The association of new-onset diabetes with subsequent diagnosis of pancreatic cancer-novel use of a large administrative database.

BACKGROUND: Screening options for pancreatic ductal adenocarcinoma (PDAC) are limited. New-onset type 2 diabetes (NoD) is associated with subsequent diagnosis of PDAC in observational studies and may afford an opportunity for PDAC screening. We evaluated this association using a large administrative database. METHODS: Patients were identified using claims data from the OptumLabs® Data Warehouse. Adult patients with NoD diagnosis were matched 1:3 with patients without NoD using age, sex and chronic obstructive pulmonary disease (COPD) status. The event of PDAC diagnosis was compared between cohorts using the Kaplan-Meier method. Factors associated with PDAC diagnosis were evaluated with Cox's proportional hazards modeling. RESULTS: We identified 640 421 patients with NoD and included 1 921 263 controls. At 3 years, significantly more PDAC events were identified in the NoD group vs control group (579 vs 505; P < 0.001). When controlling for patient factors, NoD was significantly associated with elevated risk of PDAC (HR 3.474, 95% CI 3.082-3.920, P < 0.001). Other factors significantly associated with PDAC diagnosis were increasing age, increasing age among Black patients, and COPD diagnosis (P ≤ 0.05). CONCLUSIONS: NoD was independently associated with subsequent diagnosis of PDAC within 3 years. Future studies should evaluate the feasibility and benefit of PDAC screening in patients with NoD.

Food-related parenting practices and styles in households with sibling children: A scoping review.

Interventions that promote responsive feeding in early childhood have been shown to reduce obesity risks. However, interventions mostly target parent-child dyads without considering the complexities of implementing responsive feeding across multiple children within a family unit. This scoping review aims to assess the extent and nature of current literature examining feeding in the context of siblings. Six electronic databases were searched (APA PsycINFO, CINAHL, Embase, Medline, ProQuest Dissertations & Theses Global, and Scopus) for articles published up until November 25, 2021. Studies were included if they compared the use of parent feeding practices and/or styles for two or more siblings aged ≤18 years. Data were extracted from relevant studies and analysed using basic descriptive statistics. A total of 18 studies from North America (n = 12) and Europe (n = 6) were included, with the majority targeting children between 6 and 18 years of age (n = 12). All studies were cross-sectional, with most designed to test differences in parent-reported feeding practices for siblings, primarily restriction and/or pressure to eat, in relation to differences in their characteristics (n = 12). The studies provide some evidence that parents may modify certain feeding practices or styles for siblings in response to differences in their characteristics, such as weight status and eating behaviours. Future research should examine processes that underlie feeding decisions in the context of siblings, including the contexts and consequences of differential feeding, with particular focus on early childhood when feeding interventions may be most effective.

An epistatic interaction between pre-natal smoke exposure and socioeconomic status has a significant impact on bronchodilator drug response in African American youth with asthma.

BACKGROUND: Asthma is one of the leading chronic illnesses among children in the United States. Asthma prevalence is higher among African Americans (11.2%) compared to European Americans (7.7%). Bronchodilator medications are part of the first-line therapy, and the rescue medication, for acute asthma symptoms. Bronchodilator drug response (BDR) varies substantially among different racial/ethnic groups. Asthma prevalence in African Americans is only 3.5% higher than that of European Americans, however, asthma mortality among African Americans is four times that of European Americans; variation in BDR may play an important role in explaining this health disparity. To improve our understanding of disparate health outcomes in complex phenotypes such as BDR, it is important to consider interactions between environmental and biological variables. RESULTS: We evaluated the impact of pairwise and three-variable interactions between environmental, social, and biological variables on BDR in 233 African American youth with asthma using Visualization of Statistical Epistasis Networks (ViSEN). ViSEN is a non-parametric entropy-based approach able to quantify interaction effects using an information-theory metric known as Information Gain (IG). We performed analyses in the full dataset and in sex-stratified subsets. Our analyses identified several interaction models significantly, and suggestively, associated with BDR. The strongest interaction significantly associated with BDR was a pairwise interaction between pre-natal smoke exposure and socioeconomic status (full dataset IG: 2.78%, p = 0.001; female IG: 7.27%, p = 0.004)). Sex-stratified analyses yielded divergent results for females and males, indicating the presence of sex-specific effects. CONCLUSIONS: Our study identified novel interaction effects significantly, and suggestively, associated with BDR in African American children with asthma. Notably, we found that all of the interactions identified by ViSEN were "pure" interaction effects, in that they were not the result of strong main effects on BDR, highlighting the complexity of the network of biological and environmental factors impacting this phenotype. Several associations uncovered by ViSEN would not have been detected using regression-based methods, thus emphasizing the importance of employing statistical methods optimized to detect both additive and non-additive interaction effects when studying complex phenotypes such as BDR. The information gained in this study increases our understanding and appreciation of the complex nature of the interactions between environmental and health-related factors that influence BDR and will be invaluable to biomedical researchers designing future studies.

