Extended MRI-based PET motion correction for cardiac PET/MRI.

PURPOSE: A 2D image navigator (iNAV) based 3D whole-heart sequence has been used to perform MRI and PET non-rigid respiratory motion correction for hybrid PET/MRI. However, only the PET data acquired during the acquisition of the 3D whole-heart MRI is corrected for respiratory motion. This study introduces and evaluates an MRI-based respiratory motion correction method of the complete PET data. METHODS: Twelve oncology patients scheduled for an additional cardiac 18F-Fluorodeoxyglucose (18F-FDG) PET/MRI and 15 patients with coronary artery disease (CAD) scheduled for cardiac 18F-Choline (18F-FCH) PET/MRI were included. A 2D iNAV recorded the respiratory motion of the myocardium during the 3D whole-heart coronary MR angiography (CMRA) acquisition (~ 10 min). A respiratory belt was used to record the respiratory motion throughout the entire PET/MRI examination (~ 30-90 min). The simultaneously acquired iNAV and respiratory belt signal were used to divide the acquired PET data into 4 bins. The binning was then extended for the complete respiratory belt signal. Data acquired at each bin was reconstructed and combined using iNAV-based motion fields to create a respiratory motion-corrected PET image. Motion-corrected (MC) and non-motion-corrected (NMC) datasets were compared. Gating was also performed to correct cardiac motion. The SUVmax and TBRmax values were calculated for the myocardial wall or a vulnerable coronary plaque for the 18F-FDG and 18F-FCH datasets, respectively. RESULTS: A pair-wise comparison showed that the SUVmax and TBRmax values of the motion corrected (MC) datasets were significantly higher than those for the non-motion-corrected (NMC) datasets (8.2 ± 1.0 vs 7.5 ± 1.0, p < 0.01 and 1.9 ± 0.2 vs 1.2 ± 0.2, p < 0.01, respectively). In addition, the SUVmax and TBRmax of the motion corrected and gated (MC_G) reconstructions were also higher than that of the non-motion-corrected but gated (NMC_G) datasets, although for the TBRmax this difference was not statistically significant (9.6 ± 1.3 vs 9.1 ± 1.2, p = 0.02 and 2.6 ± 0.3 vs 2.4 ± 0.3, p = 0.16, respectively). The respiratory motion-correction did not lead to a change in the signal to noise ratio. CONCLUSION: The proposed respiratory motion correction method for hybrid PET/MRI improved the image quality of cardiovascular PET scans by increased SUVmax and TBRmax values while maintaining the signal-to-noise ratio. Trial registration METC162043 registered 01/03/2017.

New Device to Measure Cross-Sectional Areas and Segmental Volumes of Objects and Limbs.

Purpose: High accuracy volume measurements have important implications in different medical and non-medical situations. All methods used to date have challenges to achieve a usable clinical accuracy. Moreover, current methods have limitations to measure segmental volumes. We developed a new device that is able to measure a continuous profile of the cross-sectional areas along an object. Herewith the total volume of an object or any part of it are correspondingly determined. Methods: The Peracutus Aqua Meth (PAM) generates continuous profiles of cross-sectional areas. Water is pumped in or out of a measuring unit at a nearly fixed flow rate and the speed of the water level (dh/dt) is measured continuously using a pressure sensor at the bottom. The change of the water level is a measure for the cross-sectional area of an object at any height. Signal processing is required to obtain valuable measurements. Three static objects and an arm of a test object were measured to demonstrate the accuracy and repeatability of the new device. Results: Cross-sectional areas of a PVC pipe obtained with the PAM and with a caliper were compared. The differences between the two methods were less than 1.3%. Volume measurements of two mannequin arms show standard deviations of 0.37% and 0.34%, respectively, whereas the standard deviation of the volume measurement of a genuine arm was only 1.07%. These figures surpass reported clinical accuracy. Conclusion: The new device demonstrates that determining the cross-section and its volumes of objects is possible in an accurate, reliable, and objective way. The results show that segmental volume measurements of human limbs are possible. Application in clinical and non-clinical situations seems meaningful.

