Registration Artifacts Research Articles

Investigation of Added Value of Imaging Performed in a Prone Position to Standard 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Imaging for Staging in Patients with Breast Cancer.

Objectives:To investigate whether additional imaging in a prone position has any value to the supine whole-body 18fluorine-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) images by comparing the visual and quantitative data about a local disease in the breast and axilla for the initial staging of breast cancer (BC).Methods:In this study, a total of 91 female patients with the BC were studied. Both the supine and prone images were examined based on the axial diameter, number and location of the primary tumor, local invasion signs of the tumor, the number of axillary lymph nodes with a suspected metastasis, metabolic parameters of the primary tumor and axillary lymph nodes, and registration artifacts of the PET and CT images were evaluated individually. These findings were compared with the histopathological data obtained after a surgery.Results:In the evaluation of a supine and prone imaging, tumor diameter and metabolic tumor volume (MTV) values of the breast lesions were greater in the supine position than in the prone position. However, there was no significant difference found between the other metabolic parameters of a primary tumor and axilla in both positions. In the supine and prone images, accuracy for skin involvement was 84% and 91.3%, respectively.Conclusion:In our study, we observed that, obtaining additional images in the prone position does not significantly benefit the evaluation of a local disease. The average values of the primary tumor diameter and MTV in the prone position appear to be smaller than the one in the supine position. However, the prone imaging in the patients with a newly diagnosed BC may be beneficial in selected patients and may contribute to preventing the false-positive results especially in patients with a suspected skin involvement.

Personalized microstructural evaluation using a Mahalanobis-distance based outlier detection strategy on epilepsy patients' DTI data - Theory, simulations and example cases.

Quantitative MRI methods have recently gained extensive interest and are seeing substantial developments; however, their application in single patient vs control group comparisons is often limited by inherent statistical difficulties. One such application is detecting malformations of cortical development (MCDs) behind drug resistant epilepsies, a task that, especially when based solely on conventional MR images, may represent a serious challenge. We aimed to develop a novel straightforward voxel-wise evaluation method based on the Mahalanobis-distance, combining quantitative MRI data into a multidimensional parameter space and detecting lesion voxels as outliers. Simulations with standard multivariate Gaussian distribution and resampled DTI-eigenvalue data of 45 healthy control subjects determined the optimal critical value, cluster size threshold, and the expectable lesion detection performance through ROC-analyses. To reduce the effect of false positives emanating from registration artefacts and gyrification differences, an automatic classification method was applied, fine-tuned using a leave-one-out strategy based on diffusion and T1-weighted data of the controls. DWI processing, including thorough corrections and robust tensor fitting was performed with ExploreDTI, spatial coregistration was achieved with the DARTEL tools of SPM12. Additional to simulations, clusters of outlying diffusion profile, concordant with neuroradiological evaluation and independent calculations with the MAP07 toolbox were identified in 12 cases of a 13 patient example population with various types of MCDs. The multidimensional approach proved sufficiently sensitive in pinpointing regions of abnormal tissue microstructure using DTI data both in simulations and in the heterogeneous example population. Inherent limitations posed by registration artefacts, age-related differences, and the different or mixed pathologies limit the generalization of specificity estimation. Nevertheless, the proposed statistical method may aid the everyday examination of individual subjects, ever so more upon extending the framework with quantitative information from other modalities, e.g. susceptibility mapping, relaxometry, or perfusion.

Improved gray matter surface based spatial statistics in neuroimaging studies

Neuroimaging often involves acquiring high-resolution anatomical images along with other low-resolution image modalities, like diffusion and functional magnetic resonance imaging. Performing gray matter statistics with low-resolution image modalities is a challenge due to registration artifacts and partial volume effects. Gray matter surface based spatial statistics (GS-BSS) has been shown to provide higher sensitivity using gray matter surfaces compared to that of skeletonization approach of gray matter based spatial statistics which is adapted from tract based spatial statistics in diffusion studies. In this study, we improve upon GS-BSS incorporating neurite orientation dispersion and density imaging (NODDI) based search (denoted N-GSBSS) by 1) enhancing metrics mapping from native space, 2) incorporating maximum orientation dispersion index (ODI) search along surface normal, and 3) proposing applicability to other modalities, such as functional MRI (fMRI). We evaluated the performance of N-GSBSS against three baseline pipelines: volume-based registration, FreeSurfer's surface registration and ciftify pipeline for fMRI and simulation studies. First, qualitative mean ODI results are shown for N-GSBSS with and without NODDI based search in comparison with ciftify pipeline. Second, we conducted one-sample t-tests on working memory activations in fMRI to show that the proposed method can aid in the analysis of low resolution fMRI data. Finally we performed a sensitivity test in a simulation study by varying percentage change of intensity values within a region of interest in gray matter probability maps. N-GSBSS showed higher sensitivity in the simulation test compared to the other methods capturing difference between the groups starting at 10% change in the intensity values. The computational time of N-GSBSS is 68 times faster than that of traditional surface-based or 86 times faster than that of ciftify pipeline analysis.

