Dual energy MDCT assessment of renal lesions: an overview

Spectral CT imaging versus conventional CT post-processing technique in differentiating malignant and benign renal tumors

OBJECTIVE

Quantitative comparison of the diagnostic value of spectral CT imaging and conventional CT post-processing technique in differentiating malignant and benign renal tumors.

METHODS

A total of 209 patients with renal tumors who had undergone CT enhancement were assigned to three groups-clear cell renal cell carcinoma (ccRCC, n = 106), non-ccRCC (n = 60), and benign renal tumor (n = 43) groups. Parametric CT enhancement of each tumor based on spectral CT and conventional CT was performed using in-house software, and the iodine concentration, water content, slope, and density values among the three groups were compared. The receiver operating characteristic (ROC) curve analysis was performed to determine the optimum diagnostic thresholds, the area under the ROC curve (AUC), sensitivity, specificity, and accuracy of the above parameters.

RESULTS

The iodine concentration, slope, and density values were higher in the ccRCCs group compared to the non-ccRCCs and benign renal tumor groups (p < 0.05). Moreover, the iodine concentration, slope, and density values were higher in benign renal tumors compared to non-ccRCCs (p < 0.05). According to the ROC curve analysis, iodine concentration presented the highest diagnostic efficacy in differentiating ccRCCs/non-ccRCCs from benign renal tumors. The pairwise comparisons of the ROC curves and the diagnostic efficacies revealed that ROI-based CT enhancement was worse than the spectral CT imaging analysis in terms of density (p < 0.05).

CONCLUSION

Iodine concentration presented the highest diagnostic efficacy in differentiating ccRCCs/non-ccRCCs from benign renal tumors.

ADVANCES IN KNOWLEDGE

1. The iodine concentration, slope, and density values were higher for the ccRCCs compared to non-ccRCCs and benign renal tumors.2. Iodine concentration presented the highest diagnostic efficacy in differentiating ccRCCs/non-ccRCCs from benign renal tumors.3. Spectral CT imaging analysis performed better than conventional CT in differentiating malignant and benign renal tumors.

Virtual monoenergetic dual-layer dual-energy CT images in colorectal cancer: CT diagnosis could be improved?

PURPOSE

To compare conventional CT images and virtual monoenergetic images (VMI) at dual-layer dual-energy CT (dlDECT) in patients with colorectal cancer (CRC) through quantitative analysis and to investigate the added value of VMI.

MATERIAL AND METHODS

Sixty-six consecutive patients with histologically documented CRC and available VMI reconstructions were retrospectively investigated. Subsequently, forty-two patients, without any colonic disease at colonoscopy, were selected as control group. Conventional CT images and VMI reconstructions at energy levels ranging from 40 (VMI₄₀) to 100 keV (VMI₁₀₀) in 10 keV increments, were obtained from the late arterial phase. First, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were obtained to select the best VMI reconstruction. Finally, the diagnostic accuracy of conventional CT and VMI₄₀ in late arterial phase was evaluated.

RESULTS

On quantitative analysis, SNR and CNR were higher for VMI₄₀ (19.5 ± 7.7 and 11.8 ± 6.2, respectively) with statistically significant differences compared to conventional CT (P < 0.05) and all the other VMI reconstructions (P < 0.05), except for VMI₅₀ (P > 0.05). The addition of VMI₄₀ to conventional CT images significantly improved the area under the curve (AUC) for the diagnosis of CRC, increasing it from 0.875 to 0.943 for reader 1 (P < 0.05) and from 0.916 to 0.954 for reader 2 (P < 0.05). The improvement was greater in the less experienced radiologist (0.068) compared to the more experienced one (0.037).

CONCLUSION

VMI₄₀ has showed the highest quantitative image parameters. Furthermore, the use of VMI₄₀ can lead to a significant improvement in the diagnostic performance for detecting CRC.

Use of dual energy CT urography in evaluation of urinary stone and complex cyst

BACKGROUND

Dual-energy computed tomography scans can provide significant benefits to the urinary system. The aim of this study is to determine the limitations and benefits of using dual energy CT urography in patients with urinary system stones and cysts.

