Impact of Obesity on Nuclear Medicine Imaging

Exponential dosing to standardize myocardial perfusion image quality with rubidium-82 PET

BACKGROUND

82Rb PET is commonly performed using the same injected activity in all patients, resulting in lower image quality in larger patients. This study compared 82Rb dosing with exponential vs proportional functions of body weight on the standardization of myocardial perfusion image (MPI) quality.

METHODS

Two sequential cohorts of N = 60 patients were matched by patient weight. Rest and dipyridamole stress 82Rb PET was performed using 0.1 MBq·kg-2 exponential and 9 MBq·kg-1 proportional dosing. MPI scans were compared qualitatively with visual image quality scoring (IQS) and quantitatively using the myocardium-to-blood contrast-to-noise ratio (CNR) and blood background signal-to-noise ratio (SNR) as a function of body weight.

RESULTS

Average (min-max) patient body weight was 81 ± 18 kg (46-137 kg). Proportional dosing resulted in decreasing CNR, SNR, and visual IQS with increasing body weight (P < 0.05). Exponential dosing eliminated the weight-dependent decreases in these image quality metrics that were observed in the proportional dosing group.

CONCLUSION

82Rb PET dosing as an exponential (squared) function of body weight produced consistent stress perfusion image quality over a wide range of patient weights. Dramatically lower doses can be used in lighter patients, with the equivalent population dose shifted toward the heavier patients to standardize diagnostic image quality.

Deep Learning Denoising Improves and Homogenizes Patient [18F]FDG PET Image Quality in Digital PET/CT

Given the constant pressure to increase patient throughput while respecting radiation protection, global body PET image quality (IQ) is not satisfactory in all patients. We first studied the association between IQ and other variables, in particular body habitus, on a digital PET/CT. Second, to improve and homogenize IQ, we evaluated a deep learning PET denoising solution (Subtle PET^TM) using convolutional neural networks. We analysed retrospectively in 113 patients visual IQ (by a 5-point Likert score in two readers) and semi-quantitative IQ (by the coefficient of variation in the liver, CV_liv) as well as lesion detection and quantification in native and denoised PET. In native PET, visual and semi-quantitative IQ were lower in patients with larger body habitus (p < 0.0001 for both) and in men vs. women (p ≤ 0.03 for CV_liv). After PET denoising, visual IQ scores increased and became more homogeneous between patients (4.8 ± 0.3 in denoised vs. 3.6 ± 0.6 in native PET; p < 0.0001). CV_liv were lower in denoised PET than in native PET, 6.9 ± 0.9% vs. 12.2 ± 1.6%; p < 0.0001. The slope calculated by linear regression of CV_liv according to weight was significantly lower in denoised than in native PET (p = 0.0002), demonstrating more uniform CV_liv. Lesion concordance rate between both PET series was 369/371 (99.5%), with two lesions exclusively detected in native PET. SUV_max and SUV_peak of up to the five most intense native PET lesions per patient were lower in denoised PET (p < 0.001), with an average relative bias of -7.7% and -2.8%, respectively. DL-based PET denoising by Subtle PET^TM allowed [¹⁸F]FDG PET global image quality to be improved and homogenized, while maintaining satisfactory lesion detection and quantification. DL-based denoising may render body habitus adaptive PET protocols unnecessary, and pave the way for the improvement and homogenization of PET modalities.

Cardiovascular positron emission tomography: established and emerging role in cardiovascular diseases

Cardiac positron emission tomography (PET) imaging has established themselves firmly as excellent and reliable functional imaging modalities in assessment of the spectrum of coronary artery disease. With the explosion of technology advances and the dream of flow quantification now a reality, the value of PET is now well realized. Cardiac PET has proved itself as precise imaging modality that provides functional imaging of the heart in addition to anatomical imaging. It has established itself as one of the best available techniques for evaluation of myocardial viability. Hybrid PET/computed tomography provides simultaneous integration of coronary anatomy and function with myocardial perfusion and metabolism, thereby improving characterization of the dysfunctional area and chronic coronary artery disease. The availability of quantitative myocardial blood flow evaluation with PET provides additional prognostic information and increases diagnostic accuracy in the management of patients with coronary artery disease. Hybrid imaging seems to hold immense potential in optimizing management of cardiovascular diseases and furthering clinical research.

