Pancreatic cancer in photon-counting CT: Low keV virtual monoenergetic images improve tumor conspicuity

PURPOSE OF THE STUDY

The aim of the study was to identify differences in the tumor conspicuity of pancreatic adenocarcinomas in different monoenergetic or polyenergetic reconstructions and contrast phases in photon-counting CT (PCCT).

MATERIAL AND METHODS

34 patients were retrospectively enrolled in this study. Quantitative image analysis was performed with region of interest (ROI) measurements in different monoenergetic levels ranging from 40 up to 70 keV (5-point steps) and polyenergetic series. Tumor-parenchyma attenuation differences and contrast-to-noise-ratio (CNR) were calculated. A qualitative image analysis was accomplished by 4 radiologists using a 5-point Likert scale (1 = "not recognizable" up to 5 = "easy recognizable"). Differences between groups were evaluated for statistical significance using the Friedman test and in case of significant differences pair-wise post-hoc testing with Bonferroni correction was applied.

RESULTS

Tumor-parenchyma attenuation difference was significantly different between the different image reconstructions for both arterial- and portal-venous-phase-images (p < 0.001). Tumor-parenchyma attenuation difference was significantly higher on arterial-phase-images at mono40keV compared to polyenergetic images (p < 0.001) and mono55keV images or higher (p < 0.001). For portal-venous-phase-images tumor-parenchyma attenuation difference was significantly higher on mono40keV images compared to polyenergetic images (p < 0.001) and mono50keV images (p = 0.03) or higher (p < 0.001). The same trend was seen for CNR. Tumor conspicuity was rated best on mono40keV images with 4.3 ± 0.9 for arterial-phase-images and 4.3 ± 1.1 for portal-venous-phase-images. In contrast, overall image quality was rated best on polyenergetic-images with 4.8 ± 0.5 for arterial-phase-images and 4.7 ± 0.6 for portal-venous-phase-images.

CONCLUSION

Low keV virtual monoenergetic images significantly improve the tumor conspicuity of pancreatic adenocarcinomas in PCCT based on quantitative and qualitative results. On the other hand, readers prefer polyenergetic images for overall image quality.

Improving image quality consistency and diagnostic accuracy in lower extremity CT angiography using a split-bolus contrast injection protocol

OBJECTIVES

To evaluate the clinical value of using a split-bolus contrast injection protocol in improving image quality consistency and diagnostic accuracy in lower extremity CT angiography (CTA).

METHODS

Fifty (mean age, 66 ± 12 years) and 39 (mean age, 66 ± 11 years) patients underwent CTA in the lower extremity arteries using split-bolus and fixed-bolus injection schemes, respectively. The objective and subjective image quality of the 2 groups were compared and the diagnostic efficacy for the degree of vessel stenosis was compared using digital subtraction angiography as the gold standard. A P < .05 was considered statistically significant.

RESULTS

In comparison with the fixed-bolus scheme, the split-bolus scheme greatly improved the consistency of image quality of the low extremities by significantly increasing the arterial enhancement (337.87 ± 64.67HU vs. 254.74 ± 71.58HU, P < .001), signal-to-noise ratio (22.58 ± 11.64 vs. 7.14 ± 1.98, P < .001), and contrast-to-noise ratio (37.21 ± 10.46 vs. 31.10 ± 15.40, P = .041) in the infrapopliteal segment. The subjective image quality was better (P < .001) and the diagnostic accuracy was higher in the split-bolus group than in the fixed-bolus group (96.00% vs. 91.67%, P < .05, for diagnosing >50% stenosis, and 97.00% vs. 89.10%, P < .05, for diagnosing occlusion) for the infrapopliteal segment arteries.

CONCLUSIONS

Compared with the fixed-bolus injection scheme, the split-bolus injection scheme improves the image quality consistency and diagnostic accuracy especially for the infrapopliteal segment arteries in lower extremity CTA.

ADVANCES IN KNOWLEDGE

(1) The split-bolus injection scheme of CTA of the lower extremity arteries improves the overall image quality, uniformity of contrast enhancement. (2) Compared with the fixed-bolus injection scheme, the split-bolus injection scheme especially improves the infrapopliteal segment arteries image quality and diagnostic efficacy.

Pancreatic Cancer and Its Mimics

Pancreatic ductal adenocarcinoma (PDAC) is the most common primary pancreatic malignancy, ranking fourth in cancer-related mortality in the United States. Typically, PDAC appears on images as a hypovascular mass with upstream pancreatic duct dilatation and abrupt duct cutoff, distal pancreatic atrophy, and vascular encasement, with metastatic involvement including lymphadenopathy. However, atypical manifestations that may limit detection of the underlying PDAC may also occur. Atypical PDAC features include findings related to associated conditions such as acute or chronic pancreatitis, a mass that is isointense to the parenchyma, multiplicity, diffuse tumor infiltration, associated calcifications, and cystic components. Several neoplastic and inflammatory conditions can mimic PDAC, such as paraduodenal "groove" pancreatitis, autoimmune pancreatitis, focal acute and chronic pancreatitis, neuroendocrine tumors, solid pseudopapillary neoplasms, metastases, and lymphoma. Differentiation of these conditions from PDAC can be challenging due to overlapping CT and MRI features; however, certain findings can help in differentiation. Diffusion-weighted MRI can be helpful but also can be nonspecific. Accurate diagnosis is pivotal for guiding therapeutic planning and potential outcomes in PDAC and avoiding biopsy or surgical treatment of some of these mimics. Biopsy may still be required for diagnosis in some cases. The authors describe the typical and atypical imaging findings of PDAC and features that may help to differentiate PDAC from its mimics. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Zins in this issue.

Influence of Baseline CT Body Composition Parameters on Survival in Patients with Pancreatic Adenocarcinoma

Pancreatic cancer is the seventh leading cause of cancer death in both sexes. The aim of this study is to analyze baseline CT body composition using artificial intelligence to identify possible imaging predictors of survival. We retrospectively included 103 patients. First, the presence of surgical treatment and cut-off values for sarcopenia and obesity served as independent variates. Second, the presence of surgery, subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and skeletal muscle index (SMI) served as independent variates. Cox regression analysis was performed for 1-year, 2-year, and 3-year survival. Possible differences between patients undergoing surgical versus nonsurgical treatment were analyzed. Presence of surgery significantly predicted 1-year, 2-year, and 3-year survival (p = 0.01, <0.001, and <0.001, respectively). Across the follow-up periods of 1-year, 2-year, and 3-year survival, the presence of sarcopenia became an equally important predictor of survival (p = 0.25, 0.07, and <0.001, respectively). Additionally, increased VAT predicted 2-year and 3-year survival (p = 0.02 and 0.04, respectively). The impact of sarcopenia on 3-year survival was higher in the surgical treatment group (p = 0.02 and odds ratio = 2.57) compared with the nonsurgical treatment group (p = 0.04 and odds ratio = 1.92). Fittingly, a lower SMI significantly affected 3-year survival only in patients who underwent surgery (p = 0.02). Especially if surgery is performed, AI-derived sarcopenia and reduced muscle mass are unfavorable imaging predictors.

Resectable and Borderline Resectable Pancreatic Ductal Adenocarcinoma: Role of the Radiologist and Oncologist in the Era of Precision Medicine

The incidence and mortality of pancreatic ductal adenocarcinoma are growing over time. The management of patients with pancreatic ductal adenocarcinoma involves a multidisciplinary team, ideally involving experts from surgery, diagnostic imaging, interventional endoscopy, medical oncology, radiation oncology, pathology, geriatric medicine, and palliative care. An adequate staging of pancreatic ductal adenocarcinoma and re-assessment of the tumor after neoadjuvant therapy allows the multidisciplinary team to choose the most appropriate treatment for the patient. This review article discusses advancement in the molecular basis of pancreatic ductal adenocarcinoma, diagnostic tools available for staging and tumor response assessment, and management of resectable or borderline resectable pancreatic cancer.

Simulated twin-phase pancreatic CT generated using single portal venous phase dual-energy CT acquisition in pancreatic ductal adenocarcinoma

PURPOSE

To evaluate the diagnostic performance of a simulated twin-phase pancreatic protocol CT generated from a single portal venous phase (PVP) dual-energy CT (DECT) acquisition in patients with pancreatic ductal adenocarcinoma (PDAC).

METHODS

In this retrospective study, we included 63 patients with PDAC who underwent pancreatic protocol (pancreatic phase [PP] and PVP) DECT. Two data sets were created from this original acquisition-(1) Standard protocol (50 keV PP/65 keV PVP) and (2) Simulated protocol (40 keV/65 keV PVP). Using a 5-point scale, three readers scored image quality, tumor conspicuity, and arterial involvement by the PDAC. Signal-to-noise ratio (SNR) of the pancreas and tumor-to-pancreas contrast-to-noise ratio (CNR) were calculated. Qualitative scores, quantitative parameters, and radiation dose were compared between standard and simulated protocols.