METHODS

In the analysis of the images, the virtual noncontrasted images obtained from the combined nephrogenicexcretory phase and the true noncontrasted images were evaluated. The true noncontrast images were accepted as the gold standard for stone detection.

RESULTS

Eighty-three different stones were detected in 26 of the 115 patients included in the study. Sensibilities of virtual noncontrast images in detecting urinary system stones were 66.7% and 65.4% according to the first and second radiologists, respectively. In this study, 32 hyperdense cysts were detected. According to iodine map images, there was no enhancement in 26 of 32 cysts; only 5 cysts showed minimal contrast enhancement. One patient could not decide on contrast enhancement.

DISCUSSION

As a result, if CT urography is performed with dual energy, it can provide additional information in patients with urinary system disorder.

Quantitative dual-energy CT techniques in the abdomen

Advances in dual-energy CT (DECT) technology and spectral techniques are catalyzing the widespread implementation of this technology across multiple radiology subspecialties. The inclusion of energy- and material-specific datasets has ushered overall improvements in CT image contrast and noise as well as artifacts reduction, leading to considerable progress in radiologists' ability to detect and characterize pathologies in the abdomen. The scope of this article is to provide an overview of various quantitative clinical DECT applications in the abdomen and pelvis. Several of the reviewed applications have not reached mainstream clinical use and are considered investigational. Nonetheless awareness of such applications is critical to having a fully comprehensive knowledge base to DECT and fostering future clinical implementation.

Recent advances in imaging techniques of renal masses

Multiphasic multidetector computed tomography (CT) forms the mainstay for the characterization of renal masses whereas magnetic resonance imaging (MRI) acts as a problem-solving tool in some cases. However, a few of the renal masses remain indeterminate even after evaluation by conventional imaging methods. To overcome the deficiency in current imaging techniques, advanced imaging methods have been devised and are being tested. This review will cover the role of contrast-enhanced ultrasonography, shear wave elastography, dual-energy CT, perfusion CT, MR perfusion, diffusion-weighted MRI, blood oxygen level-dependent MRI, MR spectroscopy, positron emission tomography (PET)/prostate-specific membrane antigen-PET in the characterization of renal masses.

Dual-energy CT: minimal essentials for radiologists

Dual-energy CT, the object is scanned at two different energies, makes it possible to identify the characteristics of materials that cannot be evaluated on conventional single-energy CT images. This imaging method can be used to perform material decomposition based on differences in the material-attenuation coefficients at different energies. Dual-energy analyses can be classified as image data-based- and raw data-based analysis. The beam-hardening effect is lower with raw data-based analysis, resulting in more accurate dual-energy analysis. On virtual monochromatic images, the iodine contrast increases as the energy level decreases; this improves visualization of contrast-enhanced lesions. Also, the application of material decomposition, such as iodine- and edema images, increases the detectability of lesions due to diseases encountered in daily clinical practice. In this review, the minimal essentials of dual-energy CT scanning are presented and its usefulness in daily clinical practice is discussed.

Dual-energy CT arthrography: a feasibility study

OBJECTIVE

To evaluate the feasibility of producing 2-dimensional (2D) virtual noncontrast images and 3-dimensional (3D) bone models from dual-energy computed tomography (DECT) arthrograms and to determine whether this is best accomplished using 190 keV virtual monoenergetic images (VMI) or virtual unenhanced (VUE) images.

MATERIALS AND METHODS

VMI and VUE images were retrospectively reconstructed from patients with internal derangement of the shoulder or knee joint who underwent DECT arthrography between September 2017 and August 2019. A region of interest was placed in the area of brightest contrast, and the mean attenuation (in Hounsfield units [HUs]) was recorded. Two blinded musculoskeletal radiologists qualitatively graded the 2D images and 3D models using scores ranging from 0 to 3 (0 considered optimal).

