Role of advanced imaging techniques in the evaluation of oncological therapies in patients with colorectal liver metastases

In patients with colorectal liver metastasis(CRLMs)unsuitable for surgery,oncological treatments,such as chemotherapy and targeted agents,can be performed.Cross-sectional imaging[computed tomography(CT),magnetic resonance imaging(MRI),18-fluorodexoyglucose positron emission tomography with CT/MRI]evaluates the response of CRLMs to therapy,using post-treatment lesion shrinkage as a qualitative imaging parameter.This point is critical because the risk of toxicity induced by oncological treatments is not always balanced by an effective response to them.Consequently,there is a pressing need to define biomarkers that can predict treatment responses and estimate the likelihood of drug resistance in individual patients.Advanced quantitative imaging(diffusionweighted imaging,perfusion imaging,molecular imaging)allows the in vivo evaluation of specific biological tissue features described as quantitative parameters.Furthermore,radiomics can represent large amounts of numerical and statistical information buried inside cross-sectional images as quantitative parameters.As a result,parametric analysis(PA)translates the numerical data contained in the voxels of each image into quantitative parameters representative of peculiar neoplastic features such as perfusion,structural heterogeneity,cellularity,oxygenation,and glucose consumption.PA could be a potentially useful imaging marker for predicting CRLMs treatment response.This review describes the role of PA applied to cross-sectional imaging in predicting the response to oncological therapies in patients with CRLMs.

Hepatocellular carcinoma treated with transarterial chemoembolization:Evaluation with parametric contrast-enhanced ultrasonography

AIM: To evaluate the response of hepatocellular carcinoma (HCC) to transarterial chemoembolization (TACE) using a simplified protocol of parametric contrast-enhanced ultrasound (pCEUS). METHODS: Eighteen patients with HCC (18 target tumors, diameter: 2.8-12 cm) were evaluated before, and 20 d after TACE. The distribution and morphology of TACE-induced necrosis in these tumors precluded accurate evaluation by visual assessment or by simple measurements. For pCEUS, a 4.8 mL bolus of SonoVue (Bracco, Milan, Italy) was intravenously administered and analysis of tumor perfusion during the initial phase of enhancement (0-30 s post injection) was performed with dedicated software (Qontrast, Bracco, Milan, Italy). Time-intensity curves were plotted and three parameters were calculated: peak intensity (PI, in percentage %), time to peak (TTP in seconds, s) and area under the curve during wash-in (AUC-WI, in arbitrary units, a.u). Magnetic resonance imaging was the standard imaging modality for post-treatment evaluation. Changes in tumor size were recorded and response was assessed according to response evaluation criteria in solid tumors criteria. RESULTS: A statistically significant decrease in PI and AUC-WI was observed in the treated tumors post TACE; PIpre: 21.5% ± 8.7% (mean ± SD), PIpost: 12.7% ± 6.7%, P < 0.001, AUC-WI pre: 17493 ± 9563 a.u, AUC-WI post: 9585 ± 5494 a.u, P < 0.001. A slight increase in TTP was noted post TACE, but this was not statistically significant; TTP pre: 13.1 ± 4.3 s, TTP post: 13.6 ± 4.2 s , P = 0.058). The changes in the aforementioned parameters were not accompanied by significant tumor shrinkage. CONCLUSION: pCEUS, even when limited to the study of the arterial phase of tumoral enhancement, can detect and quantify early perfusional changes in HCC post TACE.

Differentiation of atypical hepatic hemangioma from liver metastases: Diagnostic performance of a novel type of color contrast enhanced ultrasound

