A JAFROC study of nodule detection performance in CT images of a thorax acquired during PET/CT

Purpose Two types of CT images (modalities) are acquired in PET/CT: for attenuation correction (AC) and diagnosis. The purpose of the study was to compare nodule detection and localization performance between these two modalities. Methods CT images, using both modalities, of an anthropomorphic chest phantom containing zero or more simulated spherical nodules of 5, 8, 10 and 12 mm diameters and contrasts −800, −630 and 100 HU were acquired. An observer performance study using nine observers interpreting 45 normal (zero nodules) images and 47 abnormal images (1–3 nodules; average 1.26) was conducted using the free-response receiver operating characteristic (FROC) paradigm. Data were analysed using an R software package implemented jackknife alternative FROC (JAFROC) analysis. Both empirical areas under the equally weighted AFROC curve (wAFROC) and under the highest rating inferred ROC (HR-ROC) curve were used as figures of merit (FOM). To control the probability of Type I error test alpha was set at 0.05. Results Nodule detection as measured by either FOM was significantly better on the diagnostic quality images (2nd modality), irrespective of the method of analysis, [reader averaged inter-modality wAFROC FOM difference = −0.07 (−0.11,−0.04); reader averaged inter-modality HR-ROC FOM difference = −0.05 (−0.09, −0.01)]. Conclusion Nodule detection was statistically worse on images acquired for AC; suggesting that images acquired for AC should not be used to evaluate pulmonary pathology. Keywords PET/CT; Nodule detection; JAFRO

Validation of the Cloud_CCI (Cloud Climate Change Initiative) cloud products in the Arctic

The role of clouds in the Arctic radiation budget is not well understood. Ground-based and airborne measurements provide valuable data to test and improve our understanding. However, the ground-based measurements are intrinsically sparse, and the airborne observations are snapshots in time and space. Passive remote sensing measurements from satellite sensors offer high spatial coverage and an evolving time series, having lengths potentially of decades. However, detecting clouds by passive satellite remote sensing sensors is challenging over the Arctic because of the brightness of snow and ice in the ultraviolet and visible spectral regions and because of the small brightness temperature contrast to the surface. Consequently, the quality of the resulting cloud data products needs to be assessed quantitatively. In this study, we validate the cloud data products retrieved from the Advanced Very High Resolution Radiometer (AVHRR) post meridiem (PM) data from the polar-orbiting NOAA-19 satellite and compare them with those derived from the ground-based instruments during the sunlit months. The AVHRR cloud data products by the European Space Agency (ESA) Cloud Climate Change Initiative (Cloud_CCI) project uses the observations in the visible and IR bands to determine cloud properties. The ground-based measurements from four high-latitude sites have been selected for this investigation: Hyytiälä (61.84∘ N, 24.29∘ E), North Slope of Alaska (NSA; 71.32∘ N, 156.61∘ W), Ny-Ålesund (Ny-Å; 78.92∘ N, 11.93∘ E), and Summit (72.59∘ N, 38.42∘ W). The liquid water path (LWP) ground-based data are retrieved from microwave radiometers, while the cloud top height (CTH) has been determined from the integrated lidar–radar measurements. The quality of the satellite products, cloud mask and cloud optical depth (COD), has been assessed using data from NSA, whereas LWP and CTH have been investigated over Hyytiälä, NSA, Ny-Å, and Summit. The Cloud_CCI COD results for liquid water clouds are in better agreement with the NSA radiometer data than those for ice clouds. For liquid water clouds, the Cloud_CCI COD is underestimated roughly by 3 optical depth (OD) units. When ice clouds are included, the underestimation increases to about 5 OD units. The Cloud_CCI LWP is overestimated over Hyytiälä by ≈7 g m−2, over NSA by ≈16 g m−2, and over Ny-Å by ≈24 g m−2. Over Summit, CCI LWP is overestimated for values ≤20 g m−2 and underestimated for values &gt;20 g m−2. Overall the results of the CCI LWP retrievals are within the ground-based instrument uncertainties. To understand the effects of multi-layer clouds on the CTH retrievals, the statistics are compared between the single-layer clouds and all types (single-layer + multi-layer). For CTH retrievals, the Cloud_CCI product overestimates the CTH for single-layer clouds. When the multi-layer clouds are included (i.e., all types), the observed CTH overestimation becomes an underestimation of about 360–420 m. The CTH results over Summit station showed the highest biases compared to the other three sites. To understand the scale-dependent differences between the satellite and ground-based data, the Bland–Altman method is applied. This method does not identify any scale-dependent differences for all the selected cloud parameters except for the retrievals over the Summit station. In summary, the Cloud_CCI cloud data products investigated agree reasonably well with those retrieved from ground-based measurements made at the four high-latitude sites.</p

Evidence for sparse synergies in grasping actions

Converging evidence shows that hand-actions are controlled at the level of synergies and not single muscles. One intriguing aspect of synergy-based action-representation is that it may be intrinsically sparse and the same synergies can be shared across several distinct types of hand-actions. Here, adopting a normative angle, we consider three hypotheses for hand-action optimal-control: sparse-combination hypothesis (SC) – sparsity in the mapping between synergies and actions - i.e., actions implemented using a sparse combination of synergies; sparse-elements hypothesis (SE) – sparsity in synergy representation – i.e., the mapping between degrees-of-freedom (DoF) and synergies is sparse; double-sparsity hypothesis (DS) – a novel view combining both SC and SE – i.e., both the mapping between DoF and synergies and between synergies and actions are sparse, each action implementing a sparse combination of synergies (as in SC), each using a limited set of DoFs (as in SE). We evaluate these hypotheses using hand kinematic data from six human subjects performing nine different types of reach-to-grasp actions. Our results support DS, suggesting that the best action representation is based on a relatively large set of synergies, each involving a reduced number of degrees-of-freedom, and that distinct sets of synergies may be involved in distinct tasks