RESULTS

Twenty-six patients (mean age ± SD, 57.5 ± 16.8 years; 6 women) were included in the study. The contrast attenuation on VUE images (overall mean ± SD, 10.5 ± 16.4 HU; knee, 19.3 ± 10.7 HU; shoulder, 5.0 ± 17.2 HU) was significantly lower (p < 0.001 for all comparisons) than on VMI (overall mean ± SD, 107.7 ± 43.8 HU; knee, 104.6 ± 31.1 HU; shoulder, 109.6 ± 51.0 HU). The proportion of cases with optimal scores (0 or 1) was significantly higher with VUE than with VMI for both 2D and 3D images (p < 0.001).

CONCLUSIONS

DECT arthrography can be used to produce 2D virtual noncontrast images and to generate 3D bone models. The VUE technique is superior to VMI in producing virtual noncontrast images.

Dual energy CT in clinical routine: how it works and how it adds value

Dual energy computed tomography (DECT), also known as spectral CT, refers to advanced CT technology that separately acquires high and low energy X-ray data to enable material characterization applications for substances that exhibit different energy-dependent x-ray absorption behavior. DECT supports a variety of post-processing applications that add value in routine clinical CT imaging, including material selective and virtual non-contrast images using two- and three-material decomposition algorithms, virtual monoenergetic imaging, and other material characterization techniques. Following a review of acquisition and post-processing techniques, we present a case-based approach to highlight the added value of DECT in common clinical scenarios. These scenarios include improved lesion detection, improved lesion characterization, improved ease of interpretation, improved prognostication, inherently more robust imaging protocols to account for unexpected pathology or suboptimal contrast opacification, length of stay reduction, reduced utilization by avoiding unnecessary follow-up examinations, and radiation dose reduction. A brief discussion of post-processing workflow approaches, challenges, and solutions is also included.

Diagnostic accuracy of dual-energy CT in gout: a systematic review and meta-analysis

OBJECTIVE

Dual-energy CT (DECT) is being widely used in suspected gout patients in recent years. Many clinicians tend to use DECT instead of aspiration biopsy in the diagnosis of gout, but its accuracy has shown controversial results. In this systematic review and meta-analysis, we sought to evaluate the accuracy of DECT in the diagnosis of gout.

MATERIALS AND METHODS

We performed a systematic review of the literature published in Medline, Embase, PubMed, and Cochrane databases. Studies included are all clinical trials of DECT in the diagnosis of gout. Quality assessment of bias and applicability was conducted using the Quality of Diagnostic Accuracy Studies-2 (QUADAS-2). We recorded sensitivity and specificity of algorithms and calculated positive likelihood ratio (PLR), negative likelihood ratio (NLR) and diagnostic odd ratio (DOR), and respective confidence intervals (CI). The summary receiver operating characteristic curve (sROC) was drawn to get the Cochran Q-index and the area under the curve (AUC).

RESULTS

Seven studies were included in this review and showed high homogeneity. The analysis results presented the pooled sensitivity was 88% (95% CI 84-90%) and specificity was 90% (95% CI 85-93%). Then, we figured out that the pooled PLR was 8.48 (95% CI 5.89-12.22) and NLR was 0.10 (95% CI 0.04-0.24) respectively. In addition, Cochran-Q was 0.90 and AUC was 0.9565 in sROC curve.

CONCLUSIONS

DECT showed relatively high sensitivity and specificity in the diagnosis of gout. Synthetically considering these DECT abnormalities could improve the diagnostic sensitivity. More rigorous and standardized studies are still needed to support these findings.

Assessing Chemotherapeutic Response in Pancreatic Ductal Adenocarcinoma: Histogram Analysis of Iodine Concentration and CT Number in Single-Source Dual-Energy CT

OBJECTIVE

The objective of this study was to evaluate the feasibility of histographic analysis of iodine concentration (IC) and CT number on single-source dual-energy CT (DECT) to assess response to first-line chemotherapy in patients with pancreatic ductal adenocarcinoma (PDAC) who received first-line chemotherapy but not radiation therapy.