RESULTS

No significant difference in detection rate of PDAC was seen between the standard (58/63, 92.1%) and simulated protocols (56/63, 88.9%) (P = 0.76). Subjective scoring for arterial involvement for celiac (P = 0.86), superior mesenteric (P = 0.88), splenic (P = 0.86), common hepatic (P = 0.52), gastroduodenal (P = 0.95), first jejunal (P = 0.48) arteries, and aorta (P = 1.00) were comparable between two protocols. The image quality (P = 0.14), the SNR of the pancreas (P = 0.15), and CNR (P = 0.54) were comparable between two protocols. The projected mean dose-length product (DLP) (629.6 ± 148.3 mGy cm) in the simulated protocol showed a 44% reduction in radiation dose compared to the standard protocol (mean DLP, 1123.3 ± 268.9 mGy cm) (P < 0.0001).

CONCLUSIONS

Low keV images generated from a PVP DECT acquisition allows creation of a twin-phase pancreatic protocol CT with comparable diagnostic accuracy for detecting PDAC with significant reduction in radiation dose. Reduced radiation dose is desirable in surveillance and screening for pancreatic diseases.

Intraductal papillary mucinous neoplasm (IPMN) of the pancreas: recommendations for Standardized Imaging and Reporting from the Society of Abdominal Radiology IPMN disease focused panel

There have been many publications detailing imaging features of malignant transformation of intraductal papillary mucinous neoplasms (IPMN), management and recommendations for imaging follow-up of diagnosed or presumed IPMN. However, there is no consensus on several practical aspects of imaging IPMN that could serve as a clinical guide for radiologists and enable future data mining for research. These aspects include how to measure IPMN, define reporting terminology, standardize reporting and unify guidelines for surveillance. The Society of Abdominal Radiology (SAR) created multiple Disease-Focused Panels (DFP) comprised multidisciplinary panel members who focus on a particular disease, with the goal to develop ways for radiologists to improve patient care, education, and research. DFP members met to identify the current controversies and limitations of imaging pancreatic IPMN. This paper aims to provide a practical review of the key imaging characteristics of IPMN for trainees and practicing radiologists, to guide uniformity of performance and interpretation of surveillance imaging studies, and to improve communication with clinicians by providing a lexicon and reporting template based on the experience of the SAR-DFP panel members.

Low keV portal venous phase as a surrogate for pancreatic phase in a pancreatic protocol dual-energy CT: feasibility, image quality, and lesion conspicuity

OBJECTIVE

To assess the feasibility of a proposed pancreatic protocol CT generated from portal-venous phase (PVP) dual-energy CT (DECT) acquisition and its impact on image quality, lesion conspicuity, and arterial visualization/involvement.

METHODS

We included 111 patients (mean age, 66.8 years) who underwent pancreatic protocol DECT (pancreatic phase, PP, and PVP). The original DECT acquisition was used to create two data sets-standard protocol (50 keV PP/65 keV PVP) and proposed protocol (40 keV/65 keV PVP). Three reviewers evaluated the two data sets for image quality, lesion conspicuity, and arterial visualization/involvement using a 5-point scale. The signal-to-noise ratio (SNR) of pancreas and lesion-to-pancreas contrast-to-noise ratio (CNR) was calculated. Qualitative scores, quantitative parameters, and dose-length product (DLP) were compared between standard and proposed protocols.

RESULTS

The image quality, SNR of pancreas, and lesion-to-pancreas CNR of the standard and proposed protocol were comparable (p = 0.11-1.00). Lesion conspicuity was comparable between the standard and proposed protocols for pancreatic ductal adenocarcinoma (p = 0.55) and pancreatic cysts (p = 0.28). The visualization of larger arteries and arterial involvement were comparable between the two protocols (p = 0.056-1.00) while the scores were higher for smaller vessels in the standard protocol (p < 0.0001-0.0015). DLP of the proposed protocol (670.4 mGy·cm) showed a projected 42% reduction than the standard protocol (1145.9 mGy·cm) (p < 0.0001).

CONCLUSION

Pancreatic protocol CT generated from a single PVP DECT acquisition is feasible and could potentially be an alternative to the standard pancreatic protocol with PP and PVP.

KEY POINTS

• The lesion conspicuity for focal pancreatic lesions was comparable between the proposed protocol and standard dual-phase pancreatic protocol CT. • Qualitative and quantitative image assessments were almost comparable between two protocols. • The radiation dose of a proposed protocol showed a projected 42% reduction from the conventional protocol.

New advances in CT imaging of pancreas diseases: a narrative review

Computed tomography (CT) plays a pivotal role as a diagnostic tool in many diagnostic and diffuse pancreatic diseases. One of the major limits of CT is related to the radiation exposure of young patients undergoing repeated examinations. Besides the standard CT protocol, the most recent technological advances, such as low-voltage acquisitions with high performance X-ray tubes and iterative reconstructions, allow for significant optimization of the protocol with dose reduction. The variety of CT tools are further expanded by the introduction of dual energy: the production of energy-selective images (i.e., virtual monochromatic images) improves the image contrast and lesion detection while the material-selective images (e.g., iodine maps or virtual unenhanced images) are valuable for lesion detection and dose reduction. The perfusion techniques provide diagnostic and prognostic information lesion and parenchymal vascularization and interstitium. Both dual energy and perfusion CT have the potential for pushing the limits of conventional CT from morphological evaluation to quantitative imaging applied to inflammatory and oncological diseases. Advances in post-processing of CT images, such as pancreatic volumetry, texture analysis and radiomics provide relevant information for pancreatic function but also for the diagnosis, management and prognosis of pancreatic neoplasms. Artificial intelligence is promising for optimization of the workflow in qualitative and quantitative analyses. Finally, basic concepts on the role of imaging on screening of pancreatic diseases will be provided.

Clinical Implementation of Dual-Energy CT for Gastrointestinal Imaging

Dual-energy CT (DECT) overcomes several limitations of conventional single-energy CT (SECT) for the evaluation of gastrointestinal diseases. This article provides an overview of practical aspects of the DECT technology and acquisition protocols, reviews existing clinical applications, discusses current challenges, and describes future directions, with a focus on gastrointestinal imaging. A head-to-head comparison of technical specifications among DECT scanner implementations is provided. Energy- and material-specific DECT image reconstructions enable retrospective (i.e., after examination acquisition) image quality adjustments that are not possible using SECT. Such adjustments may, for example, correct insufficient contrast bolus or metal artifacts, thereby potentially avoiding patient recalls. A combination of low-energy monochromatic images, iodine maps, and virtual unenhanced images can be included in protocols to improve lesion detection and disease characterization. Relevant literature is reviewed regarding use of DECT for evaluation of the liver, gallbladder, pancreas, and bowel. Challenges involving cost, workflow, body habitus, and variability in DECT measurements are considered. Artificial intelligence and machine-learning image reconstruction algorithms, PACS integration, photon-counting hardware, and novel contrast agents are expected to expand the multienergy capability of DECT and further augment its value.

Split-bolus injection protocol with optimized timings of contrast medium injection and CT scanning for 3D CT angio-venography before laparoscopic gastrectomy

PURPOSE

To propose an optimization method of contrast medium injection for the split-bolus protocol based on the contrast medium pharmacokinetics and investigate the utility of the optimized split-bolus protocol in 3D CT angio-venography for laparoscopic gastrectomy.

MATERIALS AND METHODS

A pharmacokinetic relationship between injection duration and time to the peak enhancement was taken into account in the protocol design. The first 20 consecutive patients underwent a multi-phase scan with a single-bolus injection (single-bolus protocol), and the next 20 underwent the proposed split-bolus protocol. CT attenuations of the arteries and veins and dose-length products (DLPs) were compared between the two protocols. Two radiologists visually assessed arterial and venous depictions and the misregistrations.

RESULTS

Mean arterial CT attenuations were not significantly different between the two protocols. Though mean venous CT attenuations for the split-bolus protocol were 7-11% lower than those of the single-bolus protocol, they were visually evaluated as similar. The mean DLP of the split-bolus protocol was 46% lower than that of the single-bolus protocol. Misregistration between the arteries and veins occurred 35-80% during the single-bolus protocol, but was not indicated in the split-bolus protocol.

CONCLUSION

The split-bolus protocol with optimized timing was more effective for providing improved image quality with reduced radiation dose compared with the single-bolus protocol in 3D CT angio-venography for laparoscopic gastrectomy.

