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Background: For dosimetry, the demand for whole-body SPECT/CT imaging, which require long acquisition durations with dual-head Anger cameras, is increasing. Here we evaluated sparsely acquired projections and assessed whether the addition of deep-learning-generated synthetic intermediate projections (SIPs) could improve the image quality while preserving dosimetric accuracy. Methods: This study included 16 patients treated with 177Lu-DOTATATE with SPECT/CT imaging (120 projections, 120P) at four time points. Deep neural networks (CUSIPs) were designed and trained to compile 90 SIPs from 30 acquired projections (30P). The 120P, 30P, and three different CUSIP sets (30P + 90 SIPs) were reconstructed using Monte Carlo-based OSEM reconstruction (yielding 120P_rec, 30P_rec, and CUSIP_recs). The noise levels were visually compared. Quantitative measures of normalised root mean square error, normalised mean absolute error, peak signal-to-noise ratio, and structural similarity were evaluated, and kidney and bone marrow absorbed doses were estimated for each reconstruction set. Results: The use of SIPs visually improved noise levels. All quantitative measures demonstrated high similarity between CUSIP sets and 120P. Linear regression showed nearly perfect concordance of the kidney and bone marrow absorbed doses for all reconstruction sets, compared to the doses of 120P_rec (R2 ≥ 0.97). Compared to 120P_rec, the mean relative difference in kidney absorbed dose, for all reconstruction sets, was within 3%. For bone marrow absorbed doses, there was a higher dissipation in relative differences, and CUSIP_recs outperformed 30P_rec in mean relative difference (within 4% compared to 9%). Kidney and bone marrow absorbed doses for 30P_rec were statistically significantly different from those of 120_rec, as opposed to the absorbed doses of the best performing CUSIP_rec, where no statistically significant difference was found. Conclusion: When performing SPECT/CT reconstruction, the use of SIPs can substantially reduce acquisition durations in SPECT/CT imaging, enabling acquisition of multiple fields of view of high image quality with satisfactory dosimetric accuracy. [ABSTRACT FROM AUTHOR]

Background: Early cancer detection is crucial for patients' survival. The image quality in 111In-octreotide SPECT imaging could be improved by using Monte Carlo (MC)-based reconstruction. The aim of this observational study was to determine the detection rate of simulated liver lesions for MC-based ordered subset expectation maximization (OSEM) reconstruction compared to conventional attenuation-corrected OSEM reconstruction. Methods: Thirty-seven SPECT/CT examinations with 111In-octreotide were randomly selected. The inclusion criterion was no liver lesions at the time of examination and for the following 3 years. SPECT images of spheres representing lesions were simulated using MC. The raw data of the spheres were added to the raw data of the established healthy patients in 26 of the examinations, and the remaining 11 examinations were not modified. The images were reconstructed using conventional OSEM reconstruction with attenuation correction and post filtering (fAC OSEM) and MC-based OSEM reconstruction without and with post filtering (MC OSEM and fMC OSEM, respectively). The images were visually and blindly evaluated by a nuclear medicine specialist. The criteria evaluated were liver lesion yes or no, including coordinates if yes, with confidence level 1–3. The percentage of detected lesions and accuracy (percentage of correctly classified cases), as well as tumor-to-normal tissue concentration (TNC) ratios and signal-to-noise ratios (SNRs), were evaluated. Results: The detection rates were 30.8% for fAC OSEM, 42.3% for fMC OSEM, and 50.0% for MC OSEM. The accuracies were 45.9% for fAC OSEM, 45.9% for fMC OSEM, and 54.1% for MC OSEM. The number of false positives was higher for fMC and MC OSEM. The observer's confidence level was higher in filtered images than in unfiltered images. TNC ratios were significantly higher, statistically, with MC OSEM and fMC OSEM than with AC OSEM, but SNRs were similar due to higher noise with MC OSEM. Conclusion: One in two lesions were found using MC OSEM versus one in three using conventional reconstruction. TNC ratios were significantly improved, statistically, using MC-based reconstruction, but the noise levels increased and consequently the confidence level of the observer decreased. For further improvements, image noise needs to be suppressed. [ABSTRACT FROM AUTHOR]