SUBJECTS AND METHODS

This prospective study was approved by our institutional review board, and patients gave written informed consent. Sixty consecutive patients with PDAC undergoing first-line chemotherapy underwent DECT during the pancreatic parenchymatous phase (PPP) and the equilibrium phase (EP). The IC and CT number of PDAC were measured using PPP and EP iodine-based material decomposition and monochromatic images (65 keV), respectively. Histographic parameters for the IC and CT number of PDACs were obtained, and differences in mean IC (ΔIC) and CT number (ΔHU) between the PPP and the EP were calculated. These parameters were then compared between the response (partial response or stable disease) and nonresponse (progressive disease) groups.

RESULTS

Among the histographic parameters, the kurtosis of IC during the PPP (p = 0.018) and ΔIC (p = 0.0004) were identified as significant for differentiating between the two groups. IC diagnostic factor was calculated using the following coefficients of logistic regression analysis: 0.52 - (1.45 × kurtosis of IC during PPP) + (0.69 × ΔIC). The sensitivity, specificity, and area under the ROC curve for differentiating between the two groups were 97.7%, 70.6%, and 0.889, respectively.

CONCLUSION

The IC diagnostic factor is a potential biomarker for assessing chemotherapeutic response in patients with PDAC.

Dual-energy CT-based iodine quantification to differentiate abdominal malignant lymphoma from lymph node metastasis

PURPOSE

To investigate the value of dual-energy computed tomography (DECT)-derived iodine and fat quantification in differentiating malignant abdominal lymphoma from lymph node metastasis.

MATERIALS AND METHODS

In this retrospective study, 59 patients (39 men; mean age, 62.7 years) with histopathologically-confirmed diagnosis of either malignant lymphoma or lymph node metastasis were included. For each lesion, contrast-enhanced attenuation, as well as DECT-derived iodine density and fat fraction measurements were recorded. Mean attenuation and material density values were compared between malignant lymphomas and lymph node metastases. The receiver operating characteristic (ROC) curve analysis was adopted to estimate the optimal threshold for discriminating between both entities. A control group (n = 60) was analyzed for comparison of attenuation and material density values of normal abdominal lymph nodes.

RESULTS

Assessment of DECT-derived iodine density and fat fraction values revealed significant differences between lymph node metastases (1.7 ± 0.4 mg/ml and 15.5 ± 7.3%) and malignant lymphomas (2.5 ± 0.5 mg/ml and 26.7 ± 12.2%) as well as normal lymph nodes (2.4 ± 0.8 mg/ml and 24.1 ± 10.8%) (P ≤ 0.013). An iodine concentration of 2.0 mg/ml represented the optimal threshold to discriminate between lymphoma and lymph node metastasis (sensitivity, 87%; specificity, 89%). Moreover, a significant correlation was found between iodine concentration and fat fraction for both lymphomas and lymph node metastases (P = 0.001).

CONCLUSION

DECT enables characterization of abdominal masses as derived iodine and fat fraction values differ significantly between malignant abdominal lymphomas and lymph node metastases.

Use of Dual-Energy Computed Tomography for Evaluation of Genitourinary Diseases

Since its clinical inception a decade ago, dual-energy computed tomography has expanded the array of computed tomography imaging tools available to the practicing abdominal radiologist. Of note, diagnostic solutions for imaging-based evaluation of genitourinary diseases, foremost kidney calculi and renal tumors characterization, represent the apogee applications of dual-energy computed tomography in abdominal imaging. This article reviews clinical applications of dual-energy computed tomography for the assessment of genitourinary diseases.

Analysis of dual energy spectral CT and pathological grading of clear cell renal cell carcinoma (ccRCC)

OBJECTIVE

To discuss the dual energy spectral computer tomography (CT) imaging features of the pathological grading of clear cell renal cell carcinoma (ccRCC) and the correlation between spectral CT imaging features and pathology.