Optimization of Pediatric Body CT Angiography: What Radiologists Need to Know

OBJECTIVE. Pediatric CT angiography (CTA) presents unique challenges compared with adult CTA. Because of the ionizing radiation exposure, CTA should be used judiciously in children. The pearls offered here are observations gleaned from the authors' experience in the use of pediatric CTA. We also present some potential follies to be avoided. CONCLUSION. Understanding the underlying principles and paying meticulous attention to detail can substantially optimize dose and improve the diagnostic quality of pediatric CTA.

Split-bolus single-pass CT for vascular complications in acute pancreatitis: assessment of radiation dose and multi-phasic contrast enhancement compared to single-bolus multi-pass CT

AIM

To assess vascular contrast enhancement and radiation dose of split-bolus single-pass computed tomography (CT) compared to single-bolus multi-pass CT for acquiring a multi-phasic study.

MATERIALS AND METHODS

Patients who underwent CT for acute pancreatitis were included retrospectively. Thirty consecutive patients scanned with a split-bolus protocol were compared to 30 consecutive patients scanned with a single-bolus protocol. Data were collected on attenuation measurements (aorta, portal vein and spleen) and images were assessed for subjective vascular enhancement quality and splenic homogeneity. Radiation dose was measured by dose-length product (DLP).

RESULTS

There was no significant difference in the aortic (p = 0.88) or portal vein (p = 0.35) attenuation values between the two groups. The percentage of examinations reaching the target aortic and portal attenuation in the split-bolus group were 96.7% and 93.3%, and in the single-bolus group were 96.7% and 85.7%, respectively. The mean DLP was 492 mGy.cm for the single-bolus group and 940 mGy.cm for the split-bolus group (p < 0.0001). Subjective assessment revealed higher rates of splenic heterogeneity in the split-bolus group.

DISCUSSION

In acute pancreatitis, split-bolus imaging can produce arterial and venous enhancement comparable to a multi-pass technique with a significant reduction in radiation dose. Loss of temporal resolution and increased splenic heterogeneity are the main disadvantages. The low prevalence of pseudoaneurysms favours the lower-dose imaging technique.

Split-bolus CTA for mesenteric ischemia with a single scan opacifying arterial and mesenteric venous systems

OBJECTIVE

To evaluate the diagnostic accuracy of split-bolus single-scan computed tomography angiography (CTA) protocol for evaluation of acute mesenteric ischemia and alternate diagnoses.

MATERIALS AND METHODS

In this IRB-approved, HIPAA-compliant retrospective study, consecutive patients from 21 October 2016 to 6 May 2018 evaluated for mesenteric ischemia with split-bolus CTA (a single scan in concurrent arterial and portal venous phase) in a single tertiary academic institution were included. Intravenous contrast was administered on weight-based basis. Quantitative and qualitative assessments of superior mesenteric artery (SMA) and superior mesenteric vein (SMV) attenuation and patency were performed by two independent reviewers. CT imaging findings were correlated with clinical reference outcomes.

RESULTS

One hundred fifty-four patients (age 66.3 ± 14.1 years, BMI 27.3 ± 6, 86 (56%) female) were included. CTA studies were performed with a volumetric CT dose index of 15.9 ± 5.5 mSv and dose length product of 1042.9 ± 389.4 mGy cm. Average intravenous contrast volume administered was 164.3 ± 12.1 cc. SMA attenuation was 263.6 ± 92.4HU, SMV was 190 ± 50.2HU. Qualitative assessment of SMA and SMV showed good opacification in all patients. 17/154 (11%) patients were diagnosed on CT with mesenteric ischemia; in 6/154 (4%), CTA studies were indeterminate; in 131/154 (85%), CTA confidently ruled out mesenteric ischemia. Alternate diagnoses were made in 38/154 (25%) patients. Using composite clinical outcomes as a reference standard, sensitivity of split-bolus CTA protocol for diagnosis of mesenteric ischemia is 100% (95% CI 79-100%), and specificity is 99% (95% CI 96-100%).

CONCLUSIONS

Split-bolus CTA has high sensitivity and specificity for diagnosis of acute mesenteric ischemia.

KEY POINTS

• Split-bolus CTA protocol for mesenteric ischemia has great diagnostic accuracy with lower radiation exposure and fewer images to interpret compared with standard multiphasic CTA.

White paper on pancreatic ductal adenocarcinoma from society of abdominal radiology's disease-focused panel for pancreatic ductal adenocarcinoma: Part II, update on imaging techniques and screening of pancreatic cancer in high-risk individuals

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive gastrointestinal malignancy with a poor 5-year survival rate. Its high mortality rate is attributed to its aggressive biology and frequently late presentation. While surgical resection remains the only potentially curative treatment, only 10-20% of patients will present with surgically resectable disease. Over the past several years, development of vascular bypass graft techniques and introduction of neoadjuvant treatment regimens have increased the number of patients who can undergo resection with a curative intent. While the role of conventional imaging in the detection, characterization, and staging of patients with PDAC is well established, its role in monitoring treatment response, particularly following neoadjuvant therapy remains challenging because of the complex anatomic and histological nature of PDAC. Novel morphologic and functional imaging techniques (such as DECT, DW-MRI, and PET/MRI) are being investigated to improve the diagnostic accuracy and the ability to measure response to therapy. There is also a growing interest to detect PDAC and its precursor lesions at an early stage in asymptomatic patients to increase the likelihood of achieving cure. This has led to the development of pancreatic cancer screening programs. This article will review recent updates in imaging techniques and the current status of screening and surveillance of individuals at a high risk of developing PDAC.

Resectable pancreatic ductal adenocarcinoma: association between preoperative CT texture features and metastatic nodal involvement

Background

To explore the relationship between the lymph node status and preoperative computed tomography images texture features in pancreatic cancer.

Methods

A total of 155 operable pancreatic cancer patients (104 men, 51 women; mean age 63.8 ± 9.6 years), who had undergone contrast-enhanced computed tomography in the arterial and portal venous phases, were enrolled in this retrospective study. There were 73 patients with lymph node metastases and 82 patients without nodal involvement. Four different data sets, with thin (1.25 mm) and thick (5 mm) slices (at arterial phase and portal venous phase) were analysed. Texture analysis was performed by using MaZda software. A combination of feature selection algorithms was used to determine 30 texture features with the optimal discriminative performance for differentiation between lymph node positive and negative groups. The prediction performance of the selected feature was evaluated by receiver operating characteristic (ROC) curve analysis.

Results

There were 10 texture features with significant differences between two groups and significance in ROC analysis were identified. They were WavEnLH_s-2(wavelet energy with rows and columns are filtered with low pass and high pass frequency bands with scale factors 2) from wavelet-based features, 135dr_LngREmph (long run emphasis in 135 direction) and 135dr_Fraction (fraction of image in runs in 135 direction) from run length matrix-based features, and seven variables of sum average from coocurrence matrix-based features (SumAverg). The ideal cutoff value for predicting lymph node metastases was 270 for WavEnLH_s-2 (positive likelihood ratio 2.08). In addition, 135dr_LngREmph and 135dr_Fraction were correlated with the ratio of metastatic to examined lymph nodes.

Conclusions

Preoperative computed tomography high order texture features provide a useful imaging signature for the prediction of nodal involvement in pancreatic cancer.

Follow-up Recommendation Rates Associated With Spectral Detector Dual-Energy CT of the Abdomen and Pelvis: A Retrospective Comparison to Single-Energy CT

BACKGROUND

Dual-energy CT image sets have many applications in abdominopelvic imaging but no demonstrated clinical effect.

PURPOSE

To determine the effect of dual-energy CT iodine maps on abdominopelvic imaging follow-up recommendation rates.

MATERIALS AND METHODS

Retrospective study of abdominopelvic CTs acquired from April 2017 through June 2018. CT reports were analyzed for radiologic follow-up recommendation and follow-up recommendation reason. Follow-up MRI reports were analyzed for benign or nonbenign diagnosis. CT scans with iodine maps (CTIMs) and conventional CT scans (CCTs) subgroups were compared using χ² testing.

RESULTS

In all, 3,221 abdominopelvic CT scans of 2,401 patients (1,326 men, 1,075 women, mean age 54.1 years) were analyzed; 1,423 were CTIMs and 1,798 were CCTs. Follow-up recommendation rates were not significantly different for CTIMs and CCTs (19.5% and 21.4%, respectively, P = .19). Follow-up recommendations because of incomplete diagnosis were significantly lower in CTIMs (9.1%) than in CCTs (11.9%, P = .01). Follow-up recommendations for MRI and PET/CT were significantly lower in CTIMs (9.6%) than CCTs (13.0%, P = .003). Follow-up MRI outcomes (n = 111) were not different between CTIMs (61.2% benign) and CCTs (59.6%, P = .87).

