Post-contrast Phase Research Articles

Accelerated dynamic contrast enhanced MRI based on region of interest compressed sensing

Magnetic Resonance Imaging (MRI) provides excellent soft tissue contrast with one significant limitation of slow data acquisition. Dynamic Contrast Enhanced MRI (DCE-MRI) is one of the widely employed techniques to estimate tumor tissue physiological parameters using contrast agents. DCE-MRI data acquisition and reconstruction requires high spatiotemporal resolution, especially during the post-contrast phase. The region of Interest Compressed Sensing (ROICS) is based on Compressed Sensing (CS) framework and works on the hypothesis that limiting CS to an ROI can achieve superior CS performance. In this work, ROICS has been demonstrated on breast DCE-MRI data at chosen acceleration factors and the results are compared with conventional CS implementation. Normalized Root Mean Square Error (NRMSE) was calculated to compare ROICS with CS quantitatively. CS and ROICS reconstructed images were used to compare Ktrans and ve values derived using standard Tofts Model (TM). This also validated the superior performance of ROICS over conventional CS. ROICS generated Concentration Time Curves (CTC's) at chosen acceleration factors follow similar trend as the ground truth data as compared to CS. Both qualitative and quantitative analyses show that ROICS outperforms CS particularly at acceleration factors of 5× and above.

Errors in Interpretation of Magnetic Resonance Imaging for Thymic Lesions.

The objectives of this study were to evaluate the magnetic resonance imaging (MRI) features of thymic lesions and to review those features that may result in diagnostic uncertainty or error. This multicenter retrospective study included patients with pathologically proven thymic epithelial neoplasms (TEN) and thymic cysts who underwent preoperative MRI. Clinical reports were evaluated for the radiologist's first-choice diagnosis, if not already known before the MRI. MR images were reviewed by thoracic radiologists to identify cystic components on T2-weighted imaging (T2WI) as well as the presence of enhancement on postcontrast series. Through a search of electronic medical records of 3 tertiary academic medical centers, we identified 41 TEN and 13 cysts. Of 35 evaluable clinical reports, 9 (26%) gave an incorrect diagnosis. Of these, 5 cases were misdiagnosed related to contrast enhancement, and 3 cases of cysts were misdiagnosed because of lack of fluid signal on T2WI. Upon rereview of images, of the 41 TENs, 4 (10%) did not show qualitative enhancement on the first postcontrast phase (although all enhanced eventually), and 4 cysts (31%) did not show fluid signal on T2WI. In addition, 4 cases of cysts (31%) showed mural or septal enhancement. Although atypical or misleading imaging features are uncommon in TEN and thymic cysts, they do occur and may lead to diagnostic error. We suggest that lesions with a T2 signal less than simple fluid and without enhancement on postcontrast images undergo follow-up imaging to confirm a benign diagnosis.

Association of tumor grade, enhancement on multiphasic CT and microvessel density in patients with clear cell renal cell carcinoma.

Clear cell renal cell carcinoma (ccRCC) comprises nearly 90% of all diagnosed RCC subtypes and has the worst prognosis and highest metastatic potential. The strongest prognostic factors for patients with ccRCC include histological subtype and Fuhrman grade, which are incorporated into prognostic models. Since ccRCC is a highly vascularized tumor, there may be differences in enhancement patterns on multidetector CT (MDCT) due to the hemodynamics and microvessel density (MVD) of the lesions. This may provide a noninvasive method to characterize incidentally detected low- and high-grade ccRCCs on MDCT. The purpose of our study was to determine the correlation between MDCT enhancement parameters, ccRCC MVD, and Fuhrman grade to determine its utility and value in assessing tumor vascularity and grade in vivo. In this retrospective, HIPAA-compliant, institutional review board-approved study with waiver of informed consent, 127 consecutive patients with 89 low-grade (LG), and 43 high-grade (HG) ccRCCs underwent preoperative four-phase MDCT. A 3D volume of interest (VOI) was obtained for every tumor and absolute enhancement and the wash-in/wash-out of enhancement for each phase was assessed. Immunohistochemistry on resected specimens was used to quantify MVD. Linear regression and Pearson correlation were used to investigate the strength of the association between3D VOI enhancement and MVD. Stepwise logistic regression analysis determined independent predictors of HG ccRCC. Cut-off values and odds Ratio (OR) with 95% CIs were reported. The clinical, radiomic, and pathologic features with the highest performance in the stepwiselogistic regression analysis were evaluated using receiver operator characteristics (ROC) and area under the curve (AUC). Absolute enhancement in the nephrographic phase < 52.1 Hounsfield Units (HU) (HR 0.979, 95% CI 0.964-0.994, p value = 0.006), lesion size > 4.3cm (HR 1.450, 95% CI 1.211-1.738, p value < 0.001), and an intratumoral MVD < 15% (HR 0.932, 95% CI 0.867-1.002, p value = 0.058) were independent predictors of HG ccRCC with an AUC of 0.818 (95% CI 0.725-0.911). HG ccRCCs had a significant association between3D VOI enhancement and MVD in each post-contrast phase (r2 = 0.238 to 0.455, p < 0.05). Absolute enhancement of the entire lesion obtained from a 3DVOI in the nephrographic phase on preoperative MDCT can provide quantitative data that are a significant, independent predictor of a high-grade clear cell RCC and can be used to assess tumor vascularity and grade in vivo.