Nuclear medicine services after COVID-19 : gearing up back to normality

The COVID-19 pandemic is in transition. It may pass or may define a “new normal” over a variable period and might force us to turn our united and undivided attention as a global nuclear medicine community to address the global health of our specialty jointly. The severe acute respiratory syndromecoronavirus-2 (SARS-CoV-2) and the disease it causes (coronavirus disease-2019 or COVID-19 for short) have been the topic of much discussion in the nuclear medicine and radiology literature. Since the first reports of the new virus emerged from China in late December 2019, the World Health Organization (WHO) declared it a public health emergency of international concern on 30 January 2020. WHO declared COVID-19 as a pandemic on 11 March 2020 ; it has swept the globe, with no respect for national boundaries, causing widespread infections, mortality, human suffering, and upending lives in all socioeconomic groups. Governments around the world have rushed to implement measures aimed initially at containing the spread of the virus, but after that, mainly at slowing the COVID-19 spread and mitigating the impact of the virus on local healthcare systems and supply chains. Despite this, there is significant heterogeneity in the degree of success of the various measures, in keeping with differing political, sociological, and economic factors around the world.http://link.springer.com/journal/2592021-05-04pm2020Nuclear Medicin

Genetic and metabolic predictors of chemosensitivity in oligodendroglial neoplasms

The −1p/−19q genotype predicts chemosensitivity in oligodendroglial neoplasms, but some with intact 1p/19q also respond and not all with 1p/19q loss derive durable benefit from chemotherapy. We have evaluated the predictive and prognostic significance of pretherapy 201Tl and 18F-FDG SPECT and genotype in 38 primary and 10 recurrent oligodendroglial neoplasms following PCV chemotherapy. 1p/19q loss was seen in 8/15 OII, 6/15 OAII, 7/7 OIII, 3/11 OAIII and was associated with response (Fisher-Exact: P=0.000) and prolonged progression-free (log-rank: P=0.002) and overall survival (OS) (log-rank: P=0.0048). Response was unrelated to metabolism, with tumours with high or low metabolism showing response. Increased 18F-FDG or 201Tl uptake predicted shorter progression-free survival (PFS) in the series (log-rank: 201Tl P=0.0097, 18F-FDG P=0.0170) and in cases with or without the −1p/−19q genotype. Elevated metabolism was associated with shorter OS in cases with intact 1p/19q (log-rank: 18F-FDG P=0.0077; 201Tl P=0.0004) and shorter PFS in responders (log-rank: 18F-FDG P=0.005; 201Tl P=0.0132). 201Tl uptake and 1p/19q loss were independent predictors of survival in multivariate analysis. In this initial study, 201Tl and 18F-FDG uptake did not predict response to PCV, but may be associated with poor survival following therapy irrespective of genotype. This may be clinically useful warranting further study

Analysis of plain X-ray and low resolution CT gonad dose arising from supplementary imaging after bone scanning

Introduction:Bone scintigraphy has long been the first stop for patients undergoing investigation of bone metastases. The procedure is recognised as being highly sensitive to the disease however this corresponds to a low specificity. As a result supplementary imaging to characterise and localise lesions is often required to aid definitive diagnosis. There is a range of modalities that can be utilised for this purpose including computed radiography (CR) digital radiography (DR), multidetector computed tomography (MCDT) or CT acquisition using hybrid SPECTCT systems.The choice of modality has implications for patient dose, and therefore careful justification of the chosen procedure is required. The reproductive organs are recognised as radiosensitive, and so dose to these organs needs to be considered.Aim:To compare the absorbed dose by the male and female reproductive organs when imaging the lumbar spine using local protocols in CR, DR, CT component of a SPECT-CT scanner and MDCT.Method:An ATOM 701-D dosimetry phantom and calibrated thermoluminescent dosimeters (TLD) were subjected to radiographic examinations of the lumbar spine using standard department protocols. The TLDs were positioned within the phantom to measure the absorbed dose of the ovaries and testes. Using three repeated measures, antero-posterior and left lateral lumbar spine radiographs were acquired using local diagnostic reference levels on CR and DR technology. CT Imaging of the lumbar spine was carried out using a GE Infinia Hawkeye gamma camera and a GE Lightspeed 64 CT scanner. The TLDs were read using a Hardshaw 3500 manual TLD reader 24 hours after acquisition.Results:The absorbed dose to the ovaries was found to be: DR 6.6mGy; CR 4.4mGy; MDCT 7.1mGy; hybrid CT 3.6mGy (p<0.05)The absorbed dose to the testes was found to be: DR 8.1mGy; CR 4.9mGy; MDCT 4.0mGy; hybrid CT 1.7mGy (p>0.05)Comparison of results using ANNOVA found that the organ dose from the different modalities were significantly different for females, but not for males. Numerical comparison of the results demonstrates that the hybrid CT acquisition resulted in a lower absorbed dose compared to the other modalities for both males and females.Conclusion:This research demonstrates that the dose from the CT component of the hybrid scanner results in the lowest absorbed dose to the reproductive organs. However, surprisingly, the dose to the testes from DR was found to be the highest dose