The Effect of Including Bone in Dixon-Based Attenuation Correction for 18F-Fluciclovine PET/MRI of Prostate Cancer.

The objective of this study was to evaluate the effect of including bone in Dixon-based attenuation correction for 18F-fluciclovine PET/MRI of primary and recurrent prostate cancer. Methods:18F-fluciclovine PET data from 2 PET/MRI studies-one for staging of high-risk prostate cancer (28 patients) and one for diagnosis of recurrent prostate cancer (81 patients)-were reconstructed with a 4-compartment (reference) and 5-compartment attenuation map. In the latter, continuous linear attenuation coefficients for bone were included by coregistration with an atlas. The SUVmax and mean 50% isocontour SUV (SUViso) of primary, locally recurrent, and metastatic lesions were compared between the 2 reconstruction methods using linear mixed-effects models. In addition, mean SUVs were obtained from bone marrow in the third lumbar vertebra (L3) to investigate the effect of including bone attenuation on lesion-to-bone marrow SUV ratios (SUVRmax and SUVRiso; recurrence study only). The 5-compartment attenuation maps were visually compared with the in-phase Dixon MR images for evaluation of bone registration errors near the lesions. P values of less than 0.05 were considered significant. Results: Sixty-two lesions from 39 patients were evaluated. Bone registration errors were found near 19 (31%) of these lesions. In the remaining 8 primary prostate tumors, 7 locally recurrent lesions, and 28 lymph node metastases without bone registration errors, use of the 5-compartment attenuation map was associated with small but significant increases in SUVmax (2.5%; 95% confidence interval [CI], 2.0%-3.0%; P < 0.001) and SUViso (2.5%; 95% CI, 1.9%-3.0%; P < 0.001), but not SUVRmax (0.2%; 95% CI, -0.5%-0.9%; P = 0.604) and SUVRiso (0.2%; 95% CI -0.6%-1.0%; P = 0.581), in comparison to the 4-compartment attenuation map. Conclusion: The investigated method for atlas-based inclusion of bone in 18F-fluciclovine PET/MRI attenuation correction has only a small effect on the SUVs of soft-tissue prostate cancer lesions, and no effect on their lesion-to-bone marrow SUVRs when using signal from L3 as a reference. The attenuation maps should always be checked for registration artifacts for lesions in or close to the bones.

Detection and quantification of coronary calcium from dual energy chest x-rays: Phantom feasibility study.

We have demonstrated the ability to identify coronary calcium, a reliable biomarker of coronary artery disease, using nongated, 2-shot, dual energy (DE) chest x-ray imaging. Here we will use digital simulations, backed up by measurements, to characterize DE calcium signals and the role of potential confounds such as beam hardening, x-ray scatter, cardiac motion, and pulmonary artery pulsation. For the DE calcium signal, we will consider quantification, as compared to CT calcium score, and visualization. We created stylized and anatomical digital 3D phantoms including heart, lung, coronary calcium, spine, ribs, pulmonary artery, and adipose. We simulated high and low kVp x-ray acquisitions with x-ray spectra, energy dependent attenuation, scatter, ideal detector, and automatic exposure control (AEC). Phantoms allowed us to vary adipose thickness, cardiac motion, etc. We used specialized dual energy coronary calcium (DECC) processing that includes corrections for scatter and beam hardening. Beam hardening over a wide range of adipose thickness (0-30 cm) reduced the change in intensity of a coronary artery calcification (ΔICAC ) by < 3% in DECC images. Scatter correction errors of ±50% affected the calcium signal (ΔICAC ) in DECC images ±9%. If a simulated pulmonary artery fills with blood between exposures, it can give rise to a residual signal in DECC images, explaining pulmonary artery visibility in some clinical images. Residual misregistration can be mostly compensated by integrating signals in an enlarged region encompassing registration artifacts. DECC calcium score compared favorably to CT mass and volume scores over a number of phantom perturbations. Simulations indicate that proper DECC processing can faithfully recover coronary calcium signals. Beam hardening, errors in scatter estimation, cardiac motion, calcium residual misregistration etc., are all manageable. Simulations are valuable as we continue to optimize DE coronary calcium image processing and quantitative analysis.