Prediction of Histopathologic Growth Patterns of Colorectal Liver Metastases with a Noninvasive Imaging Method.

To predict histopathologic growth patterns (HGPs) in colorectal liver metastases (CRLMs) with a noninvasive radiomics model. Patients with chemotherapy-naive CRLMs who underwent abdominal contrast-enhanced multidetector CT (MDCT) followed by partial hepatectomy between January 2007 and January 2019 from two institutions were included in this retrospective study. Hematoxylin- and eosin-stained histopathologic sections of CRLMs were reviewed, with HGPs defined according to international consensus. Lesions were divided into training and validation datasets based on patients' sources. Radiomic features were extracted from pre- and post-contrast (arterial and portal venous) phase MDCT images, with review focusing on the segmented tumor-liver interface zones of CRLMs. Minimum redundancy maximum relevance and decision tree methods were used for radiomics modeling. Multivariable logistic regression analyses and ROC curves were used to assess the predictive performance of these models in predicting HGP types. A total of 126 CRLMs with histopathologic-demonstrated desmoplastic (n = 68) or replacement (n = 58) HGPs were assessed. The radiomics signature consisted of 20 features of each phase selected. The 3 phases fused radiomics signature demonstrated the best predictive performance in distinguishing between replacement and desmoplastic HGPs (AUCs of 0.926 and 0.939 in the training and external validation cohorts, respectively). The clinical-radiomics combined model showed good discrimination (C-indices of 0.941 and 0.833 in the training and external validation cohorts, respectively). A radiomics model derived from MDCT images may effectively predict the HGP of CRLMs, thus providing a basis for prognostic stratification and therapeutic decision-making.

3000 A Diagnostic Dilemma: Ovarian Cancer or a Pancreatic Neuroendocrine Carcinoma

INTRODUCTION: Small cell pancreatic neuroendocrine carcinoma (P-NEC) is in a group of malignancies described as Gastroenteropancreatic (GEP) NEC, and is an extremely rare neoplasm. We present a case of P-NEC with confounding findings of multiple ovarian and pancreatic masses. CASE DESCRIPTION/METHODS: A 33-year-old European female with history of ovarian cysts (∼4 cm × 5 cm) presented with a ten-day history of lower abdominal/pelvic pain with new onset ascites and weight gain. No family history of GI or gynecologic malignancy. A CT (Figure 1a,b) of her abdomen and pelvis showed ascites, multiple pancreatic hypodense lesions and enlarged cystic ovaries (10 × 11 cm). Subsequent MRI pancreatic protocol (Figure 1c,d), and an endoscopic ultrasound (EUS-FNB) was performed. MRI showed diffusely abnormal pancreas with multiple focal solid masses with T2 hyper intense, T1 hypo intense, and hypo-enhancing lesions on early post contrast phases with no pancreatic ductal dilation or cystic component. EUS confirmed multiple hypodense pancreatic lesions but the findings were not consistent with primary pancreatic malignancy. Cytopathology of gastric nodules (Figure 2) and the pancreatic FNB (Figure 3) showed small cell NEC with a Ki-67 proliferative index (PI) of 43%. Pathology showed infiltrative process with small blue cells and scant cytoplasm. The IHC was positive for synaptophysin, chromogranin, CD56, weakly positive for CAM5.2 and AE1/AE3, negative for TTF-1, PAX8, CD45, CDX2, ER, and inhibin. The diagnosis was pancreatic small cell NEC. The enlarged ovarian cysts were determined to be an incidental finding, and not a primary source of the malignancy. DISCUSSION: Generally, the well differentiated pancreatic neuroendocrine tumors (NET) are hormone secreting; however, the GEP NEC are a highly aggressive poorly differentiated carcinoma and designated as grade 3 tumors. Grading is based on the Ki-67 PI and mitotic count/index (Table 1). Our patient had GEP NEC given her Ki-67 PI was 43%. Chemotherapy and/or surgical resection are the two treatment options, but by the time of late diagnosis the goal of the treatment is generally palliative. Our case emphasizes the importance of pursuing accurate pathological diagnosis, role of EUS in management of pancreatic neoplasms and eliminating the confounding factors (eg ovarian cysts/masses).

