| 1. |
- Cederkrantz, Elin, et al.
(author)
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Absorbed Doses and Risk Estimates of (211)At-MX35 F(ab')2 in Intraperitoneal Therapy of Ovarian Cancer Patients.
- 2015
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In: International journal of radiation oncology, biology, physics. - : Elsevier BV. - 1879-355X .- 0360-3016. ; 93:3, s. 569-76
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Journal article (peer-reviewed)abstract
- Ovarian cancer is often diagnosed at an advanced stage with dissemination in the peritoneal cavity. Most patients achieve clinical remission after surgery and chemotherapy, but approximately 70% eventually experience recurrence, usually in the peritoneal cavity. To prevent recurrence, intraperitoneal (i.p.) targeted α therapy has been proposed as an adjuvant treatment for minimal residual disease after successful primary treatment. In the present study, we calculated absorbed and relative biological effect (RBE)-weighted (equivalent) doses in relevant normal tissues and estimated the effective dose associated with i.p. administration of (211)At-MX35F(ab')2.
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| 2. |
- Hagmarker, Linn, et al.
(author)
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Characterisation of a planar dosimetry method estimating the absorbed dose to the bone marrow during 177Lu-DOTATATE treatment
- 2016
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In: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer. - 1619-7070 .- 1619-7089.
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Conference paper (other academic/artistic)abstract
- Aim: An image based method for bone marrow dosimetry, earlier presented by our research group, has shown a significant correlation between the absorbed dose to the bone marrow and haematological toxicity in 177Lu-DOTATATE treatment. The aim of this study was to further evaluate and optimise the method. Materials and Methods: 46 patients with advanced neuroendocrine tumours were treated with 177Lu -DOTATATE on 2-6 occasions. The patients were evaluated using the 4 planar gamma camera images collected at 2, 24, 48 and 168 hours after injection. The whole body was divided into a high- and a low uptake compartment, using a threshold based segmentation tool in the image platform PhONSAi, developed in-house. The segmentation tool starts by including the highest uptake focus and then gradually includes foci with lower and lower uptakes until a threshold is reached where the number of foci escalates. The threshold determines the proportion of the foci that is included in the two compartments. Visual inspection was used to determine the threshold valuewhere all high uptake tissues (i.e. kidney, spleen, liver and tumours) were included in the high uptake compartment. For thresholds around this value the activity in the two compartments was determined by the conjugate view method and the bonemarrow dose was calculated as a sum of the self and cross dose in the low uptake compartment and the cross dose from the high uptake compartment. Results: The visual analysis implies a threshold value of 10%of the maximum number of foci. A correlation was found between the absorbed bone marrow dose and haematological toxicity with p-values ranging from 0.001 to 0.02 for thresholds between 2 % and 25 %, the strongest correlation was found at 15 %. The mean absorbed bone marrow dose were 0.20-0.22 Gy per 7.4 GBq for threshold values between 10-25 %, and increased to 0.28 Gy for the lower values. No significant difference was observed in coefficient of variation (8.2-8.7 %) for the individual mean absorbed doses when varying the threshold value. Conclusion: The individual variation in absorbed dose is maintained at a low level when varying the threshold value for the determination of the compartment sizes. This implies that the method is stable for estimation of bone marrow doses and its correlation to haematological toxicity.
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| 3. |
- Hagmarker, Linn, et al.
(author)
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Evaluation of the correlations between the absorbed bone marrow dose and bone marrow response during the first cycle of 177Lu-DOTATATE treatment
- 2017
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In: European Association of Nuclear Medicine.
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Conference paper (other academic/artistic)abstract
- The bone marrow is one of the organs at risk during 177Lu-DOTATATE treatments. To monitor the bone marrow function, the levels of hemoglobin, white blood cells and platelet counts serves as a substitute for bone marrow response. The aim of this study is to evaluate different ways to measure hematological reponse and investigate if its possible to acchieve a dose response relationship already after the first treatment cycle, this using an image-based two-compartment method. Significant correlations were found after the first treatment cycle between the absorbed bone marrow dose and the response of platelet counts using nadir, the response rate and a trinomial function.