CONCLUSION

Dual-energy CT iodine maps are associated with decreased follow-up examinations because of incomplete diagnosis and decreased recommendations for follow-up MRI, suggesting that abdominopelvic iodine maps may benefit patient care and decrease institutional cost.

Differential diagnosis of solid pancreatic masses

Solid pancreatic lesions include mainly adenocarcinoma, neuroendocrine tumors pancreatic cystic neoplasms with solid component, solid pseudopapillary tumor, pancreatoblastoma, pancreatic lymphoma, and pancreatic metastasis. The most frequent pancreatic lesion is the adenocarcinoma, representing between 70% and 95% of all solid pancreatic neoplasm. The diagnosis of these lesions can be a challenge and currently, there are different imaging techniques such as CT scan, EUS and MRI with high sensitivity and specificity. The most widely used technique for the initial evaluation is the CT scan with a sensitivity between 76% and 92% for the diagnosis of pancreatic cancer. The EUS has a sensitivity for the detection of pancreatic lesions of around 98% and is accepted to be the most sensitive technique for the detection of small pancreatic tumors (<2 cm). The MRI, with a very high soft-tissue contrast resolution, provides an accuracy in the detection and staging of adenocarcinoma of 90-100%. A multimodality approach is usually necessary in patients with clinical suspicion of pancreatic lesion. The EUS is required for the local evaluation of the relation of the lesion with vessels and for tissue acquisition and the CT scan and/or MRI is usually required for the local and distance staging in case of pancreatic cancer. The purpose of this review is to provide an overview of solid pancreatic lesions and the role of the different imaging techniques in their evaluation.

Split-bolus vs. multiphasic contrast bolus protocol in patients with pancreatic cancer or cholangiocarcinoma

PURPOSE

To investigate the image quality, diagnostic accuracy, and dose reduction potential of a split-bolus protocol(SBP) compared with a multiphasic protocol(MPP) in the detection of recurrent or progressive pancreatic ductal adenocarcinoma(PDAC) or cholangiocarcinoma(CC) using contrast- enhanced computed tomography(CECT).

MATERIALS AND METHODS

This prospective study included 56 patients who underwent CECT, 28 with our institutional standard MPP(100 ml contrast bolus) and 28 with a novel SBP(110 ml). Radiation exposure was determined in terms of total dose- length product(DLP) and computed tomography dose index(CTDI). Image quality was measured objectively by analysis of attenuation in Hounsfield units(HU) in regions of interest(ROIs) and subjectively by two blinded readers using a Likert scale. Diagnostic accuracy and interreader variability were tested.

RESULTS

The total DLP of the SBP group(498.1 ± 43.7 mGy*cm) was significantly lower than in the MPP group(1,092.5 ± 106.9 mGy*cm; p < 0.001). The SBP showed higher contrast enhancement of all critical anatomical structures including portal vein, liver, and pancreas compared with the MPP, except for the aorta(SBP: 326.9 ± 15.7 HU vs. MPP: 246.7 ± 12.2 HU; p < 0.001). Subjective analysis revealed poorer image quality ratings for important landmarks with the MPP (resection surface: p = 0.624, portal vein: p = 0.395, liver p = 0.361). The two blinded readers correlated significantly. Sensitivity, specificity, positive and negative predictive values (PPV/NPV), and overall interreader variabilities correlated significantly. Furthermore, significantly fewer slices per exam were required for the SBP(1,823 vs. 3,235; p < 0.001).

CONCLUSION

The SBP provides the same image quality and diagnostic accuracy as an MPP while significantly lowering radiation exposure in CT follow-up of PDAC or CC.

Diagnosis of lymph node metastasis on rectal cancer by PET-CT computer imaging combined with MRI technology

To compare the diagnostic efficacy and clinical application value of Positron Emission Tomography-Computed Tomography (PET-CT) metabolic computer Imaging imaging and Magnetic Resonance Imaging (MRI) diffusion imaging technology for regional lymph node metastasis in rectal cancer, 41 patients with rectal cancer confirmed by colonoscopy were collected and underwent 3.0T pelvic MRI and PET-CT examination, respectively. PET-CT/MRI fusion software was used to fuse magnetic resonance images and PET-CT images and accurately locate the rectal cancer lesions and lymph nodes, and image-operation-pathology control method was used to identify the lymph nodes around the rectum. In addition, independent sample t-test or Mann-Whitney U test were used to compare the differences in the values of various parameters between the two groups of metastatic lymph nodes and non-metastatic lymph nodes, Spearman correlation was used to analyze the correlation between SUV value and ADC value of metastatic lymph node, and the diagnostic value of SUV value and ADC value was evaluated by drawing ROC curve. The results showed that when SUV took 2.0 as the diagnostic threshold, the accuracy of PET-CT in diagnosing metastatic lymph nodes was 90.1%; when the diagnostic threshold of ADC was 1.0×10^-3mm²/s, the accuracy of DWI in diagnosing metastatic lymph nodes was 84.2%; the accuracy of the combination of the two methods for the diagnosis of metastatic lymph nodes was 94.4%. Therefore, it can be concluded that both PET-CT and MRI diffusion images were of high diagnostic value in the diagnosis of lymph node metastasis of rectal cancer, and their diagnostic results were highly consistent. When combined, the diagnostic accuracy can be further improved.

Reduced Contrast Volume and Radiation Dose During Computed Tomography of the Pancreas: Timing-Specific Contrast Media Protocol

RATIONALE AND OBJECTIVE

To investigate the opacification of the pancreatic vasculature and parenchyma during computed tomography utilizing a patient-specific contrast formula.

MATERIALS AND METHODS

This hybrid prospective and retrospective study was approved by the institution review board. In 220 consecutive patients, pancreatic CT was performed with one of two protocols: protocol A, 100mL of contrast material injected via timed bolus triggering technique; or protocol B, employing a patient-specific contrast media protocol specifically timed at the gastroduodenal artery; both protocols employed 4.5 mL/s contrast media and 100mL saline chaser. Attenuation of pancreatic parenchymal, arterial, and venous vasculature supplying the pancreas was measured. Effective dose was calculated. Data were compared to the independent two-sample t test. Receiver operating characteristic, visual grading characteristic, and Cohens' kappa analyses were performed.

RESULTS

Mean pancreatic density measurements in each of the pancreatic segments during the arterial and venous phase were significantly higher in Protocol B (mean ± standard deviation, art: 96.59 HU ± 27.37; venous: 91.28 HU ± 20.88) compared to A (art: 77.86 HU ± 21.14; venous: 73.99 HU ± 14.75) (p < 0.0001). Mean arterial opacification was significantly higher in protocol B compared to A with the abdominal aorta (p < 0.007), superior mesenteric (p < 0.0002), gastroduodenal (proximal segment only p < 0.014), and splenic arteries (p < 0.036). In the venous circulation, the inferior vena cava, superior mesenteric, portal and splenic veins (all segments) demonstrated significant reduction in vascular opacification protocol B compared to A (p < 0.001). The contrast media volume in protocol B (57.60 ± 12.25 mL) was significantly lower than in protocol A (100 ± 1 mL) (p < 0.001). Effective dose was significantly reduced in protocol B (2.75 ± 0.63 mSv) compared to A (4.015 ± 0.89 mSv) (p < 0.001). Receiver operating characteristic and visual grading characteristic analysis demonstrated significantly higher area under the curve for protocol B (p < 0.0001) (p < 0.034) respectively, with inter-reader agreement increasing from good to excellent in pancreatic lesion detection.

CONCLUSION

Timing-specific contrast media protocol enhances image quality at reduced contrast volume and radiation dose during computed tomography of the pancreas.

Combined application of virtual monoenergetic high keV images and the orthopedic metal artifact reduction algorithm (O-MAR): effect on image quality

PURPOSE

To determine whether there is any additional metal artifact reduction when virtual monochromatic images (VMI) and metal artifact reduction for orthopedic implants (O-MAR) are applied together compared to their separate application in both phantom and clinical abdominopelvic CT studies.

METHODS

An agar phantom containing a spinal prosthesis was scanned using a dual-layer, energy CT scanner (IQon, Philips Healthcare), and reconstructed with the filtered back-projection algorithm without O-MAR (FBP), filtered back-projection algorithm with O-MAR (O-MAR), VMI₁₄₀ without O-MAR (VMI₁₄₀), and VMI₁₄₀ with O-MAR (VMI₁₄₀ + O-MAR). Abdominopelvic CT images of 47 patients with metallic prostheses were also reconstructed in the same manner for clinical study. Noise measured as the standard deviation of CT Hounsfield units was compared between the four reconstruction methods in both phantom and clinical studies. Improvements in metal artifact reduction, image quality, and diagnostic improvement were further analyzed in the clinical study.