Image quality and pathology assessment in CT Urography: when is the low-dose series sufficient?

BackgroundOur aim was to compare CT images from native, nephrographic and excretory phases using image quality criteria as well as the detection of positive pathological findings in CT Urography, to explore if the radiation burden to the younger group of patients or patients with negative outcomes can be reduced.MethodsThis is a retrospective study of 40 patients who underwent a CT Urography examination on a 192-slice dual source scanner. Image quality was assessed for four specific renal image criteria from the European guidelines, together with pathological assessment in three categories: renal, other abdominal, and incidental findings without clinical significance. Each phase was assessed individually by three radiologists with varying experience using a graded scale. Certainty scores were derived based on the graded assessments. Statistical analysis was performed using visual grading regression (VGR). The limit for significance was set at p = 0.05.ResultsFor visual reproduction of the renal parenchyma and renal arteries, the image quality was judged better for the nephrogram phase (p < 0.001), whereas renal pelvis/calyces and proximal ureters were better reproduced in the excretory phase compared to the native phase (p < 0.001). Similarly, significantly higher certainty scores were obtained in the nephrogram phase for renal parenchyma and renal arteries, but in the excretory phase for renal pelvis/calyxes and proximal ureters. Assessment of pathology in the three categories showed no statistically significant differences between the three phases. Certainty scores for assessment of pathology, however, showed a significantly higher certainty for renal pathology when comparing the native phase to nephrogram and excretory phase and a significantly higher score for nephrographic phase but only for incidental findings.ConclusionVisualisation of renal anatomy was as expected with each post-contrast phase showing favourable scores compared to the native phase. No statistically significant differences in the assessment of pathology were found between the three phases. The low-dose CT (LDCT) seems to be sufficient in differentiating between normal and pathological examinations. To reduce the radiation burden in certain patient groups, the LDCT could be considered a suitable alternative as a first line imaging method. However, radiologists should be aware of its limitations.

Evaluation of liver MRI examinations with two dosages of gadobenate dimeglumine: a blinded intra-individual study.

There is discrepancy in the literature regarding the optimal dose of gadobenate for liver MRI. We evaluated the quality of liver MRIs performed in the same individual using two dosages. With ethics approval, this retrospective study evaluated sixty patients who underwent liver MRIs between July 2015 and May 2017 (low dose, 0.06mmol/kg) and May 2017 and September 2018 (standard dose, 0.10mmol/kg). Regions of interest were drawn over the aorta, portal veins, and liver on unenhanced and post-contrast phases; relative enhancement values were compared (paired t-tests). Two blinded radiologists graded the arterial and portal venous sequences of each MRI from 1 to 4 (1 = suboptimal, 2 = adequate, 3 = good, 4 = excellent); grades were compared overall and in cirrhotic and non-cirrhotic subgroups (Wilcoxon signed-rank test). Radiologists graded each MRI pair from 1 to 5 (1 = substantially inferior, 2 = slightly inferior, 3 = equivalent, 4 = slightly improved, 5 = substantially improved). Inter-reader agreement was assessed (kappa statistic). Relative enhancement increased significantly with the standard dose for all structures on all phases (p < 0.05). For both radiologists and both post-contrast phases, individual grades of the low- and standard-dose MRIs were similar, including the cirrhotic and non-cirrhotic subgroups (p > 0.05). Compared to the low-dose MRIs, the number of standard-dose MRIs graded 1-5 were 9, 31, 97, 88, and 11 for all patients, and 6, 13, 26, 45, and 6 in cirrhotics. Inter-observer agreement was fair-moderate (Κ range 0.23-0.45). Although the standard dose of gadobenate yields greater relative enhancement, there is overall little improvement in subjective imaging quality. A trend towards better image quality is observed in cirrhotics.