25 Years of psychological research investigating disordered eating in people with diabetes: what have we learnt?

Disordered eating is a serious and under-recognized problem in people with diabetes. This narrative review summarizes the research contributions made by psychological science over the past 25 years to the study of disordered eating in people with type 1 or type 2 diabetes, and identifies gaps and future directions relevant to both healthcare professionals and researchers. Key focus areas of psychological research investigating disordered eating in people with diabetes have been: (1) defining and classifying types of disordered eating; (2) identifying demographic, diabetes-specific and psychosocial correlates of disordered eating, and developing theoretical models of disordered eating in people with type 1 diabetes; (3) identifying the physical and psychosocial consequences of disordered eating; and (4) developing screening measures to identify disordered eating in people with type 1 diabetes. Psychological science has made significant contributions over the past 25 years to our understanding of the nature of this problem and the multiple factors which may interrelate with disordered eating in people with diabetes. Key areas for further attention include: (1) a better definition of disordered eating subtypes in people with type 1 diabetes; (2) characterizing disordered eating in people with type 2 diabetes; and (3) developing multidisciplinary, evidence-based prevention and treatment interventions for comorbid disordered eating and diabetes.

Admission cardiotocography versus intermittent auscultation of the fetal heart in low-risk pregnancy during evaluation for possible labour admission - a multicentre randomised trial: the ADCAR trial.

OBJECTIVE: To assess the effect of admission cardiotocography (ACTG) versus intermittent auscultation (IA) of the fetal heart (FH) in low-risk pregnancy during assessment for possible labour on caesarean section rates. DESIGN: A parallel multicentre randomised trial. SETTING: Three maternity units in the Republic of Ireland. POPULATION: Healthy, low-risk pregnant women, at term and ≥ 18 years old, who provided written informed consent. METHODS: Women were randomised to receive IA of the FH or 20 minutes ACTG on admission for possible labour onset, using remote telephone randomisation. Both groups received IA during labour, with conversion to continuous CTG as clinically indicated. MAIN OUTCOME MEASURES: Caesarean section (primary outcome), obstetric interventions (e.g. continuous CTG during labour, fetal blood sampling, augmentation of labour) and neonatal morbidity (e.g. metabolic acidosis, admission to the neonatal intensive care unit, neonatal death). RESULTS: Based on 3034 women (1513 and 1521 randomised to IA and ACTG, respectively), there was no statistical difference between the groups in caesarean section [130 (8.6%) and 105 (6.9%) for IA and ACTG groups, respectively; relative risk (RR) 1.24; 95% CI 0.97-1.58], or in any other outcome except for use of continuous CTG during labour, which was lower in the IA group (RR 0.90, 95% CI 0.86-0.93). CONCLUSION: Our study demonstrates no differences in obstetric or neonatal outcomes between IA and ACTG for women with possible labour onset, other than an increased risk for continuous CTG in women receiving ACTG. TWEETABLE ABSTRACT: No differences in outcomes between intermittent auscultation and admission cardiotocography for women with possible labour onset.

BEARscc determines robustness of single-cell clusters using simulated technical replicates.