MATERIALS AND METHODS

We performed analyses of 62 patients with confirmed diagnosis of ccRCC. All patients underwent non-enhanced CT and dual-phase (cortex phase, CP and parenchyma phase, PP) contrast-enhanced CT with dual energy spectral mode. The subjects were pathologically divided into two groups: low-grade group (Fuhrman 1/2) and high-grade group (Fuhrman 3/4). The CT value of each lesion was measured on the monochromatic image at 70 keV. The normalized iodine concentrations (NIC) and the slope of the spectrum curve were calculated. The qualitative morphological parameters, including tumor shape, calcification, pseudocapsule, necrosis, and enhancement mode, were compared between the two groups. The quantitative data were compared using Student's t-test, and the enumeration data were analyzed using the chi-square test between low-grade and high-grade ccRCC.Receiver operating characteristic curve was used to determine the sensitivity and specificity of the quantitative parameters in two groups.

RESULTS

The CT value, NIC, and mean slope of the low-grade group were increased compared with the high-grade group during CP (P = 0.001, P = 0.043, and P<0.001, respectively). The CT did not differ significantly during PP (P = 0.134); however, the NIC and mean slope varied considerably in the low grade compared with the high-grade group (P = 0.048, P = 0.017, respectively). The CT threshold value, NIC, and slope had high sensitivity and specificity in differentiating low-grade ccRCC from high-grade ccRCC. The tumor shape, pseudocapsule, and necrosis differed significantly between the two groups (P<0.05).

CONCLUSIONS

Dual energy spectral CT with the quantitative analysis of iodine concentration and qualitative analysis of morphological characteristics increases the accuracy of diagnosing the pathological grade of ccRCC.

Systematic radiation dose optimization of abdominal dual-energy CT on a second-generation dual-source CT scanner: assessment of the accuracy of iodine uptake measurement and image quality in an in vitro and in vivo investigations

PURPOSE

To assess the accuracy of iodine quantification in a phantom study at different radiation dose levels with dual-energy dual-source CT and to evaluate image quality and radiation doses in patients undergoing a single-energy and two dual-energy abdominal CT protocols.

METHODS

In a phantom study, the accuracy of iodine quantification (4.5-23.5 mgI/mL) was evaluated using the manufacturer-recommended and three dose-optimized dual-energy protocols. In a patient study, 75 abdomino-pelvic CT examinations were acquired as follows: 25 CT scans with the manufacturer-recommended dual-energy protocol (protocol A); 25 CT scans with a dose-optimized dual-energy protocol (protocol B); and 25 CT scans with a single-energy CT protocol (protocol C). CTDI_vol and objective noise were measured. Five readers scored each scan according to six subjective image quality parameters (noise, contrast, artifacts, visibility of small structures, sharpness, overall diagnostic confidence).

RESULTS

In the phantom study, differences between the real and measured iodine concentrations ranged from -8.8% to 17.0% for the manufacturer-recommended protocol and from -1.6% to 20.5% for three dose-optimized protocols. In the patient study, the CTDI_vol of protocol A, B, and C were 12.5 ± 1.9, 7.5 ± 1.2, and 6.5 ± 1.7 mGycm, respectively (p < 0.001), and the average image noise values were 6.6 ± 1.2, 7.8 ± 1.4, and 9.6 ± 2.2 HU, respectively (p < 0.001). No significant differences in the six subjective image quality parameters were observed between the dose-optimized dual-energy and the single-energy protocol.

CONCLUSION

A dose reduction of 41% is feasible for the manufacturer-recommended, abdominal dual-energy CT protocol, as it maintained the accuracy of iodine measurements and subjective image quality compared to a single-energy protocol.

Dual-Energy Computed Tomography in Genitourinary Imaging

Reignited by innovations in scanner engineering and software design, dual-energy computed tomography (CT) has come back into the clinical radiology arena in the last decade. Possibilities for noninvasive in vivo characterization of genitourinary disease, especially for renal stones and renal masses, have become the pinnacle offerings of dual-energy CT for body imaging in clinical practice. This article renders a state-of-the-art review on clinical applications of dual-energy CT in genitourinary imaging.

Use of a Noise Optimized Monoenergetic Algorithm for Patient-Size Independent Selection of an Optimal Energy Level During Dual-Energy CT of the Pancreas

PURPOSE

To investigate the impact of a second-generation noise-optimized monoenergetic algorithm on selection of the optimal energy level, image quality, and effect of patient body habitus for dual-energy multidetector computed tomography of the pancreas.