Three-dimensional histopathological reconstruction as a reliable ground truth for prostate cancer studies

To validate new imaging modalities for prostate cancer, images must be three-dimensionally correlated with the histological ground truth. In this work, an interpolation algorithm is described to construct a reliable three-dimensional reference from two-dimensional (2D) histological slices. Eight clinically relevant in silico phantoms were designed to represent difficult-to-reconstruct tumour structures. These phantoms were subjected to different slicing procedures. Additionally, controlled errors were added to investigate the impact of varying slicing distance, front-face orientation, and inter-slice misalignment on the reconstruction performance. Using a radial-basis-function interpolation algorithm, the 2D data were reconstructed in three dimensions. Our results demonstrate that slice thicknesses up to 4 mm can be used to reliably reconstruct tumours of clinically significant size; the surfaces lay within a 1.5 mm 90%-error margin from each other and the volume difference between the original and reconstructed tumour structures does not exceed 10%. With these settings, Dice coefficients above 0.85 are obtained. The presented interpolation algorithm is able to reconstruct clinically significant tumour structures from 2D histology slices. Errors occurring are in the order of magnitude of common registration artefacts. The method’s applicability to real histopathological data is also shown in two resected prostates. An inter-slice spacing of 4 mm or less is recommended during histopathology; the use of a 1.5 mm error margin along the tumour contours can then ensure reliable mapping of the ground truth.

3D reconstruction methods and quality assessment for visual inspection of welds

Abstract Welding surface inspection and evaluation are the main tasks of the visual inspection process. The presence of flaws and/or geometrical imperfections can affect the safety of the structures. This paper presents an evaluation of geomatic techniques that complement the inspector expertise and knowledge during the visual inspection, by means of a dense and complete record of the weld. Particularly, an articulated coordinate measuring machine, widely used in industrial environments, versus a novel macro-photogrammetric technique are tested and compared thought an ad-hoc external reference frame, supported by 2D/3D registration artefacts and an automated identification methodology. The resulting 3D models are evaluated in terms of accuracy, precision and resolution.

EP 77. Target identification in deep brain stimulation for Parkinson’s disease: The role of probabilistic tractography