RESULTS

Noise was significantly decreased when both VMI and O-MAR were applied in conjunction compared to their separate application in both phantom (16.3 HU vs. 25.0 and 26.4 HU) and clinical studies (15.8 HU vs. 19.2 and 26.2 HU). In the clinical study, the qualitative degree of artifacts was also significantly reduced with VMI₁₄₀ + O-MAR (2.85 and 2.87) compared to VMI₁₄₀ (2.36 and 2.26) or O-MAR (2.13 and 2.04) alone for both reviewers (P < 0.001) and improvements in image quality were observed in all 47 patients, with actual diagnostic improvements observed in three.

CONCLUSIONS

Metal artifacts can be additionally reduced by applying O-MAR and VMI in conjunction, compared to their separate application, thereby improving diagnostic performance.

Visibility of Hypovascularized Liver Tumors during Intra-Arterial Therapy Using Split-Bolus Single-Phase Cone Beam CT

PURPOSE

To validate a split-bolus contrast injection protocol for single-phase CBCT in terms of detectability of hypovascular liver tumors compared to digital subtraction angiography (DSA).

MATERIALS AND METHODS

In this retrospective, single-center study, 20 consecutive patients with in total 77 hypovascularized tumors referred for intra-arterial therapy received a split-bolus single-phase CBCT. Two readers rated the visibility of the target tumors scheduled for embolization in CBCT and DSA compared to the pre-interventional multiphasic CT or MRI used as reference on a 3-point scoring system (1 = optimal, 3 = not visible) and catheter-associated artifacts (1 = none, 3 = extended). SNR, CNR and contrast values were derived from 37 target tumors in CBCT and MRI. Statistical analysis included the kappa test to determine interrater reliability, the Friedman's test for the inter-modality comparison evaluating tumor visibility in DSA and CBCT as well as for quantitative assessment. Post hoc analysis included the Wilcoxon signed-rank test. p values < 0.05 were considered significant.

RESULTS

Ninety percentage of target tumors were rated as visible in CBCT and 37.5% in DSA (p < 0.001). 70.1% of pre-interventionally detected hypovascularized tumors were depicted with CBCT and 31.2% by DSA (p < 0.001). 7.8% of known tumors were outside the FOV. Quantitative assessment showed higher image contrasts in CBCT (1.91 ± 7.01) compared to hepatobiliary-phase MRI (0.29 ± 0.14, p = 0.003) and to portal-venous (p.v.) MRI (0.31 ± 0.13, p < 0.001), but higher CNR for MRI (1.18 ± 0.80; 13.92 ± 15.82; 13.79 ± 6.65).

CONCLUSION

In conclusion, the split-bolus single-phase CBCT detects significantly more hypovascularized liver tumors compared to DSA performed through the proper hepatic artery with high image contrasts.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Triple-split-bolus versus single-bolus CT in abdominal trauma patients: a comparative study

Background Split-bolus computed tomography (CT) is a recent development in trauma imaging. Instead of multiple scans in different contrast phases after a single contrast bolus, split-bolus protocols consist of one single scan of the thorax and abdomen after two or three contrast injections at different points of time. Purpose To evaluate and compare image quality and injury findings of a new triple-split-bolus CT (TS-CT) protocol of thorax and abdomen with those of a portal venous phase CT (PV-CT) in the same patient group. Material and Methods Trauma patients in 2009-2012 who underwent both the TS-CT initially and a PV-CT during the next six weeks were included. The TS-CT examination was performed as one CT run after application of three contrast boluses (total 175 mL) to enhance renal pelvis and urinary tract, the abdominal organs, and the large arterial vessels. The PV-CT had a fixed delay of 85 s. We measured attenuation in Hounsfield units (HU), evaluated possible organ injury and assessed image quality on a 5-point scale. Results Thirty-five patients were included. Attenuation measurements of major abdominal vessels, organs, and renal pelvis were significantly higher with the TS-CT protocol. Performance in organ injury diagnosis and image quality was equal in both protocols. Conclusion The overall performance of the TS-CT protocol is similar to the standard PV-CT. Excellent visualization of the arterial tree and the collecting system may eliminate the need for separate scans.

The Role of Dual-Energy Computed Tomography in Assessment of Abdominal Oncology and Beyond

The added value and strength of dual energy computed tomography for the evaluation of oncologic patients revolve around the use of lower energy reconstructed images and iodine material density images. Lower keV simulated monoenergetic images optimize soft tissue tumor to nontumoral attenuation differences and increase contrast to noise ratios to improve lesion detection. Iodine material density images or maps are helpful from a qualitative standpoint for image interpretation because they result in improved detection and characterization of tumors and lymph node involvement, and from a quantitative assessment by enabling interrogation of specific properties of tissues to predict and assess therapeutic response.

Dual-Energy Computed Tomography: Dose Reduction, Series Reduction, and Contrast Load Reduction in Dual-Energy Computed Tomography

Evolution in computed tomography technology and image reconstruction have significantly changed practice. Dual energy computed tomography is being increasingly adopted owing to benefits of material separation, quantification, and improved contrast-to-noise ratio. The radiation dose can match that from single energy computed tomography. Spectral information derived from a polychromatic x-ray beam at different energies yields in image reconstructions that reduce the number of phases in a multiphasic examination and decrease the absolute amount of contrast media. This increased analytical and image processing capability provides new avenues for addressing radiation dose and iodine exposure concerns.

Split-bolus single scan CTA for evaluation of mesenteric ischemia

PURPOSE

To evaluate split-bolus single scan CTA protocol for evaluation of acute mesenteric ischemia.

MATERIALS AND METHODS

In this HIPAA-compliant IRB-approved study, consecutive patients evaluated for mesenteric ischemia between 11/2015 and 10/2016 were included. Patients scanned prior to 4/2016 were scanned with multiphasic CTA protocol and after with split-bolus single scan CTA. Objective and subjective evaluation was performed by three board-certified readers. Findings were correlated to composite clinical reference outcome.

RESULTS

Eighty patients were included: 40 with split-bolus and 40 with multiphasic CTA protocol with similar age (60.3 ± 16.2 years vs. 64.7 ± 17.0 years, p = 0.19) and BMI (28.0 ± 6.7 vs. 27.0 ± 8.7, p = 0.56). SMA attenuation was higher in multiphasic protocol compared to split-bolus protocol (336.5 ± 97.5 HU vs. 258.0 ± 67.3 HU, p < 0.001) with similar SMV attenuation (multiphasic 213.7 ± 58.4 HU vs. split-bolus 194.2 ± 52.2 HU, p = 0.14). Optimal phase of bowel, liver, and spleen enhancement was seen in similar high proportion (94-99%) in both protocols. There were 8/40 (20%) positive cases of mesenteric ischemia in each group. There was no difference in the diagnostic confidence of the readers for evaluation of the mesenteric vessels and bowel ischemia. There were no missed cases of mesenteric ischemia in either group. Mean effective dose was 42% lower in the split-bolus group, p < 0.001. There was a higher number of axial images to review in multiphasic protocol compared to split-bolus protocol (437.9 ± 48.7 vs. 263.5 ± 31.2, p < 0.001).

CONCLUSIONS

The split-bolus protocol for evaluation of mesenteric ischemia is clinically feasible with confident and accurate diagnostic ability, while reducing number of images and decreasing radiation exposure to the patient.

Pancreatic Adenocarcinoma Staging in the Era of Preoperative Chemotherapy and Radiation Therapy

Pancreatic ductal adenocarcinoma (PDA) remains among the most challenging malignancies to treat. At diagnosis, the tumor often already extends beyond the confines of the pancreas, spreading to an extent such that primary surgery with curative intent is very rarely feasible. Considerable momentum is now being given to a treatment strategy involving neoadjuvant chemotherapy or chemotherapy and radiation therapy in patients with nonmetastatic PDA. The main advantage of this strategy is better selection of patients likely to benefit from curative-intent surgery through the achievement of negative resection margins. Patients with rapidly progressive disease are identified and are spared ineffective surgery with its attendant morbidity. Neoadjuvant therapy can downstage tumors classified as locally advanced at initial imaging studies to resectable tumors. However, the imaging study evaluation of the response to neoadjuvant therapy is extremely complex. Thus, the diagnostic performance of imaging studies is not sufficient to ensure the accurate selection of patients in whom negative-margin resection is likely to be achieved. More specifically, standard criteria for predicting vascular invasion, based on the amount of tumor-vessel contact, are not valid after neoadjuvant therapy. ^©RSNA, 2018.

