18F-FDG PET cannot predict expression of clinically relevant histopathological biomarkers in head and neck squamous cell carcinoma: a meta-analysis.

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) is a common cancer. Positron emission tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG) is a widely used imaging modality in HNSCC. PURPOSE: To provide evident data about associations between 18F-FDG PET and histopathology in HNSCC. MATERIAL AND METHODS: The MEDLINE database was screened for associations between maximum standard uptake values (SUVmax) derived from 18F-FDG PET and histopathological features in HNSCC up to May 2020. Only papers containing correlation coefficients between SUVmax and histopathology were acquired. Overall, 23 publications were collected. RESULTS: The following correlations were calculated: KI 67: 12 studies (345 patients), pooled correlation coefficient (PCC): 0.23 (95% confidence interval [CI] 0.06-0.40); hypoxia-inducible factor-1α: eight studies (240 patients), PCC: 0.24 (95% CI 0.06-0.42); microvessel density: three studies (64 patients), PCC: 0.33 (95% CI 0.02-0.65); vascular endothelial growth factor: two studies (59 cases), PCC: 0.27 (95% CI 0.02-0.51); tumor suppressor protein p53: four studies (159 patients), PCC: 0.05 (95% CI -0.41 to 0.51); epidermal growth factor receptor: two studies (124 patients), PCC: 0.21 (95% CI 0.05-0.37); tumor cell count: three studies (67 patients), PCC: 0.18 (95% CI -0.06 to 0.42); tumor cell apoptosis: two studies (40 patients), PCC: 0.07 (95% CI = -0.85 to 0.99); B-cell lymphoma-2 protein: two studies (118 patients); PCC: 0.04 (95% CI -0.65 to 0.74); glucose-transporter 1: 10 studies (317 patients), PCC: 0.20 (95% CI 0.10-0.30). CONCLUSION: SUVmax derived from 18F-FDG PET cannot reflect relevant histopathological features in HNSCC.

International recommendations for personalised selective internal radiation therapy of primary and metastatic liver diseases with yttrium-90 resin microspheres.

PURPOSE: A multidisciplinary expert panel convened to formulate state-of-the-art recommendations for optimisation of selective internal radiation therapy (SIRT) with yttrium-90 (90Y)-resin microspheres. METHODS: A steering committee of 23 international experts representing all participating specialties formulated recommendations for SIRT with 90Y-resin microspheres activity prescription and post-treatment dosimetry, based on literature searches and the responses to a 61-question survey that was completed by 43 leading experts (including the steering committee members). The survey was validated by the steering committee and completed anonymously. In a face-to-face meeting, the results of the survey were presented and discussed. Recommendations were derived and level of agreement defined (strong agreement ≥ 80%, moderate agreement 50%-79%, no agreement ≤ 49%). RESULTS: Forty-seven recommendations were established, including guidance such as a multidisciplinary team should define treatment strategy and therapeutic intent (strong agreement); 3D imaging with CT and an angiography with cone-beam-CT, if available, and 99mTc-MAA SPECT/CT are recommended for extrahepatic/intrahepatic deposition assessment, treatment field definition and calculation of the 90Y-resin microspheres activity needed (moderate/strong agreement). A personalised approach, using dosimetry (partition model and/or voxel-based) is recommended for activity prescription, when either whole liver or selective, non-ablative or ablative SIRT is planned (strong agreement). A mean absorbed dose to non-tumoural liver of 40 Gy or less is considered safe (strong agreement). A minimum mean target-absorbed dose to tumour of 100-120 Gy is recommended for hepatocellular carcinoma, liver metastatic colorectal cancer and cholangiocarcinoma (moderate/strong agreement). Post-SIRT imaging for treatment verification with 90Y-PET/CT is recommended (strong agreement). Post-SIRT dosimetry is also recommended (strong agreement). CONCLUSION: Practitioners are encouraged to work towards adoption of these recommendations.

Improvement of image quality and dose management in CT fluoroscopy by iterative 3D image reconstruction.

