Association of intraplacental oxygenation patterns on dual-contrast MRI with placental abnormality and fetal brain oxygenation.

OBJECTIVES: Most human in-vivo placental imaging techniques are unable to distinguish and characterize various placental compartments, such as the intervillous space (IVS), placental vessels (PV) and placental tissue (PT), limiting their specificity. We describe a method that employs T2* and diffusion-weighted magnetic resonance imaging (MRI) data to differentiate automatically placental compartments, quantify their oxygenation properties and identify placental lesions (PL) in vivo. We also investigate the association between placental oxygenation patterns and fetal brain oxygenation. METHODS: This was a prospective study conducted between 2018 and 2021 in which dual-contrast clinical MRI data (T2* and diffusion-weighted MRI) were acquired from patients between 20 and 38 weeks' gestation. We trained a fuzzy clustering method to analyze T2* and diffusion-weighted MRI data and assign placental voxels to one of four clusters, based on their distinct imaging domain features. The new method divided automatically the placenta into IVS, PV, PT and PL compartments and characterized their oxygenation changes throughout pregnancy. RESULTS: A total of 27 patients were recruited, of whom five developed pregnancy complications. Total placental oxygenation level and T2* did not demonstrate a statistically significant temporal correlation with gestational age (GA) (R2 = 0.060, P = 0.27). In contrast, the oxygenation level reflected by T2* values in the placental IVS (R2 = 0.51, P = 0.0002) and PV (R2 = 0.76, P = 1.1 × 10-7 ) decreased significantly with advancing GA. Oxygenation levels in the PT did not show any temporal change during pregnancy (R2 = 0.00044, P = 0.93). A strong spatial-dependent correlation between PV oxygenation level and GA was observed. The strongest negative correlation between PV oxygenation and GA (R2 = 0.73, P = 4.5 × 10-7 ) was found at the fetal-vessel-dominated region close to the chorionic plate. The location and extent of the placental abnormality were automatically delineated and quantified in the five women with clinically confirmed placental pathology. Compared to the averaged total placental oxygenation, placental IVS oxygenation level best reflected fetal brain oxygenation level during fetal development. CONCLUSION: Based on clinically feasible dual-MRI, our method enables accurate spatiotemporal quantification of placental compartment and fetal brain oxygenation across different GAs. This information should improve our knowledge of human placenta development and its relationship with normal and abnormal pregnancy. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Evaluation of attenuation correction in cardiac PET using PET/MR.

BACKGROUND: Simultaneous acquisition Positron emission tomography/magnetic resonance (PET/MR) is a new technology that has potential as a tool both in research and clinical diagnosis. However, cardiac PET acquisition has not yet been validated using MR imaging for attenuation correction (AC). The goal of this study is to evaluate the feasibility of PET imaging using a standard 2-point Dixon volume interpolated breathhold examination (VIBE) MR sequence for AC. METHODS AND RESULTS: Evaluation was performed in both phantom and patient data. A chest phantom containing heart, lungs, and a lesion insert was scanned by both PET/MR and PET/CT. In addition, 30 patients underwent whole-body 18F-fluorodeoxyglucose PET/CT followed by simultaneous cardiac PET/MR. Phantom study showed 3% reduction of activity values in the myocardium due to the non-inclusion of the phased array coil in the AC. In patient scans, average standardized uptake values (SUVs) obtained by PET/CT and PET/MR showed no significant difference (n = 30, 4.6 ± 3.5 vs 4.7 ± 2.8, P = 0.47). There was excellent per patient correlation between the values acquired by PET/CT and PET/MR (R 2 = 0.97). CONCLUSIONS: Myocardial SUVs PET imaging using MR for AC shows excellent correlation with myocardial SUVs obtained by standard PET/CT imaging. The 2-point Dixon VIBE MR technique can be used for AC in simultaneous PET/MR data acquisition.

The Resolution Rate of Pulmonary Embolism on CT Pulmonary Angiography: a Prospective Study.