Estimates for Assessment of Lymphedema: Reliability and Validity of Extremity Measurements.

Background: Measuring lymphedema with high accuracy is important for several reasons. The aim of this study was to assess the reliability and validity of three routinely used methods to estimate limb volumes. Methods and Results: Inverse water displacement, girth measurements, and Perometer measurements were executed. Although standard techniques were used, extra precautions were taken to maximize accuracy within and between observers. Water displacement, and girth and Perometer measurements resulted in standard deviations of 0.7%-0.8%, 0.5%, and 0.4%-1.0%, respectively. Conclusion: Measuring limb volumes using routine methods is not easy. Even under optimal conditions, the measurements are quite dependent on the observer. For practical situations, an easy, objective, and reliable method is lacking.

[CT colonography as first-line diagnostic procedure in patients with bowel symptoms]. / CT-colografie als eerstelijnsdiagnosticum bij patiënten met darmklachten.

OBJECTIVE: To investigate in how many patients with bowel or abdominal complaints, referred by the primary care physician (PCP) for exclusion of colorectal carcinoma (CRC), the more invasive colonoscopy could be avoided on the basis of the findings of CT colonography. DESIGN: Retrospective, descriptive. METHODS: All consecutive patients who underwent CT colonography in our centre on the request of their PCP from December 2006 to June 2009 were included. Demographic and referral data were collected. CT colonography results were described according to the 'CT Colonography Reporting and Data System'. We also investigated how many patients had to undergo colonoscopy in the 6 months following CT colonography. RESULTS: 398 patients (154 men and 244 women) with a median age of 61 years (range: 22-91) were included. Follow-up colonoscopy was indicated by CT colonography in 30 patients (7.5%) for suspected colorectal carcinoma, polyps > 10 mm, or 3 or more polyps 6-9 mm in size. In 33 patients (8.3%) follow-up colonoscopy or CT colonography was indicated for 1 or 2 polyps 6-9 mm in size, or suspicious lesions. 11 of these patients (2.8%) underwent colonoscopy. In 335 patients (84.2%) polyps > 6 mm or malignancies could be excluded. 18 of these patients (4.5%) still had a colonoscopy. In total, colonoscopy was spared in 341 patients (85.7%). Significant or potentially significant extra-colonic pathological abnormalities were found in 63 patients (15.8%). CONCLUSION: Our results support the theory that in the vast majority of patients with low or moderate suspicion of CRC referred by their PCP, invasive colonoscopy could be avoided, because CRC and polyps could be excluded by CT colonography. CT colonography could be a valuable additional diagnostic tool in primary care.

Interobserver variability of ankle-brachial index measurements at rest and post exercise in patients with intermittent claudication.

The ankle-brachial index (ABI) post exercise is claimed to play a complementary role in the diagnosis or exclusion of intermittent claudication (IC). The interobserver variability of ABI measurements at rest and post exercise in patients with typical symptoms of IC is the subject of this study with emphasis on ABI post exercise. ABI at rest and post exercise were measured in both legs of 20 patients with typical symptoms of IC. After 15 minutes of rest these measurements were repeated by another observer. Analysis according to Bland-Altman was performed on 40 paired leg measurements at rest and 40 paired leg measurements post exercise. The average ABI at rest for the first observer was 0.84 (standard deviation +/-0.18) and for the second was 0.84 (+/-0.17). Post-exercise averages were 0.73 (+/-0.25) and 0.74 (+/-0.27), respectively. The standard deviation of the ABI difference between observers was 0.08 at rest and 0.15 post exercise. The interobserver variability of the ABI was 10% at rest and 21% post exercise. The interobserver variability post exercise is an important given when rules are defined about how the ABI post exercise translates into a more reliable and objective diagnosis of IC.

Durability of imaging plates in clinical use.

