Search Results (88)

Tumor hypoxia involves limited oxygen supply within the tumor microenvironment and is closely associated with aggressiveness, metastasis, and resistance to common cancer treatment modalities such as chemotherapy and radiotherapy. Traditional methodologies for hypoxia assessment, such as the use of invasive probes and clinical biomarkers, are generally not very suitable for routine clinical applications. Radiomics provides a non-invasive approach to hypoxia assessment by extracting quantitative features from medical images. Thus, radiomics is important in diagnosis and the formulation of a treatment strategy for tumor hypoxia. This article discusses the various imaging techniques used for the assessment of tumor hypoxia including magnetic resonance imaging (MRI), positron emission tomography (PET), and computed tomography (CT). It introduces the use of radiomics with machine learning and deep learning for extracting quantitative features, along with its possible clinical use in hypoxic tumors. This article further summarizes the key challenges hindering the clinical translation of radiomics, including the lack of imaging standardization and the limited availability of hypoxia-labeled datasets. It also highlights the potential of integrating radiomics with multi-omics to enhance hypoxia visualization and guide personalized cancer treatment. Full article

Stereotactic Body Radiotherapy (SBRT) has emerged as a pivotal treatment modality for early-stage non-small cell lung cancer (NSCLC), offering highly precise, high-dose radiation delivery. However, several clinical challenges remain, particularly in the treatment of central or ultracentral tumors, which are located near critical structures such as the heart, bronchi, and great vessels. The introduction of MRI-guided SBRT has significantly improved targeting precision, allowing for better assessment of tumor motion and adjacent organ structures. Additionally, SBRT has demonstrated efficacy in multifocal NSCLC, providing an effective option for patients with multiple primary tumors. Recent advances also highlight the role of SBRT in locally advanced NSCLC, where it is increasingly used as a complementary approach to concurrent chemotherapy or in cases where surgery is not feasible. Moreover, the combination of SBRT with immunotherapy has shown promising potential, enhancing tumor control and immunological responses. Furthermore, SBRTs application in SCLC is gaining momentum as a palliative and potentially curative option for selected patients. This narrative review explores these evolving clinical scenarios, the technical innovations supporting SBRT, and the integration of immunotherapy, providing an in-depth look at the new frontiers of SBRT in lung cancer treatment. Despite the challenges, the ongoing development of personalized approaches and technological advancements continues to push the boundaries of SBRTs clinical utility in lung cancer. Full article

Background/Objectives: Non-ablative stereotactic body radiation therapy (SBRT) is commonly employed for locally advanced pancreatic cancer (LAPC) using computed tomography-guided radiotherapy (CTgRT) without online adaptive radiation therapy (oART). The safe delivery of ablative SBRT has been demonstrated using stereotactic magnetic resonance-guided online adaptive radiation therapy (SMART). We performed an in silico comparison of non-adapted CTgRT versus SMART to better understand the potential benefit of oART for ablative pancreatic SBRT. Methods: We retrospectively evaluated original and daily adapted SMART plans that were previously delivered for 20 consecutive LAPC cases (120 total plans across all patients) treated on a 0.35 T MR-linac prescribed to 50 Gy (gross disease) and 33 Gy (elective sites) simultaneously in five fractions. Six comparative CTgRT plans for each patient (one original, five daily treatment) were retrospectively generated with the same prescribed dose and planning parameters as the SMART plans assuming no oART availability. The impact of daily anatomic changes on CTgRT and SMART plans without oART was evaluated across each treatment day MRI scan acquired for SMART. Results: Ninety percent of cases involved the pancreatic head. No statistically significant differences were seen between CTgRT and SMART with respect to target coverage. Nearly all (96%) fractions planned on either CT or MRI platforms exceeded at least one GI organ at risk (OAR) constraint without oART. Significant differences favoring SMART over non-adaptive CTgRT were observed for the duodenum V35 Gy ≤ 0.5 cc (34.2 vs. 41.9 Gy, p = 0.0035) and duodenum V40 Gy ≤ 0.03 cc (37 vs. 52.5 Gy, p = 0.0006) constraints. Stomach V40 Gy trended towards significance favoring SMART (37 vs. 40.3 Gy, p = 0.057) while no significant differences were seen. Conclusions: This is the first study that quantifies the frequency and extent of GI OAR constraint violations that would occur during ablative five-fraction SBRT using SMART vs. CTgRT. GI OAR constraint violations are expected for most fractions without oART whereas all constraints can be achieved with oART. As such, these data suggest that oART should be required for ablative five-fraction pancreatic SBRT. Full article