PURPOSE: To prospectively assess the rate of clot resolution from CT pulmonary angiography (CTPA) in patients with acute pulmonary embolism (PE). MATERIALS AND METHODS: This prospective cohort study included 290 patients (136 men, 154 women; mean age, 51.9 years) with acute PE. All patients had a CTPA at the presentation and had at least one follow-up within 6 months (mean 72.7 days). Sixty-four percent of patients had follow-up scans for research purposes within a pre-determined period (between 28 and 184 days; mean, 78.27 days) and 36 % had (between 2 and 184 days; mean, 62.78 days) for a clinical indication. The volume of each clot was measured using a semi-automated quantification program. The resolution rate was evaluated by interval-censored analysis. RESULTS: The overall estimated probability of complete resolution was 42 % at 7 days, 56 % at 10 days, and 71 % at 45 days. Achieving complete resolution was significantly faster in patients with peripheral clots (HR: 1.78; CI: 1.05-3.03, p = 0.032) but slower in patients with consolidation and history of venous thromboembolism (VTE), (HR: 0.37; CI: 0.18-0.79, p = 0.01 and HR: 0.57; CI: 0.35-0.91, p = 0.019, respectively). Although the patients with cancer showed a faster resolution rate (HR: 1.67; CI: 1.05-2.68, p = 0.032), the mortality rate was significantly higher than non-cancer patients. CONCLUSION: The resolution rate of clot burden in acute PE was associated with patients' clinical presentation variables and CTPA imaging biomarkers. This information may be incorporated into designing a prediction rule and determining the appropriate duration of anticoagulation therapy in patients with acute PE.

Contrast-enhanced magnetic resonance imaging of the coronary arteries. A review.

The advent and continued improvement of T1-shortening contrast media have revolutionized magnetic resonance angiography (MRA) of the entire body in recent years. The technical basis for contrast-enhanced MRA is fast three-dimensional (3D) imaging. A brief historic review of the technical advances in MR coronary artery imaging clearly points to the importance of improved gradient capabilities that led to the development and wide application of fast 3D imaging. The use of contrast agents in coronary artery imaging has been expected for many years, given its success in other parts of the body. Nevertheless, because of the potential difficulties and unique characteristics of fast 3D imaging in the heart, the utility of contrast agents in coronary artery imaging has been systematically investigated only in the last 2 years. Initial experience from our group and others showed that contrast agents have great potential in pushing MR coronary artery imaging to a much higher level in terms of speed and signal-to-noise ratio (SNR), and intravascular agents are more desirable than extracellular agents. Nevertheless, because of the technical challenges and the diversity of methods used for coronary artery imaging, much more effort is needed to continue to improve the imaging techniques and further to define the roles of contrast agents in coronary artery imaging.

Radiologic diagnosis of extrathoracic metastases to the lung.

Because many types of cancers metastasize to the lungs, early detection may affect both tumor staging and treatment planning. On the other hand, it is also important to refrain from subjecting patients to procedures that are unnecessary because of the low likelihood of positive yield. The radiologic modalities of greatest benefit in screening for pulmonary metastases are the standard chest radiograph and thoracic computed tomography (CT). Other modalities that may be of value in answering specific questions are positron emission tomography (PET) and magnetic resonance imaging (MRI). Factors that help determine which tests will be most useful in demonstrating pulmonary metastasis from extrathoracic primary tumors include the mechanisms of hematogenous tumor spread, the likelihood of distant metastasis vs spread to nearby nodal groups, and the probability of distant metastasis in the absence of local invasion.

Coronary MR angiography.

Coronary MR angiography has developed rapidly over the past several years. Not only is research being performed at academic centers but industry is also investing in dedicated contrast agents and cardiac MR imaging platforms. Although current coronary MR angiography has limited clinical utility, its place within the assessment of ischemic cardiac disease is evolving. The technology currently under investigation holds much promise, especially when one considers that MR has the potential to provide information currently supplied by the performance of a number of screening tests. It would be far more cost-effective to perform a single MR examination than to perform a stress echo, rest-stress nuclear medicine examination and a conventional coronary angiogram. In addition, clinicians need information about coronary flow and myocardial perfusion. Although some of this information can be currently obtained with an intravascular Doppler flow wire or by positron emission tomography, MR angiography offers the advantages of being both noninvasive and more easily accessible in comparison to either method. The combined information promised by a comprehensive cardiac MR examination that includes coronary MR angiography as a component is an exciting prospect.

Detection of pulmonary embolism: comparison of contrast-enhanced spiral CT and time-of-flight MR techniques.

