3D voxel-based dosimetry to predict contralateral hypertrophy and an adequate future liver remnant after lobar radioembolization.

INTRODUCTION: Volume changes induced by selective internal radiation therapy (SIRT) may increase the possibility of tumor resection in patients with insufficient future liver remnant (FLR). The aim was to identify dosimetric and clinical parameters associated with contralateral hepatic hypertrophy after lobar/extended lobar SIRT with 90Y-resin microspheres. MATERIALS AND METHODS: Patients underwent 90Y PET/CT after lobar or extended lobar (right + segment IV) SIRT. 90Y voxel dosimetry was retrospectively performed (PLANET Dose; DOSIsoft SA). Mean absorbed doses to tumoral/non-tumoral-treated volumes (NTL) and dose-volume histograms were extracted. Clinical variables were collected. Patients were stratified by FLR at baseline (T0-FLR): < 30% (would require hypertrophy) and ≥ 30%. Changes in volume of the treated, non-treated liver, and FLR were calculated at < 2 (T1), 2-5 (T2), and 6-12 months (T3) post-SIRT. Univariable and multivariable regression analyses were performed to identify predictors of atrophy, hypertrophy, and increase in FLR. The best cut-off value to predict an increase of FLR to ≥ 40% was defined using ROC analysis. RESULTS: Fifty-six patients were studied; most had primary liver tumors (71.4%), 40.4% had cirrhosis, and 39.3% had been previously treated with chemotherapy. FLR in patients with T0-FLR < 30% increased progressively (T0: 25.2%; T1: 32.7%; T2: 38.1%; T3: 44.7%). No dosimetric parameter predicted atrophy. Both NTL-Dmean and NTL-V30 (fraction of NTL exposed to ≥ 30 Gy) were predictive of increase in FLR in patients with T0 FLR < 30%, the latter also in the total cohort of patients. Hypertrophy was not significantly associated with tumor dose or tumor size. When ≥ 49% of NTL received ≥ 30 Gy, FLR increased to ≥ 40% (accuracy: 76.4% in all patients and 80.95% in T0-FLR < 30% patients). CONCLUSION: NTL-Dmean and NTL exposed to ≥ 30 Gy (NTL-V30) were most significantly associated with increase in FLR (particularly among patients with T0-FLR < 30%). When half of NTL received ≥ 30 Gy, FLR increased to ≥ 40%, with higher accuracy among patients with T0-FLR < 30%.

The joint use of 99mTc-MAA-SPECT/CT and cone-beam CT optimizes radioembolization planning.

PURPOSE: To determine which imaging method used during radioembolization (RE) work-up: contrast-enhanced computed tomography (CECT), 99mTc-MAA-SPECT/CT or cone beam-CT (CBCT), more accurately predicts the final target volume (TgV) as well as the influence that each modality has in the dosimetric calculation. METHODS: TgVs from 99mTc-MAA-SPECT/CT, CECT and CBCT were consecutively obtained in 24 patients treated with RE and compared with 90Y PET/CT TgV. Using the TgVs estimated by each imaging modality and a fictitious activity of 1 GBq, the corresponding absorbed doses by tumor and non-tumoral parenchyma were calculated for each patient. The absorbed doses for each modality were compared with the ones obtained using 90Y PET/CT TgV. RESULTS: 99mTc-MAA-SPECT/CT predicted 90Y PET/CT TgV better than CBCT or CECT, even for selective or superselective administrations. Likewise, 99mTc-MAA-SPECT/CT showed dosimetric values more similar to those obtained with 90Y PET/CT. Nevertheless, CBCT provided essential information for RE planning, such as ensuring the total coverage of the tumor and, in cases with more than one feeding artery, splitting the activity according to the volume of tumor perfused by each artery. CONCLUSION: The joint use of 99mTc-MAA-SPECT/CT and CBCT optimizes dosimetric planning for RE procedures, enabling a more accurate personalized approach.

18F-FDG-PET Imaging Patterns in Autoimmune Encephalitis: Impact of Image Analysis on the Results.