Background: Combining external beam radiotherapy (EBRT) with high-dose-rate (HDR) brachytherapy (BT) enables biologically effective dose escalation in prostate cancer. However, comparative evaluation of such regimens using radiobiological modeling remains limited. Methods: Dose regimens based on clinical practice were analyzed using α/β values of 1.5 and 3 Gy for the prostate. Ten patients with available planning CT, pelvic MRI, and ultrasound-guided BT plans were retrospectively evaluated. Physical and biological dose distributions were recalculated for various EBRT and HDR-BT combinations. Biological effective dose (BED) values were determined for the prostate and organs at risk (OARs: anterior rectal wall, bladder base, urethra). Regimens yielding the highest ΔBED between prostate and OARs were considered most favorable. Results: All regimens met clinical dose constraints. The most favorable ΔBED profiles for bladder and rectum were observed with HDR-BT regimens (2 × 15 Gy) combined with either 23 × 2 Gy or 15 × 2.5 Gy EBRT, independent of the assumed α/β value. EBRT-only regimens achieved superior urethral sparing, while higher HDR doses led to increased urethral exposure. Conclusions: This study underscores the value of radiobiological modeling in differentiating and optimizing prostate cancer radiotherapy strategies. While the trade-offs between dose escalation and OAR sparing are clinically known, our biologically driven analysis provides a more quantitative foundation for selecting and tailoring combined EBRT/HDR-BT regimens in practice. Full article

Purpose/Objective: The clinical implementation of MR-guided radiotherapy on MR-linacs (MRL) hasrapidly increased in recent years. The advantages represented by the MR-based daily online plan adaptation and real-time monitoring have been exploited for different tumor sites. Nevertheless, some concerns remain, mainly related to the longer treatment time and limited patient eligibility. We report here the experience of our center, where a 1.5T MRL was clinically implemented in 2019 and, since then, more than 1200 patients have been treated. Material and Methods: The first 1000 patients treated at the MRL in our department were selected. Technical information such as treatment time and adaptive technic have been prospectively recorded, while toxicity data were retrospectively collected. Results: Between October 2019 and June 2024, 1000 patients for a total of 1061 treatment courses were included. Prostate and prostate bed were irradiated in 57.1% and 10.2% of the cases, respectively, including regional pelvic lymphnodes in 4.7%. Other frequent treated sites were lymph node metastases, pancreas and liver. The most frequent prescribed doses were 36.25 Gy (31%), 35 Gy (28.3%) and 30 Gy (9.4%) in five fractions. On a total of 9076 administered fractions, 80.8% were performed with adapt-to-shape and 19.2% with adapt-to-position method. The mean in-room time was 38 min (range, 18–103), with 74.4% of patients completing the session within 40 min. Acute grade (G) 3 toxicity was recorded in 1.6% of the cases, while, on a total of 858 patients available for late toxicity, G3 was recorded in 0.3% of the cases, with no >G3. Conclusions: Our real-world experience of an early-adopter center confirms that MRL treatments are feasible for different tumor entities in several anatomical sites. We showed that most of the patients could be treated within 40 min and showed low toxicity rates. Protocols for dose escalation and margin reduction, by adopting new comprehensive motion monitoring strategies, are under development. Full article

Background/Objectives: Radiotherapy for tumors of the central nervous system (CNS) could be improved by incorporating advanced imaging techniques into treatment planning and response assessment. The objective of this narrative review is to highlight the recent developments in magnetic resonance imaging (MRI) and positron emission tomography (PET) for applications in CNS radiotherapy. Methods: Recent articles were selected for discussion, covering the following topics: advanced imaging on MRI-linear accelerators for early response assessment in glioma; PET for guiding treatment planning and response assessment in glioma; and contrast-enhanced imaging and metabolic imaging for differentiating tumor progression and radiation necrosis for brain metastasis treatment. Where necessary, searches of scholarly databases (e.g., Google Scholar, PubMed) were used to find papers for each topic. The topics were chosen based on the perception of promise in advancing specific applications of CNS radiotherapy and not covered in detail elsewhere. This review is not intended to be comprehensive. Results: Advanced MRI sequences and PET could have a substantial impact on CNS radiotherapy. For gliomas, the tumor response to therapy could be assessed much earlier than using the conventional technique of measuring changes in tumor size. Using advanced imaging on combined imaging/therapy devices like MR-Linacs would enable response monitoring throughout radiotherapy. For brain metastases, radiation necrosis and tumor progression might be reliably differentiated with imaging techniques sensitive to perfusion or metabolism. However, the lack of level 1 evidence supporting specific uses for each imaging technique is an impediment to widespread use. Conclusions: Advanced MRI and PET have great promise to change the standard of care for CNS radiotherapy, but clinical trials validating specific applications are needed. Full article

