substantially reduced dose(30.8-65%) which paralleled reduced data processing time (3-10 min).

CONCLUSION

Limiting CTp cine-phase to 30 sec results in comparable BF&MTT values and increasing cine-phase sampling interval to 2 sec provides good correlation for all CTp parameters with substantial dose reduction and improved computational efficiency.

Tracer kinetic modelling of tumour angiogenesis based on dynamic contrast-enhanced CT and MRI measurements

PURPOSE

Technical developments in both magnetic resonance imaging (MRI) and computed tomography (CT) have helped to reduce scan times and expedited the development of dynamic contrast-enhanced (DCE) imaging techniques. Since the temporal change of the image signal following the administration of a diffusible, extracellular contrast agent (CA) is related to the local blood supply and the extravasation of the CA into the interstitial space, DCE imaging can be used to assess tissue microvasculature and microcirculation. It is the aim of this review to summarize the biophysical and tracer kinetic principles underlying this emerging imaging technique offering great potential for non-invasive characterization of tumour angiogenesis.

METHODS

In the first part, the relevant contrast mechanisms are presented that form the basis to relate signal variations measured by serial CT and MRI to local tissue concentrations of the administered CA. In the second part, the concepts most widely used for tracer kinetic modelling of concentration-time courses derived from measured DCE image data sets are described in a consistent and unified manner to highlight their particular structure and assumptions as well as the relationships among them. Finally, the concepts presented are exemplified by the analysis of representative DCE data as well as discussed with respect to present and future applications in cancer diagnosis and therapy.

RESULTS

Depending on the specific protocol used for the acquisition of DCE image data and the particular model applied for tracer kinetic analysis of the derived concentration-time courses, different aspects of tumour angiogenesis can be quantified in terms of well-defined physiological tissue parameters.

CONCLUSIONS

DCE imaging offers promising prospects for improved tumour diagnosis, individualization of cancer treatment as well as the evaluation of novel therapeutic concepts in preclinical and early-stage clinical trials.

Perfusion characterization of liver metastases from endocrine tumors: Computed tomography perfusion

AIM: To assess prospectively parameters of computed tomography perfusion (CT p) for evaluation of vascularity of liver metastases from neuroendocrine tumors.

METHODS: This study was approved by the hospital’s institutional review board. All 18 patients provided informed consent. There were 30 liver metastases from neuroendocrine tumors. Patients were divided into three groups depending on the appearance of the liver metastases at the arterial phase of morphological CT (hyperdense, hypodense and necrotic). Sequential acquisition of the liver was performed before and for 2 min after intravenous injection of 0.5 mg/kg contrast medium, at 4 mL/s. Data were analyzed using deconvolution analysis to calculate blood flow (BF), blood volume (BV), mean transit time (MTT), hepatic arterial perfusion index (HAPI) and a bi-compartmental analysis was performed to obtain vascular permeability-surface area product (PS). Post-treatment analysis was performed by a radiologist and regions of interest were plotted on the metastases, normal liver, aorta and portal vein.

RESULTS: At the arterial phase of the morphological CT scan, the aspects of liver metastases were hyperdense (n = 21), hypodense (n = 7), and necrotic (n = 2). In cases of necrotic metastases, none of the CT p parameters were changed. Compared to normal liver, a significant difference in all CT p parameters was found in cases of hyperdense metastases, and only for HAPI and MTT in cases of hypodense metastases. No significant difference was found for MTT and HAPI between hypo- and hyperdense metastases. A significant decrease of PS, BV and BF was demonstrated in cases of patients with hypodense lesions PS (23 ± 11.6 mL/100 g per minute) compared to patients with hyperdense lesions; PS (13.5 ± 10.4 mL/100 g per minute), BF (93.7 ± 75.4 vs 196.0 ± 115.6 mL/100 g per minute) and BV (9.7 ± 5.9 vs 24.5 ± 10.9 mL/100 g).

CONCLUSION: CT p provides additional information compared to the morphological appearance of liver metastases.