We compared the conspicuity of acute pulmonary emboli with contrast-enhanced spiral computed tomography (CT) and two- and three-dimensional time-of-flight magnetic resonance (MR) techniques. Seven dogs who received experimental pulmonary emboli and one control were imaged with spiral CT and with 2-D (FMPVAS and FASTCARD) and 3-D time-of-flight MR. Blinded, independent, prospective evaluations of the CT and MR images by two MR radiologists and two chest radiologists were then compared to the location of the emboli as determined by subsequent pathologic evaluation of the excised lungs. Embolus/blood contrast-to-noise ratios (CNRs) were calculated on both MR and CT images for pulmonary emboli that could be identified. Fifty emboli ranging from 1.0 to 5.5 mm (mean, 2.7, +/- 0.14 SEM) in diameter and from 3.0 to 60 mm (mean, 28.1 +/- 1.9 SEM) in length were found in the seven embolized dogs on pathologic examination. Three of the four radiologists identified more thrombi on CT images than they did on their best MR pulse sequence (FASTCARD) and with greater confidence. The fourth radiologist identified an equal percentage of clot on CT and FASTCARD images with confidence slightly greater on FASTCARD MR than on spiral CT. Mean CNR for the best MR technique was 43.4 (+/- 3.9 SEM) and for CT was 20.7 (+/- 1.3 SEM). In general, pulmonary emboli were detected more accurately on contrast-enhanced spiral CT than on MR. This occurred although the embolus/blood CNR was higher on MR than on CT. Better pulmonary embolus conspicuity on CT images was attributed to better spatial resolution and fewer artifacts on CT than on MR. One MR radiologist performed equally well with both spiral CT and FASTCARD techniques, suggesting that experience may be a factor in performance.

The coronary CT angiography vision protocol: a prospective observational imaging cohort study in patients undergoing non-cardiac surgery.

INTRODUCTION: At present, physicians have a limited ability to predict major cardiovascular complications after non-cardiac surgery and little is known about the anatomy of coronary arteries associated with perioperative myocardial infarction. We have initiated the Coronary CT Angiography (CTA) VISION Study to (1) establish the predictive value of coronary CTA for perioperative myocardial infarction and death and (2) describe the coronary anatomy of patients that have a perioperative myocardial infarction. METHODS AND ANALYSIS: The Coronary CTA VISION Study is prospective observational study. Preoperative coronary CTA will be performed in 1000-1500 patients with a history of vascular disease or at least three cardiovascular risk factors who are undergoing major elective non-cardiac surgery. Serial troponin will be measured 6-12 h after surgery and daily for the first 3 days after surgery. Major vascular outcomes at 30 days and 1 year after surgery will be independently adjudicated. ETHICS AND DISSEMINATION: Coronary CTA results in a measurable radiation exposure that is similar to a nuclear perfusion scan (10-12 mSV). Treating physicians will be blinded to the CTA results until 30 days after surgery in order to provide the most unbiased assessment of its prognostic capabilities. The only exception will be the presence of a left main stenosis >50%. This approach is supported by best available current evidence that, excluding left main disease, prophylatic revascularisation prior to non-cardiac surgery does not improve outcomes. An external safety and monitoring committee is overseeing the study and will review outcome data at regular intervals. Publications describing the results of the study will be submitted to major peer-reviewed journals and presented at international medical conferences.

Cardiac magnetic resonance imaging abnormalities in systemic lupus erythematosus: a preliminary report.

The purpose of this prospective, pilot study was to determine whether differences in myocardial T2 relaxivity can be identified among active systemic lupus erythematosus (SLE) patients with clinically suspected SLE myocarditis, other active SLE patients, inactive SLE patients and age and gender matched controls. Eleven consecutive female patients (six with active SLE and five with inactive SLE), and five age, gender and race matched healthy controls underwent imaging with echocardiography and cardiac magnetic resonance imaging (MRI). Echocardiographic measurements included left ventricular end diastolic (LVEDV) and end systolic volumes (LVESV), and mass (LVM) (all indexed to body mass); ejection fraction and cardiac output. The cardiac MRI measurement was the T2 relaxation time (an index of soft tissue signal, with higher levels suggestive of increased tissue water content). Patients with active SLE had significantly higher LVEDV and LVM than inactive SLE patients and healthy controls, and significantly larger LVESV than healthy controls. Myocardial T2 relaxation times were significantly higher in patients with active SLE compared to those with inactive SLE and to healthy controls, and remained higher even after excluding the two active SLE patients who had clinical myocarditis. The four active SLE patients who underwent repeat cardiac imaging studies after clinical improvement showed normalization of these myocardial abnormalities. The conclusion was that active SLE patients demonstrate abnormalities in myocardial structure manifested by high myocardial T2 relaxation times that normalized after clinical improvement in disease activity. These findings suggest that T2 relaxation values are a sensitive indicator of myocardial disease in patients with SLE and that myocardial T2 relaxation abnormality frequently occur in patients with active SLE, even in the absence of myocardial involvement by clinical criteria.

