MR-PET co-registration in upper abdominal imaging: quantitative comparison of two different T1-weighted gradient echo sequences: initial observations.

PURPOSE: The purpose of this study is to quantitatively compare the accuracy of spatial registration of Cartesian breath-hold 3D-GRE and non-respiratory-triggered free-breathing radial 3D-GRE images with PET data acquisition on whole-body hybrid MR-PET system. MATERIALS AND METHODS: Eight patients (six men and two women; mean age, 56.6 ± 5.5 years) with nine ablated hepatocellular carcinomas constituted our study population. Spatial coordinates (x, y, z) of the estimated isocenters of the ablated areas were independently determined by two radiologists. Both T1-weighted sequences were performed in the axial plane. Distance between the isocenter of the lesion on PET images and on both T1-weighted images was measured, and misregistration was calculated. Statistical analysis was performed using Student t test. RESULTS: Misalignment values of the hepatic ablation zones between PET and MR images were calculated at 4.94 ± 1.35 mm (reader 1) and 4.89 ± 2.21 mm (reader 2) for Cartesian 3D-GRE sequence, and 2.48 ± 0.65 mm (reader 1) and 2.72 ± 0.44 mm (reader 2) for the radial 3D-GRE sequence, with p values of 0.0011 and 0.0133, respectively. CONCLUSION: Radial 3D-GRE offers improved registration accuracy with PET, supporting the use of this T1-weighted sequence in upper abdominal MR-PET studies.

Patterns of [18F]FDG myocardial uptake in oncology patients as a predictor of myocardial ischaemia on stress myocardial perfusion imaging.

BACKGROUND: There is variable cardiac uptake observed on oncological ¹8F-fludeoxyglucose ([¹8F]FDG) positron emission/computed tomography (PET/CT). The main purpose of this study is to evaluate patterns of overnight fasting myocardial [¹8F]FDG uptake in oncological PET/CT and analyse the relationship between myocardial [¹8F]FDG uptake and myocardial ischaemia on stress single-photon emission CT (SPECT) myocardial perfusion imaging (MPI). MATERIAL AND METHODS: A total of 362 subjects underwent both oncological PET/CT and stress SPECT MPI within 3 months of each other. Subjects with focal-mass-like [¹8F]FDG myocardial uptake raising the suspicion of cardiac metastasis and subjects with coronary artery disease (CAD) were excluded. The myocardial [18F]FDG uptake was classified into four patterns. RESULTS: Abnormal SPECT MPI was noted in 91 (25%) patients; 220 (61%) patients had completely absent [18F]FDG uptake, 80 (22%) had diffuse [¹8F]FDG uptake, 39 (11%) had focal on diffuse [¹8F]FDG uptake, and 23 (6%) had focal or regional myocardial [¹8F]FDG uptake, the regional [¹8F]FDG myocardial uptake was the most predictive of myocardial ischaemia on SPECT MPI, and there were positive associations between age, sex, hypertension, tobacco smoking, hypercholesterolemia, and left ventricular ejection, a fair agreement was noted between the focal or regional FDG uptake and presence of ischaemia on SPECT, K = 0.394 (95% CI 0.164 to 0.189). CONCLUSIONS: Based on the presented findings, the physiological myocardial [¹8F]FDG uptake in fasting oncology patients is variable. The regional myocardial [¹8F]FDG uptake pattern is the most frequent pattern associated with myocardial ischaemia on stress SPECT MPI, however, the agreement between regional FDG uptake and presence of ischaemia on SPECT is fair.

Cardiac and pericardial tumors: A potential application of positron emission tomography-magnetic resonance imaging.