Single-cell messenger RNA sequencing (scRNA-seq) has emerged as a powerful tool to study cellular heterogeneity within complex tissues. Subpopulations of cells with common gene expression profiles can be identified by applying unsupervised clustering algorithms. However, technical variance is a major confounding factor in scRNA-seq, not least because it is not possible to replicate measurements on the same cell. Here, we present BEARscc, a tool that uses RNA spike-in controls to simulate experiment-specific technical replicates. BEARscc works with a wide range of existing clustering algorithms to assess the robustness of clusters to technical variation. We demonstrate that the tool improves the unsupervised classification of cells and facilitates the biological interpretation of single-cell RNA-seq experiments.

9.4 T MR microscopy of the substantia nigra with pathological validation in controls and disease.

BACKGROUND: The anatomy of the substantia nigra on conventional MRI is controversial. Even using histological techniques it is difficult to delineate with certainty from surrounding structures. We sought to define the anatomy of the SN using high field spin-echo MRI of pathological material in which we could study the anatomy in detail to corroborate our MRI findings in controls and Parkinson's disease and progressive supranuclear palsy. METHODS: 23 brains were selected from the Queen Square Brain Bank (10 controls, 8 progressive supranuclear palsy, 5 Parkinson's disease) and imaged using high field 9.4 Tesla spin-echo MRI. Subsequently brains were cut and stained with Luxol fast blue, Perls stain, and immunohistochemistry for substance P and calbindin. Once the anatomy was defined on histology the dimensions and volume of the substantia nigra were determined on high field magnetic resonance images. RESULTS: The anterior border of the substantia nigra was defined by the crus cerebri. In the medial half it was less distinct due to the deposition of iron and the interdigitation of white matter and the substantia nigra. The posterior border was flanked by white matter bridging the red nucleus and substantia nigra and seen as hypointense on spin-echo magnetic resonance images. Within the substantia nigra high signal structures corresponded to confirmed nigrosomes. These were still evident in Parkinson's disease but not in progressive supranuclear palsy. The volume and dimensions of the substantia nigra were similar in Parkinson's disease and controls, but reduced in progressive supranuclear palsy. CONCLUSIONS: We present a histologically validated anatomical description of the substantia nigra on high field spin-echo high resolution magnetic resonance images and were able to delineate all five nigrosomes. In accordance with the pathological literature we did not observe changes in the nigrosome structure as manifest by volume or signal characteristics within the substantia nigra in Parkinson's disease whereas in progressive supranuclear palsy there was microarchitectural destruction.

Molecular analyses of circadian gene variants reveal sex-dependent links between depression and clocks.

An extensive literature links circadian irregularities and/or sleep abnormalities to mood disorders. Despite the strong genetic component underlying many mood disorders, however, previous genetic associations between circadian clock gene variants and major depressive disorder (MDD) have been weak. We applied a combined molecular/functional and genetic association approach to circadian gene polymorphisms in sex-stratified populations of control subjects and case subjects suffering from MDD. This approach identified significant sex-dependent associations of common variants of the circadian clock genes hClock, hPer3 and hNpas2 with major depression and demonstrated functional effects of these polymorphisms on the expression or activity of the hCLOCK and hPER3 proteins, respectively. In addition, hCLOCK expression is affected by glucocorticoids, consistent with the sex-dependency of the genetic associations and the modulation of glucocorticoid-mediated stress response, providing a mechanism by which the circadian clock controls outputs that may affect psychiatric disorders. We conclude that genetic polymorphisms in circadian genes (especially hClock and hPer3, where functional assays could be tested) influence risk of developing depression in a sex- and stress-dependent manner. These studies support a genetic connection between circadian disruption and mood disorders, and confirm a key connection between circadian gene variation and major depression.

Common variants of the G protein-coupled receptor type 4 are associated with human essential hypertension and predict the blood pressure response to angiotensin receptor blockade.