Molecular imaging with dynamic contrast-enhanced computed tomography

Dynamic contrast-enhanced computed tomography (DCE-CT) is a quantitative technique that employs rapid sequences of CT images after bolus administration of intravenous contrast material to measure a range of physiological processes related to the microvasculature of tissues. By combining knowledge of the molecular processes underlying changes in vascular physiology with an understanding of the relationship between vascular physiology and CT contrast enhancement, DCE-CT can be redefined as a molecular imaging technique. Some DCE-CT derived parameters reflect tissue hypoxia and can, therefore, provide information about the cellular microenvironment. DCE-CT can also depict physiological processes, such as vasodilatation, that represent the physiological consequences of molecular responses to tissue hypoxia. To date the main applications have been in stroke and oncology. Unlike some other molecular imaging approaches, DCE-CT benefits from wide availability and ease of application along with the use of contrast materials and software packages that have achieved full regulatory approval. Hence, DCE-CT represents a molecular imaging technique that is applicable in clinical practice today.

Radiation dose from volumetric helical perfusion CT of the thorax, abdomen or pelvis

PURPOSE

To evaluate the radiation doses delivered during volumetric helical perfusion CT of the thorax, abdomen or pelvis.

MATERIALS AND METHODS

The dose-length product (DLP) and CT dose index (CTDIvol) were recorded and effective dose (E) determined for patients undergoing CT (4D adaptive spiral) for tumour evaluation. Image noise and contrast to noise (CNR) at peak enhancement were also assessed for quality.

RESULTS

Forty two consecutive examinations were included: thorax (16), abdomen (10), pelvis (16). Z-axis coverage ranged from 11.4 to 15.7 cm. Mean DLP was 1288.8 mGy.cm (range: 648 to 2456 mGy.cm). Mean CTDIvol was 96.2 mGy (range: 32.3 to 169.4 mGy). Mean effective dose was 19.6 mSv (range: 12.3 mSv to 36.7 mSv). In comparison mean DLP and effective dose was 885.2 mGy.cm (range: 504 to 1633 mGy.cm) and 13.3 mSV (range: 7.8 to 24.5 mSv) respectively for the standard staging CT thorax, abdomen and pelvis. Mean tumour CNR at peak enhancement was 1.87.

CONCLUSION

The radiation dose imposed by perfusion CT was on average 1.5 times that of a CT thorax, abdomen and pelvis. The dose is not insubstantial, and must be balanced by the potential clinical utility of additional physiologic data. Further efforts towards dose reduction should be encouraged.

Perfusion CT and US of colorectal cancer liver metastases: a correlative study of two dynamic imaging modalities

The purpose of this study was to evaluate the correlation between dynamic-contrast-enhanced computed tomography (DCE-CT) and first-pass dynamic-contrast-enhanced ultrasound (DCE-US) of normal appearing liver parenchyma and of colorectal cancer liver metastases. Thirty patients with hepatic metastases from colorectal cancer underwent DCE-CT and DCE-US. To obtain DCE-US reproducibility measurements, double contrast-passages (2 × 2.4 mL SonoVue intravenous) were acquired. From several DCE-US-derived perfusion indices, the slope-value scored best with a reproducibility concordance correlation coefficient ranging from 0.75-0.93 and overall highest correlation to DCE-CT-derived variables (r = 0.52 to 0.73). The DCE-US-based tumor-to-liver perfusion gradient also showed a low test-retest variability and moderately correlated to DCE-CT (concordance correlation coefficient 0.87-0.92; r = 0.57 to 0.59). To conclude, DCE-US-based slope-value and tumor-to-liver perfusion gradient correlate best with DCE-CT perfusion values. However, both techniques cannot be used interchangeably. DCE-US should be restricted for studies in which a considerable change in perfusion is expected and for patients with a relatively high tumor blood flow at baseline.

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).

Targeted therapies in renal cell cancer: recent developments in imaging

Targeted therapy has significantly improved the perspectives of patients with metastatic renal cell cancer (mRCC). Frequently, these new molecules cause disease stabilization rather than substantial tumor regression. As treatment options expand with the growing number of targeted agents, there is an increasing need for surrogate markers to early assess tumor response. Here, we review the currently available imaging techniques and response evaluation criteria for the assessment of tumor response in mRCC patients. For computed tomography (CT), different criteria are discussed including the Response Evaluation Criteria in Solid Tumors (RECIST), the Choi criteria, the modified Choi criteria, and the size and attenuation CT (SACT) criteria. Functional imaging modalities are discussed, such as dynamic contrast-enhanced CT (DCE-CT), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), dynamic contrast-enhanced ultrasonography (DCE-US), and positron emission tomography (PET).

Dynamic contrast-enhanced CT in patients treated with sorafenib and erlotinib for non-small cell lung cancer: a new method of monitoring treatment?