OBJECTIVES: The objective of this study was to assess the influence of an iterative CT reconstruction algorithm (IA), newly available for CT-fluoroscopy (CTF), on image noise, readers' confidence and effective dose compared to filtered back projection (FBP). METHODS: Data from 165 patients (FBP/IA = 82/74) with CTF in the thorax, abdomen and pelvis were included. Noise was analysed in a large-diameter vessel. The impact of reconstruction and variables (e.g. X-ray tube current I) influencing noise and effective dose were analysed by ANOVA and a pairwise t-test with Bonferroni-Holm correction. Noise and readers' confidence were evaluated by three readers. RESULTS: Noise was significantly influenced by reconstruction, I, body region and circumference (all p ≤ 0.0002). IA reduced the noise significantly compared to FBP (p = 0.02). The effect varied for body regions and circumferences (p ≤ 0.001). The effective dose was influenced by the reconstruction, body region, interventional procedure and I (all p ≤ 0.02). The inter-rater reliability for noise and readers' confidence was good (W ≥ 0.75, p < 0.0001). Noise and readers' confidence were significantly better in AIDR-3D compared to FBP (p ≤ 0.03). Generally, IA yielded a significant reduction of the median effective dose. CONCLUSION: The CTF reconstruction by IA showed a significant reduction in noise and effective dose while readers' confidence increased. KEY POINTS: • CTF is performed for image guidance in interventional radiology. • Patient exposure was estimated from DLP documented by the CT. • Iterative CT reconstruction is appropriate to reduce image noise in CTF. • Using iterative CT reconstruction, the effective dose was significantly reduced in abdominal interventions.

Intrahepatic Activity Distribution in Radioembolization with Yttrium-90-Labeled Resin Microspheres Using the Body Surface Area Method--A Less than Perfect Model.

PURPOSE: To retrospectively assess the influence of the parameters of the body surface area (BSA) method in hepatic radioembolization using yttrium-90-labeled microspheres on the determination of the prescribed activity. MATERIALS AND METHODS: Data from 283 consecutive patients treated with radioembolization (BSA method) were included. For interindividual comparisons, activity concentrations (ACs; MBq/mL) were calculated for each liver. The impact of the BSA method parameters was assessed by analysis of variance and pairwise t test with Bonferroni-Holm correction. RESULTS: Prescribed activity was 1.01-2.71 GBq, with BSA, liver volume (LV), tumor burden, and the liver-lung shunt reduction factor (LLS RF) being significant contributing factors to the AC (all P < .0001, analysis of variance). BSA and LV correlated only moderately (ρ = 0.46, P < .0001). Compared with base activity defined by the BSA (median = 1.67 GBq; range, 1.20-2.32 GBq), the activity contribution of tumor burden was small (median = 150 MBq; range, 3-800 MBq). Resulting activities were reduced according to LLS RF by 20% in 12.4% and by 40% in 3.5% of patients. AC was significantly (up to 56%) lower in association with larger LV than in small LV (LV < 1,500 mL vs ≥ 2,500 mL, P < .0001). CONCLUSIONS: In the BSA model, BSA and LV showed only a moderate correlation, resulting in a significantly lower AC in patients with larger livers. Tumor burden percentage contributed little to the prescribed activity because the BSA model did not account for actual LVs and tumor volumes. These inaccuracies may potentially result in underdosage in patients with larger livers, especially if further LLS RF needs to be applied.

Hybrid SPECT/CT for the assessment of a painful hip after uncemented total hip arthroplasty.

BACKGROUND: The diagnosis of hip pain after total hip replacement (THR) represents a highly challenging question that is of increasing concern to orthopedic surgeons. This retrospective study assesses bone scintigraphy with Hybrid SPECT/CT for the diagnosis of painful THR in a selected cohort of patients. METHODS: Bone SPECT/CT datasets of 23 patients (mean age 68.9 years) with a painful hip after THR were evaluated. Selection of the patients required an inconclusive radiograph, normal serum levels of inflammatory parameters (CRP and ESR) or a negative aspiration of the hip joint prior to the examination. The standard of reference was established by an interdisciplinary adjudication-panel using all imaging data and clinical follow-up data (>12 month). Pathological and physiological uptake patterns were defined and applied. RESULTS: The cause of pain in this study group could be determined in 18 out of 23 cases. Reasons were aseptic loosening (n = 5), spine-related (n = 5), heterotopic ossification (n = 5), neuronal (n = 1), septic loosening (n = 1) and periprosthetic stress fracture (n = 1). In (n = 5) cases the cause of hip pain could not be identified. SPECT/CT imaging correctly identified the cause of pain in (n = 13) cases, in which the integrated CT-information led to the correct diagnosis in (n = 4) cases, mainly through superior anatomic correlation. Loosening was correctly assessed in all cases with a definite diagnosis. CONCLUSIONS: SPECT/CT of THA reliably detects or rules out loosening and provides valuable information about heterotopic ossifications. Furthermore differential diagnoses may be detected with a whole-body scan and mechanical or osseous failure is covered by CT-imaging. SPECT/CT holds great potential for imaging-based assessment of painful prostheses.