Diagnosis of pulmonary embolism with spiral computed tomography and magnetic resonance angiography.

Radiologic imaging techniques such as contrast-enhanced spiral computed tomography (CT) and magnetic resonance (MR) angiography provide noninvasive means of diagnosing pulmonary thromboembolic disease. In addition, both techniques permit direct visualization of the embolus. Although imperfect, both CT and MR angiography in various circumstances fit diagnostic pathways for pulmonary embolism detection. Recent advances in both CT (multidetector ring spiral units and electron beam) and MR technology allow not only depiction of the pulmonary arteries, but also are capable of providing information about the lower extremity deep venous system in a single examination.

Pseudoaneurysms at aortic cannulation site after coronary artery bypass graft: MR findings.

Pseudoaneurysm at the aortic cannulation site is a rare but potentially fatal complication of coronary artery bypass surgery. We present two cases in which MRI provided significant information regarding the anatomy and extent of a pseudoaneurysm. In one case both spin-echo imaging and cine MRI with and without gradient moment nulling (flow compensation) were used. The absence of gradient moment nulling in cine MRI provides additional contrast between flowing and static blood. This contrast may complement conventional cine images with gradient moment nulling, providing further information.

Midgut carcinoid tumors: CT findings and biochemical profiles.

OBJECTIVE: Our goal was to describe the abdominal CT findings in 52 patients with midgut carcinoid tumors and correlate these findings with their biochemical profiles. MATERIALS AND METHODS: Abdominal/pelvic CTs of 52 patients with midgut carcinoid tumors were reviewed retrospectively for the presence of liver metastases, mesenteric and peritoneal disease, bowel changes, lymphadenopathy, and the presence of the primary tumor. Logistic regression models were used to evaluate the association between these findings and the serum and platelet serotonin and urine 5-hydroxyindolacetic acid levels. RESULTS: The most common finding was hepatic metastases (34/52). Nonspecific mesenteric soft tissue stranding was present in 26 of 52 and a discrete mesenteric mass was present in 25 of 52. These masses had linear, radiating soft tissue spokes in 16 of 25 and contained calcification in 10 of 25. Retroperitoneal and mesenteric lymphadenopathy was present in 14 of 52 and 11 of 52 cases, respectively. Carcinomatosis was present in 11 of 52. Bowel wall thickening was seen in 9 of 52. Six patients had a small bowel obstruction. Elevated serum serotonin, platelet serotonin, and urine 5-hydroxyindolacetic acid levels were significantly associated with the presence of liver metastases (p = 0.0032, 0.0098, and 0.0450, respectively). Elevated platelet serotonin levels were also significantly associated with the presence of a mesenteric mass (p = 0.0101). CONCLUSION: In our population, the most common findings of a midgut carcinoid tumor are liver metastases, nonspecific mesenteric soft tissue changes, a discrete mesenteric mass with radiating soft tissue spokes, often containing calcification, and lymphadenopathy. As expected, liver metastases correlate strongly with the presence of elevated biochemical levels. A new observation is the correlation of elevated platelet serotonin levels and mesenteric masses. We hypothesize that platelet serotonin may be the factor that stimulates stromal cells to produce mesenteric fibrosis and mass formation.

Efficacy of slow infusion of gadolinium contrast agent in three-dimensional MR coronary artery imaging.

The impact of the contrast infusion scheme on contrast-enhanced coronary artery imaging was investigated. The imaging technique was a retrospective respiratory-gated gradient-echo sequence. To improve the contrast between blood vessels and myocardium, an inversion pulse was applied to null the myocardial signal. Extravascular contrast agent was infused slowly during data acquisition. Two contrast infusion schemes were compared in animal and volunteer studies and with simulations. One scheme enhanced blood signals during acquisition of both peripheral and central k-space data, which resulted in a relatively flat low-pass k-space filter. The other scheme mainly enhanced blood signals during acquisition of central k-space data, which resulted in a sharp low-pass k-space filter. It is concluded that the former scheme improves the signal-to-noise ratio and edge definition of coronary arteries compared with the latter scheme. J. Magn. Reson. Imaging 1999;10:800-805.

Metastatic involvement of the heart and pericardium: CT and MR imaging.