Non-synonymous GRK4 variants, R65L, A142V and A486V, are associated with essential hypertension in diverse populations. This study replicated the association of GRK4 variants, including GRK4(142V), with human essential hypertension in a Japanese population (n=588; hypertensive, n=486 normotensive controls) and determined whether the presence of GRK4 variants predicted the blood pressure (BP) response to angiotensin receptor blockers (ARBs) in patients with essential hypertension. We analyzed 829 patients and compared the response to ARBs between individuals with no GRK4 variants (n=136) and those with variants at one or any of the three loci (n=693). Carriers of hGRK4(142V) had a greater decrease in systolic BP in response to ARBs than non-carrier hypertensive patients. By contrast, those with variants only at GRK4(486V) were less likely to achieve the BP goal in response to an ARB than those with no variants. These studies showed for the first time the association between GRK4(142V) and a larger decrease in BP with ARBs in hypertensive patients.

Nuclear iASPP may facilitate prostate cancer progression.

One of the major challenges in prostate cancer (PCa) research is the identification of key players that control the progression of primary cancers to invasive and metastatic disease. The majority of metastatic PCa express wild-type p53, whereas loss of p63 expression, a p53 family member, is a common event. Here we identify inhibitor of apoptosis-stimulating protein of p53 (iASPP), a common cellular regulator of p53 and p63, as an important player of PCa progression. Detailed analysis of the prostate epithelium of iASPP transgenic mice, iASPP(Δ8/Δ8) mice, revealed that iASPP deficiency resulted in a reduction in the number of p63 expressing basal epithelial cells compared with that seen in wild-type mice. Nuclear and cytoplasmic iASPP expression was greater in PCa samples compared with benign epithelium. Importantly nuclear iASPP associated with p53 accumulation in vitro and in vivo. A pair of isogenic primary and metastatic PCa cell lines revealed that nuclear iASPP is enriched in the highly metastatic PCa cells. Nuclear iASPP is often detected in PCa cells located at the invasive leading edge in vivo. Increased iASPP expression associated with metastatic disease and PCa-specific death in a clinical cohort with long-term follow-up. These results suggest that iASPP function is required to maintain the expression of p63 in normal basal prostate epithelium, and nuclear iASPP may inactivate p53 function and facilitate PCa progression. Thus iASPP expression may act as a predictive marker of PCa progression.

Epiregulin (EREG) and human V-ATPase (TCIRG1): genetic variation, ethnicity and pulmonary tuberculosis susceptibility in Guinea-Bissau and The Gambia.

We analyzed two West African samples (Guinea-Bissau: n=289 cases and 322 controls; The Gambia: n=240 cases and 248 controls) to evaluate single-nucleotide polymorphisms (SNPs) in Epiregulin (EREG) and V-ATPase (T-cell immune regulator 1 (TCIRG1)) using single and multilocus analyses to determine whether previously described associations with pulmonary tuberculosis (PTB) in Vietnamese and Italians would replicate in African populations. We did not detect any significant single locus or haplotype associations in either sample. We also performed exploratory pairwise interaction analyses using Visualization of Statistical Epistasis Networks (ViSEN), a novel method to detect only interactions among multiple variables, to elucidate possible interaction effects between SNPs and demographic factors. Although we found no strong evidence of marginal effects, there were several significant pairwise interactions that were identified in either the Guinea-Bissau or the Gambian samples, two of which replicated across populations. Our results indicate that the effects of EREG and TCIRG1 variants on PTB susceptibility, to the extent that they exist, are dependent on gene-gene interactions in West African populations as detected with ViSEN. In addition, epistatic effects are likely to be influenced by inter- and intra-population differences in genetic or environmental context and/or the mycobacterial lineages causing disease.

High resolution MR anatomy of the subthalamic nucleus: imaging at 9.4 T with histological validation.

Using conventional MRI the subthalamic nucleus (STN) is not clearly defined. Our objective was to define the anatomy of the STN using 9.4 T MRI of post mortem tissue with histological validation. Spin-echo (SE) and 3D gradient-echo (GE) images were obtained at 9.4 T in 8 post mortem tissue blocks and compared directly with corresponding histological slides prepared with Luxol Fast Blue/Cresyl Violet (LFB/CV) in 4 cases and Perl stain in 3. The variability of the STN anatomy was studied using internal reference points. The anatomy of the STN and surrounding structures was demonstrated in all three anatomical planes using 9.4 T MR images in concordance with LFB/CV stained histological sections. Signal hypointensity was seen in 6/8 cases in the anterior and medial STN that corresponded with regions of more intense Perl staining. There was significant variability in the volume, shape and location of the borders of the STN. Using 9.4 T MRI, the internal signal characteristics and borders of the STN are clearly defined and significant anatomical variability is apparent. Direct visualisation of the STN is possible using high field MRI and this is particularly relevant, given its anatomical variability, for planning deep brain stimulation.