MRI in differentiating malignant versus benign portal vein thrombosis in patients with hepatocellular carcinoma: Value of post contrast imaging with subtraction

PurposeTo evaluate MR imaging parameters including quantitative multiphasic post-contrast enhancement with subtraction and qualitative diffusion weighted imaging (DWI) in differentiating benign versus malignant portal venous thrombosis (PVT) in patients with hepatocellular carcinoma (HCC). MethodRadiology reports over a 6-year period ending February 2016 were searched for key words indicating presence of both HCC and PVT on abdominal MRI. 39 patients were identified with PVT characterized as benign or malignant based on pathologic data or serial imaging growth criteria. Image review was performed by two subspecialized radiologists blinded to the diagnosis and medical chart. Signal intensity for regions of interest were recorded within the portal vein thrombus as well as the portal vein on pre-contrast and dynamic post-contrast phases without and with subtraction. Qualitative parameters for DWI and presence of PV expansion were also evaluated. ResultsPercent enhancement generated high area under the curve (AUC) for both readers on all non-subtraction phases: arterial (0.95/0.98), portal venous (0.97/0.97) and delayed phase (0.96/0.99) and subtraction phases: arterial (0.91/0.96), portal venous (0.94/0.99) and delayed phases (0.96/0.97). Statistically significant differences were observed between benign and malignant PVT for both readers for PV expansion (p= <0.001/0.006). No qualitative DWI parameter reached statistical significance for both readers. ConclusionsPost-contrast and subtraction MRI can reliably distinguish malignant from benign PVT in patients with HCC using subtracted or non-subtracted images and at arterial, portal venous, or delayed phase timing.

Kinetic Analysis of Lesions Identified on a Rapid Abridged Multiphase (RAMP) Breast MRI Protocol

We implemented a rapid abridged multiphase (RAMP) breast magnetic resonance imaging (MRI) protocol to reduce scan time and increase workflow efficiency. In this study, we compared delayed-phase kinetic analyses of benign and malignant lesions on the RAMP protocol versus a full dynamic contrast-enhanced (DCE) MRI protocol. Consecutive breast MRI examinations obtained from October 2015 to August 2016 with tissue diagnoses of suspicious MRI lesions were identified. RAMP MRI included one precontrast and two postcontrast phases. Full DCE MRI included one precontrast and at least three postcontrast phases. Lesion kinetic analyses including mean delayed-phase volume percentage of washout, predominant curve type, and worst curve type were assessed. Kinetic analyses assessed on RAMP and DCE MRI protocols were compared using Wilcoxon rank-sum test and Chi-Square test. Receiver operating characteristic analysis was performed to discriminate benign and malignant lesions based on delayed-phase parameters. The study included 177 consecutive breast lesions (50 benign, 127 malignant) in 162 women. RAMP MRI (23 benign, 61 malignant) and DCE MRI examinations (27 benign, 66 malignant) demonstrated 8.4% vs 9.3% washout (p = 0.36) for benign lesions and 18.5% vs 17% washout (p = 0.66) for malignancies, respectively. There was no difference in the predominant and worst curve types for malignant and benign lesions or in area under the receiver operating characteristic curves for delayed-phased parameters between the two protocols (p > 0.05). Lesion kinetic analyses from the RAMP MRI protocol can achieve the same discriminatory ability as the full DCE protocol. By reducing scan time, the RAMP MRI protocol improves patient comfort and enhances workflow efficiency and can be easily implemented in any clinical setting.

Dynamic contrast-enhanced MRI to predict intratumoral molecular heterogeneity in clear cell renal cell carcinoma.

4580 Background: Mutation/inactivation of VHL in clear cell renal cell carcinoma (ccRCC) leads to upregulation of hypoxia inducible factors ( HIFs) and angiogenesis. However, ccRCC is characterized by high intra-tumor heterogeneity (ITH). Random small samples such as those in percutaneous biopsies are likely limited for characterization of molecular alterations in heterogeneous ccRCCs. We hypothesize that whole-tumor dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) is useful to noninvasively identify ITH in ccRCC. Methods: This IRB-approved, prospective, HIPAA-compliant study, included 62 ccRCCs. 3T DCE MRI was obtained prior to nephrectomy. Surgical specimens were sectioned to match MRI acquisition plane. 182 snap frozen samples (49 tumors) and adjacent uninvolved renal parenchyma (URP) were collected. RNA isolations, cDNA library preparation and mRNA sequencing were performed using standard protocols. RNA expression in 81 tumor samples were correlated (Spearman ranked) with % enhancement in a region of interest (ROI) drawn in the same location of the tumor on pre- and 3 different post-contrast DCE MRI phases. Gene function overrepresentation (OR) analyses were done on top positively and negatively correlated genes. False discovery rate (FDR) &lt; 0.1 was considered statistically significant. Results: Principal component analysis of &gt; 20,000 genes indicated distinct gene expression in tumors from URP. Unsupervised clustering showed enrichment of ccA samples (better prognosis) compared to ccB samples (worse prognosis). Importantly, ccA and ccB samples coexisted in 25% of tumors. DCE-MRI % enhancement correlated with expression of &gt; 300 genes (p &lt; 0.003, FDR &lt; 0.1). OR analyses placed angiogenic pathway gene processes and the immune/inflammatory response processes within the top 5 positively- and negatively-correlated gene functions, respectively. HIF2 target genes correlated positively with % enhancement. Conclusions: DCE MRI detects specific molecular signatures and may help overcome the challenges of ITH in ccRCC. Further research is needed to explore the potential role of DCE MRI to assess response to antiangiogenic and immune-based therapies.