SPECT-imaging of activity-dependent changes in regional cerebral blood flow induced by electrical and optogenetic self-stimulation in mice.

Electrical and optogenetic methods for brain stimulation are widely used in rodents for manipulating behavior and analyzing functional connectivities in neuronal circuits. High-resolution in vivo imaging of the global, brain-wide, activation patterns induced by these stimulations has remained challenging, in particular in awake behaving mice. We here mapped brain activation patterns in awake, intracranially self-stimulating mice using a novel protocol for single-photon emission computed tomography (SPECT) imaging of regional cerebral blood flow (rCBF). Mice were implanted with either electrodes for electrical stimulation of the medial forebrain bundle (mfb-microstim) or with optical fibers for blue-light stimulation of channelrhodopsin-2 expressing neurons in the ventral tegmental area (vta-optostim). After training for self-stimulation by current or light application, respectively, mice were implanted with jugular vein catheters and intravenously injected with the flow tracer 99m-technetium hexamethylpropyleneamine oxime (99mTc-HMPAO) during seven to ten minutes of intracranial self-stimulation or ongoing behavior without stimulation. The 99mTc-brain distributions were mapped in anesthetized animals after stimulation using multipinhole SPECT. Upon self-stimulation rCBF strongly increased at the electrode tip in mfb-microstim mice. In vta-optostim mice peak activations were found outside the stimulation site. Partly overlapping brain-wide networks of activations and deactivations were found in both groups. When testing all self-stimulating mice against all controls highly significant activations were found in the rostromedial nucleus accumbens shell. SPECT-imaging of rCBF using intravenous tracer-injection during ongoing behavior is a new tool for imaging regional brain activation patterns in awake behaving rodents providing higher spatial and temporal resolutions than 18F-2-fluoro-2-dexoyglucose positron emission tomography.

Technical note: Quantifying radionuclide residues in hospital wastewater: A case study on [131I]I and [177mLu]Lu/[177Lu]Lu.

BACKGROUND: Historically, [131I]I has been a common isotope in radionuclide therapy, with [177Lu]Lu-labelled radiopharmaceuticals now seeing a surge in use. These can include no-carrier-added or carrier-added [177Lu]Lu with slight impurities of [177mLu]Lu with a significantly longer half-life than [131I]I. Wastewater from therapy wards can contain a mixture of these radioisotopes. In some countries, national regulations require wastewater to be stored in dedicated systems before it is discharged into the public sewage system. To fulfill legal requirements, the nuclide specific activity concentration must be verified. PURPOSE: We evaluate a method for determining the activity concentration of [177mLu]Lu /[177Lu]Lu at equilibrium and [131I]I in pure and mixed samples in order to prove that the determined values are reliably below the limits for release. METHODS: We analysed the emitted energy spectrum of 1 L samples with a wastewater counter using an energy window-based approach by evaluating measurements from two different time points. Based on the law of decay and the time and energy-dependent measured values, equation systems were set up to calculate the count rates for [131I]I and [177mLu]Lu, which were converted into activity concentration using calibration factors. RESULTS: There is strong linear correlation between the nominal and determined activity concentrations (correlation coefficients R = 0.99; coefficient of determinations R2 = 0.99). We underestimate the actual activity concentration by a median of -1.4% for [177mLu]Lu and overestimate the activity concentration for [131I]I by a median of 7.1%. CONCLUSION: We show that an undercut of the clearance levels for material release is measurable. We analyse and determine activity concentrations of mixed samples consisting of [131I]I and [177mLu]Lu/[177Lu]Lu in equilibrium. The method is simple to implement using a conventional wastewater counter, however with a slightly increased effort, as two samples and measurements are required. The methodology can be adapted for the analysis of other nuclide mixtures.

In vivo evaluation of tumor uptake and bio-distribution of 99mTc-labeled 1-thio-ß-D-glucose and 5-thio-D-glucose in mice model.

