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

MR imaging for acute pancreatitis: the current status of clinical applications

Acute pancreatitis is a common clinical acute abdomen. Imaging examinations play an important role in the management of acute pancreatitis. MR imaging is a noninvasive examination with high tissue contrast and a variety of acquisition sequences that can help determine the diagnosis, complications and severity of acute pancreatitis. The acute pancreatitis classification working group modified the Atlanta classification in 2012 to improve clinical evaluations and standardize the radiologic nomenclature for acute pancreatitis. In particular, the redefinition of necrotizing pancreatitis offers a new understanding of this disease. In clinical practice, there is still a lack of unifying standards between radiologists and physicians, such as for the imaging features of pseudocysts, walled-off necrosis, peripancreatic necrosis and especially for the MR imaging features of acute pancreatitis. In this article, we review the 2012 revised Atlanta classification of acute pancreatitis and recent advances in the clinical applications of MR imaging (MRI) in acute pancreatitis by showing how MRI can provide more optimized information for clinical diagnosis and treatment plan.

Multimodality imaging-guided local injection of eccentric magnetic microcapsules with electromagnetically controlled drug release

BACKGROUND

In the past decade, trackable smart drug delivery systems have played important roles in the treatment of many diseases such as cancer because the drug carriers can be visualized through their distinct physical properties. However, it is still difficult to achieve precise drug delivery because such systems usually rely on a single imaging system.

AIM

This study aimed to present a novel type of multimodality imaging-guided strategy to visualize the drug carriers of eccentric magnetic microcapsule (EMM) designed for potential treatment of hepatocellular carcinoma (HCC).

METHOD AND RESULTS

The EMMs were prepared by using a three-phase microfluidic device. The as-prepared EMMs embedded with Fe₃O₄ nanoparticles are magnetic, with high density and acoustic impedance, allowing for visualization by magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound (US) imaging during local injection. The release of drug from these EMMs can be further controlled by an external electromagnetic field (EMF). As a proof of concept, we demonstrated the process of multimodality imaging to guide local injection and the controlled release of doxorubicin (DOX) from the EMMs in a phantom. We showed that the release rate of DOX was directly correlated to the strength of the EMF. In addition, we cocultured green fluorescent protein (GFP)-transfected HeLa cancer cells with the DOX-loaded EMMs and documented their apoptosis by DOX following the release triggered by EMF.

CONCLUSION

The results suggest that these EMMs serve both as contrast agents that can be visualized by multimodality imaging techniques and as smart drug delivery systems, with great potential for precision medicine.

Eccentric magnetic microcapsules for MRI-guided local administration and pH-regulated drug release

In this work, we present a novel class of uniform eccentric magnetic microcapsules based on polydimethylsiloxane (PDMS) for magnetic resonance imaging (MRI)-guided local injection and pH-regulated drug release. The microcapsules contained magnetic nanoparticles in their PDMS shells, which allowed them to be easily tracked by MRI during administration. Besides, they showed pH-dependent drug release profiles due to dissolution of the embedded magnetic nanoparticles in acidic solutions. Moreover, by tuning the mass fraction of the magnetic nanoparticles, we could further regulate the release rate of drug molecules from them. As a demonstration, we investigated the delivery of cis-platinum using the microcapsules through an in vitro cell test, which confirmed the pH-controlled release of the drug in phantom tissues. Our study suggests that this type of eccentric magnetic microcapsules could be simultaneously employed as a potential imaging contrast and a smart drug delivery system, holding great potential for guided local therapy.

Reproducibility and variability of very low dose hepatic perfusion CT in metastatic liver disease

PURPOSE

We aimed to determine the intra- and interobserver agreement on the software analysis of very low dose hepatic perfusion CT (pCT).

METHODS

A total of 53 pCT examinations were obtained from 21 patients (16 men, 5 women; mean age, 60.4 years) with proven liver metastasis from various primary cancers. The pCT examinations were analyzed by two readers independently and perfusion parameters were noted for whole liver, whole metastasis, metastasis wall, and normal-looking liver (liver tissue without metastasis) in regions of interest (ROIs). Readers repeated the analysis after an interval of one month. Intra- and interobserver agreements were assessed with intraclass correlation coefficients (ICC) and Bland-Altman statistics.

RESULTS

The mean ICCs of all ROIs between readers were 0.91, 0.93, 0.86, 0.45, 0.53, and 0.66 for blood flow (BF), blood volume (BV), permeability, arterial liver perfusion (ALP), portal venous perfusion (PVP) and hepatic perfusion index (HPI), respectively. The mean ICCs of all ROIs between readings were 0.86, 0.91, 0.81, 0.53, 0.56, and 0.71 for BF, BV, permeability, ALP, PVP, and HPI, respectively. There was greater agreement on the parameters measured for the whole metastasis than on the parameters measured for the metastasis wall. The effective dose of all perfusion CT studies was 2.9 mSv.