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| 4. |
- Magnander, Tobias, et al.
(author)
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A fast GPU code for full Monte Carlo based SPECT reconstruction
- 2016
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In: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer. - 1619-7070 .- 1619-7089.
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Conference paper (other academic/artistic)abstract
- To improve image quality in SPECT/CT reconstructions, various approximate recovery resolution techniques have been developed and implemented in clinical practice. However, optimal image reconstruction requires accounting for all physical interactions of the emitted photons in the individual patient. The objectives for this study were to develop a novel Monte Carlo (MC) code for fast simulation of individual image projections, and to implement these projections in ordered subset expectation maximum (OSEM) reconstructions of SPECT/CTimages.Method: The MC code was written in Compute Unified Device Architecture language for a computer with four graphic processing units (GeForce GTX Titan X, Nvidia, USA). This enables simulations of parallel photon emission from the voxels matrix (1283 or 2563). Each CT number was converted to attenuation coefficients for photo absorption, coherent scattering and incoherent scattering. The type of interaction was determined by the ratio of attenuation coefficients in the CT voxels. For photon scattering the deflection angle was determined by the differential scattering cross sections. The accepted angle for photon interaction with the crystal was determined from the diameter and height of the collimator hole. Predefined energy and spatial resolution kernels for the crystal were used. TheMCcode was implemented intoOSEMreconstruction of 177Lu, 111In and 99mTc SPECT/CT images. The National Electrical Manufacturers Association (NEMA) image quality phantom was used to evaluate the performance of the MC reconstruction in comparison with clinical standard OSEM reconstructions and clinical state-of-the-art OSEM reconstructions with recovery resolution corrections. Results and conclusion: The performance of the MC code was 500 millions photons/s. The required number of photons emitted per voxel for obtaining low noise in the simulated image was 400 for a 1283 voxel matrix. With this number of emitted photons/voxel the MC-based OSEM reconstruction with 10 subsets was performed within 60 s/iteration. The images converged after 2-4 iterations, depending on the sphere sizes in the NEMAphantom. Thereby, the reconstruction time was <4 minutes. The contrast-to-noise level was slightly improved with increased number of emitted photons/voxel, and the reconstruction time was linearly depending on the number of emitted photons/voxel. The signal-to-background for the spheres in the NEMA phantom was clearly improved with MC-based OSEM reconstruction: e.g. for 177Lu the improvement was 37% compared to standard OSEM and 20 % compared to state-of-the-art OSEM. Furthermore, visual inspection of clinical investigations revealed clearly improved resolution and contrast with MC-based reconstruction.
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| 5. |
- Magnander, Tobias, et al.
(author)
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A novel statistical analysis method to improve the detection of hepatic foci of (111)In-octreotide in SPECT/CT imaging.
- 2016
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In: EJNMMI physics. - : Springer Science and Business Media LLC. - 2197-7364. ; 3:1
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Journal article (peer-reviewed)abstract
- Low uptake ratios, high noise, poor resolution, and low contrast all combine to make the detection of neuroendocrine liver tumours by (111)In-octreotide single photon emission tomography (SPECT) imaging a challenge. The aim of this study was to develop a segmentation analysis method that could improve the accuracy of hepatic neuroendocrine tumour detection.
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| 6. |
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| 7. |
- Magnander, Tobias, et al.
(author)
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Comparison of the accuracy in kidney activity concentration estimates by the conjugate view and posterior view methods
- 2015
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In: Optimisation in X-ray and Molecular Imaging 2015 - the Fourth Malmö Conference on Medical Imaging, Gothenburg, Sweden, 28-30 May 2015.