Advances in Pancreatic CT Imaging

OBJECTIVE

The purpose of this article is to discuss the advances in CT acquisition and image postprocessing as they apply to imaging the pancreas and to conceptualize the role of radiogenomics and machine learning in pancreatic imaging.

CONCLUSION

CT is the preferred imaging modality for assessment of pancreatic diseases. Recent advances in CT (dual-energy CT, CT perfusion, CT volumetry, and radiogenomics) and emerging computational algorithms (machine learning) have the potential to further increase the value of CT in pancreatic imaging.

Applicability of current NCCN Guidelines for pancreatic adenocarcinoma resectability: analysis and pitfalls

PURPOSE

To test the applicability of National Comprehensive Cancer Network (NCCN v 3.2017) resectability criteria for pancreatic ductal adenocarcinoma (PDAC) in clinical practice, at a high-volume tertiary referral center.

MATERIALS AND METHODS

102 consecutive patients (53 female; mean age 66.2 years, range 34-90 years) with biopsy proven, non-metastatic PDAC were evaluated by our multidisciplinary pancreatic cancer program between July 2013 and February 2016. Retrospective review of staging pancreatic CT angiography was performed, and radiographic features were categorized as conforming to or non-conforming to existing v 3.2017 definitions.

RESULTS

Among 102 patients, 10 (10%) had CTA evidence of vascular involvement that did not conform to existing NCCN Guidelines. Six new scenarios of vascular involvement were identified. The remaining 92 patients presented with resectable (n = 20 [22%]), borderline resectable (n = 42 [45.6%]), or unresectable (n = 30 [33%]) PDAC. Approximately half (n = 21 [51%]) of borderline resectable patients' tumors demonstrated isolated venous involvement, whereas 39% had both arterial and venous involvement. A minority (11%) demonstrated only major arterial involvement. Assignment to unresectable status reflected both arterial and venous involvement (11, 37%), arterial involvement only (10, 33%) patients, and unreconstructible venous involvement in 9 (30%).

CONCLUSION

In our experience, current NCCN resectability guidelines for PDAC do not accurately classify vascular involvement identified in approximately 10% of patients. Revision of the current guidelines could be helpful to clinical practice.

Pancreatic adenocarcinoma: cross-sectional imaging techniques

Pancreatic adenocarcinoma is a common malignancy that has a poor prognosis. Imaging is vital in its detection, staging, and management. Although a variety of imaging techniques are available, MDCT is the preferred imaging modality for staging and assessing the resectability of pancreatic adenocarcinoma. MR also has an important adjunct role, and may be used in addition to CT or as a problem-solving tool. A dedicated pancreatic protocol should be acquired as a biphasic technique optimized for the detection of pancreatic adenocarcinoma and to allow accurate local and distant disease staging. Emerging techniques like dual-energy CT and texture analysis of CT and MR images have a great potential in improving lesion detection, characterization, and treatment monitoring.

Split-bolus pancreas CTA protocol for local staging of pancreatic cancer and detection and characterization of liver lesions

PURPOSE

To validate the use of a split-bolus pancreas CTA protocol for local staging of pancreatic cancer and to evaluate its ability to detect and characterize liver lesions.

METHODS

Consecutive patients with pancreatic cancer who underwent split-bolus pancreas CTA between 12/2015 and 12/2016 were included in this IRB-approved HIPAA-compliant retrospective study. Objective evaluation of the abdominal vessels, the pancreas, the liver, and lesions, if present, was performed with attenuation measurements and tumor conspicuity and contrast-to-noise ratio (CNR) calculations. An abdominal radiologist with 20 years of experience performed subjective evaluation of image quality and blindly detected and characterized liver lesions. Any inconclusive findings or grading scores were evaluated in consensus with another abdominal radiologist with 7 years of experience. Liver findings were validated using a composite reference standard to assess accuracy.

RESULTS

There were 82 pancreatic cancer patients with a total of 91 liver findings. Tumor conspicuity and CNR were 60.8 ± 35.1 HU and 8.0 ± 5.8 for the pancreatic lesions and 58 ± 34.7 HU and 9.7 ± 6.3 for the liver lesions, respectively. The accuracy, sensitivity, and specificity of the split-bolus protocol for the hepatic findings were correspondingly 89/91 (97.8%, 95% CI 92.3-99.4), 58/60 (96.7%, 95% CI 88.6-99.1), and 33/33 (100%, 95% CI 89.6-100). The subjective image quality ratings were optimal in more than 89% of the cases for various structures, with no non-diagnostic ratings.

CONCLUSION

Split-bolus pancreas CTA protocol allows for detection and staging of pancreatic cancer, both for the primary tumor and detection and characterization of liver lesions.

Split-bolus intravenous contrast material injection vs. single-bolus injection in patients following endovascular abdominal aortic repair (EVAR)

PURPOSE

To investigate the feasibility and accuracy of a split-bolus contrast injection CTA (SB-CTA) compared to a single-bolus injection CTA (SI-CTA) protocol of post-EVAR patients.

MATERIALS AND METHODS

In this IRB-approved study, patients who underwent SB-CTA and SI-CTA after EVAR were evaluated. Attenuation and contrast-to-noise ratio (CNR) of vessels and parenchymal organs were assessed. Subjective enhancement of vessels, quality of 3D reconstructions, and enhancement phase of parenchymal organs were assessed by two independent readers. Endoleak visibility and incidental findings were evaluated.

RESULTS

Fifty-six patients with SB-CTA and SI-CTA at two different time points after EVAR were included in the study (112 imaging studies, mean age 75 ± 9 years). There was no difference in attenuation and CNR for aorta between SB-CTA and SI-CTA (310 ± 87 vs. 311 ± 80 HU, p = 0.88; 31.1 ± 12.6 vs. 29.0 ± 12.2, p = 0.20), although both were improved in the venous structures and parenchymal organs with SB-CTA (portal vein: 149 ± 33 vs. 88 ± 32 HU, 11.6 ± 5.6 vs. 4.3 ± 3.4; liver: 91 ± 19 vs. 68 ± 20 HU, 4.4 ± 2.8 vs. 2.1 ± 2.0; pancreas: 108 ± 27 vs. 82 ± 23 HU, 6.4 ± 3.1 vs. 3.6 ± 2.4; p < 0.0001). Subjectively, enhancement of veins, liver, spleen, bowel, and kidneys was improved (p < 0.001), while there was no difference for the aorta (p = 0.46) and 3D reconstructions (p = 0.58). None of the 18/56 (32.1%) endoleaks was missed with the SB-CTA. More incidental findings were detected with SB-CTA (158/56) compared to SI-CTA (135/56), p < 0.001. SB-CTA was able to adequately characterize 7/15 (47%) of the findings that needed further evaluation in SI-CTA. 4/15 (26%) incidental findings that were missed with SI-CTA but seen with SB-CTA required further evaluation.

CONCLUSION

Split-bolus injection CTA in the follow-up of EVAR patients allows reliable visualization of endoleaks with improved subjective and objective image quality.

Split-Bolus Injection Producing Simultaneous Late Arterial and Portal Venous Phases in CT Enterography: Preliminary Results

OBJECTIVE

The purpose of this article is to evaluate the image quality and added value of split-bolus contrast agent injection combining late arterial and portal venous phases compared with single-bolus contrast agent injection late arterial phase CT enterography.

MATERIALS AND METHODS

Consecutive patients who underwent CT enterography before and after implementation of a single-bolus CT enterography protocol were included. Attenuation and contrast-to-noise ratio (CNR) were assessed by ROI measurements of the bowel wall and arterial and venous structures. Subjective enhancement of the bowel wall (1, arterial; 2, mucosal; 3, transmural; 4, transmural with mucosal hyperenhancement) and bowel abnormalities were assessed by two independent readers. MR enterography examinations, endoscopy reports, and surgery reports within 30 days after CT enterography were used to produce a composite outcome.

RESULTS

Sixty-six patients were included in our study: 33 (mean [± SD] age, 46.0 ± 19.8 years) who underwent split-bolus CT enterography and 33 (mean age, 49.9 ± 19.0 years) who underwent single-bolus CT enterography. Bowel wall attenuation and CNR were higher for split-bolus CT enterography than for single-bolus CT enterography at 120 kVp (enhancement, 98.7 ± 23.1 HU vs 85.1 ± 23.3 HU; CNR, 6.4 ± 2.5 vs 4.4 ± 2.3; p < 0.01). Subjective ratings of bowel wall enhancement were higher with the split-bolus CT enterography than the single-bolus CT enterography (2.6 ± 0.8 vs 2.3 ± 0.6; p < 0.001). Split-bolus CT enterography led to a higher detection rate of mucosal hyperenhancement than did single-bolus CT enterography in patients with active inflammatory bowel disease (100.0% [7/7; 95% CI, 59.0-100.0%] vs 33.3% [2/6; 95% CI, 4.3-77.7%]; p = 0.02), whereas both protocols had a specificity of 100.0% (9/9).