Objectives: Somatostatin receptors (SSTRs) are potential targets for detecting pituitary neuroendocrine tumours (PitNETs) that can be visualized effectively with 68Ga‐labelled PET tracers. With this study, we have evaluated the diagnostic properties of such a tracer, 68Ga‐DOTATOC, in patients with hormone‐producing PitNETs before and after surgery. Design/Methods: This prospective case‐control study presents preoperative positron emission tomography (PET) and histopathological data in 18 patients with somatotroph (n = 8), corticotroph (n = 7) and thyrotroph (n = 3) PitNETs. Patients were scanned pre‐ and postoperatively with 68Ga‐DOTATOC PET. For the postoperative part of the study, patients with gonadotroph tumours (n = 7) were also included. Fifteen pituitary healthy controls underwent the same protocol once. The maximum standard uptake value (SUVmax) was analysed in manually outlined regions around the tumour in patients and around the pituitary gland in controls. specimens were collected during surgery in subjects for assessment of adenohypophyseal tumour cell type and the SSTR expression. Results: Thyrotroph tumours showed higher uptake (median SUVmax 41.1; IQR 37.4‐60.0) and corticotroph tumours lower uptake (SUVmax 6.8; 2.6‐9.3) than normal pituitary gland (SUVmax 13.8; 12.1‐15.5). The uptake in somatotroph tumours (SUVmax 15.9; 11.6‐19.7) was similar to the uptake in the pituitary gland. There was a strong correlation between SUVmax and SSTR2 expression (r =.75 (P <.01)). In the postoperative evaluation, PET was able to correlate tracer uptake with biochemical cure and noncure in patients with an abnormal postoperative magnetic resonance image and a preoperative tumour uptake SUVmax > 13.8. Conclusions: 68Ga‐DOTATOC PET can be used to detect thyrotroph tumours in the pre‐ and postoperative imaging assessment. Corticotroph tumours had a significantly lower uptake compared to the pituitary gland but without a distinct increased tumour uptake the clinical postoperative value is limited. [ABSTRACT FROM AUTHOR]

Objectives: 68 Ga‐DOTATOC PET targets somatostatin receptors (SSTRs) and is well established for the detection of SSTR‐expressing tumors, such as gastrointestinal neuroendocrine tumors. Pituitary adenomas, recently designated as pituitary neuroendocrine tumors (PitNETs), also express SSTRs, but there has been no previous evaluations of 68 Ga‐DOTATOC PET in PitNET patients. The aim of this pilot study was to evaluate the diagnostic properties of 68 Ga‐DOTATOC PET in the most common PitNET, ie non‐functioning (NF)‐PitNET. Design/Patients: NF‐PitNET patients (n = 9) and controls (n = 13) were examined preoperatively with 68 Ga‐DOTATOC PET for 45 min after tracer injection in dynamic list mode. Tumor specimens were collected during surgery in patients. MRI and PET images were co‐registered using PMOD software. The maximum standard uptake value (SUVmax) was analyzed in manually outlined regions of interest (ROI) around the tumor in patients and around the pituitary gland in controls. Immunohistochemical analyses were conducted on tumor specimens for assessment of tumor cell type and SSTR expression. Results: Median SUVmax (IQR) was lower in patients than in controls (3.9 [3.4‐8.5] vs 14.1 [12.5‐15.9]; P <.01]. In ROC analysis, the area under the curve was 0.87 (P <.01) for SUVmax, with 78% sensitivity and 92% specificity. Immunohistochemical analysis showed NF‐PitNETs were of gonadotroph (n = 7) and corticotroph (n = 2) origin. SSTR expression was high for SSTR3, low‐to‐moderate for SSTR2, and low for SSTR1 and SSTR5. Conclusions: This proof‐of‐concept study shows that 68Ga‐DOTATOC PET can be used to differentiate between normal pituitary tissue and NF‐PitNET. [ABSTRACT FROM AUTHOR]

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 177Lu-DOTA-octreatate (177Lu-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 177Lu-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) 5 25-181 %] and from 0.44 to 1.52 (CV 5 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 177Lu-DOTATATE treatments. [ABSTRACT FROM AUTHOR]

