Image Derived Input Functions: Effects of Motion on Tracer Kinetic Analyses

Purpose: To quantify the effects of motion affected image-derived input functions (IDIF) on the outcome of tracer kinetic analyses. Procedures: Two simulation studies, one based on high and the other on low cortical uptake, were performed. Different degrees of rotational and axial translational motion were added to the final frames of simulated dynamic positron emission tomography scans. Extracted IDIFs from motion affected simulated scans were compared to original IDIFs and to outcome of tracer kinetic analysis (volume of distribution, V T). Results: Differences in IDIF values of up to 239 % were found for the last frames. Patient motion of more than 6 ° or 5 mm resulted in at least 10 % higher or lower VT values for the high cortical tracer. Conclusion: The degrees of motion studied are commonly observed in clinical studies and hamper the extraction of accurate IDIFs. Therefore, it is essential to ensure that patient motion is minimal and corrected for

Randomized controlled trial comparing magnetic marker localization (MaMaLoc) with wire-guided localization in the treatment of early-stage breast cancer

Wire-guided localization (WGL) is the standard of care in the surgical treatment of nonpalpable breast tumors. In this study, we compare the use of a new magnetic marker localization (MaMaLoc) technique to WGL in the treatment of early-stage breast cancer patients. Open-label, single-center, randomized controlled trial comparing MaMaLoc (intervention) to WGL (control) in women with early-stage breast cancer. Primary outcome was surgical usability measured using the System Usability Scale (SUS, 0-100 score). Secondary outcomes were patient reported, clinical, and pathological outcomes such as retrieval rate, operative time, resected specimen weight, margin status, and reoperation rate. Thirty-two patients were analyzed in the MaMaLoc group and 35 in the WGL group. Patient and tumor characteristics were comparable between groups. No in situ complications occurred. Retrieval rate was 100% in both groups. Surgical usability was higher for MaMaLoc: 70.2 ± 8.9 vs. 58.1 ± 9.1, p < 0.001. Patients reported higher overall satisfaction with MaMaLoc (median score 5/5) versus WGL (score 4/5), p < 0.001. The use of magnetic marker localization (MaMaLoc) for early-stage breast cancer is effective and has higher surgical usability than standard WGL

Gamma camera-specific reference standards for radioactive iodine uptake measurements

Abstract Background Current guidelines of the radioiodine uptake (RAIU) test allow the use of different equipment, isotopes, activity and region-of-interest (ROI). We evaluated presence and extent of these differences in clinical practice and evaluated the effect of some of these variations on RAIU outcomes. Also, gamma camera-specific reference standards were calculated and retrospectively compared with measurements obtained during clinical RAIU tests. Materials and methods First, questionnaires were sent to Dutch nuclear medicine departments requesting information about equipment usage, isotope, isotope formulation, activity and measurement techniques. Secondly, a neck phantom containing a range of activities in capsule or water-dissolved formulation was scanned. Counts were measured using automatic ROI, square box ROI or all counts in the image. Thirdly, clinical RAIU data were collected during 2015–2018 using three different gamma cameras. Reference standards for each scanner were calculated using regression analysis between reference activity and measured counts. Uptake measurements using this gamma camera-specific reference standard were compared with original measurements. Results The survey demonstrated significant differences in isotope, isotope formulation, activity, use of neck phantoms, frequency and duration of reference measurements, distance to collimator, use of background measurements and ROI delineation. The phantom study demonstrated higher counts for the water-dissolved formulation than capsules using both automatic and square box ROI. Also, higher counts were found using a square box ROI than an automatic ROI. The retrospective study showed feasibility of RAIU calculations using camera-specific reference standards and good correlation with the original RAIU measurements. Conclusions This study demonstrated considerable technical variation in RAIU measurement in clinical practice. The phantom study demonstrated that these differences could result in differences in count measurements, potentially resulting in different dose calculations for radioactive iodine therapy. Retrospective data suggest that camera-specific reference standards may be used instead of individual reference measurements using separate activity sources, which may thus eliminate some sources of variation

Use of image derived input functions for [11C]PIB studies: Assessment of accuracy and test-retest variability