CONCLUSION

Split-bolus CT enterography led to improved CNR (47%) compared with single-bolus CT enterography and significantly increased the detection rate of mucosal hyperenhancement in patients with active inflammatory bowel disease.

Simplified split-bolus intravenous contrast injection technique for pediatric abdominal CT

PURPOSE

To investigate pediatric abdominal CT using a simplified split-bolus (Split group) contrast injection compared with a single bolus (Control group).

METHODS

Radiation dose, image quality and diagnostic accuracy were compared.

RESULTS

Split group demonstrated lower effective dose (2.46 vs. 2.85mSv, p=0.002) and noise levels in aorta, liver and portal vein (p<0.001). There was one false-negative case of portal vein obliteration in the Split group.

CONCLUSIONS

A simple method of split-bolus intravenous contrast injection technique can provide adequate and homogeneous enhancement in pediatric abdominal CT.

Variations in the functional visual field for detection of lung nodules on chest computed tomography: Impact of nodule size, distance, and local lung complexity

PURPOSE

To explore the characteristics that impact lung nodule detection by peripheral vision when searching for lung nodules on chest CT-scans.

METHODS

This study was approved by the local IRB and is HIPAA compliant. A simulated primary (1°) target mass (2 × 2 × 5 cm) was embedded into 5 cm thick subvolumes (SV) extracted from three unenhanced lung MDCT scans (64 row, 1.25 mm thickness, 0.7 mm increment). One of 30 solid, secondary nodules with either 3-4 mm and 5-8 mm diameters were embedded into 192 of 207 SVs. The secondary nodule was placed at a random depth within each SV, a transverse distance of 2.5, 5, 7.5, or 10 mm, and along one of eight rays cast every 45° from the center of the 1° mass. Video recordings of transverse paging in cranio-caudal direction were created for each SV (frame rate three sections/sec). Six radiologists observed each cine-loop once while gaze-tracking hardware assured that gaze was centered on the 1° mass. Each radiologist assigned a confidence rating (0-5) to the detection of a secondary nodule and indicated its location. Detection sensitivity was analyzed relative to secondary nodule size, transverse distance, radial orientation, and lung complexity. Lung complexity was characterized by the number of particles (connected pixels) and the sum of the area of all particles above a -500 HU threshold within regions of interest around the 1° mass and secondary nodule.

RESULTS

Using a proportional odds logistic regression model and eliminating redundant predictors, models fit individually to each reader resulted in the following decreasing order of association based on greatest reduction in Akaike Information Criterion: secondary nodule diameter (6/6 readers, P < 0.001), distance from central mass (6/6 readers, P < 0.001), lung complexity particle count (5/6 readers, P = 0.05), and lung complexity particle area (3/6 readers, P = 0.03). Substantial inter-reader differences in sensitivity to decreasing nodule diameter, distance, and complexity characteristics were observed.

CONCLUSIONS

Of the investigated parameters, secondary nodule size, distance from the gaze center and lung complexity (particle number and area) significantly impact nodule detection with peripheral vision.

Abdominal Applications of a Novel Detector-Based Spectral CT

Detector-based spectral computed tomography (SDCT) is a recently introduced technology that uses a single x-ray tube and 2 layers of detectors to simultaneously collect low- and high-energy data. In this article, we provide an overview of this novel SDCT technology in abdominal imaging. Several applications of SDCT in abdominal imaging are discussed and illustrated, along with a brief description of current literature on the status of dual-energy computed tomography in these applications. This includes urinary calculus composition, characterization of masses (renal, adrenal, hepatic, and others), tumor perfusion, improving vascular contrast, improving lesion conspicuity, decreasing artifacts, and reducing radiation dose.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 4: Abdominal and Pelvic Applications

This is the fourth of a series of 4 white papers that represent expert consensus documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This article, part 4, discusses DECT for abdominal and pelvic applications and, at the end of each, will offer our consensus opinions on the current clinical utility of the application and opportunities for further research.

Multidetector computer tomography in the pancreatic adenocarcinoma assessment: an update

Ductal adenocarcinoma of the pancreas is one of the most aggressive forms of cancer, with only a minority of cases being resectable at the moment of their diagnosis. The accurate detection and characterization of pancreatic carcinoma is very important for patient management. Multidetector-row computed tomography (MDCT) has become the cross-sectional modality of choice in the diagnosis, staging, treatment planning, and follow-up of patients with pancreatic tumors. However, approximately 11% of ductal adenocarcinomas still remain undetected at MDCT because of the lack of attenuation gradient between the lesion and the adjacent pancreatic parenchyma. In this systematic literature review we investigate the current evolution of the CT technique, limitations, and perspectives in the evaluation of pancreatic carcinoma.

Split-Bolus Multidetector-Row Computed Tomography Technique for Characterization of Focal Liver Lesions in Oncologic Patients

BACKGROUND

In oncologic patients, the liver is the most common target for metastases. An accurate detection and characterization of focal liver lesions in patients with known primary extrahepatic malignancy are essential to define management and prognosis.

OBJECTIVES

To assess the diagnostic accuracy of the split-bolus multidetector-row computed tomography (MDCT) protocol in the characterization of focal liver lesions in oncologic patients.

PATIENTS AND METHODS

We retrospectively analyzed the follow-up split-bolus 64-detector row CT protocol in 36 oncologic patients to characterize focal liver lesions. The split-bolus MDCT protocol by intravenous injection of two boluses of contrast medium combines the hepatic arterial phase (HAP) and hepatic enhancement during the portal venous phase (PVP) in a single-pass.

RESULTS

The split-bolus MDCT protocol detected 208 lesions and characterized 186 (89.4%) of them: typical hemangiomas (n = 9), atypical hemangiomas (n = 3), cysts (n = 78), hypovascular (n = 93) and hypervascular (n = 3) metastases. Twenty two (10.6%) hypodense lesions were categorized as indeterminate (≤5 mm). The mean radiation dose was 24.5±6.5 millisieverts (mSv).

CONCLUSION

The designed split-bolus MDCT technique can be proposed alternatively to triphasic MDCT and in a single-pass to PVP in the initial staging and in the follow-up respectively in oncologic patients.

Utility of virtual unenhanced images and split-bolus injection using spectral multidetector CT for the assessment of renal cell carcinoma conspicuity and radiation dose

OBJECTIVE

The aim of this study was to evaluate the radiation dose and renal cell carcinoma conspicuity with virtual unenhanced images and split-bolus injection from spectral multidetector CT (MDCT).

MATERIAL AND METHODS

This prospective study was approved by the Ethics Committee, and informed consent was obtained. Ninety suspected patients of renal cell carcinoma diagnosed by abdominal ultrasonography and CEUS were randomly divided into two groups by a radiographer. Patients of the first group underwent spectral MDCT with virtual unenhanced imaging and split-bolus injection, while patients in the second group underwent conventional unenhanced as well as tri-phasic enhanced CT. Group A (split-bolus spectral MDCT group): The contrast material was administered at a dose of 1.5 mL/kg body weight at a flow rate of 4 mL/s, with a ratio of 7 to 5 before the CT scan with an interval of 60 seconds. Virtual unenhanced images were generated using a standard three-material decomposition algorithm, and the best mono-energy (keV) was calculated to show the tumour, renal artery and renal vein. Group B (conventional tri-phasic enhanced CT group): the contrast agent was injected with a dose of 1.5 mL/kg body weight at a flow rate of 4 mL/s. The corticomedullary phase scanning was performed once the arterial CT value reached 100 HU; the nephrographic phase was scanned 60 seconds later. And the excretory phase was scanned 5 min after onset of contrast injection. The LKR (lesion kidney ratio), CNR, and CT value of the corticomedullary and nephrographic phase were measured. The opacification of the renal collection system (including calices, infundibula and renal pelvis) was scored. The radiation dose was recorded. Statistical analysis was performed using Student's t-test, Fisher's exact test, the Mann-Whitney U-test, and k statistics.