MATERIALS AND METHODS

Fifty-nine patients (38 men, 21 women) underwent dual-energy multidetector computed tomography (80/Sn140 kV) in the pancreatic parenchymal phase. Image data sets, at energy levels ranging from 40 to 80 keV (in 5-keV increments), were reconstructed using first-generation and second-generation noise-optimized monoenergetic algorithm. Noise, pancreatic contrast-to-noise ratio (CNRpancreas), and CNR with a noise constraint (CNRNC) were calculated and compared among the different reconstructed data sets. Qualitative assessment of image quality was performed by 3 readers.

RESULTS

For all energy levels below 70 keV, noise was significantly lower (P ≤ 0.05) and CNRpancreas significantly higher (P < 0.001), with the second-generation monoenergetic algorithm. Furthermore, the second-generation algorithm was less susceptible to variability related to patient body habitus in the selection of the optimal energy level. The maximal CNRpancreas occurred at 40 keV in 98% (58 of 59) of patients with the second-generation monoenergetic algorithm. However, the CNRNC and readers' image quality scores showed that, even with a second-generation monoenergetic algorithm, higher reconstructed energy levels (60-65 keV) represented the optimal energy level.

CONCLUSIONS

Second-generation noise-optimized monoenergetic algorithm can improve the image quality of lower-energy monoenergetic images of the pancreas, while decreasing the variability related to patient body habitus in selection of the optimal energy level.

Lesion Size and Iodine Quantification to Distinguish Low-Grade From High-Grade Clear Cell Renal Cell Carcinoma Using Dual-Energy Spectral Computed Tomography

OBJECTIVE

The aim of this study was to assess the utility of lesion size and iodine quantification using dual-energy spectral computed tomography to distinguish between low-grade and high-grade clear cell renal cell carcinomas (ccRCCs).

METHODS

Spectral parameters of 75 patients with pathologically proven ccRCCs who underwent preoperative dual-energy spectral computed tomography examinations were divided into low-grade and high-grade groups. Independent sample t test, receiver operating characteristic curve analysis, and Spearman rank correlation were analyzed.

RESULTS

The lesion size was significantly smaller, and spectral parameters were significantly higher in the low-grade ccRCC. The significant correlation (r = -0.412, P < 0.001) by the Spearman rank correlation was between the normalized iodine concentration and lesion size. The receiver operating characteristic analysis demonstrated that 0.710 was the optimal cutoff value, which yielded the following: sensitivity, 97.6%; specificity, 97.1%; positive predictive value, 97.6%; negative predictive value, 97.1%; and accuracy, 97.3%.

CONCLUSIONS

Iodine quantification can play an important role in distinguishing low-grade from high-grade ccRCC.

In vivo small animal micro-CT using nanoparticle contrast agents

Computed tomography (CT) is one of the most valuable modalities for in vivo imaging because it is fast, high-resolution, cost-effective, and non-invasive. Moreover, CT is heavily used not only in the clinic (for both diagnostics and treatment planning) but also in preclinical research as micro-CT. Although CT is inherently effective for lung and bone imaging, soft tissue imaging requires the use of contrast agents. For small animal micro-CT, nanoparticle contrast agents are used in order to avoid rapid renal clearance. A variety of nanoparticles have been used for micro-CT imaging, but the majority of research has focused on the use of iodine-containing nanoparticles and gold nanoparticles. Both nanoparticle types can act as highly effective blood pool contrast agents or can be targeted using a wide variety of targeting mechanisms. CT imaging can be further enhanced by adding spectral capabilities to separate multiple co-injected nanoparticles in vivo. Spectral CT, using both energy-integrating and energy-resolving detectors, has been used with multiple contrast agents to enable functional and molecular imaging. This review focuses on new developments for in vivo small animal micro-CT using novel nanoparticle probes applied in preclinical research.

Utility of MRI in the Characterization of Indeterminate Small Renal Lesions Previously Seen on Screening CT Scans of Potential Renal Donor Patients

OBJECTIVE

The purpose of this study was to determine whether MRI could more confidently characterize indeterminate small renal lesions (< 15 mm) previously seen on CT scans of potential renal donor patients and whether such characterization could impact surgical management and donor candidate status.

