Zeitschrift fur Medizinische Physik最新文献

{"title":"Quantifying myocardial perfusion during MR-guided interventions without exogenous contrast agents: intra-arterial spin labeling","authors":"Simon Reiss ,&nbsp;Kevin Wäscher ,&nbsp;Ali Caglar Özen ,&nbsp;Thomas Lottner ,&nbsp;Timo Heidt ,&nbsp;Constantin von zur Mühlen ,&nbsp;Michael Bock","doi":"10.1016/j.zemedi.2023.01.002","DOIUrl":"10.1016/j.zemedi.2023.01.002","url":null,"abstract":"<div><h3>Purpose</h3><div>To test intra-arterial spin labeling (iASL) using active guiding catheters for myocardial perfusion measurements during magnetic resonance (MR)-guided interventions in a pig study.</div></div><div><h3>Methods</h3><div>In this work, a single-loop radiofrequency (RF) coil at the tip of a 6F active coronary catheter was used as a transmit coil for local spin labeling. The transmit magnetic RF field (B₁) of the coil and the labeling efficiency were determined, and iASL was tested in two pigs after the catheter was engaged in the aortic root, the ostium of the left coronary artery (LCA) under MR-guidance. The iASL effect was assessed by the signal difference between spin-labeling On and control (spin-labeling OFF) images, and in a cross-correlation between ON/Off states of spin-labeling a binary labeling paradigm. In addition, quantitative myocardial perfusion was calculated from the iASL experiments.</div></div><div><h3>Results</h3><div>The maximum B₁ in the vicinity of the catheter coil was 2.1 µT. A strong local labeling effect with a labeling efficiency of 0.45 was achieved with iASL both in vitro and in vivo. In both pigs, the proximal myocardial segments supplied by the LCA showed significant labelling effect up to distances of 60 mm from the aortic root with a relative signal difference of (3.14 ± 2.89)% in the first and (3.50 ± 1.25)% in the second animal. The mean correlation coefficients were R = 0.63 ± 0.22 and 0.42 ± 0.16, respectively. The corresponding computed myocardial perfusion values in this region of the myocardium were similar to those obtained with contrast perfusion methods ((1.2 ± 1.1) mL/min/g and (0.8 ± 0.6) mL/min/g).</div></div><div><h3>Conclusion</h3><div>The proposed iASL method demonstrates the feasibility of selective myocardial perfusion measurements during MR-guided coronary interventions, which with further technical improvements may provide an alternative to exogenous contrast-based perfusion. Due to the invasive nature of the iASL method, it can potentially be used in concert with MRI-guided coronary angioplasty.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 4","pages":"Pages 596-609"},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10587236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-stage image registration based on list-mode proton radiographies for small animal proton irradiation: A simulation study","authors":"Prasannakumar Palaniappan,&nbsp;Yana Knudsen,&nbsp;Sebastian Meyer ,&nbsp;Chiara Gianoli,&nbsp;Katrin Schnürle,&nbsp;Matthias Würl,&nbsp;Jonathan Bortfeldt,&nbsp;Katia Parodi ,&nbsp;Marco Riboldi","doi":"10.1016/j.zemedi.2023.04.003","DOIUrl":"10.1016/j.zemedi.2023.04.003","url":null,"abstract":"<div><div>We present a multi-stage and multi-resolution deformable image registration framework for image-guidance at a small animal proton irradiation platform. The framework is based on list-mode proton radiographies acquired at different angles, which are used to deform a 3D treatment planning CT relying on normalized mutual information (NMI) or root mean square error (RMSE) in the projection domain.</div><div>We utilized a mouse X-ray micro-CT expressed in relative stopping power (RSP), and obtained Monte Carlo simulations of proton images in list-mode for three different treatment sites (brain, head and neck, lung). Rigid transformations and controlled artificial deformation were applied to mimic position misalignments, weight loss and breathing changes. Results were evaluated based on the residual RMSE of RSP in the image domain including the comparison of extracted local features, i.e. between the reference micro-CT and the one transformed taking into account the calculated deformation.</div><div>The residual RMSE of the RSP showed that the accuracy of the registration framework is promising for compensating rigid (&gt;97% accuracy) and non-rigid (∼95% accuracy) transformations with respect to a conventional 3D-3D registration. Results showed that the registration accuracy is degraded when considering the realistic detector performance and NMI as a metric, whereas the RMSE in projection domain is rather insensitive.</div><div>This work demonstrates the pre-clinical feasibility of the registration framework on different treatment sites and its use for small animal imaging with a realistic detector. Further computational optimization of the framework is required to enable the use of this tool for online estimation of the deformation.