BACKGROUND: To investigate the capacity of 99mTc-labeled 1-thio-ß-D-glucose (1-TG) and 5-thio-D-glucose (5-TG) to act as a marker for glucose consumption in tumor cells in vivo as well as to evaluate the biodistribution of 1-TG and 5-TG. We investigated the biodistribution, including tumor uptake, of 1-TG and 5-TG at various time points after injection (0.5, 2 and 4 h) in human colorectal carcinoma (HCT-116) and human lung adenocarcinoma (A549) xenograft bearing nude mice (N = 4 per tracer and time point). RESULTS: Ex vivo biodistribution studies revealed a moderate uptake with a maximum tumor-to-muscle ratio of 4.22 ± 2.7 and 2.2 ± 1.3 (HCT-116) and of 3.2 ± 1.1 and 4.1 ± 1.3 (A549) for 1-TG and 5-TG, respectively, with a peak at 4 h for 1-TG and 5-TG. Biodistribution revealed a significantly higher uptake compared to blood in kidneys (12.18 ± 8.77 and 12.69 ± 8.93%ID/g at 30 min) and liver (2.6 ± 2.8%ID/g) for 1-TG and in the lung (7.24 ± 4.1%ID/g), liver (6.38 ± 2.94%ID/g), and kidneys (4.71 ± 1.97 and 4.81 ± 1.91%ID/g) for 5-TG. CONCLUSIONS: 1-TG and 5-TG showed an insufficient tumor uptake with a moderate tumor-to-muscle ratio, not reaching the levels of commonly used tracer, for diagnostic use in human colorectal carcinoma and human lung adenocarcinoma xenograft model.

Assessing regional hepatic function changes after hypertrophy induction by radioembolisation: comparison of gadoxetic acid-enhanced MRI and 99mTc-mebrofenin hepatobiliary scintigraphy.

BACKGROUND: To compare Gd-ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) and 99mTc-labelled mebrofenin hepatobiliary scintigraphy (HBS) as imaging-based liver function tests after unilateral radioembolisation (RE) in patients with primary or secondary liver malignancies. METHODS: Twenty-three patients with primary or secondary liver malignancies who underwent Gd-EOB-DTPA-enhanced MRI within a prospective study (REVoluTion) were evaluated. REVoluTion was a prospective open-label, non-randomised, therapy-optimising study of patients undergoing right-sided or sequential RE for contralateral liver hypertrophy at a single centre in Germany. MRI and hepatobiliary scintigraphy were performed before RE (baseline) and 6 weeks after (follow-up). This exploratory subanalysis compared liver enhancement on hepatobiliary phase MRI normalised to the spleen (liver-to-spleen ratio (LSR)) and the muscle (liver-to-muscle ratio (LMR)) with mebrofenin uptake on HBS for the total liver (TL) and separately for the right (RLL) and left liver lobe (LLL). RESULTS: Mebrofenin uptake at baseline and follow-up each correlated significantly with LSR and LMR on MRI for TL (≤ 0.013) and RLL (≤ 0.049). Regarding the LLL, mebrofenin uptake correlated significantly with LMR (baseline, p = 0.013; follow-up, p = 0.004), whereas with LSR, a borderline significant correlation was only seen at follow-up (p = 0.051; p = 0.046). CONCLUSION: LSRs and LMR correlate with mebrofenin uptake in HBS. This study indicates that Gd-EOB-DTPA-enhanced MRI and 99mTc-labelled mebrofenin HBS may equally be used to assess an increase in contralateral liver lobe function after right-sided RE. RELEVANCE STATEMENT: MRI may be a convenient and reliable method for assessing the future liver remnant facilitating treatment planning and monitoring of patients after RE-induced hypertrophy induction. KEY POINTS: • Both MRI and HBS can assess liver function after RE. • Liver enhancement on MRI correlates with mebrofenin uptake on HBS. • MRI might be a convenient alternative for estimating future liver remnants after hypertrophy induction.

Technical note: Assessment of radiation measurement devices for the detection of [177 Lu]Lu-labeled radiopharmaceuticals containing [177m Lu]Lu-impurities.