Modification of [18F]-FDG PET/CT imaging protocols in obese oncology patients: A nationwide survey

INTRODUCTION

The use of medical imaging for diagnosis, staging and follow-up in Oncology context is incredibly important, being the use of [18F]-FDG PET/CT particularly advantageous in specific contexts like the case of obese patients. However, imaging the latter can be challenging sometimes, since their own body size may affect overall image quality and adds technical difficulties for the operator(s) performing the examination.

METHODS

This research project was developed with the aim of analysing the current personal practices of Portuguese Nuclear Medicine Technologists (NMTs) in the adaptation of ¹⁸F-FDG PET/CT oncological protocols for obese patients and comparing the results with parameters referenced in literature. A non-experimental research study was conducted using a survey delivered online to NMTs through social media platforms (Facebook® and LinkedIn®) and by sending the link directly to contacts within the research team professional and personal networks.

RESULTS

Answers from a total of 26 participants were obtained, with 88.5% of participants admitting modifying technical protocols in examinations for obese patients. Changes in PET protocols included an increase in the administered activity (60.9%), an increase in scan time per individual bed position (69.6%) and the use of Time-of-Flight (TOF) technology whenever available. Protocol changes in CT included increasing the mA (82.6%), raising the KVp (47.8%), the application of iterative reconstruction (69.6%) and the use of automatic exposure control (AEC) (52.2%). The remaining parameters (pitch, algorithm, slice thickness, display FOV, gantry rotation time and energy acceptance window) were claimed not to be modified by around 90% of professionals.

CONCLUSION

Portuguese NMTs tend to change the [18F]-FDG PET/CT protocols for obese patients. However, while some of the parameters appear to be contradictory or redundant, others require further optimisation, especially in the CT component.

IMPLICATIONS FOR PRACTICE

Efforts should be made to optimize acquisition protocols used in [18F]-FDG PET/CT scans for obese patients.

Inpatient medical management of severe pediatric obesity: Literature review and case reports

Pediatric obesity rates continue to rise steeply with significant adverse effects on health outcomes across the lifespan. Significant obesity can affect the efficacy, side effects, and ability to use certain treatment, medication, or imaging modalities needed in the evaluation and management of acute pediatric conditions. Inpatient settings are rarely used as an opportunity for weight counseling and thus there is a paucity of clinical guidelines on how to manage severe obesity in the inpatient setting. We present a literature review and three patient cases with single-center protocol for non-surgical management of severe obesity in children admitted for other acute medical reasons. We performed a PubMed review from January 2002 to February 2022 utilizing keywords: "inpatient," "obesity," and "intervention." For our cases, we identified three patients with severe obesity acutely impacting their health while admitted for medical treatment who concurrently underwent acute, inpatient, weight loss regimens at a single children's hospital. The literature search yielded 33 articles describing inpatient weight loss treatments. Three patients met case criteria, all three of which demonstrated a decrease in their weight in excess percent of the 95th percentile after inpatient weight-management protocol implementation (% reduction BMI_p95: 16%-30%). This highlights obesity acutely limits or impacts specific medical care required during inpatient admissions in pediatric patients. It also suggests that implementation of an inpatient weight-management protocol during admission may provide an opportune setting to support acute weight loss and overall improved health outcomes in this high-risk cohort.