BACKGROUND In clinical practice,the diagnosis is sometimes difficult with contrast-enhanced ultrasound(CEUS)when the case has an atypical perfusion pattern.Color parametric imaging(CPI)is an analysis software for CEUS with better detection of temporal differences in CEUS imaging using arbitrary colors.It measures the differences in arrival time of the contrast agent in lesions so that the perfusion features of atypical hemangioma and colorectal cancer(CRC)liver metastasis can be distinguished.AIM To evaluate the role of a novel type of CPI of CEUS in the differential diagnosis of atypical hemangioma from liver metastases in patients with a history of CRC.METHODS From January 2016 to July 2018,42 patients including 20 cases of atypical hemangioma and 22 cases of liver metastases from CRC were enrolled.These patients had a mean age of 60.5±9.3 years(range:39-75 years).All patients received ultrasound,CEUS and CPI examinations.Resident and staff radiologists independently and retrospectively reviewed CEUS and CPI images.Two sets of criteria were assigned:(1)Routine CEUS alone;and(2)CEUS and CPI.The diagnostic sensitivity,specificity,accuracy and receiver operating characteristic(ROC)curve of resident and staff radiologists were analyzed.RESULTS The following CPI features were significantly different between liver hemangioma and liver metastases analyzed by staff and resident radiologists:Peripheral nodular enhancement(65%-70.0%vs 4.5%-13.6%,P<0.001,P=0.001),mosaic/chaotic enhancement(5%-10%vs 68.2%-63.6%,P<0.001,P<0.001)and feeding artery(20%vs 59.1%-54.5%,P=0.010,P=0.021).CPI imaging offered significant improvements in detection rates compared with routine CEUS in both resident and staff groups.By resident radiologists,the specificity and accuracy of CEUS+CPI were significantly increased compared with that of CEUS(77.3%vs 45.5%,P=0.030;78.6%vs 50.0%,P=0.006).In addition,the area under the curve(AUC)of CEUS+CPI was significantly higher than that of CEUS(0.803 vs 0.757,P=0.036).By staff radiologists,accuracy was improved in CEUS+CPI(81.0%vs 54.8%,P=0.010),whereas no significant differences in specificity and sensitivity were found(P=0.144,P=0.112).The AUC of CEUS+CPI was significantly higher than that of CEUS(0.890 vs 0.825,P=0.013)by staff radiologists.CONCLUSION Compared with routine CEUS,CPI could provide specific information on the hemodynamic features of liver lesions and help to differentiate atypical hemangioma from liver metastases in patients with CRC,even for senior radiologists.

Diagnosis of Dental Caries Using Terahertz Technology

Recently,the diagnoses of dental caries and other dental issues are in a queue as only X-ray-based techniques are available in most hospitals around the world.Terahertz(THz)parametric imaging(TPI)is the latest technology that can be applied for medical applications,especially dental caries.This technology is harmless and thus suitable for biological samples owing to the low energy of THz emission.In this paper,a developed TPI system is used to investigate the two-dimensional(2 D)and three-dimensional(3D)images of different samples from human teeth.After analyzing the measured images of human teeth,the results suggest that the THz parametric technology is capable of investigating the inner side structure of the teeth.This technique can be useful in detecting the defects in all types of human and animal teeth.The measurement and analytical calculations have been performed by using the TPI system and MATLAB,respectively,and both are in good agreement.The characteristics of THz waves and their interactions with the tooth samples are summarized.And the available THz-based technologies,such as TPI,and their potential applications of diagnoses are also presented.

Frequency up-conversion imaging with 60-dB gain using picosecond optical parametric amplifier

A weak infrared （IR） image amplifier with more than 60-dB optical gain and is developed from a picosecond （PS） 355-nm pumped gated optical parametric frequency up-conversion amplifier （OPA） in a/% BaB204 （BBO） crystal. The IR image at 1064 nm is amplified and up-converted into the visible region at 532 nm by parametric amplification and up-conversion. With the optimized optical gain, the lowest detectable energy of the image can be as low as 1.8 femto-Joule per pulse, which is three orders of magnitude lower than the detection limit of a charge-coupled device （CCD） camera. The transversal resolution of the OPA imaging is investigated, and the approaches for higher detection sensitivity and higher transversal resolution are proposed.

Recent advances in parametric neuroreceptor mapping with dynamic PET:basic concepts and graphical analyses

Tracer kinetic modeling in dynamic positron emission tomography （PET） has been widely used to investigate the characteristic distribution patterns or dysfunctions of neuroreceptors in brain diseases. Its practical goal has progressed from regional data quantification to parametric mapping that produces images of kinetic-model parameters by fully exploiting the spatiotemporal information in dynamic PET data. Graphical analysis （GA） is a major parametric mapping technique that is independent on any compartmental model configuration, robust to noise, and computationally efficient. In this paper, we provide an overview of recent advances in the parametric mapping of neuroreceptor binding based on GA methods. The associated basic concepts in tracer kinetic modeling are presented, including commonly-used compartment models and major parameters of interest. Technical details of GA approaches for reversible and irreversible radioligands are described, considering both plasma input and reference tissue input models. Their statistical properties are discussed in view of parametric imaging.