Introduction: Derivation of input functions directly from dynamic PET images obviates the need for arterial sampling and will enhance clinical applicability of quantitative brain studies. The aim of the present study was to assess accuracy and test-retest variability of [11C]PIB studies when using image derived input functions (IDIF) obtained using reconstruction-based partial volume correction (PVC) [1]. Methods: PET and arterial blood data from five repeat dynamic [11C]PIB scans, acquired using an ECAT EXACT HR+ scanner and an on-line blood sampler, were used in the present study. Test and retest scans were performed on the same day. Scans were reconstructed using standard (no PVC) ordered subset expectation maximization (OSEM, 2 iteration (i), 16 subsets (s)) and a PVC-OSEM reconstruction algorithm, which corrects for the spatial resolution of the scanner. PVC-OSEM scans were reconstructed using 4i, 16s and a Gaussian recovery kernel of 5.5 mm FWHM. For the region below the base of the skull, regions of interest (ROIs) were drawn semiautomatically over the four hottest pixels of the carotid arteries using a pseudo blood volume image, generated by summation of the early time frames (<60s). These ROIs were projected onto all dynamic frames, thereby generating corresponding IDIFs. Both IDIFs with and without calibration to manual samples taken during the scans were used for further analysis. Parametric images of volume of distribution (Vd), based on Logan analysis, were generated using both the on-line blood sampler input function (BSIF) and the various IDIFs. For each subject, 15 tissue ROIs were drawn and projected on all Vd images. The validity of each IDIF was assessed by correlating IDIF-based Vd values with the corresponding BSIF-based values. In addition, test-retest variability was investigated. Results: Image quality of BSIF- and IDIF-based Logan Vd images was similar. A summary of the quantitative comparison of IDIF- and BSIF-based Vd values is given in figure 1 and 2. Calibration of the IDIFs did not result in better correlation coefficients, but significantly reduced differences in Vd. For PVC-OSEM, calibration resulted in a slope of 1.00 (figure 1). No significant differences in test-retest variability were found between BSIF- and IDIF-based Vd values. Discussion and Conclusions: For [C11]PIB studies, an image derived input function is an accurate alternative to arterial blood sampling, provided that scans are reconstructed using a reconstruction-based partial volume correction method. Manual samples, however, are still needed for calibrating the IDIF, and for determining plasma/blood ratio and metabolites. These samples can probably taken from venous blood

ORIGINAL ARTICLE Off-line motion correction methods for multi-frame

# The Author(s) 2009. This article is published with open access at Springerlink.com Purpose Patient motion during PET acquisition may affect measured time-activity curves, thereby reducing accuracy of tracer kinetic analyses. The aim of the present study was to evaluate different off-line frame-by-frame methods to correct patient motion, which is of particular interest when no optical motion tracking system is available or when older data sets have to be reanalysed. Methods Four different motion correction methods were evaluated. In the first method attenuation-corrected frames were realigned with the summed image of the first 3 min. The second method was identical, except that nonattenuation-corrected images were used. In the third and fourth methods non-attenuation-corrected images were realigned with standard and cupped transmission images, respectively. Two simulation studies were performed, based on [ 11 C]flumazenil and (R)- [ 11 C]PK11195 data sets, respectively. For both simulation studies different types (rotational, translational) and degrees of motion were added. Simulated PET scans were corrected for motion using all correction methods. The optimal method derived from these simulation studies was used to evaluate two (one with and one without visible movement) clinical data sets of [ 11 C]flumazenil, (R)- [ 11 C]PK11195 and [ 11 C]PIB. For these clinical data sets, the volume of distribution (VT) was Electronic supplementary material The online version of this article (doi:10.1007/s00259-009-1193-y) contains supplementary material, which is available to authorised users

Comparison of plasma input and reference tissue models for analysing [(11)C]flumazenil studies

A single-tissue compartment model with plasma input is the established method for analysing [(11)C]flumazenil ([(11)C]FMZ) studies. However, arterial cannulation and measurement of metabolites are time-consuming. Therefore, a reference tissue approach is appealing, but this approach has not been fully validated for [(11)C]FMZ. Dynamic [(11)C]FMZ positron emission tomography scans with arterial blood sampling were performed in nine drug-free depressive patients and eight healthy subjects. Regions of interest were defined on co-registered magnetic resonance imaging scans and projected onto dynamic [(11)C]FMZ images. Using a Hill-type metabolite function, single (1T) and reversible two-tissue (2T) compartmental models were compared. Simplified reference tissue model (SRTM) and full reference tissue model (FRTM) were investigated using both pons and (centrum semiovale) white matter as reference tissue. The 2T model provided the best fit in 59% of cases. Two-tissue V(T) values were on average 1.6% higher than 1T V(T) values. Owing to the higher rejection rate of 2T fits (7.3%), the 1T model was selected as plasma input method of choice. SRTM was superior to FRTM, irrespective whether pons or white matter was used as reference tissue. BP(ND) values obtained with SRTM correlated strongly with 1T V(T) (r=0.998 and 0.995 for pons and white matter, respectively). Use of white matter as reference tissue resulted in 5.5% rejected fits, primarily in areas with intermediate receptor density. No fits were rejected using pons as reference tissue. Pons produced 23% higher BP(ND) values than white matter. In conclusion, for most clinical studies, SRTM with pons as reference tissue can be used for quantifying [(11)C]FMZ bindin