Investigating the lesion detectability of Tc-99m planar scintigraphy acquired with LEHRS collimator for patients with different body sizes: A phantom study

Purpose

The aim of this work was to investigate the lesion detectability of Tc‐99m planar scintigraphy acquired with a low‐energy high‐resolution and sensitivity (LEHRS) collimator and processed by Clarity 2D for patients with different body sizes through phantom study.

Methods

A NEMA IEC body phantom set was covered by two layers of 25‐mm‐thick bolus to construct phantom in three different sizes. All image data were performed on a Discovery NM/CT 870 DR with an LEHRS collimator and processed by Clarity 2D with blend ratio a of 0%, 20%, 40%, 60%, 80%, and 100%. The lesion detectability in gamma scintigraphy was evaluated by calculating the contrast‐to‐noise ratio (CNR). Multiple linear regression methods were used to analyze the impact of body size, target size, and Clarity 2D blending weight on the lesion detectability of Tc‐99m planar scintigraphy.

Results

It was found that changing the blend ratio could improve CNR, and this phenomenon was more significant in anterior view than in posterior view. Our results also suggested that the blend ratio should be selected according to patient body size in order to maintain consistent CNR. Hence, when a blend ratio of 60% was used for a patient before cancer treatment, a lower blend ratio should be used for the same patient experiencing treatment‐related weight loss to achieve consistent lesion detectability in Tc‐99m planar scintigraphy acquired with LEHRS and processed by Clarity 2D.

Conclusion

The magnitude of photon attenuation and scattering is higher in patients with larger body size, so Tc‐99m planar scintigraphy usually has lower lesion detectability in obese patients. Although photon attenuation and scattering are inevitable during image formation, their impacts on image quality can be eased by employing appropriate image protocol parameters.

Elgazzar A. Potential Pitfalls of Steatopygia on Bone Scintigraphy and the Added Value of Single Photon Emission Computed Tomography and Single Photon Emission Computed Tomography/Computed Tomography

OBJECTIVES

The aims of the study were to assess the prevalence of steatopygia on bone scintigraphy of obese patients and to evaluate its effect on the appearance of the lumbar spine, and the added benefit of single photon emission computed tomography (SPECT) and SPECT/computed tomography (SPECT/CT) in overcoming possible artifacts.

METHODS

Patients with BMI ≥30 who underwent bone scintigraphy between 2016 and 2019 were included. Three nuclear medicine consultants reviewed the studies to determine whether significant steatopygia was present, and whether it resulted in attenuation of underlying lumber spine and crease edge artifact. SPECT or SPECT/CT images were reviewed to evaluate their impact on diagnosis.

RESULTS

56 out of the 100 patients were noted to have steatopygia on planar images. Among the group of 80 obese patients, 50% showed steatopygia, while in the group of 20 morbidly obese patients, 80% showed steatopygia. 32 of the 56 patients with steatopygia had significant attenuation at the lower lumber vertebrae. Nine of these patients showed crease edge artifact. SPECT and SPECT/CT clarified the scintigraphic abnormalities noted in all patients including those with edge artifact alleviating diagnostic difficulty. Among the 9 patients with edge artifact, 6 patients showed normal appearance on SPECT/CT images while three showed true abnormalities.

CONCLUSIONS

Steatopygia is common on bone scintigraphy of obese patients, higher in females and morbidly obese patients. Obesity-related artifacts in bone scintigraphy, including attenuation effect and edge artifact, are common in this patient group. SPECT or SPECT/CT improves the diagnostic accuracy by overcoming the effects of steatopygia seen on planar images.