Introduction Deep brain stimulation (DBS) is a widely accepted therapeutic choice in the management of Parkinson’s disease. Optimal location of the implantable DBS lead should be chosen according to intraoperative electrophysiology, and macrostimulation, while preoperative targeting is still heavily influenced by standard stereotactic coordinates. Previous electrophysiological and in vitro studies were able to identify functional subgroups within the subthalamic nucleus (STN), but noninvasive methods are yet to be developed to achieve the same distinction. Methods 7 patients suffering from Parkinson’s disease, who underwent bilateral STN DBS, were enrolled in this study. Preoperative 3D T2 (isotropic, 2 × 2 × 2 mm), 3D T1 (isotropic, 1 × 1 × 1 mm), and DTI (isotropic, 2 × 2 × 2 mm, 32 and 60 directions) sequences were acquired from each participant using a 3T Phillips Achieva and a 1.5 T GE Signa Excite scanner in two different centers. Postoperative CT scans were acquired at least 6 weeks after implantation to rule out undesired MR-CT registration artifacts. Given as the result of cortical and subcortical parcellation (Freesurfer 5.3), 8 target regions (limbic system (LS), dorsal prefrontal cortex (DPFC), premotor cortex (PM), primary motor cortex (M1), primary sensory cortex, parietal lobe, occipital lobe, temporal lobe) were selected for probabilistic tractography. Segmentation of the STN, by determining the probability of its connections to the aforementioned cortical regions, was carried out using FSL 5.0.9 (Oxford University, FMRIB Software Library). Postoperative CT images were registered to the preoperative T1 images using linear registration with 6 degrees of freedom (Flirt, FSL 5.0.9). DBS lead position was correlated with the results of probabilistic tractography, intraoperative microelectrode recordings and macrostimulation. Results Probabilistic tractography resulted in significant connections between the STN and the LS, the DPFC, the PM, and the M1. Higher intersubject variability was found in limbic connectivity. Remaining cortical targets were excluded from further analysis due to significantly lower probability. LS portion of the STN was situated in the ventral inferomedial region in each patient followed by portions connecting to the DPFC, PM, M1 respectively. Overlapping connections were found in the LS-DPFC, and in the PM-M1 regions. Intraoperative macrostimulation resulted in significant decrease of symptoms at levels where the DBS leads entered the PM-M1 portion of the nucleus in all patients. Intraoperative assessment of tremor and rigidity showed decreased symptoms on both sides (mean symptom reduction on the left side: 71.43%, right side: 67.86%). Mean distance between the most distal point of the first stimulation contact and the weighted average of connectivity probabilities in the PM-M1 portion of the STN are as follows: Right side: x : 2.2 mm y :1.2 mm z : 3.4 mm; Left side: x : 1.4 mm y : 0.3 mm z : 4 mm. Conclusion Probabilistic tractography can reveal distinct functional subgroups within the STN, resulting in that this method might be a suitable alternative to invasive intraoperative electrophysiology providing an optimal target for DBS lead placement. Levels of leads penetrating the PMM1 portion of the STN on postoperative scans were in accordance with levels of macrosimulation electrodes and decrease of clinical signs during intraoperative neurological examination. KTIA_NAP_13-1-2013-0001.

Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications.

High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixel pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications.

Integral-geometry characterization of photobiomodulation effects on retinal vessel morphology.

The morphological characterization of quasi-planar structures represented by gray-scale images is challenging when object identification is sub-optimal due to registration artifacts. We propose two alternative procedures that enhances object identification in the integral-geometry morphological image analysis (MIA) framework. The first variant streamlines the framework by introducing an active contours segmentation process whose time step is recycled as a multi-scale parameter. In the second variant, we used the refined object identification produced in the first variant to perform the standard MIA with exact dilation radius as multi-scale parameter. Using this enhanced MIA we quantify the extent of vaso-obliteration in oxygen-induced retinopathic vascular growth, the preventative effect (by photobiomodulation) of exposure during tissue development to near-infrared light (NIR, 670 nm), and the lack of adverse effects due to exposure to NIR light.

Modeling and incorporating cardiac‐induced lung tissue motion in a breathing motion model

The purpose of this work is to develop a cardiac-induced lung motion model to be integrated into an existing breathing motion model. The authors' proposed cardiac-induced lung motion model represents the lung tissue's specific response to the subject's cardiac cycle. The model is mathematically defined as a product of a converging polynomial function h of the cardiac phase (c) and the maximum displacement y(X0) of each voxel (X0) among all the cardiac phases. The function h(c) was estimated from cardiac-gated MR imaging of ten healthy volunteers using an Akaike Information Criteria optimization algorithm. For each volunteer, a total of 24 short-axis and 18 radial planar views were acquired on a 1.5 T MR scanner during a series of 12-15 s breath-hold maneuvers. Each view contained 30 temporal frames of equal time-duration beginning with the end-diastolic cardiac phase. The frames in each of the planar views were resampled to create a set of three-dimensional (3D) anatomical volumes representing thoracic anatomy at different cardiac phases. A 3D multiresolution optical flow deformable image registration algorithm was used to quantify the difference in tissue position between the end-diastolic cardiac phase and the remaining cardiac phases. To account for image noise, voxel displacements whose maximum values were less than 0.3 mm, were excluded. In addition, the blood vessels were segmented and excluded in order to eliminate registration artifacts caused by blood-flow. The average cardiac-induced lung motions for displacements greater than 0.3 mm were found to be 0.86 ± 0.74 and 0.97 ± 0.93 mm in the left and right lungs, respectively. The average model residual error for the ten healthy volunteers was found to be 0.29 ± 0.08 mm in the left lung and 0.38 ± 0.14 mm in the right lung for tissue displacements greater than 0.3 mm. The relative error decreased with increasing cardiac-induced lung tissue motion. While the relative error was > 60% for submillimeter cardiac-induced lung tissue motion, the relative error decreased to < 5% for cardiac-induced lung tissue motion that exceeded 10 mm in displacement. The authors' studies implied that modeling and including cardiac-induced lung motion would improve breathing motion model accuracy for tissues with cardiac-induced motion greater than 0.3 mm.