Cardiac and pericardial masses may be neoplastic, benign and malignant, non-neoplastic such as thrombus or simple pericardial cysts, or normal variants cardiac structure can also be a diagnostic challenge. Currently, there are several imaging modalities for diagnosis of cardiac masses; each technique has its inherent advantages and disadvantages. Echocardiography, is typically the initial test utilizes in such cases, Echocardiography is considered the test of choice for evaluation and detection of cardiac mass, it is widely available, portable, with no ionizing radiation and provides comprehensive evaluation of cardiac function and valves, however, echocardiography is not very helpful in many cases such as evaluation of extracardiac extension of mass, poor tissue characterization, and it is non diagnostic in some cases. Cross sectional imaging with cardiac computed tomography provides a three dimensional data set with excellent spatial resolution but utilizes ionizing radiation, intravenous iodinated contrast and relatively limited functional evaluation of the heart. Cardiac magnetic resonance imaging (CMR) has excellent contrast resolution that allows superior soft tissue characterization. CMR offers comprehensive evaluation of morphology, function, tissue characterization. The great benefits of CMR make CMR a highly useful tool in the assessment of cardiac masses. (Fluorine 18) fluorodeoxygluocse (FDG) positron emission tomography (PET) has become a corner stone in several oncological application such as tumor staging, restaging, treatment efficiency, FDG is a very useful imaging modality in evaluation of cardiac masses. A recent advance in the imaging technology has been the development of integrated PET-MRI system that utilizes the advantages of PET and MRI in a single examination. FDG PET-MRI provides complementary information on evaluation of cardiac masses. The purpose of this review is to provide several clinical scenarios on the incremental value of PET and MRI in the evaluation of cardiac masses.

Analysis of metastatic involvement in bone using anatomical and functional information from 18F-FDG PET/CT.

PURPOSE: Although the overall incidence of bone metastasis is not known, over one-half of the people who die of cancer in the USA every year are thought to have bone involvement. In this study we have developed a method to quantify the metabolic and anatomic changes induced by different types of bone metastases in cancer patients using PET/CT images. PATIENTS AND MATERIALS: Seventy-three cancer patients with no previous history of chemotherapy or radiotherapy who had definite bone metastases documented by PET/CT and other conventional modalities were selected for this study. PET and computed tomography (CT) images were resampled to the same pixel size. Thereafter, the bone structure was segmented using thresholding. The 50% of the maximum standardized uptake value within the bone mask was used to identify bone lesions in each slice. Using the final regions of interest defined at 70% of the maximum, the lesion characteristics including the mean Hounsfield Units were computed from the PET/CT images. The lesions were subjected to visual confirmation by an experienced physician who also categorized them on the basis of the appearances in CT as lytic, sclerotic, mixed, or no-change type. The lesion characteristics were compared using statistical methods. RESULTS: In all, 340 bony lesions in 73 patients with different cancer types were analyzed. The lesions were further categorized into four groups on the basis of their anatomical location. The spine hosts the largest number of lesions. The lumbar bones are the most preferential sites within the spine. Statistical comparison of CT values indicated that the difference between no-change and lytic types was significant. Uptake period did not seem to have a significant impact on no-change and sclerotic types. Quantitatively, maximum standardized uptake value for lytic, no change, mixed, and sclerotic lesions were 7.4, 6.1, 8.2, and 7.2, respectively. CONCLUSION: A quantitative method provides a convenient way that may serve as a useful tool in monitoring and assessing the response to therapy.

Breast Arterial Calcifications on Mammography Do Not Predict Myocardial Ischemia on Myocardial Perfusion Single-Photon Emission Computed Tomography.

BACKGROUND: The aim of this study was to determine if breast arterial calcification (BAC) on mammography predicts myocardial ischemia (MI) on stress myocardial perfusion single-photon emission computed tomography (MPS). BAC is a type of medial artery calcification that can be seen incidentally on mammography, but the relationship between coronary artery calcification and MI on MPS is yet unknown. METHODS: A total of 435 consecutive women underwent mammography and stress MPS within 1 year of each other. BAC was quantitatively evaluated (0 - 13). Patients with known coronary artery diseases (CADs) such as coronary artery bypass grafting (CABG), percutaneous coronary intervention (PCI), MI, positive coronary angiogram or positive MPS were excluded from the study. Risk factors for CAD were obtained from a chart review. RESULTS: The mean age was 58 ± 8 years. BAC was found in 258 (59%) of the study population. BAC-positive patients were significantly older than BAC-negative patients (P < 0.0001), there were strong associations between BAC and hypertension (P = 0.0309), chronic kidney disease (CKD) (P = 0.0001), and diabetes (P = 0.0309), but there were significant associations between BACV and hyperlipidemia, family history of CAD, and smoking (P = 0.6856, P = 0.9642, and P = 0.087, respectively). The mean score of BAC was 5 ± 5 in patients with normal MPS and was 6 ± 6 in patients with abnormal MPS. There were no associations between total BAC and MPS results (P = 0.2095), and between BAC categories and MPS result (P = 0.3069). CONCLUSIONS: Based on our study, the presence and severity of BAC on screening or diagnostic mammography do not predict MI on stress MPS, and further cardiac workup based on the presence of BAC is not warranted. BAC is very common in mammography up to 59% and associated with age, diabetes, CKD, and hypertension. In contrast, the prevalence of MI is only 13% in women with BAC and associated with age, diabetes, CKD, hyperlipidemia, and impaired left ventricular function.