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 4","pages":"Pages 521-532"},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9678593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Post-mastectomy radiotherapy: Impact of bolus thickness and irradiation technique on skin dose","authors":"Frédéric A. Miéville,&nbsp;Nicolas Pitteloud,&nbsp;Vérane Achard,&nbsp;Giorgio Lamanna,&nbsp;Olivier Pisaturo,&nbsp;Pierre-Alain Tercier,&nbsp;Abdelkarim S. Allal","doi":"10.1016/j.zemedi.2023.03.004","DOIUrl":"10.1016/j.zemedi.2023.03.004","url":null,"abstract":"<div><h3>Purpose</h3><div>To determine 10 MV IMRT and VMAT based protocols with a daily bolus targeting a skin dose of 45 Gy in order to replace the 6 MV tangential fields with a 5 mm thick bolus on alternate days method for post-mastectomy radiotherapy.</div></div><div><h3>Method</h3><div>We measured the mean surface dose along the chest wall PTV as a function of different bolus thicknesses for sliding window IMRT and VMAT plans. We analyzed surface dose profiles and dose homogeneities and compared them to our standard 6 MV strategy. All measurements were performed on a thorax phantom with Gafchromic films while dosimetric plans were computed using the Acuros XB algorithm (Varian).</div></div><div><h3>Results</h3><div>We obtained the best compromise between measured surface dose (mean dose and homogeneity) and skin toxicity threshold obtained from the literature using a daily 3 mm thick bolus. Mean surface doses were 91.4 ± 2.8% [85.7% – 95.4%] and 92.2 ± 2.3% [85.6% – 95.2%] of the prescribed dose with IMRT and VMAT techniques, respectively. Our standard 6 MV alternate days 5 mm thick bolus leads to 89.0 ± 3.7% [83.6% – 95.5%]. Mean dose differences between measured and TPS results were &lt; 3.2% for depths as low as 2 mm depth.</div></div><div><h3>Conclusion</h3><div>10 MV IMRT-based protocols with a daily 3 mm thick bolus produce a surface dose comparable to the standard 6 MV 5 mm thick bolus on alternate days method but with an improved surface dose homogeneity. This allows for a better control of skin toxicity and target volume coverage.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 4","pages":"Pages 542-554"},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9480352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"35 Jahre im Dienste des Strahlenschutzes: Verantwortung, Fortschritt, Innovation","authors":"Inge Paulini","doi":"10.1016/j.zemedi.2024.09.001","DOIUrl":"10.1016/j.zemedi.2024.09.001","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 4","pages":"Pages 485-489"},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142485129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Editorial Board + Consulting Editorial Board","authors":"","doi":"10.1016/S0939-3889(24)00103-X","DOIUrl":"10.1016/S0939-3889(24)00103-X","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 4","pages":"Page iii"},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Risk management in radiation-based therapies","authors":"","doi":"10.1016/j.zemedi.2024.05.002","DOIUrl":"10.1016/j.zemedi.2024.05.002","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 3","pages":"Pages 355-356"},"PeriodicalIF":2.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388924000503/pdfft?md5=99b38827af2117ecd295bc9dd7a2269f&pid=1-s2.0-S0939388924000503-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141319449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Triple-source saddle-curve cone-beam photon counting CT image reconstruction: A simulation study","authors":"","doi":"10.1016/j.zemedi.2022.10.003","DOIUrl":"10.1016/j.zemedi.2022.10.003","url":null,"abstract":"<div><h3>Purpose</h3><p>The most common detector material in the PC CT system, cannot achieve the best performance at a relatively higher photon flux rate. In the reconstruction view, the most commonly used filtered back projection, is not able to provide sufficient reconstructed image quality in spectral computed tomography (CT). Developing a triple-source saddle-curve cone-beam photon counting CT image reconstruction method can improve the temporal resolution.</p></div><div><h3>Methods</h3><p>Triple-source saddle-curve cone-beam trajectory was rearranged into four trajectory sets for simulation and reconstruction. Projection images in different energy bins were simulated by forward projection and photon counting CT respond model simulation. After simulation, the object was reconstructed using Katsevich’s theory after photon counts correction using the pseudo inverse of photon counting CT response matrix. The material decomposition can be performed based on images in different energy bins.