Dosing Therapeutic Radiopharmaceuticals in Obese Patients

The prevalence of obesity has increased dramatically in the Western population. Obesity is known to influence not only the proportion of adipose tissue but also physiological processes that could alter drug pharmacokinetics. Yet, there are no specific dosing recommendations for radiopharmaceuticals in this patient population. This could potentially lead to underdosing and thus suboptimal treatment in obese patients, while it could also lead to drug toxicity due to high levels of radioactivity. In this review, relevant literature is summarized on radiopharmaceutical dosing and pharmacokinetic properties, and we aimed to translate these data into practical guidelines for dosing of radiopharmaceuticals in obese patients. For radium-223, dosing in obese patients is well established. Furthermore, for samarium-153-ethylenediaminetetramethylene (EDTMP), dose-escalation studies show that the maximum tolerated dose will probably not be reached in obese patients when dosing on MBq/kg. On the other hand, there is insufficient evidence to support dose recommendations in obese patients for rhenium-168-hydroxyethylidene diphosphonate (HEDP), sodium iodide-131, iodide 131-metaiodobenzylguanidine (MIBG), lutetium-177-dotatate, and lutetium-177-prostate-specific membrane antigen (PSMA). From a pharmacokinetic perspective, fixed dosing may be appropriate for these drugs. More research into obese patient populations is needed, especially in the light of increasing prevalence of obesity worldwide.

Early Institutional Experience of Dual Tracer and Single-Photon Emission Computed-Tomography/Computed-Tomography Mapping for Sentinel Node Biopsy: A Report of Two Early-Stage Breast Cancer

Intraoperative sentinel lymph node mapping (SLNM) with methylene blue dye (MBD) tracer has been the recommended method to detect SLN in early-stage breast cancer patients in low-resource settings. However, the use of MBD alone is hampered by the high false-negative rate; thus, it requires coupling with other mapping methods if the appropriate infrastructure and services are available. In this article, we present two prospective cases detailing our initial experience using the gold-standard dual tracer technique (DTT: MBD and 99mTc-nanocolloid radioisotope) in combination with hybrid single-photon emission computed-tomography/computed-tomography (SPECT/CT) preoperative mapping for image-guided SLN biopsy (SLNB). Overall, both studies were successful in identifying the SLNs, which aided in mapping the possible anatomical spread of the disease.

Stress CMR in patients with obesity: insights from the Stress CMR Perfusion Imaging in the United States (SPINS) registry

AIMS

Non-invasive assessment and risk stratification of coronary artery disease in patients with large body habitus is challenging. We aim to examine whether body mass index (BMI) modifies the prognostic value and diagnostic utility of stress cardiac magnetic resonance imaging (CMR) in a multicentre registry.

METHODS AND RESULTS

The SPINS Registry enrolled consecutive intermediate-risk patients who presented with a clinical indication for stress CMR in the USA between 2008 and 2013. Baseline demographic data including BMI, CMR indices, and ratings of study quality were collected. Primary outcome was defined by a composite of cardiovascular death and non-fatal myocardial infarction. Of the 2345 patients with available BMI included in the SPINS cohort, 1177 (50%) met criteria for obesity (BMI ≥ 30) with 531 (23%) at or above Class 2 obesity (BMI ≥ 35). In all BMI categories, >95% of studies were of diagnostic quality for cine, perfusion, and late gadolinium enhancement (LGE) sequences. At a median follow-up of 5.4 years, those without ischaemia and LGE experienced a low annual rate of hard events (<1%), across all BMI strata. In patients with obesity, both ischaemia [hazard ratio (HR): 2.14; 95% confidence interval (CI): 1.30-3.50; P = 0.003] and LGE (HR: 3.09; 95% CI: 1.83-5.22; P < 0.001) maintained strong adjusted association with the primary outcome in a multivariable Cox regression model. Downstream referral rates to coronary angiography, revascularization, and cost of care spent on ischaemia testing did not significantly differ within the BMI categories.

CONCLUSION

In this large multicentre registry, elevated BMI did not negatively impact the diagnostic quality and the effectiveness of risk stratification of patients referred for stress CMR.

