Added Value of Contrast Medium in Whole-Body Hybrid Positron Emission Tomography/Magnetic Resonance Imaging: Comparison between Contrast-Enhanced and Non-Contrast-Enhanced Protocols.

OBJECTIVE: To compare the diagnostic ability and time efficiency of contrast-enhanced (CE) whole body fluorodeoxyglucose (FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) protocol and non-CE (NCE) protocol. SUBJECTS AND METHODS: Ninety-three patients with known primary tumors underwent whole-body hybrid FDG PET/MRI during the follow-up of their malignancies with the use of NCE and CE protocols. The NCE PET/MRI protocol consisted of diffusion-weighted (b = 0 and 800 s/mm2) and T1-weighted Turbo Flash in the axial plane and T2-weighted HASTE sequence in the coronal planes (Σ = 25 min). The CE PET/MRI protocol was performed by acquiring axial serial CE 3D FS VIBE images in the upper abdomen, completing the whole body in the late phase in the axial plane (Σ = 30 min). RESULTS: There was a statistically significant difference between the total number of lesions detected by the CE protocol (median 2, interquartile range (IQR) 0-14) and that detected by the NCE protocol (median 1, IQR 0-5; p < 0.001). More malignancies were detected in the abdomen (p < 0.001) and brain (p < 0.001) with the CE PET/MRI protocol, whereas no significant difference was present when comparing the 2 protocols in the detection of malignancies in the head and neck (p = 0.356), thorax (p = 0.09), lymph nodes (p = 0.196), and bone (p = 0.414). CONCLUSION: The CE FDG PET/MRI protocol enables fast and accurate detection of malignancies compared to the NCE FDG PET/MRI protocol, particularly in the upper abdomen and brain. Diagnostic ability and time efficiency can be increased with the proposed short CE protocol in place of the whole body PET/MRI protocol including both NCE and CE imaging sequences.

Diagnostic value of dynamic contrast-enhanced magnetic resonance imaging in the evaluation of the biliary obstruction.

PURPOSE: In this study, our purpose was to investigate the diagnostic efficacy of the dynamic contrast-enhanced magnetic resonance imaging (MRI) method in the patients with bile duct obstruction. MATERIALS AND METHODS: 108 consecutive patients (53 men, 55 women, mean age; 55.77 ± 14.62, range 18-86 years) were included in this study. All the patients underwent conventional upper abdomen MRI using intravenous contrast material (Gd-DTPA) and MRCP in 1.5 Tesla MRI scanner. MRCP images were evaluated together with the T1 and T2w images, and both biliary ducts and surrounding tissues were examined for possible pathologies that may cause obstruction. RESULTS: MRI/MRCP findings compared with final diagnoses, MRI/MRCP in the demonstration of bile duct obstruction sensitivity 96%, the specificity 100%, and accuracy 96.3%, in the detection of presence and level of obstruction, the sensitivity 96.7%, specificity 100%, and accuracy 97.2%, in the diagnosis of choledocholithiasis, the sensitivity 82.3%, specificity 96%, and accuracy 91.7%, and in the determination of the character of the stenosis, sensitivity 95.6%, specificity 91.3%, and accuracy 94.5% were found. CONCLUSION: The combination of dynamic contrast-enhanced MRI and MRCP techniques in patients with suspected biliary obstruction gives the detailed information about the presence of obstruction, location, and causes and is a highly specific and sensitive method.

The Role of 18F-FDG PET/MRI in the Assessment of Primary Intrahepatic Neoplasms.

RATIONALE AND OBJECTIVES: To evaluate the results of 18F-FDG PET/MRI in relation to the histopathologic subtypes and histologic grades of mass-forming primary intrahepatic neoplasms. MATERIALS AND METHODS: We retrospectively evaluated 18F-FDG positron emission tomography/magnetic resonance imaging (PET/MRI) results for 39 patients with histopathologically confirmed primary hepatic neoplasms, 15 with mass-forming intrahepatic cholangiocarcinoma (ICC) and 24 with hepatocellular carcinoma (HCC). The apparent diffusion coefficient (ADC) and standardized uptake value (SUV) were analyzed in relation to the histopathologic diagnosis and histologic grade, including calculating the sensitivity and specificity of the imaging findings. RESULTS: The median SUV of ICC (6.0 [interquartile range, 5-10]) was significantly higher than that of HCC (4.0 [2.62-6.50]) (p = 0.002). An area under the curve (AUC) of 0.79 (95% confidence interval 0.649-0.932) had a sensitivity of 86.7% and a specificity of 67% at the best cut-off SUV of 4.41 to differentiate between ICC and HCC. ADC values did not differ significantly between HCCs and ICCs (p = 0.283). Both SUV and ADC values differed significantly between low-grade (well- and moderately differentiated) and high-grade (poorly differentiated) HCCs. Combining ADC and SUV further improved differentiation of low- from high-grade HCCs to a significant level (0.929). The SUV did not differ significantly between ICC histologic grades (p = 0.280), while the ADC differed significantly only between well and poorly differentiated ICCs (p = 0.004). CONCLUSION: Assessing primary hepatic neoplasms with 18F-Fluorodeoxyglucose PET/MRI may help to predict tumor grade and differentiate between types of intrahepatic neoplasms.