Deep learning segmentation of kidneys with renal cell carcinoma.

e16098 Background: Renal cell carcinoma (RCC) is the most common kidney malignancy and the eighth most common cancer overall, with more than 60,000 new cases and nearly 15,000 deaths in the United States each year. The majority of RCC is asymptomatic and detected incidentally on computed tomography (CT) scans performed for other indications. Multiple prior studies have highlighted the potential for a lesion to be missed or mischaracterized. Artificial intelligence (AI), the mimicking of human cognition by computers, has promise for improving radiological accuracy. Convolutional neural networks (CNNs), a type of AI, apply a feed-forward design to an artificial neural network. Multi-layered CNNs thus have application in biomedical imaging and radiology. In this study we describe an approach for automatic localization and segmentation of the kidneys on contrast enhanced CT scan. Methods: This IRB approved retrospective study included patients who were diagnosed with RCC and had an abdominal CT scan with IV contrast from 2011 to 2019. For each abdominal CT scan, the kidneys and any renal lesions were manually segmented by a board-certified abdominal radiologist on the coronal post-contrast phase of the CT scan. Two CNNs were developed and trained to segment the kidneys automatically. Initially, the CNN implemented a regression algorithm that predicted a 3D bounding box around each kidney. Subsequently, the second CNN used a 3D/3D U-Net algorithm that received the bounding cube as its input and outlined the kidney as an output. After training, the CNN algorithms were assessed by a Sørensen-Dice coefficient. Results: The first CNN that predicted a 3D bounding box around each kidney was trained on 127 abdominal CT exams. The second CNN that segmented the kidneys with RCC was trained on 259 bounding boxes that encompassed the kidneys. The Sørensen–Dice coefficient for segmentation of the kidneys with RCC was 0.92. Conclusions: These results demonstrate that two CNNs can be used in succession to segment the kidneys with RCC on a coronal CT image with high accuracy. Moreover, as the subjects included patients with RCC, medical renal disease, and cystic renal disease, the outcome further supports the role of CNN in evaluation of complex cases rather than pristine training sets. Future work will focus on segmentation of RCC lesions.

Spontaneous intramural hematoma of the duodenum secondary to anticoagulant drug intoxication

Introduction. Duodenal hematomas are commonly traumatic, caused by blunt abdominal trauma. Nontraumatic spontaneous intramural hematomas of the duodenum are rare, and in most cases induced by anticoagulant therapy. The diagnosis is based on clinical and biochemical parameters, endoscopy, and radiological examinations. The objective of this report was to present a clinical and radiological presentation of an intramural duodenal hematoma caused by anticoagulant therapy. Case outline. A 43-year-old female was presented with epigastric pain, nausea, hematemesis, and melena. She had a positive medical history of deep venous thrombosis of the pelvis, which was diagnosed the previous month, for which she received oral anticoagulant therapy (coumarin). Physical examination revealed diffuse abdominal tenderness, while laboratory analyses showed markedly elevated international normalized ratio (INR) of prothrombin time (INR &gt; 7), which indicated the anticoagulant intoxication. Computed tomography (CT) showed luminal narrowing with uniform circumferential wall thickening of the descendent and horizontal part of duodenum, which was hyper dense in the native series and slight and uniform ring-formed enhancement in post-contrast phases, a typical CT presentation of intramural duodenal hematoma. Periduodenal and right sided pararenal hematomas were also visualized. After stopping the anticoagulant therapy and performing conservative treatment (vitamin K) with good therapeutic effect being monitored by physical examination, laboratory analyses and transabdominal ultrasonography, spontaneous resolution of the duodenal hematoma was revealed by follow-up CT examination two weeks after the onset. Conclusion. Ultrasonography and CT are useful diagnostic tools in recognition of the intramural duodenal hematoma and other locations of hemorrhage and in monitoring therapeutic effects.

Transarterial radioembolization with yttrium-90 of unresectable primary hepatic malignancy in children.