Molecular Breast Imaging: Administered Activity Does Not Require Adjustment Based on Patient Size

At our institution, molecular breast imaging (MBI) is performed with 300 MBq of ^99mTc-sestamibi for all patients. For some nuclear medicine procedures, administered activity or imaging time is increased for patients of larger size to obtain adequate counts. Our objective was to assess whether uptake of ^99mTc-sestamibi in the breast is influenced by patient size. Methods: Records from patients who underwent a clinical MBI examination between July and November 2016 were reviewed. Those in whom our standard injection and preparation techniques were followed were included in the analysis. Patients were injected with approximately 300 MBq of ^99mTc-sestamibi. Residual activity was measured to allow calculation of exact administered activity for each patient. Breast images were acquired at 10 min/view using a dual-head cadmium zinc telluride-based γ-camera. Breast thickness was measured as the distance between the 2 detectors. Patient height, weight, body surface area, and body mass index were obtained from records. Lean body mass with the James equation (LBM_James) and Janmahasatian correction (LBM_Janma) was calculated. Count density in the breast tissue was measured by drawing a region of interest around the central breast tissue of the right breast mediolateral-oblique view of the lower detector. Count density was expressed as cts/cm²/MBq of administered activity. Spearman correlation coefficient (r_s) was calculated. Results: A total of 200 patients were analyzed. No dose infiltration was suspected at any injection. Average administered activity was 292 MBq (SD, 13.8 MBq; range, 247-326 MBq). Average count density was 7.2 cts/cm²/MBq (SD, 2.7 cts/cm²/MBq; range, 3.1-17.8 cts/cm²/MBq). MBI count density was weakly negatively correlated with height (r_s = -0.18; P = 0.01), weight (r_s = -0.23; p = <0.001), body mass index (r_s = -0.16; P = 0.02), body surface area (r_s = -0.22; P = 0.002), LBM_James (r_s = -0.23; P = 0.001), and LBM_Janma (r_s = -0.23; P = 0.001). No correlation was observed between count density and breast thickness (r_s = 0.06; P = 0.37). Conclusion: Our results suggest a lack of relationship between uptake of ^99mTc-sestamibi in breast tissue and body size or compressed breast thickness. Altering from the standard 300 MBq of administered activity for larger patients is likely unnecessary.

Diagnostic Challenge of Staging Metastatic Bone Disease in the Morbidly Obese Patients: A Primary Study Evaluating the Usefulness of 18F-Sodium Fluoride (NaF) PET-CT

PURPOSE

Optimizing diagnostic imaging may be challenging in obese patients. The quality of conventional bone scintigraphy can be poor in the morbidly obese due to a combination of factors including high background soft tissue activity. In comparison, sodium fluoride (F-NaF PET-CT) has a better target-to-background ratio attributed to rapid single-pass extraction and fast clearance from the soft tissues. The aim of the present study is to assess the diagnostic efficacy of F-NaF PET-CT in the evaluation of bone metastases in obese cancer patients.

PATIENTS AND METHODS

Two hundred twelve morbidly obese patients (body mass index, 45 ± 5.1 kg/m; mean age, 57 years; range, 32-81 years) with body mass index greater than 40 kg/m referred for NaF PET-CT for osseous staging of malignancy were retrospectively analyzed. All patients underwent PET-CT scan by injecting 2.2 MBq/kg (0.06 mCi/kg) of F-NaF.

RESULTS

F-NaF PET-CT was definitely benign in 145, possibly benign in 3, equivocal in 4, possibly malignant in 13, and definitely malignant in 47 patients. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of F-NaF PET-CT were 93.1%, 96.1%, 90%, 97.3%, and 95.2%, respectively (95% confidence interval).

CONCLUSIONS

The results of the present study indicate that F-NaF PET-CT retains its high diagnostic accuracy in morbidly obese patients and, by inference, can be a preferred functional modality in these patients.