Role of Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography in the Evaluation of Head and Neck Carcinoma.

Fluorodeoxyglucose (FDG)-positron emission tomography-computed tomography (PET-CT) has been playing a pivotal role in tumor imaging for the past 20 years. Head and neck (HN) cancers are a good example that can illustrate such unique role of FDG imaging contributing to the patient's management. In this review article, we will describe the normal physiological distribution of FDG within HN structures focusing on its limitations and pitfalls. In addition, we will be also describing its role in the initial staging and restaging of the disease, particularly with regard to therapy response assessment. Furthermore, its role in the evaluation of patients with malignant cervical adenopathy from an unknown primary will be described. In 2016, the Royal College of Radiologists in its third edition published evidence-based guidelines for PET-CT use in HN cancer emphasizing its rule in all these clinical scenarios that are being described in this review. Finally, we will be highlighting future directions in the field of molecular imaging of HN tumors with a special emphasis on the new PET tracers.

The relationship between coronary artery calcification and myocardial perfusion in asymptomatic women.

BACKGROUND AND OBJECTIVES: No data are available in Saudi Arabia on the relationship between coronary artery calcification (CAC) and myocardial perfusion scintigraphy (MPS) in asymptomatic women, for determining subclinical coronary artery disease (CAD). The main objective of this study was to investigate the relationship between the presence of CAC and stress-induced myocardial ischemia by MPS in asymptomatic women. DESIGN AND SETTING: Single-center retrospective study over a 2-year period. METHODS: One hundred and one women (mean [SD] age, 56 [11] years) without known CAD underwent both MPS and CAC scanning within 3 months. The frequency of ischemia by MPS was compared with the presence or absence of CAC and the number of CAD risk factors. RESULTS: The prevalence of ischemic MPS was 22% (22/101). Among the 22 patients with ischemic MPS, the CAC score was 0 in 5 patients of 22 (23%), 1 to 200 in 4 patients of 22 (18%), and more than 200 in 13 patients of 22 (59%) (P=.0001). In contrast, among the 79 patients with normal MPS, the CAC score was 0 in 44 of 79 (56%) patients, 1 to 200 in 25 of 79 (32%), and more than 200 in 10 of 79 (13%). The presence or absence of CAC was the single most important predictor of the MPS result (P=.0001). CONCLUSIONS: Moderate to severe CAC is associated with ischemic MPS in more than 50% of asymptomatic women with 2 or more CAD risk factors. Abnormal MPS is rarely associated with a 0 CAC score. Normal MPS does not exclude subclinical CAD. Therefore, CAC screening is an appropriate initial screening test for CAD in asymptomatic women.

Coronary artery calcification detected by PET/CT scan as a marker of myocardial ischemia/coronary artery disease.

BACKGROUND: There have been no data with regard to the relationship between coronary artery calcification (CAC) detected with positron emission tomography (PET)/computed tomography (CT), as incidental findings, and myocardial perfusion single photon computed tomography (MPS) results in patients with cancer. OBJECTIVES: The main objective of this study was to investigate the relationship between CAC detected on the CT component of PET/CT and abnormal MPS in patients with cancer before oncologic surgery. METHOD: A total of 157 patients without known coronary disease and clinically proven indication for PET/CT underwent PET/CT and MPS as a routine preoperative workup. PET/CT and MPS were performed within 3 months. The frequency of abnormal MPS was compared with the presence or absence of CAC. CAC was evaluated visually. RESULTS: Among 81 patients with no CAC, MPS results were normal in 71 patients (88%). Only 10 patients (20%) with no CAC had abnormal MPS (P<0.005) results. However, in the total patient population with visually detectable CAC (76 patients), MPS results were normal in 36 patients (47%) and abnormal in 40 patients (53%) with no statistically significant value. CAC and diabetes mellitus were the most potent predictors of abnormal MPS by multivariable analysis. CONCLUSIONS: Visual detection of CAC in the CT component of PET/CT is a strong predictor of MPS results. The presence of CAC is associated with a high likelihood of abnormal MPS, but the absence of CAC is rarely associated with abnormal MPS. These findings imply a potential role for applying routine visual CAC detection in the CT component of PET/CT and might obviate unnecessary MPS indications in the preoperative evaluation in patients with cancer.