Metastases to the heart and pericardium are much more common than primary cardiac tumors and are generally associated with a poor prognosis. Tumors that are most likely to involve the heart and pericardium include cancers of the lung and breast, melanoma, and lymphoma. Tumor may involve the heart and pericardium by one of four pathways: retrograde lymphatic extension, hematogenous spread, direct contiguous extension, or transvenous extension. Metastatic involvement of the heart and pericardium may go unrecognized until autopsy. Impairment of cardiac function occurs in approximately 30% of patients and is usually attributable to pericardial effusion. The clinical presentation includes shortness of breath, which may be out of proportion to radiographic findings in patients with pericardial effusion or may be the result of associated pleural effusion. Patients may also present with cough, anterior thoracic pain, pleuritic chest pain, or peripheral edema. The differential diagnosis of pericardial effusion in a patient with known malignancy includes malignant pericardial effusion, radiation-induced pericarditis, drug-induced pericarditis, and idiopathic pericarditis. Any disease process that causes thickening or nodularity of the pericardium or myocardium or masses within the cardiac chambers can mimic metastatic disease.

Noninvasive coronary artery imaging in the diagnosis and management of patients with ischemic heart disease.

The inherent limitations of x-ray coronary angiography have led to the development for both noninvasive and minimally invasive techniques for imaging the coronary arteries to assist in the diagnosis and management of patients with ischemic heart disease. Significant advances in transesophageal echocardiography, electron beam computed tomography, and magnetic resonance imaging now permit imaging of the proximal to mid-coronary arteries. Moreover, results of initial studies demonstrate the promise of these methods to detect coronary artery stenoses. In addition, each of these methods provides biochemical or physiologic data about the stenoses that are not obtainable through x-ray angiography. Quantification of coronary calcification via electron beam computed tomography has shown promise as a surrogate marker of coronary atherosclerosis. Transesophageal echocardiography and magnetic resonance imaging appear useful in evaluating the physiologic significance of angiographically detectable coronary artery stenoses via assessment of coronary blood flow. However, it should be noted that significant improvements in technology or acquisition parameters must occur before these techniques can be used on a routine clinical basis for coronary artery imaging. The relative merits and ultimate clinical potential of each of these techniques are discussed in this article.

Chest radiography: depiction of normal anatomy and pathologic structures with selenium-based digital radiography versus conventional screen-film radiography.

PURPOSE: To compare the subjective visibility of normal anatomy and pathologic structures in the chest on conventional screen-film radiographs versus selenium-based digital radiographs. MATERIALS AND METHODS: Screen-film and digital standard posteroanterior (PA) and lateral chest radiographs were obtained in 49 patients (32 men, 17 women; mean age, 60 years; range, 24-91 years) undergoing chest computed tomography (CT). Conventional images were phototimed at 115 kVp with use of a wide-latitude screen-film system and an antiscatter grid. Digital images were obtained at 150 kVp with use of a commercial system with a selenium detector and an air gap alone for scatter reduction. The image sets were independently compared by four radiologists, and the relative visibility of anatomic and pathologic features (proved at CT) was graded. Statistical significance (P < .0028) was evaluated with a one-tailed t test. RESULTS: Visibility with the digital images was statistically significantly increased for 11 of 13 normal anatomic features and for pathologic structures in the lung, soft tissue, and bone. CONCLUSION: Subjective visibility of pathologic structures and most normal anatomic features in the thorax was statistically significantly improved with selenium-based digital chest radiography compared with conventional screen-film chest radiography.

Benign metastasizing leiomyoma: clinical, imaging, and pathologic correlation.

OBJECTIVE: We describe the clinical presentation and the radiographic and CT findings of benign metastasizing leiomyoma. CONCLUSION: Benign metastasizing leiomyoma is an asymptomatic disease characterized by well-defined, numerous, pulmonary lesions without a preponderant distribution.

Coronary arteries: three-dimensional MR imaging with retrospective respiratory gating.

Thin-section, three-dimensional (3D) gradient-echo magnetic resonance imaging of the coronary arteries was performed without and with retrospective respiratory gating in 12 healthy volunteers and one patient. In all examinations, results were improved with gating. In five of seven volunteer examinations, coronary artery delineation on images reconstructed by using the least-squares method for motion detection with navigator echoes was found to be equal to that obtained by using edge detection. Images in five other volunteers covered the entire heart with multiple overlapping 3D slabs. The arteries were segmented from the background and could be viewed from any orientation. The lengths of contiguously visible vessels were as follows: left main coronary artery, 11.5 mm +/- 0.4 (mean +/- standard deviation); left anterior descending branch, 115.9 mm +/- 19.7; left circumflex branch, 97.2 mm +/- 12.5; and right coronary artery, 125.9 mm +/- 18.8. This respiratory gating technique clearly improved depiction of the coronary arteries.