RESULTS

There were no statistically significant differences between the two groups in age, sex and body mass index (BMI), but there was significant difference in treatment methods. The best mono-energy was 58 keV for showing the tumour and renal artery and 67 keV for showing the renal vein. There were no differences in the mean attenuations of normal renal parenchyma, renal tumour, CNR, and imaging quality between true unenhanced images and virtual unenhanced images from the combined corticomedullary and nephrographic phase. The LKR of the mono-energy at 58 keV from the combined corticomedullary and nephrographic phase was significantly better than the corticomedullary phase of the conventional enhanced CT scan (0.74±0.18 vs 1.08±0.34, P<.01), but there was no difference in CNR (2.31±1.74 vs 2.79±1.83, P>.05). There were no differences in the CT values of the renal tumour, normal renal parenchyma and renal artery between the two groups (P>.05). The CT value of the renal vein at mono-energy (67 keV) (200.55±43.38) from the combined corticomedullary and nephrographic phase was higher than the conventional CT scan (140.90±42.64) in the nephrographic phase. The Kappa scores of the rate of the renal collection system for the conventional CT and spectral CT were 0.68 (95% confidence interval [CI]: 0.35-0.89) and 0.54 (95% CI: 0.30-0.88), respectively. The radiation dose (735±162 mGy·cm) of Group A was significantly less than that of Group B (1032±324 mGy·cm) (P<.01).

CONCLUSION

Conspicuity with virtual unenhanced imaging and split-bolus injection from spectral multidetector CT is better than or equal to the conventional three-phase enhanced CT scan in showing the RCC, renal artery and renal vein, while the radiation dose can be reduced by 28.78%.

Feasibility of spectral imaging with low-concentration contrast medium in abdominal CT angiography of obese patients

OBJECTIVE

To explore the application value of dual-energy spectral imaging scanning with low radiation dose and low-concentration contrast medium (270 mg I/mL) in abdominal CT angiography (CTA) of obese patients.

METHODS

A total of 127 obese patients (BMI≥25 kg/m(2) and waist circumference ≥900 mm) referred for abdominal CTA were prospectively enrolled in the study. The patients were divided into two groups; in group A (n=69), a spectral imaging scan mode and 270 mg I/mL iodine concentration contrast medium was used, and in group B (n=58), a conventional imaging scan mode using 120 kVp and 350 mg I/mL iodine concentration contrast medium was used. The image quality of the right renal artery in the two groups was evaluated by two observers using a 5-point scale, and the scores were compared using the Mann-Whitney U-test; the inter-observer agreement for the scores was analysed using the Kappa test. The CT values of the abdominal aorta, the superior mesenteric artery, the common hepatic artery and the splenic artery, and the CT value and standard deviation (SD) of the erector spinae at the level of the right renal hilum in groups A and B were measured by two observers; the inter-observer agreement of the measurement data was analysed using the inter-class correlation coefficient test. The following parameters were compared between the two groups using an independent sample t-test: the CT values of the abdominal aorta and its main branches; the image contrast-to-noise ratio (CNR) and figure of merit (FOM) of the abdominal aorta; the CT dose index (CTDIvol ); the dose length product (DLP); and the total iodine intake of the patients. P<.05 suggested a statistically significant difference.

RESULTS

The image scores of the right renal artery in groups A (4.59±0.60) and B (4.53±0.63) were the same (P=.57), with good inter-observer agreement. The CT values of the abdominal aorta, the superior mesenteric artery, the common hepatic artery and the splenic artery were >300 HU in both the groups; there was no statistically significant difference between the two groups (all P>.05), and inter-observer agreement was also good. Group A had significantly higher CNR and FOM values in the abdominal aorta than group B (all P<.001). Compared with group B, the CTDIvol and DLP values in group A were decreased by 46% and 35%, respectively. The total iodine intake for patients in group A was 27 g, 23% lower than the 35 g intake for patients in group B.

CONCLUSION

Compared with conventional CT, spectral CT imaging significantly reduces both radiation dose and contrast dose while maintaining image quality in abdominal CTA for patients with central obesity and high BMI.

Split-Bolus Single-Pass Multidetector-Row CT Protocol for Diagnosis of Acute Pulmonary Embolism

Background:

Currently computed tomography pulmonary angiography (CTPA) has become a widely accepted clinical tool in the diagnosis of acute pulmonary embolism (PE).

Objectives:

To report split-bolus single-pass 64-multidetector-row CT (MDCT) protocol for diagnosis of PE.

Patients and Methods:

MDCT split-bolus results in 40 patients suspicious of PE were analyzed in terms of image quality of target pulmonary vessels (TPVs) and occurrence and severity of flow-related artifact, flow-related artifact, false filling defect of the pulmonary veins and beam hardening streak artifacts. Dose radiation to patients was calculated.

Results:

MDCT split-bolus protocol allowed diagnostic images of high quality in all cases. Diagnosis of PE was obtained in 22 of 40 patients. Mean attenuation for target vessels was higher than 250 HU all cases: 361 ± 98 HU in pulmonary artery trunk (PAT); 339 ± 93 HU in right pulmonary artery (RPA); 334 ± 100 HU in left pulmonary artery (LPA). Adequate enhancement was obtained in the right atrium (RA):292 ± 83 HU; right pulmonary vein (RPV): 302 ± 91 HU, and left pulmonary vein (LPV): 291 ± 83 HU. The flow related artifacts and the beam hardening streak artifacts have been detected respectively in 4 and 25 patients. No false filling defect of the pulmonary veins was revealed.

Conclusion:

MDCT split-bolus technique by simultaneous opacification of pulmonary arteries and veins represents an accurate technique for diagnosis of acute PE, removes the false filling defects of the pulmonary veins, and reduces flow related artifacts.

Multireader evaluation of lesion conspicuity in small pancreatic adenocarcinomas: complimentary value of iodine material density and low keV simulated monoenergetic images using multiphasic rapid kVp-switching dual energy CT

OBJECTIVE

Perform multireader analysis of objective and subjective lesion conspicuity for small pancreatic adenocarcinomas using rapid switching dual energy CT (rsDECT).

MATERIALS AND METHODS

With IRB approval, 51 abdominal multiphasic rsDECT scans in 46 subjects with small (<3 cm) pancreatic adenocarcinomas were retrospectively reviewed by three independent readers for objective and subjective lesion conspicuity. Measured variables during individual, blinded interpretive sessions of separate low (52) keV, PACS-equivalent (70) keV, and iodine material density (MD) image sets included Hounsfield units (HU) and mg/cc iodine for tumor, nontumoral pancreas, and subcutaneous fat. Objective measures included absolute lesion contrast (LC) and contrast to noise ratios (CNR). Subjective measures included image quality, lesion conspicuity, and reader confidence. Reader agreement was measured with kappa statistic; correlation with truth by Pearson coefficient, CNR with repeated mANOVA; subjective quality measures utilized Tukey-Cramer corrections for multiple testing, p < 0.05 considered significant.

RESULTS

Demographics: 26 F, 20 M, mean age 68 years, weight 75 kg, tumor size of 2.3 cm. LC was highest on 52 keV images for all three readers (mean 90.1 HU). Mean CNR for iodine MD images (4.87) was significantly higher than 52 keV (4.13) or 70 keV (3.9). Very high to near-perfect kappa values were observed for all individual measured objective variables but were best for 52 keV images (52 keV 0.89-0.95, 70 keV 0.76-0.83, iodine 0.87-0.92). 70 keV images scored best for subjective image quality; iodine MD images scored best for lesion conspicuity and reader confidence.

CONCLUSION

We observed very high reader agreement for independent objective rsDECT image variables and subjective rsDECT image scores in patients with small pancreatic adenocarcinomas. Maximal objective tumor to nontumoral LC was depicted on 52 keV and highest CNR on iodine MD images; readers scored the iodine MD images best for lesion conspicuity and confidence.

Quantitative and Qualitative Comparison of Single-Source Dual-Energy Computed Tomography and 120-kVp Computed Tomography for the Assessment of Pancreatic Ductal Adenocarcinoma

PURPOSE

The aim of this study was to compare contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) between pancreatic-phase dual-energy computed tomography (DECT) and 120-kVp CT for pancreatic ductal adenocarcinoma (PDA).

MATERIALS AND METHODS

Seventy-eight patients underwent multiphasic pancreatic imaging protocols for PDA (40, DECT; 38, 120-kVp CT [control]). Using pancreatic phase, CNR and SNR for PDA were obtained for DECT at monochromatic energies 50 through 80 keV, iodine material density images, and 120-kVp images. Using a 5-point scale (1, excellent; 5, markedly limited), images were qualitatively assessed by 2 radiologists in consensus for PDA detection, extension, vascular involvement, and noise. Wilcoxon signed rank and 2-sample tests were used to compare the qualitative measures, CNR and SNR, for DECT and 120-kVp images. Bonferroni correction was applied.

RESULTS

Iodine material density image had significantly higher CNR and SNR for PDA than any monochromatic energy images (P < 0.0001) and the 120-kVp images. Qualitatively, 70-keV images were rated highest in the categories of tumor extension and vascular invasion and were similar to 120-kVp images.

CONCLUSIONS

Our results indicate that DECT improves PDA lesion conspicuity compared with routine 120-kVp CT, which may allow for better detection of PDA.