CONCLUSION

There is greater intra- and interobserver agreement for BF and BV than for permeability, ALP, PVP, and HPI at very low dose hepatic pCT. Permeability, ALP, PVP, and HPI parameters cannot be used in clinical practice for hepatic pCT with an effective dose of 2.9 mSv.

CT perfusion as an imaging biomarker in monitoring response to neoadjuvant bevacizumab and radiation in soft-tissue sarcomas: comparison with tumor morphology, circulating and tumor biomarkers, and gene expression

OBJECTIVE

The purpose of this study was to evaluate the role of CT perfusion in monitoring response to neoadjuvant antiangiogenic and radiation therapy in resectable soft-tissue sarcomas and correlate the findings with tumor size, circulating and tumor biomarkers, and gene expression.

SUBJECTS AND METHODS

This phase II clinical trial included 20 patients (13 men and 7 women; mean age, 55 years) with soft-tissue sarcomas who were undergoing treatment with the antiangiogenic drug bevacizumab followed by bevacizumab, radiation, and surgical resection. The patients underwent CT perfusion and diagnostic contrast-enhanced CT at baseline, at 2 weeks after bevacizumab therapy, and after completion of bevacizumab and radiation therapy. Multiple CT perfusion parameters (blood flow, blood volume, mean transit time, and permeability) were correlated with tumor size, circulating and tumor biomarkers, and gene expression.

RESULTS

Two weeks after bevacizumab therapy, there was substantial fall in blood volume (31.9% reduction, p = 0.01) with more pronounced reduction in blood flow, blood volume, and permeability after treatment completion (53-64% reduction in blood flow, blood volume, and permeability; p = 0.001), whereas tumor size showed no significant change (p = 0.34). Tumors with higher baseline blood volume and lower baseline tumor size showed superior response to bevacizumab and radiation (p = 0.05). There was also an increase in median plasma vascular endothelial growth factor and placental-derived growth factor concentration after bevacizumab therapy paralleled by a decrease in tumor perfusion depicted by CT perfusion, although this was not statistically significant (p = 0.4). The baseline tumor microvessel density (MVD) correlated with blood flow (p = 0.04). At least 20 different genes were differentially expressed in tumors with higher and lower baseline perfusion.

CONCLUSION

CT perfusion is more sensitive than tumor size for monitoring early and late response to bevacizumab and radiation therapy. CT perfusion parameters correlate with MVD, and the gene expression levels of baseline tumors could potentially predict treatment response.

Pancreatic Perfusion CT in Early Stage of Severe Acute Pancreatitis

Early intensive care for severe acute pancreatitis is essential for improving SAP mortality rates. However, intensive therapies for SAP are often delayed because there is no ideal way to accurately evaluate severity in the early stages. Currently, perfusion CT has been shown useful to predict prognosis of SAP in the early stage. In this presented paper, we would like to review the clinical usefulness and limitations of perfusion CT for evaluation of local and systemic complications in early stage of SAP.

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.

Perfusion CT is superior to angiography in predicting pancreatic necrosis in patients with severe acute pancreatitis

BACKGROUND

We performed perfusion computed tomography (P-CT) and angiography of the pancreas in patients with severe acute pancreatitis (SAP) and compared the usefulness of these two methods in predicting the development of pancreatic necrosis.

METHODS

We compared P-CT and angiography results taken within 3 days after symptom onset in 21 SAP patients. We divided the pancreas into three areas, the head, body, and tail, and examined each area for perfusion defects (via P-CT) and arterial vasospasms (by angiography). Three weeks later, all patients underwent contrast-enhanced CT to determine whether pancreatic necrosis had developed.

RESULTS

Of the 21 SAP patients, 16 exhibited perfusion defects, while 17 proved positive for vasospasms in at least one area. Fourteen patients developed pancreatic necrosis. Of the 63 pancreatic areas from the 21 SAP patients, perfusion defects appeared in 25 areas (39.7%), 24 of which showed vasospasms (96.0%). Angiography showed 33 areas with vasospasms (52.4%), of which 24 showed perfusion defects (72.7%). Of the 25 areas with perfusion defects, 21 developed pancreatic necrosis (84.0%). Of the 33 areas with vasospasms, 21 developed necrosis (63.6%). Pancreatic necrosis developed only in the areas positive both for perfusion defects and for vasospasms. No areas without perfusion defect or vasospasms developed pancreatic necrosis. P-CT predicted the development of pancreatic necrosis with significantly higher accuracy than angiography.

CONCLUSION

While both P-CT and angiography are useful in predicting the development of pancreatic necrosis in patients with SAP, P-CT appears to be more accurate for this purpose.