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Conference paper (other academic/artistic)abstract
- Purpose: In nuclear medicine the conjugate view method (CV) is the most common method for activity quantifications in planar images. The advantage with the CV method is its depth independence, i.e. the activity concentrations can be calculated from two opposite planar images without the knowledge of depth. However, one disadvantage of the method that the signal to background ratio is dependent on the location of the object. This effect might increase the inaccuracy in the activity concentration estimates. Therefore, the activity in off-center objects might be better estimated by the camera projection with the shortest camera to object distance. The aim of the present study was to compare the CV method with a posterior-anterior (PA) projection method for estimation of 177Lu activity concentrations in the kidneys. Methods: The two methods were used to retrospectively determine and compare the left and right kidney activity concentration in 20 patients treated with 177Lu-DOTA-octreotate at Sahlgrenska University Hospital. The kidney was segmented in the SPECT or CT image using an appropriate segmentation algorithm. An attenuation map for 177Lu was created from the CT. Attenuated planar AP and PA projections were created from the SPECT and the attenuation map. The kidney VOI was projected onto the AP and PA projections. The activity concentration in the kidney was calculated using both the PA projection method (ACPA) and the CV method (ACCV) and the results were compared to the concentration in the kidney VOI in the SPECT. Results: The mean ratio between ACCV and the SPECT determined activity concentration was 1.99 with a standard deviation (SD) equal to 1.03 and the mean ratio between ACPA and the SPECT determined concentration was 1.66 with SD=0.80. Both methods demonstrated that the main problems with activity estimates from planar images are the influences of attenuation and the activity concentration in the under and overlying tissues. Conclusions: The present study shows that a true background estimate cannot be accurately performed with neither the CV nor the PA method and that the difficulties in obtaining a true background affect the CV method more than the PA method. The study indicates that the PA method gives a more accurate estimate of the kidney activity concentration than the CV method.
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| 8. |
- Magnander, Tobias, et al.
(author)
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Improved detection rate and visualization of liver uptake foci in diagnostic 111In-octreotide SPECT/CT investigations with a novel segmentation analysis
- 2015
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In: Optimisation in X-ray and Molecular Imaging 2015 - the Fourth Malmö Conference on Medical Imaging, Gothenburg, Sweden, 28-30 May 2015.
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Conference paper (other academic/artistic)abstract
- Purpose: Detection of liver tumors will change the course of treatment of neuroendocrine tumours. In nuclear medicine 111In-octreoscan is of high value for detection of neuroendocrine tumours. However, neuroendocrine tumours disseminated to the livers is often challenging to detect from 111In-octreoscan SPECT images due to low uptake, high noise, poor resolution and low contrast. The aim of the present study was to develop a segmentation analysis method for increased diagnostic accuracy of neuroendocrine liver tumours. Methods: For the SPECT reconstruction 120 projections are acquired with 3 degrees spacing around the patient injected with 111In-octreoscan. The projections are reconstructed into a 128x128x128 voxel matrix using OSEM with CT based attenuation correction. The liver is segmented from the SPECT or CT using either an isosurface, region growing or a GPU accelerated level set algorithm. Manual editing finishes the segmentation of the liver. The segmented liver volume of interest, liver VOI, is thresholded at 125 equidistant threshold values between 0 and the maximum voxel value. At each threshold value a connected component labeling algorithm is used to calculate the number of uptake foci (NUF). The normalized NUF (nNUF) is then plotted against the threshold index (ThI), defined as ThI=(cmax-cthr)/cmax, where cmax is the maximal voxel value in the VOI, and cthr is the voxel threshold value. The method is named nNUFTI - normalized Number of Uptake Foci vs ThI. The ThI at 0.25 nNUF was used for analysis of liver tumour involvement. SPECT images from 53 patients without tumour involvement (i.e SPECT negative) in the liver were analysed with nNUFTI. A three year follow up with MRI, SPECT, PET/CT and CT was used to separate the patients into two groups: the healthy group, with still no liver tumours, and the malignant group, shown to have developed tumours in the liver. Results: 40 patients ended up in the healthy group and 13 in the malignant group. The ThI at 0.25 nNUF was significantly different between the groups (p<0.01). A probability function for the ThI values was constructed from the obtained data. This relationship might be a useful guide in the diagnostic decision making. Conclusions: Our new developed method nNUFTI has been shown to perform well. More studies on the nNUFTI method are needed.