BACKGROUND: Nuclear medicine therapies using [177 Lu]Lu-labeled radiopharmaceuticals have increased significantly in recent years. Some of these radiopharmaceuticals contain long-lived impurities of [177m Lu]Lu. Identification of this specific contamination and its quantification is important in different scenarios. PURPOSE: In this study, standard measurement hardware used for handling radioisotopes was evaluated for the measurement of [177m Lu]Lu and [177 Lu]Lu at equilibrium. Device-specific detection limits (LODs) for [177m Lu]Lu were determined according to international standards and then validated. METHODS: The LODs were determined according to the international standard ISO 11929-1 for [177m Lu]Lu for five identical portable contamination monitors (PCMs), a wastewater counter (WWC), and a release counter system (RCS) at different measuring times. Subsequent activity measurements of the defined samples were used to validate the linearity of the measurement instruments down to the LOD for each system. RESULTS: The average LOD across all PCMs was 0.249 ± 0.009 and 0.129 ± 0.005 Bq/cm2 for 10 and 30 s measurements, respectively. The LODs of WWC varied between 3.3 and 4.7 Bq/L for measurement times of 300 s and 0.8-1.3 Bq/L for 3600 s depending on the energy window studied. The LOD of the RCS depended on the container volume and was 0.08 Bq/g for the 50 L container at 60 s measurement. The measurements for all examined devices were linear down to the LOD (correlation coefficient R ≥ 0.96; coefficient of determination R2  ≥ 0.92). CONCLUSIONS: All investigated measuring instruments (PCM, WWC, RCS) were suitable for the determination of [177m Lu]Lu at equilibrium, and their specific LODs were determined. Based on the measurements performed, activity is overestimated; however, this is tolerable because assumptions and measurements in the context of radiation protection should be conservative.

SUV-measurements and patient-specific corrections in pediatric Hodgkin-lymphoma: is there a benefit for PPV in early response assessment by FDG-PET?

BACKGROUND: To evaluate the influence of different SUV-measurements and patient-specific corrections thereof on the positive predictive value (PPV) of FDG-PET in pediatric Hodgkin lymphoma (pHL) using SUV-based response assessment. METHODS: PET-datasets of 33 children [female, n = 13, male, n = 20; range of age, 8.0-17.8 (mean, 15.0) years; follow-up, 44.5-83.3 (mean 63.0) months] with HL were analyzed retrospectively. PET-scans were obtained baseline (PET1) and after two cycles of chemotherapy (PET2). Within the leading lesion maximal SUV (SUVmax) and mean SUVs were generated by using isocontur-thresholds for different volumes of interest: Absolute, SUV2.5; relative to SUVmax, SUVmean40% to SUVmean70%. Generated SUVs were adjusted to body weight (SUV) and corrected for body surface area (SUV_BSA), patient's blood glucose and a combination thereof. The decrease in SUV or respective derivates thereof between PET1 and PET2 (ΔSUV) was assessed for response prediction using receiver operating characteristics (ROC)-analysis. RESULTS: Three patients had recurrence of disease. ROC-analysis showed the most accurate differentiation of responders and non-responders for ΔSUVmax_BSA [AUC, 0.97; P = 0.0026; sensitivity, 100%; specificity, 93.3%; PPV, 60.0%; negative predictive value (NPV), 100%; accuracy, 93.3%]. However, comparable results were obtained for conventional ΔSUVmax-determination (AUC, 0.96; P = 0.0112; sensitivity, 100%; specificity, 90.0%; PPV, 50.0%; NPV, 100%; accuracy, 90.9%). Threshold-based approaches were less effective or technically not performable in all patients. CONCLUSIONS: At early response assessment by FDG-PET, patient-specific correction of ΔSUVmax by BSA improves PPV without impairment of excellent NPV in pHL. However, it is not statistically superior to simple ΔSUVmax-analyses. Larger cohorts are needed to investigate this observation.

Optimization of SPECT/CT imaging protocols for quantitative and qualitative 99mTc SPECT.