Primary malignant liver tumors are rare, accounting for 1% to 2% of all childhood cancers. When chemotherapy fails, transarterial radioembolization with yttrium-90 (TARE-Y90) may offer an alternative therapy as a bridge to surgical resection or liver transplant or for palliation. We conducted a retrospective review of 10 pediatric patients with histologically confirmed primary liver malignancy who received treatment with TARE-Y90. The median age at treatment was 5.5 years (range, 2-18 years). Median patient survival from initial diagnosis was 12.5 months (range, 10-28 months), and median patient survival after TARE-Y90 was 4 months (range, 2-20 months). Retreatment was well tolerated in three of 10 patients, with these patients demonstrating the longest survival times (range, 17-20 months). One patient was transplanted 6weeks after TARE-Y90. By RECIST 1.1 criteria of all target lesions, eight of nine patients had stable disease, and one of nine had progressive disease. By mRECIST criteria (requiring postcontrast arterial phase imaging), two of seven patients had a partial response, four of seven had stable disease, and one of seven had progressive disease. TARE-Y90 of unresectable primary liver malignancy is both technically feasible and demonstrates an anticancer effect, and retreatment is well tolerated. TARE-Y90 could be considered as adjunctive therapy in pediatric patients with unresectable hepatic malignancies and could be used as a bridge to surgical resection or liver transplant. More research is required to determine the efficacy of this treatment in children and to define the clinical scenarios where benefit is likely to be optimized.

Assessment of multiphasic contrast-enhanced MR textures in differentiating small renal mass subtypes.

This study seeks to evaluate the use of quantitative texture parameters extracted from multiphasic contrast-enhanced magnetic resonance (MR) imaging in differentiating between benign and malignant masses (oncocytoma vs. clear cell and papillary RCC) and between common subtypes of renal cell carcinoma (clear cell vs. papillary RCC) in small renal masses (< 4cm). One-hundred and forty-two renal lesions (90 clear cell and 22 papillary RCCs; 30 oncocytomas) were identified in a cohort of 41 patients (18 men, 23 women: mean age, 52.8 ± 14.4years) who underwent preoperative multiphasic contrast-enhanced MR with four phases (unenhanced, arterial, venous, and delayed) between 2015 and 2016. In this study, texture features were extracted from entire cross-sectional tumoral region in three consecutive slices containing the largest cross-sectional area from each of the four phases. The change in imaging feature between precontrast imaging and each postcontrast phase was calculated. Data dimension reduction and feature selection were performed by conducting (1) pairwise Wilcoxon rank test followed by modified false discovery rate adjustment, and (2) Lasso regression. Multivariate modeling incorporating the selected features was performed using random forest classification method. Histogram imaging features were informative variables in differentiating between benign and malignant masses, while textures imaging features were of added value in differentiating between subtypes of RCCs. Papillary RCCs were distinguished from clear cell RCCs (sensitivity 65.5%, specificity 88%, and accuracy 77.9%), oncocytomas from clear cell RCCs (sensitivity 67.3%, specificity 88.9%, and accuracy 79.3%), and oncocytomas from papillary and clear cell RCCs (sensitivity 64.7%, specificity 85.9%, and accuracy 77.9%). A combination of histogram and texture imaging features on multiphasic MR can help differentiate histologic cell types in common small renal masses (< 4cm).

Optimization of Scan and Reconstruction Parameters for Renal Artery CT Angiography with Iterative Reconstruction at Low kVp Compared with Filtered Back Projection at 120 kVp Acquisition