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| 9. |
- Magnander, Tobias, et al.
(author)
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IMPROVED PLANAR KIDNEY ACTIVITY CONCENTRATION ESTIMATE BY THE POSTERIOR VIEW METHOD IN 177LU-DOTATATE TREATMENTS.
- 2016
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In: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 169:1-4, s. 259-266
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Journal article (peer-reviewed)abstract
- The aims of this study were to determine how different background regions of interest (ROIs) around the kidney represent true background activity in over- and underlying tissues in(177)Lu-DOTA-octreatate ((177)Lu-DOTATATE) treatments and to determine the influence of the background positions on the kidney activity concentration estimates by the conjugate view (ConjV) and posterior view (PostV) methods. The analysis was performed in single-photon emission computed tomography (SPECT) images of 20 patients, acquired 24 h post injection of a(177)Lu-DOTATATE treatment, by a computer algorithm that created planar images from the SPECT data. The ratio between the activity concentration in the background and the true background varied from 0.36 to 2.08 [coefficient of variation (CV) = 25-181 %] and from 0.44 to 1.52 (CV = 16-70 %) for the right and left kidneys, respectively. The activity concentration estimate in the kidneys was most accurate with the PostV method using a background ROI surrounding the whole kidney, and this combination might be an alternative planar method for improved kidney dosimetry in the(177)Lu-DOTATATE treatments.
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| 10. |
- Svensson, Johanna, et al.
(author)
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Radiation exposure of the spleen during Lu-177-DOTATATE treatment and its correlation with haematological toxicity and spleen volume
- 2016
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In: Ejnmmi Physics. - : Springer Science and Business Media LLC. - 2197-7364. ; 3:1
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Journal article (peer-reviewed)abstract
- Background: Somatostatin analogue-based radionuclide therapy with Lu-177-DOTATATE is an important treatment option for patients with advanced neuroendocrine tumours overexpressing somatostatin receptors. In addition to the kidneys, the bone marrow is a major dose-limiting organ. The correlation between developed haematological toxicity and absorbed dose to the bone marrow is poor, which indicates that other factors affect haematological response. The spleen has an important role in the haematopoetic system, including being a reservoir for blood cells. It is also the organ that receives the highest mean absorbed dose during Lu-177-DOTATATE treatment. The aim of this study was to analyse mean absorbed dose to the spleen and its correlation with haematological toxicity, and to explore changes in splenic volume. The study included 41 patients treated with 7.2 GBq (3.5-8.3 GBq) of Lu-177-DOTATATE on two to five occasions. Following each fraction, planar whole-body scans were acquired at 2, 24, 48, and 168 h, and a SPECT/CT at 24 h post-injection. Mean absorbed spleen dose was calculated utilising planar images for time-activity data and SPECT to adjust activity amounts. Splenic volume information was collected from diagnostic CT scans at baseline and follow-up. Results: Median and total absorbed spleen doses were estimated to 4.5 and 15 Gy, respectively. Total absorbed spleen dose correlated with decrease in Hb (p = 0.02), but not WBC (p = 0.31) or PLT (p = 0.65) counts. For patients without bone metastases, mean absorbed spleen dose correlated with decrease in PLT (p = 0.04) but not Hb (p = 0.16) or WBC (p = 0.42) counts. The spleen volume was reduced to 75 % (p < 0.001) of original values (200 vs. 260 ml) at a mean followup of 36 months. Conclusions: Haematological toxicity according to Hb counts was moderately but significantly correlated with total absorbed spleen dose. This supports the possibility that radiation exposure of the spleen affects overall haematological response during Lu-177-DOTATATE treatment.
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