OBJECTIVE

We investigated the feasibility of serial dynamic contrast-enhanced computed tomography (DCE-CT) in patients with advanced/metastatic non-small cell lung cancer (NSCLC) receiving anti-angiogenic (sorafenib) and anti-EGFR (erlotinib) treatment, and correlated tumour blood flow (BF) with treatment outcome.

METHODS

DCE-CTs were performed at baseline and 3 and 6 weeks after starting treatment. Tumour BF, calculated with the maximum slope method, and percentage change were measured in 23 patients (14 male; median age 59 years). Tumour BF was compared at baseline and weeks 3 and 6; the relation with RECIST/Crabb response and progression-free survival (PFS) was assessed.

RESULTS

Mean tumour perfusion decreased from 39.2 ml/100 g/min at baseline to 15.1 ml/100 g/min at week 3 (p < 0.001) and 9.4 ml/100 g/min at week 6 (p < 0.001). Tumour perfusion was lower in RECIST and Crabb responders versus non-responders at week 3 (4.2 versus 17.7 ml/100 g/min, p = 0.03) and week 6 (0 versus 13.4 ml/100 g/min, p = 0.04). Patients with a decrease larger than the median at week 6 tended to have a longer PFS (7.1 versus 5.7 months, p = 0.06).

CONCLUSION

Serial DCE-CTs are feasible in patients with NSCLC and demonstrated a significant decrease in tumour BF following sorafenib/erlotinib therapy. Early changes in tumour BF correlated with objective response and showed a trend towards longer PFS.

Perfusion magnetic resonance imaging of the liver

Perfusion magnetic resonance imaging (MRI) studies quantify the microcirculatory status of liver parenchyma and liver lesions, and can be used for the detection of liver metastases, assessing the effectiveness of anti-angiogenic therapy, evaluating tumor viability after anti-cancer therapy or ablation, and diagnosis of liver cirrhosis and its severity. In this review, we discuss the basic concepts of perfusion MRI using tracer kinetic modeling, the common kinetic models applied for analyses, the MR scanning techniques, methods of data processing, and evidence that supports its use from published clinical and research studies. Technical standardization and further studies will help to establish and validate perfusion MRI as a clinical imaging modality.

An Introduction to MR Perfusion Imaging of the Liver

This article introduces the basic principles of magnetic resonance (MR) perfusion imaging of liver and summarized the currently available literature. Perfusion magnetic resonance imaging (MRI) is a functional imaging technique that quantifies the microcirculatory status of liver parenchyma and liver lesions such as flow, permeability, fractional intravascular volume and fractional interstitial volume. It potentially allows one to (i) detect liver metastases, (ii) assess effectiveness of anti-angiogenic therapy, (iii) assess viable tumour after therapy or ablation, and (iv) diagnose cirrhosis and assess its severity. Further work is required to establish and validate perfusion MRI as a clinical modality.

Novel VEGF signalling inhibitors: how helpful are biomarkers in their early development?

BACKGROUND

The development of vascular endothelial growth factor (VEGF) inhibitors of tumour angiogenesis can only be described as prolific. It is therefore interesting to speculate which will reach the clinic. Of course, the most effective agents will succeed, but how is effectiveness measured? When presented with a summary of competitive compounds, it can be difficult to discriminate between their potency on target, toxicity and response rates.

OBJECTIVES

A comparison was undertaken between new small-molecule tyrosine kinase inhibitors with vascular endothelial growth factor receptor as one of their targets. Factors considered included mode of action (targets), toxicity and usefulness of biomarker data.

METHODOLOGY

We carried out a systematic review using PubMed, MEDLINE and American Society of Clinical Oncologist (ASCO) databases for articles (including abstracts) presented in 2007 - 2009. Search terms included 'angiogenesis inhibitors', 'tyrosine kinase inhibitors', 'VEGF' and 'biomarkers'. Nine compounds were selected for detailed comparison.

RESULTS AND CONCLUSIONS

The toxicity profiles of the compounds were similar. Many exposure biomarkers have been identified that have informed the dose and scheduling of these compounds in clinical trials. Progress has also been made in identifying potential efficacy and predictive biomarkers for these new agents; however, these are yet to be validated.

