Perfusion computed tomography in colorectal cancer: Protocols, clinical applications and emerging trends

What scans we will read: imaging instrumentation trends in clinical oncology

Oncological diseases account for a significant portion of the burden on public healthcare systems with associated costs driven primarily by complex and long-lasting therapies. Through the visualization of patient-specific morphology and functional-molecular pathways, cancerous tissue can be detected and characterized non-invasively, so as to provide referring oncologists with essential information to support therapy management decisions. Following the onset of stand-alone anatomical and functional imaging, we witness a push towards integrating molecular image information through various methods, including anato-metabolic imaging (e.g., PET/CT), advanced MRI, optical or ultrasound imaging.This perspective paper highlights a number of key technological and methodological advances in imaging instrumentation related to anatomical, functional, molecular medicine and hybrid imaging, that is understood as the hardware-based combination of complementary anatomical and molecular imaging. These include novel detector technologies for ionizing radiation used in CT and nuclear medicine imaging, and novel system developments in MRI and optical as well as opto-acoustic imaging. We will also highlight new data processing methods for improved non-invasive tissue characterization. Following a general introduction to the role of imaging in oncology patient management we introduce imaging methods with well-defined clinical applications and potential for clinical translation. For each modality, we report first on the status quo and, then point to perceived technological and methodological advances in a subsequent status go section. Considering the breadth and dynamics of these developments, this perspective ends with a critical reflection on where the authors, with the majority of them being imaging experts with a background in physics and engineering, believe imaging methods will be in a few years from now.Overall, methodological and technological medical imaging advances are geared towards increased image contrast, the derivation of reproducible quantitative parameters, an increase in volume sensitivity and a reduction in overall examination time. To ensure full translation to the clinic, this progress in technologies and instrumentation is complemented by advances in relevant acquisition and image-processing protocols and improved data analysis. To this end, we should accept diagnostic images as "data", and - through the wider adoption of advanced analysis, including machine learning approaches and a "big data" concept - move to the next stage of non-invasive tumour phenotyping. The scans we will be reading in 10 years from now will likely be composed of highly diverse multi-dimensional data from multiple sources, which mandate the use of advanced and interactive visualization and analysis platforms powered by Artificial Intelligence (AI) for real-time data handling by cross-specialty clinical experts with a domain knowledge that will need to go beyond that of plain imaging.

Computed tomographic scan mapping of gastric wall perfusion and clinical implications

BACKGROUND

Several postoperative gastrointestinal complications are attributed to ischemia. We herein evaluate the gastric wall perfusion using computed tomography (CT) scan perfusion index on trial to address the etiology of ischemic complication after sleeve gastrectomy.

METHODS

A retrospective study of 205 patients undergoing CT scan of the abdomen to evaluate the pattern of gastric vascular perfusion was performed. The perfusion index of the gastric mucosa was measured at 5 gastric points using CT perfusion scanning.

RESULTS

Gastric perfusion at the angle of His (AOH) (53.51 ± 14.38) was statistically significantly lower (P < .001) than that at the other gastric points studied: fundus, greater curvature, lesser curvature, incisura angularis, and mid gastric points (76.16 ± 15.21, 73.27 ± 16.55, 76.12 ± 16.12, and 75.24 ± 14.9, respectively). Gastric perfusion was significantly lower at all the gastric points (and especially so at the AOH) among obese patients (33 cases) compared with nonobese patients (18 cases). Gastric perfusion at all the points studied showed a decrease as the body mass index increases. Hypertensive patients had a better gastric perfusion compared with nonhypertensive patients.

CONCLUSIONS

Gastric wall perfusion is statistically significantly decreased at the AOH and gastric fundus compared with perfusion at other gastric points. Gastric perfusion at all the gastric points studied decreased with the increase in body mass index. Gastric leakage in obese patients following sleeve gastrectomy could be attributed to a decrease in the blood supply at AOH.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Imaging assessment of tumor response: past, present and future

Anatomical response assessment criteria have been in use for decades, with the WHO guidelines being replaced by Response Evaluation Criteria in Solid Tumors (RECIST), updated in 2009 to RECIST 1.1. These methods rely on a change in size of a tumor as the main response criteria, but newer cytostatic agents tend to target tumor function at a molecular level before changing the size of a lesion. Recent modifications, such as the Choi criteria, have improved assessment by taking into account density of tumor, but all of these criteria fail to utilize functional imaging parameters, which are becoming increasingly available, including perfusion CT, perfusion MRI, diffusion-weighted imaging, magnetic resonance spectroscopy, dynamic contrast-enhanced ultrasound and combined PET/computed tomography. Developments in these modalities and standardization of imaging acquisition will help to optimize the next set of response criteria, with inclusion of multiparametric, functional modalities, evaluating tumors at the same molecular level at which they are being targeted by therapeutic agents.

Estimation of radiation exposure of 128-slice 4D-perfusion CT for the assessment of tumor vascularity

Objective

We aimed to estimate the effective dose of 4D-Perfusion-CT protocols of the lung, liver, and pelvis for the assessment of tumor vascularity.

Materials and Methods

An Alderson-Rando phantom equipped with thermoluminescent dosimeters was used to determine the effective dose values of 4D-Perfusion-CT. Phantom measurements were performed on a 128-slice single-source scanner in adaptive 4D-spiral-mode with bidirectional table movement and a total scan range of 69 mm over a time period of nearly 120 seconds (26 scans). Perfusion measurements were simulated for the lung, liver, and pelvis under the following conditions: lung (80 kV, 60 mAs), liver (80 kV/80 mAs and 80 kV/120 mAs), pelvis (100 kV/80 mAs and 100 kV/120 mAs).

Results

Depending on gender, the evaluated body region and scan protocol, an effective whole-body dose between 2.9-12.2 mSv, was determined. The radiation exposure administered to gender-specific organs like the female breast tissue (lung perfusion) or to the ovaries (pelvic perfusion) led to an increase in the female specific dose by 86% and 100% in perfusion scans of the lung and the pelvis, respectively.

Conclusion

Due to a significant radiation dose of 4D-perfusion-CT protocols, the responsible use of this new promising technique is mandatory. Gender- and organ-specific differences should be considered for indication and planning of tumor perfusion scans.

Use of computed tomography in the management of colorectal cancer

Computed tomography (CT) plays an important role in the management of colorectal cancer (CRC). The use of CT (colonography) as a screening tool for CRC has been validated and is expected to rise over time. The results of prior studies suggest that CT is suboptimal for assessment of local T stage and moderate for N stage disease. Recent advances in CT technology are expected to lead to some improvement in staging accuracy. At present, the main role of CT in pre-treatment imaging assessment lies in its use for the detection of distant metastases, especially in the liver. In a select group of patients, routine post-treatment surveillance with CT confers survival benefits. The role of CT for post-treatment assessment has been radically altered and improved with the advent of fusion positron emission tomography/CT. Perfusion CT shows promise as another functional imaging modality but further experience with this technique is necessary before it can be applied to routine clinical practice.

[Newer techniques in diagnostic imaging of colorectal carcinoma]

A wide spectrum of nowadays availible radiological and imaging methods in the diagnostic evaluation of patients with colorectal cancer enabled not only the improvement of primary colorectal malignancy detection, precise staging, regional involvement and metastatic spread assessment, but also the posttherapeutical estimation and follow-up. Having in mind that the exact diagnostic assessment of colorectal carcinoma by use of different imaging modalities still raises a lots of contradictories, in this report we have tried to present the possibilities of newer imaging techniques in the diagnostic evaluation of the patients with colorectal cancer.