Advances in breast cancer treatment have shifted the focus from maximizing local control to balancing oncologic efficacy with treatment de-escalation and toxicity reduction. Whole-breast irradiation (WBI) following breast-conserving surgery remains the standard of care, but with up to 90% of recurrences occurring near the tumor bed, partial breast irradiation (PBI) has emerged as a viable alternative. Large randomized controlled trials (such as IMPORT LOW, Florence, and GEC-ESTRO) have demonstrated comparable ipsilateral breast tumor recurrence (IBTR) rates between PBI and WBI, reinforcing its oncologic safety in well-selected patients. However, challenges remain in optimizing fractionation schedules, refining patient selection, and minimizing late toxicity. Recent innovations, including MRI-guided radiotherapy (MRgRT) and neoadjuvant PBI, offer improved tumor targeting, real-time plan adaptation, and enhanced normal tissue sparing. These advancements hold promise for further reducing radiation-related morbidity and improving cosmetic outcomes. As PBI progresses, integrating novel imaging modalities and hypofractionated regimens will be crucial to refining protocols. This review synthesizes the latest evidence on PBI techniques, clinical outcomes, and emerging technologies to guide future research and clinical decision-making in precision breast radiotherapy. Full article

Background/Objectives: Stereotactic body radiotherapy is frequently used in patients with adrenal metastases. Motion of adherent radiosensitive organs at risk (OARs) and tumors influence OAR toxicity and tumor control. Online-adaptive Magnetic Resonance-guided radiotherapy (MRgRT) can address and mitigate interfractional changes. However, the impact of intrafractional variations in adrenal MRgRT is unknown. Methods: A total of 23 patients with 24 adrenal metastases were treated with MRgRT. After daily plan adaptation and before beam application, an additional (preRT) 3d MRI was acquired. PreRT target volumes and OARs were retrospectively recontoured in 200 fractions. The delivered, online-adapted treatment plans, as well as non-adapted baseline plans, were calculated on these re-contoured structures to quantify the dosimetric impact of intrafractional variations on target volume coverage and OAR doses with and without online adaptation. Normal tissue complication probabilities (NTCPs) were calculated. Results: The median time between the two MRIs was 56.4 min. GTV and PTV coverage (dose to 95% of the PTV, D95%, and volume covered by 100% of the prescription dose, V100%) were significantly inferior in the preRT plans. GTV D_mean was significantly impaired in left-sided metastases, but not in right-sided metastases. Compared to non-adapted preRT plans, adapted preRT plans were still significantly superior for all GTV and PTV metrics. Intrafractional violations of OAR constraints were frequent. D0.5cc and the volume exposed to the near-maximum dose constraint were significantly higher in the preRT plans. The volume exposed to the D0.5cc constraints in single fractions escalated up to 1.5 cc for the esophagus, 3.2 cc for the stomach, 5.3 cc for the duodenum and 7.3 cc for the bowel. This led to significantly elevated NTCPs for the stomach, bowel and duodenum. Neither PTV D95%, nor gastrointestinal OAR maximum doses were significantly impaired by longer fraction duration. Conclusions: Intrafractional motion in adrenal MRgRT caused significant impairment of target volume coverage (D95% and V100%), potentially undermining local control. Frequent violation of gastrointestinal OAR constraints led to elevated NTCP. Compared to non-adaptive treatment, online adaptation still highly improved GTV and PTV coverage. Full article