Background: As cross-sectional images expanded in clinical practice, the number of renal lesions discovered incidentally has been increasing. CT protocols for renal mass evaluation may include pre- and post-contrast phase. However, a major concern with respect to those multiphase techniques is often the radiation dose. One further critical issue is how to minimize the radiation dose while image quality is optimized in routine daily clinical practice. Objectives: To evaluate the image quality and radiation dose of renal artery CT angiography (CTA) with optimal sinogram affirmed iterative reconstruction (SAFIRE) strength level at 80 kVp for optimizing the scan and reconstruction parameters of renal artery CTA, in comparison to 120 kVp acquisition with filtered back projection (FBP). Patients and Methods: Sixty consecutive patients were classified into three groups prospectively in this study: 1) 80 kVp group (n = 30) with FBP and 2) 80 kVp group with SAFIRE (S4) and 3) 120 kV group (n = 30) with FBP. CT values and noise were measured, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of the renal artery CTA were calculated for quantitative assessment. Subjective image quality was evaluated by two experienced abdominal radiologists with a five-point scale in a blinded and randomized setting for qualitative assessment. Volume CT dose index (CTDIvol) and size-specific dose estimate (SSDE) were calculated and estimated for each subject presented in this study. Results: As for quantitative assessment, CNR, SNR and CT values of renal artery in 80kVp group with SAFIRE strength levels or FBP were higher than those of 120 kVp group with FBP (all Ps < 0.05), the mean noise gradually decreased in 80kVp group when increasing the SAFIRE strength levels (S1 - S5). As for qualitative assessment, the overall image quality, vessel sharpness, segmental renal artery displayed in maximum intensity projection (MIP) or multiplanar reformation (MPR), and diagnostic confidence of the two groups were all accepted by two radiologists (inter-observer agreement ranged from 0.600 to 0.940) (score ≥ 3). The overall image quality of 80 kVp with SAFIRE 4 was similar to that of 120 kVp group with FBP (P = 0.412), as well as segmental renal artery displayed in MIP and diagnostic confidence (P = 0.095 and P = 0.061, respectively). As for radiation dose reduction, 80kVp group could reduce 32.7% CTDIvol and 31.2% SSDE compared to the 120 kVp group. Conclusion: In patients with BMI lower than 28 kg/m2, renal artery CTA at 80 kVp with SAFIRE is feasible and can provide satisfactory images for clinical applications. This method also provides reduction in radiation dose. SAFIRE strength level 4 is recommended for reconstructing renal artery CTA.

Improved imaging of colorectal liver metastases using single-source, fast kVp-switching, dual-energy CT: preliminary results.

PurposeComputed tomography remains the first-choice modality for assessment of colorectal cancer liver metastases (CRLM). Dual-energy computed tomography (DECT) is a relatively new technique that is becoming increasingly available. One of the advantages of DECT is the ability to maximise iodine detection. Our aim was to test whether single-source, fast kVp-switching DECT can improve imaging quality of CRLM compared to conventional (polychromatic) CT.Material and methodsTwenty consecutive patients were enrolled into a preliminary prospective study. The scanning protocol consisted of four phases: non-contrast with standard 120 kV tube voltage and three post-contrast phases with rapid voltage switching. As a result, three sets of images were reconstructed: pre- and postcontrast polychromatic (PR), monochromatic (MR), and iodine concentration map (IM). To compare the sensitivity of the tested reconstructions, the number of CRLMs and the maximum diameter of the largest lesion were calculated. Objective image quality was measured as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The radiation dose was expressed as CTDIvol.ResultsImaging was successfully performed in all patients. The number of detected lesions was significantly lower on PR images than on IM and MR 50-70 keV (mean number: 4.20 and 4.45, respectively). IM and MR at 70 keV presented the highest quality. SNR was significantly higher for IM and 70 keV images than for other reconstructions. The mean radiation dose was 14.61 mGy for non-contrast 120 kV scan and 17.89 mGy for single DECT scan (p < 0.05).ConclusionsDECT is a promising tool for CRLM imaging. IM and low-photon energy MR present the highest differences in contrast between metastases and the normal liver parenchyma.

Utility of contrast-enhanced computed tomography in the evaluation of canine insulinoma location

Objectives: To determine 1) the sensitivity of contrast-enhanced CT (CECT) for detection of primary canine insulinomas and metastases 2) the sensitivity of CECT to locate canine insulinomas within the pancreas and 3) the CECT attenuation pattern of canine insulinomas and post-contrast phase in which insulinomas have the best visibility.Methods: A retrospective review was performed of the medical records of 27 canine insulinoma patients. Simultaneous occurrence of blood glucose < 3.5 mmol/L (reference interval: 4.2–5.8 mmol/L) and plasma insulin > 10 mIU/L (reference interval: 1.4–24.5 mIU/L) were considered diagnostic for insulinoma. The dogs had a mean age of 9.0 ± 1.7 (SD) years and comprised 11 males and 17 females.Results: Using CECT-scans, 26/27 insulinomas were successfully detected. However, CECT-scans predicted the correct location of insulinomas within the pancreas in only 14/27 dogs. In 9/13 inaccurately located insulinoma cases, the location error was major. There was no significant difference between triple, double and single-phase CECT-scans with location accuracies of 54%, 50% and 50%, respectively. Also, there was no specific post-contrast phase in which insulinomas could be visualised best. Detection of lymph node metastases with CECT-scans had a sensitivity of 67% (10/15 lymph node metastases). Detection of liver metastases had a sensitivity of 75% (6/8 liver metastases). This study highlights that major location errors mainly occurred if single- or double-phase CECT-scans were used (6/9 cases).Conclusion: It is suggested that triple-phase CECT-scans have superior outcome over single- or double-phase CECT-scans in pre-operative imaging of canine insulinomas.