Assessment of cardiovascular impairment in obese patients: Limitations and troubleshooting of available imaging tools

The prevalence and severity of obesity have increased over recent decades, reaching worldwide epidemics. Obesity is associated to coronary artery disease and other risk factors, including hypertension, heart failure and atrial fibrillation, which are all increased in the setting of obesity. Several noninvasive cardiac imaging modalities, such as echocardiography, cardiac computed tomography, magnetic resonance and cardiac gated single-photon emission computed tomography, are available in assessing coronary artery disease and myocardial dysfunction. Yet, in patients with excess adiposity the diagnostic accuracy of these techniques may be limited due to some issues. In this review, we analyze challenges and possibilities to find the optimal cardiac imaging approach to obese population.

Effectiveness of Repeat 18F-Fluorodeoxyglucose Positron Emission Tomography Computerized Tomography (PET-CT) Scan in Identifying Interval Metastases for Patients with Esophageal Cancer

INTRODUCTION

An 18F-fluorodeoxyglucose positron emission tomography-computerized tomography (PET-CT) scan is performed after neoadjuvant chemoradiation (nCRT) to restage esophageal cancer. The purpose of this study was to determine the ability of PET-CT to accurately identify interval metastatic disease following nCRT.

METHODS

This was a single-institution retrospective review (January 2005-February 2012) of patients with esophageal cancer treated with nCRT who underwent pre- and post-nCRT PET-CT.

RESULTS

A total of 283 patients were treated with nCRT, of whom 258 (91.2%) had both a pre- and post-nCRT PET-CT. On the post-nCRT PET-CT, 64 patients (24.8%) had interval findings concerning for metastatic disease. Of these patients, only 10 (15.6%) had true-positive findings of metastatic disease (six biopsy proven). The sites of interval metastases included bone (4), liver (3), peritoneum (1), mediastinal lymph nodes (1), and cervical lymph nodes (1). The positive predictive value of post-nCRT PET-CT for interval metastases was 15.6% (10/64), and the yield for detecting metastases since the pre-nCRT PET-CT was 3.9% (10/258). The work-up of the 54 patients (20.9% of the initial starting group) with false-positive post-nCRT findings included biopsy (24.6%) and immediate additional imaging (45.2%). A total of 208 patients proceeded with surgery: 163 (78.4%) had no new findings on post-nCRT PET-CT, and 45 (21.6%) had new false-positive findings. False-positive sites mainly included the lung (15) and liver (14).

CONCLUSIONS

The yield of post-nCRT PET-CT for the detection of new metastatic disease was 3.9%. Post-nCRT PET-CT often leads to a high proportion of false positives and subsequent investigational work-up.

Structure and Activities of Nuclear Medicine in Kuwait

The practice of nuclear medicine in Kuwait began in 1965 as a clinic for treating thyroid diseases. The practice developed gradually and until 1981 when the Faculty of Medicine established the Division of Nuclear Medicine in the Department of Radiology, which later became a separate department responsible for establishing and managing the practice in all hospitals of Kuwait. In 1987, a nuclear medicine residency program was begun and it is administered by Kuwait Institute for Medical Specializations originally as a 4-year but currently as a 5-year program. Currently there are 11 departments in the ministry of health hospitals staffed by 49 qualified attending physicians, mostly the diplomats of the Kuwait Institute for Medical Specializations nuclear medicine residency program, 4 academic physicians, 2 radiopharmacists, 2 physicists, and 130 technologists. These departments are equipped with 33 dual-head gamma cameras, 10 SPET/CT, 5 PET/CT, 2 cyclotrons, 1 breast-specific gamma imaging, 1 positron-emitting mammography, 10 thyroid uptake units, 8 technegas machines, 7 PET infusion systems, and 8 treadmills. Activities of nuclear medicine in Kuwait include education and training, clinical service, and research. Education includes nuclear medicine technology program in the Faculty of Allied Health Sciences, the 5-year residency program, medical school teaching distributed among different modules of the integrated curriculum with 14 didactic lecture, and other teaching sessions in nuclear medicine MSc program, which run concurrently with the first part of the residency program. The team of Nuclear Medicine in Kuwait has been active in research and has published more than 300 paper, 11 review articles, 12 book chapters, and 17 books in addition to 36 grants and 2 patents. A PhD program approved by Kuwait University Council would begin in 2016.