TU-A-218-05: Evaluation of Image Registration Using Landmark Matching and Texture Analysis

Purpose: To compare demons deformable registration with rigid and affineregistration methods by measuring registration accuracy and image texture changes introduced by each algorithm. Methods: Eleven temporally sequential pairs of clinical thoracic CT scans demonstrating no abnormal pathology were collected retrospectively from different patients. Rigid, affine, and demons registration methods were applied to all scan pairs using an appropriate choice of registration parameters. 150 landmarks were automatically selected in each baseline scan, and a semi‐automated approach was used to identify corresponding landmarks in the respective deformed follow‐up scans. Eleven first‐order texture features were calculated in 32x32‐pixel regions of interest (ROIs) randomly placed in the baseline scans and at anatomically matched locations in the demons‐, rigid‐, and affine‐ registered follow‐up scans. For each ROI pair, feature value differences between the three registered follow‐up scans and the baseline scan were calculated. Results: The average per‐patient Euclidean distance between baseline scan landmarks and registered follow‐up scan landmarks ranged from 0.01–0.50 mm (overall mean: 0.18 mm), 1.6–6.8 mm (overall mean: 3.95 mm), and 2.06–7.91 mm (overall mean: 4.82 mm) for demons, affine, and rigid registration methods, respectively. Across all eleven features, the variances in feature value change for rigid and affine registration methods were at least an order of magnitude larger than the corresponding feature‐ value‐change variances for demons registration. Conclusions: Demons registration achieved more accurate spatial alignment between temporally sequential CT scans than rigid or affine registration methods. Furthermore, the variance in texture feature value changes between baseline and registered follow‐up scan ROIs was smaller for demons than for rigid or affine registration methods. These advantages of demons registration observed with “normal” thoracic CT scans indicate that future studies may incorporate demons to combine serial CT scans such that automated methods may distinguish registration artifacts from actual pathologic change.

Nonrigid Registration of CLSM Images of Physical Sections with Discontinuous Deformations

When biological specimens are cut into physical sections for three-dimensional (3D) imaging by confocal laser scanning microscopy, the slices may get distorted or ruptured. For subsequent 3D reconstruction, images from different physical sections need to be spatially aligned by optimization of a function composed of a data fidelity term evaluating similarity between the reference and target images, and a regularization term enforcing transformation smoothness. A regularization term evaluating the total variation (TV), which enables the registration algorithm to account for discontinuities in slice deformation (ruptures), while enforcing smoothness on continuously deformed regions, was proposed previously. The function with TV regularization was optimized using a graph-cut (GC) based iterative solution. However, GC may generate visible registration artifacts, which impair the 3D reconstruction. We present an alternative, multilabel TV optimization algorithm, which in the examined samples prevents the artifacts produced by GC. The algorithm is slower than GC but can be sped up several times when implemented in a multiprocessor computing environment. For image pairs with uneven brightness distribution, we introduce a reformulation of the TV-based registration, in which intensity-based data terms are replaced by comparison of salient features in the reference and target images quantified by local image entropies.

Do GPs' medical records demonstrate a good recognition of depression? A new perspective on case extraction