An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers.

Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid.

Individual and overlapping roles of BH3-only proteins Bim and Bad in apoptosis of lymphocytes and platelets and in suppression of thymic lymphoma development.

BH3-only proteins, such as Bim and Bad, contribute to tissue homeostasis by initiating apoptosis in a cell type- and stimulus-specific manner. Loss of Bim provokes lymphocyte accumulation in vivo and renders lymphocytes more resistant to diverse apoptotic stimuli and Bad has been implicated in the apoptosis of haematopoietic cells upon cytokine deprivation. To investigate whether their biological roles in apoptosis overlap, we generated mice lacking both Bim and Bad and compared their haematopoietic phenotype with that of the single-knockout and wild-type (wt) animals. Unexpectedly, bad(-/-) mice had excess platelets due to prolonged platelet life-span. The bim(-/-)bad(-/-) mice were anatomically normal and fertile. Their haematopoietic phenotype resembled that of bim(-/-) mice but lymphocytes were slightly more elevated in their lymph nodes. Although resting B and T lymphocytes from bim(-/-)bad(-/-) and bim(-/-) animals displayed similar resistance to diverse apoptotic stimuli, mitogen activated bim(-/-)bad(-/-) B cells were more refractory to cytokine deprivation. Moreover, combined loss of Bim and Bad-enhanced survival of thymocytes after DNA damage and accelerated development of γ-irradiation-induced thymic lymphoma. Unexpectedly, their cooperation in the thymus depended upon thymocyte-stromal interaction. Collectively, these results show that Bim and Bad can cooperate in the apoptosis of thymocytes and activated B lymphocytes and in the suppression of thymic lymphoma development.

Manubriosternal subluxation/dislocation can lead to manubriosternal septic arthritis in patients with kyphoscoliosis.

Locally deranged joint anatomy can predispose to septic arthritis which can be managed by surgical debridement. We present a case of manubriosternal subluxation/dislocation caused by kyphoscoliosis leading to manubriosternal septic arthritis.

Initial assessment of jaundice in otherwise healthy infants--a comparison of methods in two postnatal units.

Transcutaneous bilirubin (TcB) has the potential to reduce total serum bilirubin (TS) sampling. The principal aim of this study was to determine and compare the number of initial TSB samples (TSBs) in two postnatal units (hospitals A & B) whereby hospital A used TcB and hospital B did not. A secondary aim was to determine the clinical factors that led to initial TSBs exceeding exchange transfusion level in both hospitals. Results demonstrated both hospitals had similar populations and patient numbers following selection criteria. 1645 neonates (10.4%) had one or more TSBs performed in hospital A, versus 2373 neonates (15.1%) in hospital B (p < 0.01). Fourteen neonates in hospital A and 3 neonates in hospital B had initial TSBs above exchange transfusion level. For neonates with TSBs above exchange, preventable factors related to earlier testing and follow up. In routine clinical practice, TcB is associated with a significantly reduced number of TSB measurements. TSB levels above exchange transfusion are linked to preventable factors, in otherwise healthy neonates.

Motion artifact correction in free-breathing abdominal MRI using overlapping partial samples to recover image deformations.