Brain positron emission tomography imaging with 18Fluorine-fluorodeoxyglucose (FDG-PET) has demonstrated utility in suspected autoimmune encephalitis. Visual and/or assisted image reading is not well established to evaluate hypometabolism/hypermetabolism. We retrospectively evaluated patients with autoimmune encephalitis between 2003 and 2018. Patients underwent EEG, brain magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) sampling and autoantibodies testing. Individual FDG-PET images were evaluated by standard visual reading and assisted by voxel-based analyses, compared to a normal database. For the latter, three different methods were performed: two based on statistical surface projections (Siemens syngo.via Database Comparison, and 3D-SSP Neurostat) and one based on statistical parametric mapping (SPM12). Hypometabolic and hypermetabolic findings were grouped to identify specific patterns. We found six cases with definite diagnosis of autoimmune encephalitis. Two cases had anti-LGI1, one had anti-NMDA-R and two anti-CASPR2 antibodies, and one was seronegative. 18F-FDG-PET metabolic abnormalities were present in all cases, regardless of the method of analysis. Medial-temporal and extra-limbic hypermetabolism were more clearly depicted by voxel-based analyses. We found autoantibody-specific patterns in line with the literature. Statistical surface projection (SSP) methods (Neurostat and syngo.via Database Comparison) were more sensitive and localized larger hypermetabolic areas. As it may lead to comparable and accurate results, visual analysis of FDG-PET studies for the diagnosis of autoimmune encephalitis benefits from voxel-based analysis, beyond the approach based on MRI, CSF sample and EEG.

Encefalitis límbica asociada a anti-Caspr2: contribución del análisis visual ayudado de las imágenes PET con 18F-FDG mediante comparación con una base de datos de normalidad / Caspr2 antibody-associated limbic encephalitis: contribution of visual aided analysis of 18F-FDG PET images using normal database comparison

Un inicio temprano de la inmunoterapia es fundamental para mejorar el pronóstico de los pacientes con encefalitis aguda de origen autoinmune (EAI). Se ha propuesto un nuevo abordaje clínico para el diagnóstico temprano basado en aspectos clínicos y pruebas complementarias, pero estas pueden tener una sensibilidad limitada principalmente en las primeras semanas. Mientras que las formas más comunes de EAI (anti-LGI-1 y anti-NMDAR), muestran frecuentemente patrones de PET con 18Flúor-fluordeoxiglucosa (PET-FDG) consistentes, las anti-Caspr2 son menos frecuentes y los patrones de PET-FDG no están establecidos. En nuestra experiencia la PET-FDG en la EAI anti-Caspr2 presenta un hipermetabolismo temporal medial y un déficit difuso cortical, incluso con pruebas complementarias negativas. No obstante, es necesaria la estandarización del análisis de las imágenes PET mediante métodos basados en vóxeles con comparación con bases de datos de normalidad para definir con claridad las áreas de metabolismo alterado que pueden pasar desapercibidas al análisis visual

Early immunotherapy is of paramount importance for a positive outcome in patients suffering acute encephalitis of autoimmune origin (AIE). A new approach for early diagnosis based on clinical presentation and complementary tests has been proposed, but not all these tests show positive findings in the first weeks. While common forms of AIE (anti-LGI-1 and anti-NMDAR antibodies) exhibit consistent 18Fluor-fluorodeoxiglucose (FDG-PET) patterns in many cases, the anti-Caspr2 form of AIE is infrequent and FDG-PET patterns have not been well characterized. In our experience, FDG-PET in anti-Caspr2 limbic encephalitis shows medial temporal hypermetabolism and diffuse cortical hypometabolism, even in the absence of findings in these tests. However, it is necessary to standardize PET image analysis by means of visual and voxel-based methods compared to normal databases to define the areas of pathological metabolism that may go unnoticed when using visual analysis exclusively

Caspr2 antibody-associated limbic encephalitis: contribution of visual aided analysis of 18F-FDG PET images using normal database comparison. / Encefalitis límbica asociada a anti-Caspr2: contribución del análisis visual ayudado de las imágenes PET con 18F-FDG mediante comparación con una base de datos de normalidad.

Early immunotherapy is of paramount importance for a positive outcome in patients suffering acute encephalitis of autoimmune origin (AIE). A new approach for early diagnosis based on clinical presentation and complementary tests has been proposed, but not all these tests show positive findings in the first weeks. While common forms of AIE (anti-LGI-1 and anti-NMDAR antibodies) exhibit consistent 18Fluor-fluorodeoxiglucose (FDG-PET) patterns in many cases, the anti-Caspr2 form of AIE is infrequent and FDG-PET patterns have not been well characterized. In our experience, FDG-PET in anti-Caspr2 limbic encephalitis shows medial temporal hypermetabolism and diffuse cortical hypometabolism, even in the absence of findings in these tests. However, it is necessary to standardize PET image analysis by means of visual and voxel-based methods compared to normal databases to define the areas of pathological metabolism that may go unnoticed when using visual analysis exclusively.