Previous estimates of depression recognition in primary care are low and inconsistent. This may be due to registration artifacts and limited extraction efforts. This study investigated a) whether GPs' medical records demonstrate an accurate recognition of depression and b) which combinations of indications within the record most accurately reflect a diagnosis of depression. GPs' registrations were compared with a reference standard, the Composite International Diagnostic Interview (CIDI), according to DSM-IV criteria. Six definitions of GPs' recognition of depression were tested using diagnostic codes, medication data, referral data and free text in the medical records. The Youden-index was used to select the optimal definition of recognition. Data were derived from the Netherlands Study of Depression and Anxiety. 816 primary care patients from 33 general practitioners were included in the vicinities of Amsterdam and Leiden, The Netherlands. Registration of antidepressant prescriptions was the best single indicator of GPs' recognition of CIDI depression with a recognition rate of 0.43. The best combination of indicators increased the recognition rate to 0.69. All indications except the specific diagnostic codes for 'depressive disorder' and 'depressive feelings' were included in this definition. Potential bias due to the selection of participating GPs might have influenced our recognition rates. GPs are aware of mental health problems in most depressed patients, but labeling with specific diagnostic codes is weak. Researchers should consider that diagnostic coding alone is not an accurate measure of the diagnostic ability of depression and strongly underestimates the accuracy of the GP.

RF shimming for spectroscopic localization in the human brain at 7 T

Spectroscopic imaging of the human head at short echo times (<or=15 ms) typically requires suppression of signals from extracerebral tissues. However, at 7 T, decreasing efficiency in B1+ generation (hertz/watt) and increasing spectral bandwidth result in dramatic increases in power deposition and increased chemical shift registration artifacts for conventional gradient-based in-plane localization. In this work, we describe a novel method using radiofrequency shimming and an eight-element transceiver array to generate a B1+ field distribution that excites a ring about the periphery of the head and leaves central brain regions largely unaffected. We have used this novel B1+ distribution to provide in-plane outer volume suppression (>98% suppression of extracerebral lipids) without the use of gradients. This novel B1+ distribution is used in conjunction with a double inversion recovery method to provide suppression of extracerebral resonances with T1s greater than 400 ms, while having negligible effect on metabolite ratios of cerebral resonances with T1s>1000 ms. Despite the use of two adiabatic pulses, the high efficiency of the ring distribution allows radiofrequency power deposition to be limited to 3-4 W for a pulse repetition time of 1.5 sec. The short echo time enabled the acquisition of images of the human brain, displaying glutamate, glutamine, macromolecules, and other major cerebral metabolites.

Unexplained inversion of the incidence ratio of colon and rectal cancer among men in East Germany. A time trend analysis including 147,790 cases

The incidence rate ratio of colon to rectal cancer is usually about 2:1. It has been observed for a while that the incidence of colon cancer among men (as opposed to women) in the Former German Democratic Republic (GDR) is lower than the rate of rectal cancer. Detailed analyses of this phenomenon have not been done so far. The aim was to give insights in this observation by detailed incidence and mortality analyses and to explore the worldwide ratio of colon and rectal cancers based on population-based cancer registry data. We analyzed age-standardized incidence and mortality data of colorectal cancers in East Germany (1961-1989 and 1996-2002; mortality 1980-2002), West Germany, Saarland (1970-2002) and all over the world (1978-82 up to 1993-97). With the incidence increase of colorectal cancers in the GDR, the ratio of colon to rectal cancer incidence became larger and surpassed the reference value (ratio = 1) during the time of the reunification. Also the mortality data revealed a similar pattern. Estimated annual percentage increases of colon subsite incidences tended to be higher within the distal colon as compared to the proximal colon Our analyses of international cancer registries over a period of 20 years show that the colon-rectum cancer ratio is positively associated with the overall incidence of colorectal cancer with a stronger association among women than men. Non-causal factors such as underdetection or registration artefacts are unlikely to explain the unusual colon/rectal rate ratio among men. A gradual decrease of the job-related physical activity among men may have contributed to the findings.

Time trends of cancer incidence in European children (1978–1997): Report from the Automated Childhood Cancer Information System project

Within the framework of the Automated Childhood Cancer Information System (ACCIS), time trend analyses for childhood cancer were performed using data from 33 population-based cancer registries in 15 European countries for the period 1978–1997. The overall incidence rate based on 77,111 cases has increased significantly ( P < 0.0001), with an average annual percentage change (AAPC) of 1.1%. The rising trend was observed in all five geographical regions and in the majority of the disease groups (in order of AAPC): soft tissue sarcomas (1.8%), brain tumours, tumours of the sympathetic nervous system, germ-cell tumours, carcinomas, lymphomas, renal tumours, and leukaemias (0.6%). No change was seen in incidence of bone tumours, hepatic tumours and retinoblastoma. The increased incidence can only partly be explained by changes in diagnostic methods and by registration artefacts. The patterns and magnitude of these increases suggest that other factors, e.g. changes in lifestyle and in exposure to a variety of agents, have contributed to the increase in childhood cancer in the recent decades.