MATERIALS AND METHODS

After dedicated contrast-enhanced renal CT examinations of a population of renal donor patients identified indeterminate small renal lesions (< 15 mm), dedicated renal MRI examinations were performed for 55 of those patients. Two radiologists used consensus reading of established MRI characteristics to characterize indeterminate small lesions as simple cysts, hemorrhagic cysts, angiomyolipomas, or solid renal masses.

RESULTS

A total of 94 indeterminate small renal lesions were detected on CT. MRI was able to confidently diagnose 93 of those lesions, including 83 cysts, eight hemorrhagic cysts, and two angiomyolipomas. MRI directly affected the surgical management of four of the patients (7%).

CONCLUSION

For potential renal donor patients, MRI can be an effective means of characterizing lesions that are deemed to be too small to characterize by CT. MRI can also potentially alter the surgical management and donor status of this group of patients.

Innovation in hepatic alveolar echinococcosis imaging: best use of old tools, and necessary evaluation of new ones

Hepatic Alveolar Echinococcosis (HAE), caused by larvae of Echinococcus multilocularis, is a rare but potentially lethal parasitic disease. The first diagnostic suspicion is usually based on hepatic ultrasound exam performed because of abdominal symptoms or in the context of a general checkup; HAE diagnosis may thus also be an incidental finding on imaging. The next step should be Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). They play an important role in the initial assessment of the disease; with chest and brain imaging, they are necessary to assess the PNM stage (parasite lesion, neighboring organ invasion, metastases) of a patient with AE. Performed at least yearly, they also represent key exams for long-term follow-up after therapeutic interventions. Familiarity of radiologists with HAE imaging findings, especially in the endemic regions, will enable earlier diagnosis and more effective treatment. Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is currently considered to be the only noninvasive, albeit indirect, tool for the detection of metabolic activity in AE. Delayed acquisition of images (3 hrs after FDG injection) enhances its sensitivity for the assessment of lesion metabolism and its reliability for the continuation/withdrawal of anti-parasite treatment. However, sophisticated equipment and high cost widely limit PET/CT use for routine evaluation. Preliminary studies show that new techniques, such as contrast-enhanced ultrasound (US), Dual Energy CT or Spectral CT, and Diffusion-Weighted MRI, might also be useful in detecting the blood supply and metabolism of lesions. However, they cannot be recommended before further evaluation of their reliability in a larger number of patients with a variety of locations and stages of AE lesions.

Low enhancing papillary renal cell carcinoma diagnosed by using dual energy computerized tomography: a case report and review of literature

BACKGROUND

Papillary renal cell carcinoma (pRCC) is a mixed group of tumors that constitutes about 15-20% of all renal cortical cancers. Strong enhancement on computerized tomography (CT) is a feature of clear cell, but not of pRCC making the differentiation of papillary tumors from benign cysts a diagnostic problem in some cases.

CASE PRESENTATION

We report here a case of a female patient with pRCC that was initially diagnosed as a benign renal cyst. The patient is a 66 year old Caucasian female who initially presented with an ultrasound showing a 2.6 cm hypo-echoic lesion within the inferior pole of her left kidney. This was followed by a contrast enhanced computerized tomography that suggested the hypo-echoic lesion to be a hyper-attenuating benign renal cyst. Follow-up CT scan 4 months later demonstrated an increase in the size of the lesion to 3.2 cm with equivocal enhancement. A dual energy computerized tomography (DECT) showed the lesion to be a solid mass suspicious for renal cell carcinoma. A robotic partial nephrectomy revealed a papillary renal cell carcinoma with negative margins.

CONCLUSION

In this case report, we reviewed the literature on variations in enhancement of renal tumors and the possible role of dual energy contract enhanced CT in differentiating papillary tumors with low enhancement from benign kidney cystic lesions.