Background: Surgery is the only potential cure for patients with medullary thyroid carcinoma (MTC). Preoperative ultrasound, computed tomography and magnetic resonance imaging are not sensitive enough for detection of microscopic disease. The aim of this study was to investigate if routine preoperative In-labelled (DTPA-D-Phe)-octreotide scintigraphy (SRS) could be used as a staging procedure in planning primary surgery in patients with MTC. Methods: This study included patients with primary sporadic clinically overt MTC diagnosed between 1996 and 2009. All patients underwent conventional imaging of neck and thorax and SRS prior to standardised surgery. The findings on SRS were correlated to the findings on conventional imaging, histopathology and to postoperative biochemical results and survival. Results: A total of 19 patients with sporadic MTC were enrolled. Median follow-up was 77(9-184) months. SRS visualised the primary tumour in 16 (84 %) patients. Fifteen (79 %) patients had locoregional lymph node metastases, but SRS detected metastatic lesions in only 8 (53 %) patients. In three patients with distant spread, SRS failed to detect metastatic lesions in two. At latest follow-up, six (32 %) patients had died, nine (47 %) patients were alive with elevated tumour markers, and four (21 %) patients were considered in complete biochemical remission. Conclusions: This study provided further evidence that SRS, compared to conventional imaging, is fairly sensitive for detection of primary MTC but not metastatic disease. Although preoperative SRS may be of prognostic value, there is no indication for its routine use as a staging procedure in planning primary surgery. [ABSTRACT FROM AUTHOR]

Purpose. Two patients with liver tumours were planned for a combined treatment, including surgery with preceding injections of β- radiation emitting 90Y microspheres (SIRTEX R®). The aim of this paper is to present a method of pre-surgical computer simulations of the absorbed dose rate on the surface of tumour tissue, combined with measurements of the actual absorbed dose rate on resected tissue, in order to estimate the absorbed dose to a surgeon's fingers during such surgery procedures. Methods and Materials. The dose rates from β- radiation on the surface of tumour tissue were simulated with the software VARSKIN R® Mod 2. The activity concentrations in tumours were estimated, based on SPECT/CT distribution studies of 99mTc-MAA and confirmed by SPECT/CT bremsstrahlung studies of 90Y microspheres. The activity distributions were considered as homogeneous within the tumour regions. The absorbed dose rates at different tumour tissue spots were calculated based on measurements with thermo-luminescent dosimeters (TLD) fastened on resected tissue. Results. The simulations showed a good agreement with the averaged absorbed dose rates based on TLD measurements performed on resected tissue, differing by 13% and 4% respectively. The absorbed dose rates at the measured maximum hotspots were twice as high as the average dose rates for both patients. Conclusion. The data is not sufficient in order to draw any general conclusions about dose rates on tumour tissue during similar surgeries, neither about the influence of dose rate heterogeneities nor about average dose rates. However, the agreement between simulations and measurements on these limited data indicate that this approach is a promising method for estimations of the radiation exposure to the surgeons' fingers during this kind of surgery procedure. More data from similar surgeries are necessary in order to validate the method. [ABSTRACT FROM AUTHOR]

Background: Early cancer detection is crucial for patients' survival. The image quality in 111 In-octreotide SPECT imaging could be improved by using Monte Carlo (MC)-based reconstruction. The aim of this observational study was to determine the detection rate of simulated liver lesions for MC-based ordered subset expectation maximization (OSEM) reconstruction compared to conventional attenuation-corrected OSEM reconstruction., Methods: Thirty-seven SPECT/CT examinations with 111 In-octreotide were randomly selected. The inclusion criterion was no liver lesions at the time of examination and for the following 3 years. SPECT images of spheres representing lesions were simulated using MC. The raw data of the spheres were added to the raw data of the established healthy patients in 26 of the examinations, and the remaining 11 examinations were not modified. The images were reconstructed using conventional OSEM reconstruction with attenuation correction and post filtering (fAC OSEM) and MC-based OSEM reconstruction without and with post filtering (MC OSEM and fMC OSEM, respectively). The images were visually and blindly evaluated by a nuclear medicine specialist. The criteria evaluated were liver lesion yes or no, including coordinates if yes, with confidence level 1-3. The percentage of detected lesions and accuracy (percentage of correctly classified cases), as well as tumor-to-normal tissue concentration (TNC) ratios and signal-to-noise ratios (SNRs), were evaluated., Results: The detection rates were 30.8% for fAC OSEM, 42.3% for fMC OSEM, and 50.0% for MC OSEM. The accuracies were 45.9% for fAC OSEM, 45.9% for fMC OSEM, and 54.1% for MC OSEM. The number of false positives was higher for fMC and MC OSEM. The observer's confidence level was higher in filtered images than in unfiltered images. TNC ratios were significantly higher, statistically, with MC OSEM and fMC OSEM than with AC OSEM, but SNRs were similar due to higher noise with MC OSEM., Conclusion: One in two lesions were found using MC OSEM versus one in three using conventional reconstruction. TNC ratios were significantly improved, statistically, using MC-based reconstruction, but the noise levels increased and consequently the confidence level of the observer decreased. For further improvements, image noise needs to be suppressed., (© 2023. The Author(s).)