Registration Artifacts in International Comparisons of Infant Mortality

Although nearly all countries have noted a marked drop in infant mortality in recent decades, there are still large disparities between countries, particularly between developed and developing nations but also among industrialized countries. Nations employ different gestational age and/or birth-weight cutoff points for reporting fetal deaths and live births. Interpretations of signs of life, which classify deaths as fetal or infant, may vary widely despite attempts at standardization by the World Health Organization. There also may be differences in registering tiny preterm infants as live births or fetal deaths. The authors analyzed data on six national groups from the Internal Collaborative Effort on Perinatal and Infant Mortality (whites and blacks in the United States, Israeli Jews and non-Jews, Norwegians, and Swedes) for the years 1987 and 1988. In particular, two major potential artifacts that might help explain intercountry differences in infant mortality were examined: classification as fetal or infant death (especially at very low birth weights) and underregistration of borderline-viable infants as either fetal deaths or live births. Crude infant mortality rates (infant deaths per 1000 live births) were lowest in Sweden, where they were 25% below those for Norway, US whites, and Israeli Jews. Rates were twice as high for US blacks and Israeli non-Jews. Mortality risk was reduced in both US groups and Israeli non-Jews after adjusting for maternal age, parity, and multiple births. Excluding Sweden (because of insufficient data), stillbirths of 20 weeks' or more gestation as a proportion of all perinatal deaths were highest in Norway and lowest in US blacks. Differences were most marked when birth weight was less than 500 g. Live births of less than 500 g varied more than 50-fold between Sweden and both Israeli groups at the low end and US blacks at the high end. US whites had a 15-fold higher proportion of live births less than 500 g than did Swedes. Rates for live births at 500 to 749 g varied 7-fold among the various groups, but again were lowest in Sweden and highest in US blacks. Live births less than 750 g were much likelier to be registered in the United States than in the other countries, and this was not simply a reflection of differential classification of live births and stillbirths. Excluding births less than 750 g, the relative risk of infant mortality was somewhat reduced for Swedes, Israeli Jews and non-Jews, and US whites, and it was markedly reduced for US blacks. Relative risk figures for both Israeli groups and both US groups (especially US blacks) declined after adjusting for maternal age, parity, and multiple gestation. These findings confirm the existence of marked differences in registering infants near borderline viability as well as differences in classifying fetal versus infant deaths. Information updating these figures, now more than a decade old, is needed. In addition, more in-depth studies are required to ascertain the reasons for these differences, whether cultural, religious, or economic.

Congenital malformations in the southeast of Sweden—a registry study with validation

A study was made of the occurrence of congenital malformations in the southeast region of Sweden, utilizing all available relevant health registries. Östergötland county had been pinpointed in a routine surveillance as having an increased malformation risk. Various validations of the register data were undertaken and different types of errors were detected. An increased risk was seen, in Östergötland county compared to the reference counties, for specific types of malformations: preauricular appendices, pylorostenosis, uterine/vaginal malformations, foot deformities, limb reduction defects and cardiovascular malformations. Variable classification or registration artefacts explained the excess among the first four conditions. Limb reduction defects were also mis‐coded, but the increased risk in Östergötland county may persist. Conclusion: There is an increased risk of major cardiovascular malformations in Östergötland county compared to the reference counties that also shows an uneven distribution within the county.

Congenital malformations in the southeast of Sweden--a registry study with validation.

A study was made of the occurrence of congenital malformations in the southeast region of Sweden, utilizing all available relevant health registries. Ostergötland county had been pinpointed in a routine surveillance as having an increased malformation risk. Various validations of the register data were undertaken and different types of errors were detected. An increased risk was seen, in Ostergötland county compared to the reference counties, for specific types of malformations: preauricular appendices, pylorostenosis, uterine/vaginal malformations, foot deformities, limb reduction defects and cardiovascular malformations. Variable classification or registration artefacts explained the excess among the first four conditions. Limb reduction defects were also mis-coded, but the increased risk in Ostergötland county may persist. There is an increased risk of major cardiovascular malformations in Ostergötland county compared to the reference counties that also shows an uneven distribution within the county.