BACKGROUND: The introduction of hybrid SPECT/CT devices enables quantitative imaging in SPECT, providing a methodological setup for quantitation using SPECT tracers comparable to PET/CT. We evaluated a specific quantitative reconstruction algorithm for SPECT data using a 99mTc-filled NEMA phantom. Quantitative and qualitative image parameters were evaluated for different parametrizations of the acquisition and reconstruction protocol to identify an optimized quantitative protocol. RESULTS: The reconstructed activity concentration (ACrec) and the signal-to-noise ratio (SNR) of all examined protocols (n = 16) were significantly affected by the parametrization of the weighting factor k used in scatter correction, the total number of iterations and the sphere volume (all, p < 0.0001). The two examined SPECT acquisition protocols (with 60 or 120 projections) had a minor impact on the ACrec and no significant impact on the SNR. In comparison to the known AC, the use of default scatter correction (k = 0.47) or object-specific scatter correction (k = 0.18) resulted in an underestimation of ACrec in the largest sphere volume (26.5 ml) by - 13.9 kBq/ml (- 16.3%) and - 7.1 kBq/ml (- 8.4%), respectively. An increase in total iterations leads to an increase in estimated AC and a decrease in SNR. The mean difference between ACrec and known AC decreased with an increasing number of total iterations (e.g., for 20 iterations (2 iterations/10 subsets) = - 14.6 kBq/ml (- 17.1%), 240 iterations (24i/10s) = - 8.0 kBq/ml (- 9.4%), p < 0.0001). In parallel, the mean SNR decreased significantly from 2i/10s to 24i/10s by 76% (p < 0.0001). CONCLUSION: Quantitative SPECT imaging is feasible with the used reconstruction algorithm and hybrid SPECT/CT, and its consistent implementation in diagnostics may provide perspectives for quantification in routine clinical practice (e.g., assessment of bone metabolism). When combining quantitative analysis and diagnostic imaging, we recommend using two different reconstruction protocols with task-specific optimized setups (quantitative vs. qualitative reconstruction). Furthermore, individual scatter correction significantly improves both quantitative and qualitative results.

The Impact of Unilateral 90Y-radioembolization on Functional Changes in the Contralateral Hepatic Lobe: The Prospective, Open-label RadioEmbolization, Volumetry, and Liver FuncTion Measurements (REVoluTion) Study.

Objectives: To investigate how metabolic function of the contralateral liver lobe is affected by unilateral radioembolization (RE), and to compare the changes in volume and metabolic function. Background: Unilateral RE induces contralateral liver hypertrophy, but it is unknown if metabolic liver function improves in line with volume increases. Methods: This prospective open-label, nonrandomized, therapy-optimizing study included all consecutive patients undergoing right-sided or sequential 90Y-RE for liver malignancies without underlying liver disease or biliary obstruction at a single center in Germany. Magnetic resonance imaging volumetry and hepatobiliary scintigraphy were performed immediately before RE and approximately 6 weeks after RE. Results: Twenty-three patients were evaluated (11 metastatic colorectal cancer, 4 cholangiocellular carcinoma, 3 metastatic breast cancer, 1 each of metastatic neuroendocrine tumor, hepatocellular carcinoma, renal cell carcinoma, oesophageal cancer, pancreatic ductal adenocarcinoma). In the untreated contralateral left liver lobe, mean (SD) metabolic function significantly increased from 1.34 (0.76) %/min/m2 at baseline to 1.56 (0.75) %/min/m2 6 weeks after RE (P = 0.024). The mean (SD) functional volume (liver volume minus tumor volume) of the left liver lobe significantly increased from baseline (407.3 [170.3] mL) to follow-up (499.1 [209.8] mL; P < 0.01), with an equivalent magnitude to the metabolic function increase. There were no reports of grade ≥3 adverse events. Conclusion: This study indicates that unilobar RE produces a significant increase in the metabolic function, and equivalent volume increase, of the contralateral lobe. RE may be a useful option to induce hypertrophy of the future liver remnant before surgical resection of primary or secondary liver malignancies.

Quantitative imaging of bone remodeling in patients with a unicompartmental joint unloading knee implant (ATLAS Knee System)-effect of metal artifacts on a SPECT-CT-based quantification.