CT perfusion in oncology: how to do it

Robust technique and accurate data analysis are required for reliable computed tomography perfusion (CTp) imaging. Multislice CT is required for high temporal resolution scanning; 16-slice (or 64-slice) scanners are preferred for adequate volume coverage. After tumour localization, the volume of CTp imaging has to be positioned to include the maximum visible area of the tumour and an adequate arterial vessel. Dynamic scans at high temporal resolution (at least 1-s gantry rotation time) are performed to visualize the first pass of contrast agent within the tumour; repeated scans with low temporal resolution can be planned for late enhancement assessment. A short bolus of conventional iodinated contrast agent, preferably with high iodine concentration, is power injected at a high flow rate (>4 ml/s) in the antecubital vein. The breath-hold technique is required for CTp imaging of the chest and upper abdomen to avoid respiratory motion; free breathing is adequate for CTp imaging of the head, neck and pelvis. Using dedicated software, a region of interest (ROI) has to be placed in an adequate artery (as arterial input) to obtain density–time curves; according to different kinetic models, colour maps of different CTp parameters are generated and generally overlaid on CT images. Additional ROIs can be positioned in the tumour, and in all other parts of the CTp volume, to obtain the values of the CTp parameters within the ROI.

RECIST revised: implications for the radiologist. A review article on the modified RECIST guideline

The purpose of this review article is to familiarize radiologists with the recently revised Response Evaluation Criteria in Solid Tumours (RECIST), used in many anticancer drug trials to assess response and progression rate. The most important modifications are: a reduction in the maximum number of target lesions from ten to five, with a maximum of two per organ, with a longest diameter of at least 10 mm; in lymph nodes (LNs) the short axis rather than the long axis should be measured, with normal LN measuring <10 mm, non-target LN ≥10 mm but <15 mm and target LN ≥15 mm; osteolytic lesions with a soft tissue component and cystic tumours may serve as target lesions; an additional requirement for progressive disease (PD) of target lesions is not only a ≥20% increase in the sum of the longest diameter (SLD) from the nadir but also a ≥5 mm absolute increase in the SLD (the other response categories of target lesion are unchanged); PD of non-target lesions can only be applied if the increase in non-target lesions is representative of change in overall tumour burden; detailed imaging guidelines. Alternative response criteria in patients with hepatocellular carcinoma and gastrointestinal stromal tumours are discussed.

Perfusion-CT monitoring of cryo-ablated renal cells tumors

Background

No single and thoroughly validated imaging method in monitoring of cryoablated renal cell carcinoma (RCC) is available. The purpose of our study was to determine the feasibility of dynamic contrast-enhanced perfusion CT (pCT) in evaluating the hemodynamic response of RCC.

Methods

15 patients (14 male, 1 female; age range, 43-81 years; mean age, 62 years) with cryoablated RCC via a transperitoneal approach, underwent to pCT 6-8 months after cryo-therapy. pCT was performed for 65 seconds after intravenous injection of contrast medium (80 mL, 370 mg iodine per millilitre, 4 mL/sec). Perfusion parameters (Time/Density curve; Blood flow, BF; Blood Volume, BV; Mean Transit Time, MTT; Permeability-Surface Area Product, PS) were sampled in the cryoablated tumor area and in ipsilateral renal cortex using deconvolution-based method. A tumor was considered to be not responsive to treatment by CT evidence of pathological contrast enhancement in the cryoablated area or renal mass persistence compared with the preoperative CT control. Written informed consent was obtained from all participants before the study.

Results

After cryotherapy, successfully ablated tumor (n = 13) showed decrease in BV (5,39 +/- 1,28 mL/100 g), BF (69,92 +/- 20,12 mL/100 g/min) and PS (16,66 +/- 5,67 mL/100 g/min) value and increased value of MTT (25,35 +/- 4,3 sec) compared with those of normal renal cortex (BV: 117,86 +/- 31,87 mL/100 g/min; BF: 392,39 +/- 117,32 mL/100 g/min; MTT: 18,02 +/- 3,6 sec; PS: 81,68 +/- 22,75 mL/100 g/min). In one patient, assessment of perfusion parameters was not feasible for breathing artifacts. One tumor showed poor response to treatment by the evidence of nodular contrast enhancement in the region encompassing the original lesion. Two typical enhancement patterns were obtained comparing the Time-Density curves of responsive and not responsive ablated tumors.

Conclusion

Perfusion CT seems to be a feasible and promising technique in monitoring the effects of cryoablation therapy.