In many X-ray clinics, the traditional photographic film has been replaced by an imaging plate (IP). The IP is re-usable and the purpose of this study was to test if image deterioration occurred after successive uses of the IP. The emphasis is placed on the efficiency of image formation and on image uniformity. In a cross-sectional study, 21 clinically used IPs were exposed with a standardized phantom imaging protocol. These IPs were in clinical use between one month and two years and the IPs were exposed between 191 and 3787 times. After digitizing, the mean pixel value (MPV) in a predefined image area was determined. The relation between MPV and IP uses was assessed. In a second experiment, image uniformity of 30 other clinically used IPs was visually inspected for artifacts on a diagnostic monitor. These IPs were in clinical use between one week and two years and exposed between 76 and 5373 times. The first experiment showed that no significant deterioration of the MPV with increasing usage count of the IP was present (p = 0.15). The second experiment showed the appearance of clinically relevant artifacts on the IP before 3000 uses. It was concluded that the efficiency of the image formation process does not significantly deteriorate after successive use of IPs and is therefore not expected to limit their life span. Mechanical handling in the digitizer of the used system seems to set a limit to IP durability. Uniformity should therefore be checked regularly in clinical quality control.

[Epidemiology of bluetongue virus serotype 8 outbreaks in the Netherlands in 2006]. / Beschrijvende epidemiologie van de bluetongue serotype 8-uitbraken in Nederland in 2006.

In August 2006 a major epidemic of Bluetongue (BT) occurred in north-western Europe, affecting The Netherlands, Belgium, Germany, Luxemburg, and the north of France. It was caused by Br virus serotype 8 (BTV-8), a serotype previously unknown to the EU. Although clinical disease is usually restricted to sheep, this virus also caused clinical disease in a small proportion of cattle. The last clinical outbreak of BT in The Netherlands occurred mid-December 2006. The delay between observation of the first clinical signs by the owner and reporting of a clinically suspect BT situation to the veterinary authorities was approximately 2 weeks. BTV-8-associated clinical signs were more prominent in sheep than in cattle, and the relative frequency of specific clinical signs was different in cattle and sheep. Morbidity and mortality rates were significantly higher among sheep than among cattle, and a higher proportion of cattle than sheep recovered from clinical disease.

Does peripheral nerve degeneration affect circulatory responses to head-up tilt in spinal cord-injured individuals?

Despite the loss of centrally mediated sympathetic vasoconstriction, spinal cord-injured (SCI) individuals cope surprisingly well with orthostatic challenges. In the pathophysiology of this intriguing observation spinal sympathetic-, veno-arteriolar-(VAR), and myogenic reflexes seem to play a role. The purpose of this study was to assess whether central (stroke volume, heart rate, blood pressure and total peripheral resistance) and peripheral (leg blood flow, leg vascular resistance and femoral arterial diameter) hemodynamic responses to head-up tilt are different in two groups of SCI patients, i. e., SCI individuals with upper motor neuron lesions (who have spinal reflexes, VAR and myogenic reflexes) (U; n=6) and those with lower motor neuron lesion (who have no spinal reflexes, perhaps no VAR due to nerve degeneration, but intact myogenic reflexes) (L; n=5). Ten healthy male individuals served as controls (C) (normal supraspinal sympathetic control and presence of all reflexes). After 10 min supine rest all individuals were tilted to 30 degrees head-up tilt. Red blood cell velocity (measured by echo Doppler ultrasound) in the femoral artery decreased and vascular resistance increased significantly in all three groups in the upright position compared with supine. Mean arterial pressure (MAP) remained unchanged in U and L and increased significantly in C in the upright versus supine position. The present study shows that all SCI individuals were able to maintain MAP by increasing leg vascular resistance during head-up tilt, despite nerve degeneration in L and lack of centrally mediated sympathetic control in all SCI individuals. Results of the present study suggest that not spinal reflexes but local (myogenic) reflex activity plays a pivotal role in peripheral vascular responses upon head-up tilt when central control mechanisms fail.

Leg vascular resistance increases during head-up tilt in paraplegics.