BACKGROUND: SPECT-CT using radiolabeled phosphonates is considered a standard for assessing bone metabolism (e.g., in patients with osteoarthritis of knee joints). However, SPECT can be influenced by metal artifacts in CT caused by endoprostheses affecting attenuation correction. The current study examined the effects of metal artifacts in CT of a specific endoprosthesis design on quantitative hybrid SPECT-CT imaging. The implant was positioned inside a phantom homogenously filled with activity (955 MBq 99mTc). CT imaging was performed for different X-ray tube currents (I = 10, 40, 125 mA) and table pitches (p = 0.562 and 1.375). X-ray tube voltage (U = 120 kVp) and primary collimation (16 × 0.625 mm) were kept constant for all scans. The CT reconstruction was performed with five different reconstruction kernels (slice thickness, 1.25 mm and 3.75 mm, each 512 × 512 matrix). Effects from metal artifacts were analyzed for different CT scans and reconstruction protocols. ROI analysis of CT and SPECT data was performed for two slice positions/volumes representing the typical locations for target structures relative to the prosthesis (e.g., femur and tibia). A reference region (homogenous activity concentration without influence from metal artifacts) was analyzed for comparison. RESULTS: Significant effects caused by CT metal artifacts on attenuation-corrected SPECT were observed for the different slice positions, reconstructed slice thicknesses of CT data, and pitch and CT-reconstruction kernels used (all, p < 0.0001). Based on the optimization, a set of three protocols was identified minimizing the effect of CT metal artifacts on SPECT data. Regarding the reference region, the activity concentration in the anatomically correlated volume was underestimated by 8.9-10.1%. A slight inhomogeneity of the reconstructed activity concentration was detected inside the regions with a median up to 0.81% (p < 0.0001). Using an X-ray tube current of 40 mA showed the best result, balancing quantification and CT exposure. CONCLUSION: The results of this study demonstrate the need for the evaluation of SPECT-CT protocols in prosthesis imaging. Phantom experiments demonstrated the possibility for quantitative SPECT-CT of bone turnover in a specific prosthesis design. Meanwhile, a systematic bias caused by metal implants on quantitative SPECT data has to be considered.

Liver Function Changes After Technetium-99m-Macroaggregated Albumin Administration and Their Predictive Value Regarding Hepatotoxicity in Patients Undergoing Yttrium-90-Radioembolization.

BACKGROUND/AIM: Intraarterial Technetium-99m-Macroaggregated Albumin (99mTc-MAA) administration is an established method to predict particle distribution prior to radioembolization. This study aimed to analyse the impact of intraarterial administration of 99mTc-MAA on changes in liver-specific laboratory parameters and to assess whether such changes are associated with post-radioembolization hepatotoxicity. PATIENTS AND METHODS: A total of 202 patients treated with radioembolization received prior mapping angiography with 99mTc-MAA administration. All patients underwent clinical and laboratory examinations, including liver-specific parameters at certain times before and after mapping angiography/99mTc-MAA administration, as well as before radioembolization and during follow-up. RESULTS: Bilirubin increased temporarily after 99mTc-MAA administration (p<0.001), but was not clinically relevant, and returned close to the initial value before radioembolization. These changes showed no association with subsequent postradioembolic hepatotoxicity or shortened overall survival. CONCLUSION: 99mTc-MAA administration results in a significant, however, not clinically relevant transient increase in bilirubin levels, which does not provide a predictive value for subsequent radioembolization outcome or postradioembolic hepatotoxicity.

MR-guided liver tumor ablation employing open high-field 1.0T MRI for image-guided brachytherapy.

OBJECTIVE: To determine the feasibility and safety of image-guided brachytherapy employing a modified open high-field MR system. METHODS: This is a follow-up study of a development project enabling technologies for interventional use of 1.0T open MRI. Modifications included coils and in-bore visualization, fluoroscopic sequences and user interfaces. We recruited 104 patients with 224 liver malignancies to receive MR-guided brachytherapy. Interventions were performed >20 min after Gd-EOB-DTPA. We recorded interventional parameters including the intervention time (from acquisition of the first scout until the final sequence for brachytherapy treatment planning). Two reviewers assessed MR-fluoroscopic images in comparison to plain CT as used in CT intervention, applying a rating scale of 1-10. Statistical analysis included Friedman and Kendall's W tests. RESULTS: We employed freehand puncture with interactive dynamic imaging for navigation. Technical success rate was 218 complete ablations in 224 tumours (97%). The median intervention time was 61 min. We recorded no adverse events related to the use of MRI. No major complications occurred. The rate of minor complications was 4%. Local control at 3 months was 96%. Superiority of MR-fluoroscopic, Gd-EOB-DTPA-enhanced images over plain CT was highly significant (P < 0.001). CONCLUSION: MR-guided brachytherapy employing open high-field MRI is feasible and safe.

Early prediction of anticancer effects with diffusion-weighted MR imaging in patients with colorectal liver metastases following selective internal radiotherapy.