Preoperative Scintigrams to Identify the Sentinel Lymph Node in Breast Cancer: a Waste of Time?

Sentinel lymph node biopsy (SLNB) remains the gold standard for assessing axillary node status in breast cancer. Preoperative scintigrams have been used to identify the sentinel lymph node (SLN); however, their use is controversial. Studies suggest they add little to successful SLN detection in theatre, immediately prior to node excision. They have been associated with high false negatives, time expense, patient dissatisfaction, and unnecessary costs. The aim of the present study was to evaluate the diagnostic accuracy of scintigrams in comparison to intraoperative SLN identification techniques. This study included all patients undergoing a SLNB for breast cancer from April 2010 to 2011. Scintigram reports, operation notes, and histology results were analyzed. Mann-Whitney U and chi-squared tests were used for statistical analysis of data. Two hundred nineteen female patients with a median age of 59.6 years (24.0-89.9 years) were included in this study. Scintigram was performed in 185 and not in 34 patients due to time constraints. Combined γ-probe and Isosulfan blue dye for SLN detection (intraoperative methods) have an identification rate of 98.2 % (p = 0.005), compared to 92.4 % (p = 0.088) from scintigrams alone. Scintigrams confer no additional advantage to the operating surgeon for successful SLN detection and excision in theatre. Intraoperative SLN identification is more accurate and reliable. Routine scintigram use is unjustified and should be withdrawn from current practice.

Association of body mass index with increased cost of care and length of stay for emergency department patients with chest pain and dyspnea

BACKGROUND

High body mass index (BMI) increases the probability of indeterminate findings on diagnostic studies, length of stay, and cost of care for hospitalized patients. No study has examined the economic and operational impact of BMI in patients with chest complaints presenting to the emergency department (ED). The objective was to measure the association of BMI with the main outcomes of cost of care, length of stay (including time in the ED and time in the wards if admitted), and radiation exposure in patients presenting to the ED with chest pain and dyspnea.

METHODS AND RESULTS

This was a prospective, 4-center, outcomes study. Patients were adults with dyspnea and chest pain, nondiagnostic electrocardiograms, and no obvious diagnosis. Patients were followed for the main outcomes for 90 days. Outcomes that were stratified by BMI in 5 categories, underweight, normal weight, overweight, obese, and morbidly obese, were compared using the Kruskall-Wallis rank test, and the independent predictive value of BMI was tested with multivariate regressions. Compared with medical costs for normal weight patients, costs were 22% higher for overweight patients (P=0.077), 28% higher for obese patients (P=0.020), and 41% higher for morbidly obese patients (P=0.015). Morbidly obese patients without computerized tomographic scanning stayed in the hospital 34% longer than normal weight patients (P=0.073), and morbidly obese patients with computerized tomographic scanning stayed in the hospital 44% longer than normal weight patients (P=0.083). BMI was not a significant predictor of radiation exposure. Morbidly obese patients had the highest proportion (87%) of no significant cardiopulmonary diagnosis for 90 days after computerized tomographic pulmonary angiography.

CONCLUSIONS

BMI was associated with increases in cost of care and length of hospital stay for patients with chest pain and dyspnea. These results emphasize a need for specific protocols to manage morbidly obese patients presenting to the ED with chest pain and dyspnea. Clinical Trial Registration- http://www.clinicaltrials.gov. Unique identifier: NCT01059500.