Background: The optimal diagnostic and therapeutic strategies for prostate cancer (PCa) in patients aged ≥75 years (mild-old and oldest-old) are still contentious. Resource allocation and ideal treatment for older patients are challenges, mainly due to their comorbidities and reduced life expectancy. This survey aims to assess current clinical practices and the experiences of healthcare providers in the diagnosis and management of elderly patients with PCa. Materials and Methods: In Northeast Italy, members of the Gruppo Uro-Oncologico del Nord-Est (GUONE) conducted a survey involving 104 physicians of different specialties (Nuclear Medicine, Medical Oncology, Radiation Oncology, Radiology, Urology) between 1 November 2024 and 30 November 2024. The survey encompassed 51 questions, evaluating various diagnostic and therapeutic scenarios. Results: Digital rectal exam (DRE) was recommended by 35.9% of physicians for patients aged 75 or older at risk of PCa. PSA testing was continued in 76.3% of these patients. For 36.5% of the physicians, there should be no age limit for prostate biopsy. Moreover, 42.6% of physicians recommended a magnetic resonance imaging (MRI)-guided prostate biopsy regardless of age. A prostate biopsy was deemed mandatory before initiating any form of hormonal therapy by 57.7% of the participants. For 22.3% and 34.7% of physicians, there should be no age limit for prostate MRI and PET/CT for staging purposes. Interestingly, PET/CT was not recommended in 52% of cases as a staging tool for patients older than 85 years. For patients without comorbidities, the age limit to consider radical prostatectomy (RP) was 75, with 58.6% of physicians in favor. There were no definitive limits for radiotherapy (RT). Chemotherapy had an age limit for 81.6% of the respondents; for 18.4%, 22.5%, and 26.5% of physicians, age limits were 75, 80, and 85 years, respectively. The use of androgen receptor pathway inhibitors (ARPIs) had no definitive age limits for 46.5% of respondents. For patients with no comorbidities and low-volume metastatic PCa, the preferred option was androgen deprivation therapy + ARPIs + RT. The follow-up schedule after RP or RT exhibited heterogeneity with no consensus regarding the frequency of PSA testing or the age at which it should be discontinued. Conclusions: This survey highlights the need for consensus guidelines in diagnosing and managing mild-old and oldest-old elderly PCa patients. With the aging population, standardized protocols are essential to ensure optimal care. Full article

Linear accelerator–magnetic resonance (linac-MR) hybrid systems allow for real-time magnetic resonance imaging (MRI)-guided radiotherapy for more accurate dose delivery to the tumor and improved sparing of the adjacent healthy tissues. However, for real-time tumor detection, it is unfeasible for a human expert to manually contour (gold standard) the tumor at the fast imaging rate of a linac-MR. This study aims to develop a neural network-based tumor autocontouring algorithm with patient-specific hyperparameter optimization (HPO) and to validate its contouring accuracy using in vivo MR images of cancer patients. Two-dimensional (2D) intrafractional MR images were acquired at 4 frames/s using 3 tesla (T) MRI from 11 liver, 24 prostate, and 12 lung cancer patients. A U-Net architecture was applied for tumor autocontouring and was further enhanced by implementing HPO using the Covariance Matrix Adaptation Evolution Strategy. Six hyperparameters were optimized for each patient, for which intrafractional images and experts’ manual contours were input into the algorithm to find the optimal set of hyperparameters. For evaluation, Dice’s coefficient (DC), centroid displacement (CD), and Hausdorff distance (HD) were computed between the manual contours and autocontours. The performance of the algorithm was benchmarked against two standardized autosegmentation methods: non-optimized U-Net and nnU-Net. For the proposed algorithm, the mean (standard deviation) DC, CD, and HD of the 47 patients were 0.92 (0.04), 1.35 (1.03), and 3.63 (2.17) mm, respectively. Compared to the two benchmarking autosegmentation methods, the proposed algorithm achieved the best overall performance in terms of contouring accuracy and speed. This work presents the first tumor autocontouring algorithm applicable to the intrafractional MR images of liver and prostate cancer patients for real-time tumor-tracked radiotherapy. The proposed algorithm performs patient-specific HPO, enabling accurate tumor delineation comparable to that of experts. Full article

Background/Objectives: Predictive tools are needed to assess the response to treatment and guide treatment decisions for locally advanced rectal cancer (LARC). This study explores the value of combining the immunoscore (IS) and magnetic resonance imaging tumor regression grade (mrTRG) with pathologic and radiologic neoadjuvant rectal (NAR) scores in predicting pathologic complete response (pCRs). Methods: The scores were assessed for patients with LARC enrolled in the Averectal study (NCT03503630), who received five fractions of short-course radiotherapy, followed by six cycles of mFOLFOX-6 plus avelumab, and total mesorectal excision. The IS was calculated using the mean density percentiles of CD3- and CD8-positive T-cells on baseline biopsy samples. Baseline and post-treatment MRIs were reviewed to measure the mrTRG. NAR scores were calculated using the pre-treatment T stage and post-treatment pathologic and radiologic N and T stages. Results: Fifteen out of thirty-five patients whose data were available achieved pCR (42.8%), and seven out of fourteen patients with mrTRG = 1 (complete response) attained pCR. In patients with both a mrTRG = 1 and high IS, the pCR rate was 66.7% (6/9). All of the patients who achieved pCR had a low or intermediate pathologic NAR score with a significant correlation between pCR and pathologic NAR scores (p < 0.0001). Both pathologic and radiologic NAR scores were correlated with overall survival and disease-free survival. Conclusions: The IS can supplement the mrTRG to better predict TNT outcomes, along with the use of the NAR score. This combination could potentially help with patient selection for non-operative management and guide treatment strategies for those with different recurrence risks. Full article