</p></div><div><h3>Results</h3><p>Root mean square error (RMSE) and structural similarity index (SSIM) are calculated to quantify the image quality of reconstruction images. Compared with FDK images, the RMSE for the triple-source image was improved by 27%, 21%, 14%, 8%, and 6% for the reconstrued image of 20–33, 33–47, 47–58, 58–69, 69–80 keV energy bin. The SSIM was improved by 1.031%, 0.665%, 0.396%, 0.235%, 0.174% for corresponding energy bin. The decomposition image based on corrected images shows improved RMSE and SSIM, each by 33.861% and 0.345%. SSIM of corrected decomposition image of iodine reaches 99.415% of the original image.</p></div><div><h3>Conclusions</h3><p>A new Triple-source saddle-curve cone-beam PC CT image reconstruction method was developed in this work. The exact reconstruction of the triple-source saddle-curve improved both the image quality and temporal resolution.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 3","pages":"Pages 408-418"},"PeriodicalIF":2.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000976/pdfft?md5=cbc77a0b4c1832ccbc8b5cf2a1e8cbb2&pid=1-s2.0-S0939388922000976-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40666499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Use of dose-area product to assess plan quality in robotic radiosurgery","authors":"","doi":"10.1016/j.zemedi.2023.01.001","DOIUrl":"10.1016/j.zemedi.2023.01.001","url":null,"abstract":"<div><h3>Purpose</h3><p>In robotic stereotactic radiosurgery (SRS), optimal selection of collimators from a set of fixed cones must be determined manually by trial and error. A unique and uniformly scaled metric to characterize plan quality could help identify Pareto-efficient treatment plans.</p></div><div><h3>Methods</h3><p>The concept of dose-area product (DAP) was used to define a measure (DAP_ratio) of the targeting efficiency of a set of beams by relating the integral DAP of the beams to the mean dose achieved in the target volume. In a retrospective study of five clinical cases of brain metastases with representative target volumes (range: 0.5–5.68 ml) and 121 treatment plans with all possible collimator choices, the DAP_ratio was determined along with other plan metrics (conformity index CI, gradient index R50%, treatment time, total number of monitor units TotalMU, radiotoxicity index f12, and energy efficiency index η50%), and the respective Spearman's rank correlation coefficients were calculated. The ability of DAP_ratio to determine Pareto efficiency for collimator selection at DAP_ratio &lt; 1 and DAP_ratio &lt; 0.9 was tested using scatter plots.</p></div><div><h3>Results</h3><p>The DAP_ratio for all plans was on average 0.95 ± 0.13 (range: 0.61–1.31). Only the variance of the DAP_ratio was strongly dependent on the number of collimators. For each target, there was a strong or very strong correlation of DAP_ratio with all other metrics of plan quality. Only for R50% and η50% was there a moderate correlation with DAP_ratio for the plans of all targets combined, as R50% and η50% strongly depended on target size. Optimal treatment plans with CI, R50%, f12, and η50% close to 1 were clearly associated with DAP_ratio &lt; 1, and plans with DAP_ratio &lt; 0.9 were even superior, but at the cost of longer treatment times and higher total monitor units.</p></div><div><h3>Conclusions</h3><p>The newly defined DAP_ratio has been demonstrated to be a metric that characterizes the target efficiency of a set of beams in robotic SRS in one single and uniformly scaled number. A DAP_ratio &lt; 1 indicates Pareto efficiency. The trade-off between plan quality on the one hand and short treatment time or low total monitor units on the other hand is also represented by DAP_ratio.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 3","pages":"Pages 428-435"},"PeriodicalIF":2.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923000016/pdfft?md5=11d050dcb968a77bf2766b4dbaca3618&pid=1-s2.0-S0939388923000016-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10587237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"End-to-end testing for stereotactic radiotherapy including the development of a Multi-Modality phantom","authors":"","doi":"10.1016/j.zemedi.2022.11.006","DOIUrl":"10.1016/j.zemedi.2022.11.006","url":null,"abstract":"<div><h3><strong>Purpose</strong></h3><p>A new insert for a commercially available end-to-end test phantom was designed and in-house manufactured by 3D printing. Subsequently, the insert was tested for different stereotactic radiation therapy workflows (SRS, SBRT, FSRT, and Multimet) also in comparison to the original insert.</p></div><div><h3><strong>Material and methods</strong></h3><p>Workflows contained imaging (MR, CT), treatment planning, positioning, and irradiation. Positioning accuracy was evaluated for non-coplanar x-ray, kV- and MV-CBCT systems, as well as surface guided radiation therapy. Dosimetric accuracy of the irradiation was measured with an ionization chamber at four different linear accelerators including dynamic tumor tracking for SBRT.