Challenges of pelvic imaging in obese women

Obesity is a major global health concern affecting all ages, socioeconomic groups, and countries. Although men have higher rates of overweight, women have higher rates of obesity. In the United States, more than 60% of women are overweight or obese, with slightly more than one-third considered frankly obese. Obesity is a major risk factor for noncommunicable diseases such as diabetes mellitus, cardiovascular disease, hypertension, stroke, and specific cancers. Obesity is associated with increased mortality for all cancers, with the highest death rates occurring in the heaviest women. Obesity can contribute to missed diagnoses, nondiagnostic results of imaging studies, imaging examination cancellation because of weight or girth restrictions, scheduling of inappropriate examinations, and increased radiation dose exposure. The utility of the clinical examination is often limited in the obese woman, which results in an even greater reliance on imaging; however, the obese woman may experience a lowered quality of and less access to medical imaging. Recognition of equipment limitations, imaging artifacts, optimization techniques, and appropriateness of modality choices is critical to providing good patient care to this health-challenged group. The clinical indication, the patient's weight, and the body diameters are three key factors to consider when choosing the most appropriate examination. Familiarity with the optimization of imaging techniques across all modalities is important to convert potentially suboptimal examinations into diagnostic-quality studies. The aim of this review is to identify key areas in which obesity affects the imaging care of women with pelvic conditions and to outline strategies to address these areas.

Diagnostic imaging in obesity

Magnetic resonance of the body offers different techniques for mapping fat deposits (MR Imaging) and analysis of organs with small amounts of lipids (MR Spectroscopy). Possible approaches for whole-body assessment of adipose tissue are presented and discussed and spectroscopic examinations in different organs are depicted. With magnetic resonance imaging (MRI) it has been shown that obesity per se is not a marker for metabolic failure, but depends on regional variations of body composition and ectopic lipid accumulation. In addition MRI of the brain is a powerful research tool to understand the brain's role in the development and maintenance of obesity and the overconsumption of foods in obese individuals. Sonography has a low accuracy in estimating hepatic steatosis until now. New sonographic methods have been evaluated to detect hepatic steatosis by physical properties of fatty tissue as tissue stiffness, sound absorption or sound speed. Nuclear medicine and in particular Positron Emission Tomography (PET) methods are used to explore central pathophysiology, brown adipose tissue activity and alterations in homeostatic feedback and gut-brain communication.

Cadmium-zinc-telluride myocardial perfusion imaging in obese patients

We have evaluated the impact of increased body mass on the quality of myocardial perfusion imaging using a latest-generation γ-camera with cadmium-zinc-telluride semiconductor detectors in patients with high (≥40 kg/m(2)) or very high (≥45 kg/m(2)) body mass index (BMI).

METHODS

We enrolled 81 patients, including 18 with no obesity (BMI < 30 kg/m(2)), 17 in World Health Organization obese class I (BMI, 30-34.9 kg/m(2)), 15 in class II (BMI, 35-39.9 kg/m(2)), and 31 in class III (BMI ≥ 40 kg/m(2)), including 15 with BMI ≥ 45 kg/m(2). Image quality was scored as poor (1), moderate (2), good (3), or excellent (4). Patients with BMI ≥ 45 kg/m(2) and nondiagnostic image quality (≤2) were rescanned after repositioning to better center the heart in the field of view. Receiver-operating-curve analysis was applied to determine the BMI cutoff required to obtain diagnostic image quality (≥3).

RESULTS

Receiver-operating-curve analysis resulted in a cutoff BMI of 39 kg/m(2) (P < 0.001) for diagnostic image quality. In patients with BMI ≥ 40 kg/m(2), image quality was nondiagnostic in 81%; after CT-based attenuation correction this decreased to 55%. Repositioning further improved image quality. Rescanning on a conventional SPECT camera resulted in diagnostic image quality in all patients with BMI ≥ 45 kg/m(2).

CONCLUSION

Patients with BMI ≥ 40 kg/m(2) should be scheduled for myocardial perfusion imaging on a conventional SPECT camera, as it is difficult to obtain diagnostic image quality on a cadmium-zinc-telluride camera.