Objectives: Somatostatin receptors (SSTRs) are potential targets for detecting pituitary neuroendocrine tumours (PitNETs) that can be visualized effectively with 68 Ga-labelled PET tracers. With this study, we have evaluated the diagnostic properties of such a tracer, 68 Ga-DOTATOC, in patients with hormone-producing PitNETs before and after surgery., Design/methods: This prospective case-control study presents preoperative positron emission tomography (PET) and histopathological data in 18 patients with somatotroph (n = 8), corticotroph (n = 7) and thyrotroph (n = 3) PitNETs. Patients were scanned pre- and postoperatively with 68 Ga-DOTATOC PET. For the postoperative part of the study, patients with gonadotroph tumours (n = 7) were also included. Fifteen pituitary healthy controls underwent the same protocol once. The maximum standard uptake value (SUV max ) was analysed in manually outlined regions around the tumour in patients and around the pituitary gland in controls. specimens were collected during surgery in subjects for assessment of adenohypophyseal tumour cell type and the SSTR expression., Results: Thyrotroph tumours showed higher uptake (median SUV max 41.1; IQR 37.4-60.0) and corticotroph tumours lower uptake (SUV max 6.8; 2.6-9.3) than normal pituitary gland (SUV max 13.8; 12.1-15.5). The uptake in somatotroph tumours (SUV max 15.9; 11.6-19.7) was similar to the uptake in the pituitary gland. There was a strong correlation between SUV max and SSTR2 expression (r = .75 (P < .01)). In the postoperative evaluation, PET was able to correlate tracer uptake with biochemical cure and noncure in patients with an abnormal postoperative magnetic resonance image and a preoperative tumour uptake SUV max  > 13.8., Conclusions: 68 Ga-DOTATOC PET can be used to detect thyrotroph tumours in the pre- and postoperative imaging assessment. Corticotroph tumours had a significantly lower uptake compared to the pituitary gland but without a distinct increased tumour uptake the clinical postoperative value is limited., (© 2021 The Authors. Clinical Endocrinology published by John Wiley & Sons Ltd.)

This study aimed to compare different image-based methods for bone marrow dosimetry and study the dose-response relationship during treatment with 177 Lu-DOTATATE in patients with and without skeletal metastases. Methods: This study included 46 patients with advanced neuroendocrine tumors treated with at least 2 fractions of 177 Lu-DOTATATE at Sahlgrenska University Hospital. High- and low-uptake compartments were automatically outlined in planar images collected at 2, 24, 48, and 168 h after injection. The bone marrow absorbed doses were calculated from the cross doses of the high- and low-uptake compartments and the self-dose, using the time-activity concentration curve for the low-uptake compartment. This time-activity concentration curve was adjusted using a fixed constant of 1.8 for the planar dosimetry method and using the activity concentrations in vertebral bodies in SPECT images at 24 h after injection of 177 Lu-DOTATATE in 4 hybrid methods: L4-SPECT used the activity concentration in the L4 vertebra, whereas V-SPECT, L-SPECT, and T-SPECT used the median activity concentration in all visible vertebrae, lumbar vertebrae, and thoracic vertebrae, respectively. Results: Using the planar method, L4-SPECT, V-SPECT, L-SPECT, and T-SPECT, the estimated median bone marrow absorbed doses were 0.19, 0.36, 0.40, 0.39, and 0.46 Gy/7.4 GBq, respectively, with respective ranges of 0.12-0.33, 0.15-1.44, 0.19-1.71, 0.21-1.60, and 0.18-2.12 Gy/7.4 GBq. For all methods, the bone marrow absorbed dose significantly correlated with decreased platelet counts. This correlation increased after treatment fraction 2: the Spearman correlation ( r s ) were -0.49 for the planar method, -0.61 for L4-SPECT, -0.63 for V-SPECT, -0.63 for L-SPECT, and -0.57 for T-SPECT. A separate analysis revealed an increased correlation for patients without skeletal metastases using the planar method ( r s = -0.67). In contrast, hybrid methods had poor correlations for patients without metastases and stronger correlations for patients with skeletal metastases ( r s = -0.61 to -0.74). The mean bone marrow absorbed doses were 3%-69% higher for patients with skeletal metastases than for patients without. Conclusion: The estimated bone marrow absorbed doses by image-based techniques and the correlation with platelets are influenced by the choice of measured vertebrae and the presence of skeletal metastases., (© 2019 by the Society of Nuclear Medicine and Molecular Imaging.)