Discordance between invasive coronary flow reserve (CFR) and non-invasive myocardial flow reserve (MFR) in diffuse coronary ectasia (DCE).

Clinical use with evidence base for diagnostic and prognostic value of quantitative positron emission tomography(PET) myocardial perfusion imaging (MPI) in patients with known or suspected coronary artery disease has exponentially increased over the last decade. This case illustrates the very first time that stress myocardial blood flow(MBF) in absolute terms (ml/min/gram) and myocardial flow reserve(MFR) are augmented in three vessel diffuse coronary ectasia by N13-Ammonia PET MPI. Moreover, relative qualitative MPI demonstrated moderate-sized ischemia in right coronary artery territory with chronic total occlusion in middle segment; despite regional myocardial flow reserve remains above ischemic thresholds while regional stress myocardial blood flow is mildly reduced.

Comparison of intraoperative transit-time flow measurement with early postoperative magnetic resonance flow mapping in off-pump coronary artery surgery.

The purpose of this prospective study was to evaluate graft patency of off-pump coronary artery surgery intraoperatively by transit-time flow measurement and to compare this technique with postoperative magnetic resonance flow mapping. Twenty patients (13 men and 7 women; mean age, 679 +/- 76 yr) underwent off-pump coronary artery surgery. Intraoperative transit-time flow measurement of grafts was performed measuring maximum, minimum, and mean flows. For each graft, the pulsatile index was calculated by dividing the difference between the maximum and the minimum flow by the mean flow In the early postoperative period (1st week), magnetic resonance flow mapping was performed using phase contrast flow quantification. Mean intraoperative flow values and mean magnetic resonance flow mapping values were compared. At the same postoperative session, contrast-enhanced magnetic resonance angiography was performed to evaluate graft patency. In 20 patients, a total of 49 coronary graft flows were assessed with intraoperative transit-time flow measurement and postoperative magnetic resonance flow mapping. Upon comparison, there was a strong correlation between techniques, with stable and statistically significant differences between the intraoperative and postoperative flow mapping values. One saphenous vein graft was revised intraoperatively, due to graft failure. Our data suggest that the combined use of intraoperative transit-time flow measurement and postoperative magnetic resonance flow analysis has a potential role in the assessment of graft patency in off-pump coronary artery surgery although more study is required.

CT and MRI findings of sarcomatoid cholangiocarcinoma.

Computed tomography (CT) and magnetic resonance imaging (MRI) findings for a case of intrahepatic sarcomatoid cholangiocarcinoma is presented. A 48-year-old man with upper abdominal pain underwent contrast-enhanced CT and MRI. A 13 × 10 × 7 cm mass was seen in the left liver lobe, which had hypodense internal architecture on CT and mixed signal intensities on both T1- and T2-weighted images with an overwhelmingly hypointense signal on T1-weighted images and a hyperintense signal on T2-weighted images. The lesion had heterogeneous enhancement on both CT and MRI. A satellite nodule with the same imaging features was distinctive for the lesion.

Fulminant abdominal gas gangrene in metastatic colon cancer.

We report a case of fulminant abdominal gas gangrene in a patient with metastatic colon cancer. A 39-year-old patient with descending colon, high-grade adenocarcinoma and coexisting liver and lymph node metastases received two courses of chemotherapy. The patient developed sudden acute abdominal symptoms accompanied by septic shock parameters. The imaging findings on computed tomography were characteristic for abdominal gas gangrene, involving liver metastases, portal vein and lymph nodes with associated pneumoperitoneum. The patient succumbed to the disease within hours following the onset of symptoms.

Locally metastatic mucinous rectal adenocarcinoma: Imaging diagnosis with DW-MRI in comparison with PET-CT.

A 56-year-old male patient with locally advanced mucinous rectal cancer underwent neoadjuvant chemoradiotherapy. Follow-up imaging with positron emission tomography-computed tomography (PET-CT) revealed a local response to chemoradiotherapy, whereas diffusion-weighted magnetic resonance imaging (DW-MRI) showed newly presented sacral bone metastasis. Histopathologically confirmed bone metastasis and the local tumor were surgically removed. Repeat DW-MRI revealed tumor recurrence in the sacral excision zone eight months after surgery, which was reconfirmed by histopathology. This case shows the superior imaging ability of DW-MRI in the diagnosis of mucinous tumors in comparison to PET-CT.

MRI assessment of chronic pancreatitis.

Magnetic resonance imaging (MRI) plays an important role in the assessment of chronic pancreatitis. By standard MRI techniques, decreased parenchymal signal on T1-weighted fat-suppressed images and delayed gradual enhancement on serial contrast enhanced images represent fibrotic changes caused by chronic inflammation. Magnetic resonance cholangiopancreaticography (MRCP) can reveal ductal changes, including side branch ectasias, that are related to tissue fibrosis and destruction. The exocrine function of the gland and an increased number of side branch ectasias can be evaluated with secretin-stimulated MRCP. Diffusion weighted imaging is an emerging technology that can complement standard MRI to assess the parenchymal changes associated with chronic pancreatitis. The same technique can also quantify the parenchymal response to secretin stimulation. This article reviews standard imaging techniques and new advancements in MRI technology as they relate to the assessment of chronic pancreatitis.