Optimal Phase of Dynamic Computed Tomography for Reliable Size Measurement of Metastatic Neuroendocrine Tumors of the Liver: Comparison between Pre- and Post-Contrast Phases.

ObjectiveThe reliability of size measurements of liver metastases from neuroendocrine tumors (NETs) on contrast-enhanced computed tomography (CT) phases made by different readers may be hampered due to transient, variable rim enhancement in arterial phase (AP) or portal venous phase (PVP) images. We aimed to assess the reliability of tumor size measurements in pre- and post-contrast scans.Materials and MethodsThe study coordinator selected target lesions according to Response Evaluation Criteria in Solid Tumors 1.1 guidelines in 44 consecutive patients with pathologically confirmed NET liver metastases. Two blinded readers measured the longest diameters of target lesions on pre-contrast, AP, and PVP images twice with a 4-week interval. Inter- and intra-observer agreements were evaluated using Bland-Altman plots and 95% limit of agreement (LOA) calculations.ResultsOf the 79 target lesions (approximate mean size of 3 cm), 45 showed rim enhancement. Inter-observer agreement assessed based on LOA was highest in pre-contrast CT images (−6.1–5.7 mm), followed by PVP (−7.9–7.1 mm) and AP (−8.5–7.4 mm) images. Intra-observer agreement showed the same trend: −2.8–2.9 mm and −2.9–2.9 mm for readers 1 and 2, respectively, on pre-contrast CT, −2.8–2.9 mm and −3.0–3.2 mm, respectively, on PVP, and −3.2–4.2 mm and −3.4–3.2 mm, respectively, on AP images. Mean tumor diameters differed significantly among the phases in the following increasing order: pre-contrast CT, PVP, and AP images.ConclusionThere was better inter- and intra-observer agreement in size measurements of NET liver metastases on precontrast scans than on AP and PVP scans. Pre-contrast CT may be the optimal for measuring NET liver metastases if its accuracy is proven.

Is there an added role for diffusion weighted imaging in the staging of cervical carcinoma?

ObjectiveTo assess the diagnostic accuracy of diffusion weighted imaging (DWI-MRI) being a non-contrast based MR sequence versus dynamic contrast enhanced MRI (DCE-MRI) in the preoperative loco-regional staging of the cervical carcinoma. MethodologyFifty cases of proved cancer cervix prior staging subjected to dynamic post contrast technique: one pre-and six post contrast phases (40 s each). DWI was scanned using different b values and ADC values were measured. ResultsDWI was the most accurate in staging operable cases (93.3%).Parametrial infiltration was overestimated in 3 cases versus 4 cases in DCE-MR. DWI showed 100% sensitivity, positive predictive value and accuracy in the assessment of locally advanced carcinomas. In metastatic lymph nodes, DCE-MR showed the least accuracy of 86%. ConclusionDWI is helpful in discriminating local from locally advanced cervical carcinomas. DCE-MR can delineate cervical carcinomas confined to the uterus and exclude bladder/rectal invasion.

Abbreviated MRI and Accelerated MRI for Screening and Diagnosis of Breast Cancer.

Although published studies have revealed that magnetic resonance imaging (MRI) is by far the most effective imaging modality for cancer detection, it is currently considered cost-ineffective for screening women at an intermediate risk for breast cancer. The concept of an "abbreviated MRI" protocol has recently emerged as a possible solution for reducing the cost of MRI. The abbreviated MRI is a shortened version of the standard MRI, consisting of a single early phase dynamic contrast enhanced (DCE) series. Several clinical studies have shown that this MRI protocol would not affect sensitivity or specificity for breast MRI screening purposes. In clinical practice, morphologic evaluation and kinetic assessment are 2 major components of the interpretation process. However, kinetic assessment cannot be performed with the abbreviated protocol, because multiple sets of post-contrast images are necessary for the generation of kinetic curves. "Accelerated MRI" is a collective term for imaging techniques that acquire DCE-MR images in a very short time. Published studies suggest that the kinetic assessment during the very early post-contrast phase obtained with the accelerated MRI techniques is comparable to that with the standard MRI techniques. Applying accelerated MR techniques could potentially enhance the abbreviated MRI protocol in terms of diagnostic potential, while maintaining the shorter study time. Thus, the abbreviated MRI protocol associated with accelerated MRI techniques may provide value for screening and for diagnostic purposes.