Iodine quantification to distinguish clear cell from papillary renal cell carcinoma at dual-energy multidetector CT: a multireader diagnostic performance study

PURPOSE

To investigate whether dual-energy multidetector row computed tomographic (CT) imaging with iodine quantification is able to distinguish between clear cell and papillary renal cell carcinoma ( RCC renal cell carcinoma ) subtypes.

MATERIALS AND METHODS

In this retrospective, HIPAA-compliant, institutional review board-approved study, 88 patients (57 men, 31 women) with diagnosis of either clear cell or papillary RCC renal cell carcinoma at pathologic analysis, who underwent contrast material-enhanced dual-energy nephrographic phase study between December 2007 and June 2013, were included. Five readers, blinded to pathologic diagnosis, independently evaluated all cases by determining the lesion iodine concentration on color-coded iodine maps. The receiving operating characteristic curve analysis was adopted to estimate the optimal threshold for discriminating between clear cell and papillary RCC renal cell carcinoma , and results were validated by using a leave-one-out cross-validation. Interobserver agreement was assessed by using an intraclass correlation coefficient. The correlation between tumor iodine concentration and tumor grade was investigated.

RESULTS

A tumor iodine concentration of 0.9 mg/mL represented the optimal threshold to discriminate between clear cell and papillary RCC renal cell carcinoma , and it yielded the following: sensitivity, 98.2% (987 of 1005 [95% confidence interval: 97.7%, 98.7%]); specificity, 86.3% (272 of 315 [95% confidence interval: 85.0%, 87.7%]); positive predictive value, 95.8% (987 of 1030 [95% confidence interval: 95.0%, 96.6%]); negative predictive value, 93.7% (272 of 290 [95% confidence interval: 92.8%, 94.7%]); overall accuracy of 95.3% (1259 of 1320 [95% confidence interval: 94.6%, 96.2%]), with an area under the curve of 0.923 (95% confidence interval: 0.913, 0.933). An excellent agreement was found among the five readers in measured tumor iodine concentration (intraclass correlation coefficient, 0.9990 [95% confidence interval: 0. 9987, 0.9993). A significant correlation was found between tumor iodine concentration and tumor grade for both clear cell (τ = 0.85; P < .001) and papillary RCC renal cell carcinoma (τ = 0.53; P < .001).

CONCLUSION

Dual-energy multidetector CT with iodine quantification can be used to distinguish between clear cell and papillary RCC renal cell carcinoma , and it provides insights regarding the tumor grade.

Spectral CT imaging as a new quantitative tool? Assessment of perfusion defects of pulmonary parenchyma in patients with lung cancer

OBJECTIVE

This study investigated the capability of dual-energy spectral computed tomography (CT) to quantitatively evaluate lung perfusion defects that are induced by central lung cancer.

METHODS

Thirty-two patients with central lung cancer underwent CT angiography using spectral imaging. A univariate general linear model was conducted to analyze the variance of iodine concentration/CT value with three factors of lung fields. A paired t-test was used to compare iodine concentrations and CT values between the distal end of lung cancer and the corresponding area in the contralateral normal lung.

RESULTS

Iodine concentrations increased progressively in the far, intermediate and near ground sides in the normal lung fields at 0.60±0.28, 0.93±0.27 and 1.25±0.38 mg/mL, respectively (P<0.001). The same trend was observed for the CT values [-(840.64±49.08), -(812.66±50.85) and -(760.83±89.17) HU, P<0.001]. The iodine concentration (0.70±0.42 mg/mL) of the lung field in the distal end of lung cancer was significantly lower than the corresponding area in the contralateral normal lung (1.19±0.62 mg/mL) (t=-7.23, P<0.001). However, the CT value of lung field in the distal end of lung cancer was significantly higher than the corresponding area in the contralateral normal lung [-(765.29±93.34) HU vs. -(800.07±76.18) HU, t=3.564, P=0.001].

CONCLUSIONS

Spectral CT imaging based on the spectral differentiation of iodine is feasible and can quantitatively evaluate pulmonary perfusion and identify perfusion defects that are induced by central lung cancer. Spectral CT seems to be a promising technique for the simultaneous evaluation of both morphological and functional lung information.