</p></div><div><h3><strong>Results</strong></h3><p>CT parameters of the insert were within the specification. For MR images, the new insert allowed quantitative analysis of the MR distortion. Positioning accuracy of the phantom with the new insert using the imaging systems of the different linacs was &lt; 1 mm/degree also for MV-CBCT and a non-coplanar imaging system which caused &gt; 3 mm deviation with the original insert. Deviation of point dose values was &lt;<!--> <!-->3% for SRS, FSRT, and SBRT for both inserts. For the Multimet plans deviations exceeded 10% because the ionization chamber was not positioned in each metastasis, but in the center of phantom and treatment plan.</p></div><div><h3><strong>Conclusion</strong></h3><p>The in-house manufactured insert performed well in all steps of four stereotactic treatment end-to-end tests. Advantages over the commercially available alternative were seen for quantitative analysis of deformation correction in MR images, applicability for non-coplanar x-ray imaging, and dynamic tumor tracking.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 3","pages":"Pages 477-484"},"PeriodicalIF":2.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922001234/pdfft?md5=ddec9b262290ef8f0ca939378a7e3a7f&pid=1-s2.0-S0939388922001234-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10402545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Note on uncertainty in Monte Carlo dose calculations and its relation to microdosimetry","authors":"","doi":"10.1016/j.zemedi.2022.11.012","DOIUrl":"10.1016/j.zemedi.2022.11.012","url":null,"abstract":"<div><h3>Purpose</h3><p>The Type A standard uncertainty in Monte Carlo (MC) dose calculations is usually determined using the “history by history” method. Its applicability is based on the assumption that the central limit theorem (CLT) can be applied such that the dispersion of repeated calculations can be modeled by a Normal distribution. The justification for this assumption, however, is not obvious. The concept of stochastic quantities used in the field of microdosimetry offers an alternative approach to assess uncertainty. This leads to a new and simple expression.</p></div><div><h3>Methods</h3><p>The value of the MC determined absorbed dose is considered a random variable which is comparable to the stochastic quantity specific energy, z. This quantity plays an important role in microdosimetry and in the definition of the quantity absorbed dose, D. One of the main features of z is that it is itself the product of two other random variables, specifically of the mean dose contribution in a ‘single event’ and of the mean number of such events. The term ‘single event’ signifies the sum of energies imparted by all correlated particles to the matter in a given volume. The similarity between the MC calculated absorbed dose and the specific energy is used to establish the ‘event by event’ method for the determination of the uncertainty. MC dose calculations were performed to test and compare both methods.</p></div><div><h3>Results</h3><p>It is shown that the dispersion of values obtained by MC dose calculations indeed depend on the product of the mean absorbed dose per event, and the number of events. Applying methods to obtain the variance of a product of two random variables, a simple formula for the assessment of uncertainties is obtained which is slightly different from the ‘history by history’ method. Interestingly, both formulas yield indistinguishable results. This finding is attributed to the large number of histories used in MC simulations. Due to the fact that the values of a MC calculated absorbed dose are the product of two approximately Normal distributions it can be demonstrated that the resulting product is also approximately normally distributed.</p></div><div><h3>Conclusions</h3><p>The event by event approach appears to be more suitable than the history by history approach because it takes into account the randomness of the number of events involved in MC dose calculations. Under the condition of large numbers of histories, however, both approaches lead to the same simple expression for the determination of uncertainty in MC dose calculations. It is suggested to replace the formula currently used by the new expression. Finally, it turned out that the concept and ideas that were developed in the field of microdosimetry already 50 years ago can be usefully applied also in MC calculations.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 3","pages":"Pages 468-476"},"PeriodicalIF":2.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922001337/pdfft?md5=48e6762405035d2f14a0258e021b67b3&pid=1-s2.0-S0939388922001337-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10447934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}