Despite loss of centrally mediated sympathetic vasoconstriction to the legs, spinal cord-injured individuals cope surprisingly well with an orthostatic challenge. This study assessed changes in leg vascular resistance following head-up tilt in healthy (C) and in paraplegic (P) individuals. After 10 min of supine rest, subjects were tilted 30 degrees head-up. Mean arterial pressure (MAP) and total peripheral resistance (TPR) increased in C (MAP from 76.7 +/ -6.6 mmHg to 80.6 +/- 8.2 mmHg; TPR from 1.12 +/- 0.26 AU to 1.19 +/ -0.31 AU) while both remained unchanged in P. Echo Doppler ultrasound determined red blood cell velocity in the femoral artery, which decreased (P from 18.9+/-6.2 cm/s to 12.5 +/- 4.5 cm/s, P = 0.001; C from 16.3 +/- 6.2 cm/s to 10.8 +/- 5.0 cm/s, P = 0.001) and leg vascular resistance, which increased (P from 402 +/- 137 AU to 643 +/- 274 AU, P = 0.001; C from 238 +/- 68 AU to 400 +/- 122 AU, P = 0.003) from supine to upright. The present study shows that independent of supraspinal sympathetic control, humans are able to increase leg vascular resistance and maintain blood pressure during head-up tilt.

The development of postthrombotic syndrome in relationship to venous reflux and calf muscle pump dysfunction at 2 years after the onset of deep venous thrombosis.

OBJECTIVE: Postthrombotic syndrome (PTS) develops in 40% to 60% of patients with deep venous thrombosis. Factors that are important in the development of PTS include venous reflux, deep vein obstruction, and calf muscle pump dysfunction (CMD). METHODS: Reflux and CMD in relationship to the severity of PTS were evaluated in a 2-year follow-up study of patients with acute deep venous thrombosis. Duplex scanning was used to measure reflux. The supine venous pump function test (SVPT) measures CMD with strain-gauge plethysmography. The base-line examination was performed within 1 to 5 days after diagnosis. The next examinations were scheduled at 3, 6, 12, and 24 months. RESULTS: The study included 86 legs, and the 2-year follow-up period was completed for 70 legs. Significantly more reflux was found in previously thrombosed vein segments, with an odds ratio of 1.8 after 3 months, of 2.1 after 6 months, of 2.5 after 12 months, and of 3.2 after 24 months. Multiple regression results showed that the most important risk factor for early clinical signs of PTS was superficial reflux in months 3, 6, and 12 (P < or =.02). Deep reflux did not have a synergistic relationship with superficial reflux in correlation with the clinical signs of PTS. The SVPT was not able to predict the development of PTS. CONCLUSION: More reflux develops in previously thrombosed vein segments. As early as after the third month, patients with superficial reflux have an increased risk of development of the first clinical signs of PTS. Within 2 years, the SVPT shows no relationship with clinical signs of PTS.

Shear stress levels in paralyzed legs of spinal cord-injured individuals with and without nerve degeneration.

The purpose of this study was to assess the relationship between inactivity and shear stress, the frictional force of blood against the endothelium, in spinal cord injury (SCI) subjects. SCI group offers a unique "model of nature" to study the effects of inactivity. Nine SCI subjects with upper (SCI-U) and 5 with a lower (SCI-L) motoneuron lesion and 10 able-bodied controls (C) were included. A venous blood sample was withdrawn to determine blood viscosity. Red blood cell velocities and arterial diameters of the common carotid artery (CCA) and common femoral artery (CFA) were measured by using echo-Doppler ultrasound in a supine position. No differences were observed in wall shear stress in the CCA between groups. In the CFA, peak and mean wall shear stress were significantly increased in SCI (14.1 and 1.2 Pa, respectively) compared with C (10.2 and 0.9 Pa, respectively). Because SCI-U and SCI-L showed no differences in shear stress levels, inactivity and not nerve degeneration seems to cause the elevated shear stress levels in the CFA in SCI. However, the lack of central neural control as a causal factor cannot be ruled out.