OBJECTIVE: To prospectively evaluate diffusion-weighted imaging (DWI) for early prediction of tumour response in patients with colorectal liver metastases following selective internal radiotherapy (SIRT). METHODS: We evaluated 41 metastases in 21 patients, age 62.9 ± 9.9 years. All patients underwent magnetic resonance imaging (MRI) including breath-hold echoplanar DWI sequences. Imaging was performed before therapy (baseline MRI), 2 days after SIRT (early MRI) as well as 6 weeks later (follow-up MRI). Tumour volume (TV) and intratumoural apparent diffusion coefficient (ADC) were measured independently by two radiologists at all time points. RESULTS: Metastases were categorised as responding lesions (RL; n = 33) or non-responding lesions (NRL; n = 8) according to changes in TV after 6 weeks. We found an inverse correlation of changes in TV and ADC at follow-up MRI with a Pearson's correlation coefficient of r = -0.66 (p < 0.0001). On early MRI, no significant changes in TV were found for either RL or NRL. Conversely, ADC decreased significantly in RL by 10.7 ± 8.4% (p < 0.0001). ADC increased in NRL by 9.6 ± 20.8%, which was not statistically significant (p = 0.40). CONCLUSION: DWI was capable of predicting therapy effects of SIRT in patients with colorectal hepatic metastases as early as 2 days following treatment.

Analysis of Bone Scans in Various Tumor Entities Using a Deep-Learning-Based Artificial Neural Network Algorithm-Evaluation of Diagnostic Performance.

The bone scan index (BSI), initially introduced for metastatic prostate cancer, quantifies the osseous tumor load from planar bone scans. Following the basic idea of radiomics, this method incorporates specific deep-learning techniques (artificial neural network) in its development to provide automatic calculation, feature extraction, and diagnostic support. As its performance in tumor entities, not including prostate cancer, remains unclear, our aim was to obtain more data about this aspect. The results of BSI evaluation of bone scans from 951 consecutive patients with different tumors were retrospectively compared to clinical reports (bone metastases, yes/no). Statistical analysis included entity-specific receiver operating characteristics to determine optimized BSI cut-off values. In addition to prostate cancer (cut-off = 0.27%, sensitivity (SN) = 87%, specificity (SP) = 99%), the algorithm used provided comparable results for breast cancer (cut-off 0.18%, SN = 83%, SP = 87%) and colorectal cancer (cut-off = 0.10%, SN = 100%, SP = 90%). Worse performance was observed for lung cancer (cut-off = 0.06%, SN = 63%, SP = 70%) and renal cell carcinoma (cut-off = 0.30%, SN = 75%, SP = 84%). The algorithm did not perform satisfactorily in melanoma (SN = 60%). For most entities, a high negative predictive value (NPV ≥ 87.5%, melanoma 80%) was determined, whereas positive predictive value (PPV) was clinically not applicable. Automatically determined BSI showed good sensitivity and specificity in prostate cancer and various other entities. Particularly, the high NPV encourages applying BSI as a tool for computer-aided diagnostic in various tumor entities.

Time course and local distribution of skin exposure of hand and fingers from [68Ga]Ga-DOTA-NOC synthesis using a self-shielded module.

AIM: The study examined the local dose distribution as well as the time course of skin exposure of hand and fingers from [68Ga]Ga-DOTA-NOC synthesis using a self-shielded synthesis module. METHODS: A compact calibrated electronic dosimeter (ED) with a miniaturized probe was used for real-time measurements of skin dose equivalent Hp (0.07) (reference point: left and right index finger). A time resolved assessment of exposure during radiotracer production was performed. Additionally, thermoluminescence dosimeters (TLD) were used to determine local dose distribution for five different positions (e. g. fingertips). Cumulated Hp (0.07) estimated by ED was analysed and correlated with the measurements obtained by a TLD positioned close to the ED. RESULTS: The cumulative skin exposure from the production process measured by ED, was 74.7 ±â€Š32.7 µSv/GBq and 40.1 ± 14.3 µSv/GBq for the right and left hand, respectively. The exposure recorded by the ED was in the average 19.4 % ±â€Š40.0 % (median = 21.3 %) lower compared to the results from TLD. Highest exposure was recorded during synthesis (guided hand: 24.5 ±â€Š12.2 µSv/GBq) and measuring of product yield including preparation of probes for quality control (guided hand: 36.1 ±â€Š12.7 µSv/GBq). The highest local exposure was measured by a TLD close to the tip of the index finger of the guiding hand (range: 773-1257 µS/GBq). CONCLUSION: The chosen methodology using ED, proved to be a good concept for identifying procedure steps with an increased exposure level and to determine the time course of skin exposure and to identify procedure steps for further optimization of handling. Furthermore, miniaturized electronic dosimeters may be used for online surveillance of local exposure rates at hands and fingers.