This article presents a method to reconstruct liver MRI data acquired continuously during free breathing, without any external sensor or navigator measurements. When the deformations associated with k-space data are known, generalized matrix inversion reconstruction has been shown to be effective in reducing the ghosting and blurring artifacts of motion. This article describes a novel method to obtain these nonrigid deformations. A breathing model is built from a fast dynamic series: low spatial resolution images are registered and their deformations parameterized by overall superior-inferior displacement. The correct deformation for each subset of the subsequent imaging data is then found by comparing a few lines of k-space with the equivalent lines from a deformed reference image while varying the deformation over the model parameter. This procedure is known as image deformation recovery using overlapping partial samples (iDROPS). Simulations using 10 rapid dynamic studies from volunteers showed the average error in iDROPS-derived deformations within the liver to be 1.43 mm. A further four volunteers were imaged at higher spatial resolution. The complete reconstruction process using data from throughout several breathing cycles was shown to reduce blurring and ghosting in the liver. Retrospective respiratory gating was also demonstrated using the iDROPS parameterization.

Management of neonatal abstinence syndrome: a national survey and review of practice.

AIM: To ascertain the present management of neonatal abstinence syndrome (NAS) in neonatal units in the United Kingdom (UK) and Ireland. METHODS: Postal questionnaire to 235 neonatal units, with telephone follow-up of non-respondents. RESULTS: The response rate was 90%, and 96% of respondents had a formal NAS guideline. The median number of infants treated annually for NAS was 6 (range 1-100). The method of Finnegan was the most widely used scoring system (52%). Morphine sulphate was the most commonly used first line agent for both opiate (92%) and polysubstance (69%) withdrawal. Dosing regimens varied widely. Units using a maximum daily morphine dose of <400 microg/kg/day were more likely to require the addition of a second agent (76% vs 58%, p = 0.027). Phenobarbitone was the drug of choice to treat seizures secondary to both opiate and polydrug withdrawal in 73% and 81% of units, respectively. 29% of units allowed infants to be discharged home on medication. 58% of these allowed administration of opiates in the community and in almost half of cases this was managed by a parent. Mothers on methadone whose serology was positive for hepatitis B and/or C were four times more likely to be discouraged from breastfeeding. CONCLUSIONS: The majority of units currently use an opiate as the drug of first choice as recommended. Doses utilised and second agents added vary significantly between units. Many of our findings reflect the lack of high-quality randomised studies regarding management of NAS.

Are we teaching sufficient anatomy at medical school? The opinions of newly qualified doctors.

In recent decades wide-ranging changes have occurred in medical school curricula. Time spent studying gross anatomy has declined amidst controversy as to how, what, and when teaching is best delivered. This reduced emphasis has led to concerns amongst clinicians that a new generation of doctors are leaving medical school with insufficient anatomical knowledge. Previous studies have established that medical students value their anatomy teaching during medical school. None have sought to establish views on the sufficiency of this teaching. We investigate the opinions of newly qualified doctors at a UK medical school and relate these opinions to career intentions and academic performance in the setting of a traditional dissection and prosection-based course. Overall nearly half of respondents believe they received insufficient anatomy teaching. A substantial proportion called for the integration of anatomy teaching throughout the medical school course. Trainees intent on pursuing a surgical career were more likely to believe anatomy teaching was insufficient than those pursuing a nonsurgical career; however, overall there was no statistical difference in relation to the mean for any individual career group. This study adds to the current debates in anatomical sciences education, indicating that overall, regardless of career intentions, new doctors perceive the need for greater emphasis on anatomical teaching.

Registration of dynamic contrast-enhanced MRI using a progressive principal component registration (PPCR).

Registration of dynamic contrast-enhanced magnetic resonance images (DCE-MRI) of soft tissue is difficult. Conventional registration cost functions that depend on information content are compromised by the changing intensity profile, leading to misregistration. We present a new data-driven model of uptake patterns formed from a principal components analysis (PCA) of time-series data, avoiding the need for a physiological model. We term this process progressive principal component registration (PPCR). Registration is performed repeatedly to an artificial time series of target images generated using the principal components of the current best-registered time-series data. The aim is to produce a dataset that has had random motion artefacts removed but long-term contrast enhancement implicitly preserved. The procedure is tested on 22 DCE-MRI datasets of the liver. Preliminary assessment of the images is by expert observer comparison with registration to the first image in the sequence. The PPCR is preferred in all cases where a preference exists. The method requires neither segmentation nor a pharmacokinetic uptake model and can allow successful registration in the presence of contrast enhancement.