Background: Hypoxia plays a critical role in lung cancer progression and treatment resistance by contributing to aggressive tumor behavior and poor therapeutic response. Molecular imaging, particularly positron emission tomography (PET), has become an essential tool for noninvasive hypoxia detection, providing valuable insights into tumor biology and aiding in personalized treatment strategies. Objective: This narrative review explores recent advancements in PET imaging for detecting hypoxia in lung cancer, with a focus on the development, characteristics, and clinical applications of various radiotracers. Findings: Numerous PET-based hypoxia radiotracers have been investigated, each with distinct pharmacokinetics and imaging capabilities. Established tracers such as ¹⁸F-Fluoromisonidazole (¹⁸F-FMISO) remain widely used, while newer alternatives like ¹⁸F-Fluoroazomycin Arabinoside (¹⁸F-FAZA) and ¹⁸F-Flortanidazole (¹⁸F-HX4) demonstrate improved clearance and image contrast. Additionally, ⁶⁴Cu-ATSM has gained attention for its rapid tumor uptake and hypoxia selectivity. The integration of PET with hybrid imaging modalities, such as PET/CT and PET/MRI, enhances the spatial resolution and functional interpretation, making hypoxia imaging a promising approach for guiding radiotherapy, chemotherapy, and targeted therapies. Conclusions: PET imaging of hypoxia offers significant potential in lung cancer diagnosis, treatment planning, and therapeutic response assessment. However, challenges remain, including tracer specificity, quantification variability, and standardization of imaging protocols. Future research should focus on developing next-generation radiotracers with enhanced specificity, optimizing imaging methodologies, and leveraging multimodal approaches to improve clinical utility and patient outcomes. Full article

Goal: This study evaluates the feasibility and outcome of a personalized MRI-based liver SBRT treatment planning platform with the SPION contrast agent Ferumoxytol^® (Sandoz Inc.; Princeton, NJ, USA) to maintain a superior real-time visualization of liver tumors and volumes of functional hepatic parenchyma for radiotherapy planning throughout multi-fractionated liver SBRT with online plan adaptations on an Elekta Unity 1.5 T MR-Linac (Elekta; Stockholm, Sweden). Materials and Methods: Patients underwent SPION-enhanced MRI on the Elekta Unity MR-Linac for improved tumor and functional hepatic parenchyma visualization. An automated contouring algorithm was applied for the delineation and subsequent guided avoidance of functional liver parenchyma volumes (FLVs) on the SPION-enhanced MR-Linac. Radiation dose constraints were adapted exclusively to FLV. Local control, toxicity, and survival were assessed with at least 6-month radiographic follow-up. Pre- and post-transplant outcomes were analyzed in the subset of patients with HCC and hepatic cirrhosis who completed SBRT as a bridge to liver transplant. Model of End-Stage Liver Disease (MELD-Na) was used to score hepatic function before and after SBRT. Results: With a median follow-up of 23 months (range: 3–40 months), 23 HCC patients (26 lesions treated) and 9 patients (14 lesions treated) with hepatic metastases received SBRT (mean dose: 48 Gy, range: 36–54 Gy) in 1–5 fractions. Nearly all patients in this study had pe-existing liver conditions, including hepatic cirrhosis (23), prior TACE (7), prior SBRT (18), or history of hepatic resection (2). Compared to the non-contrast images, SPIONs improved tumor visibility on post-SPION images on the background of negatively enhancing functionally active hepatic parenchyma. Prolonged SPION-contrast retention within hepatic parenchyma enabled per-fraction treatment adaptation throughout the entire multi-fraction treatment course. FLV loss (53%, p < 0.0001) was observed in cirrhotic patients, but functional and anatomic liver volumes remained consistent in non-cirrhotic patients. Mean dose to FLV was maintained within the liver threshold tolerance to radiation in all patients after the optimization of Step-and-Shoot Intensity-Modulated Radiotherapy (SS-IMRT) on the SPION-enhanced MRI-Linac. No radiation-induced liver disease was observed within 6 months post-SBRT, and the MELD-Na score in cirrhotic patients was not significantly elevated at 3-month intervals after SBRT completion. Conclusions: SPION Ferumoxytol^® administered intravenously as an alternative MRI contrast agent on the day of SBRT planning produces a long-lasting contrast effect between tumors and functional hepatic parenchyma for precision targeting and guided avoidance during the entire course of liver SBRT, enabling fast and accurate online plan adaptation on the 1.5 T Elekta Unity MR-Linac. This approach demonstrates a safe and effective bridging therapy for patients with hepatic cirrhosis, leading to low toxicity and favorable transplant outcomes. Full article

This study investigates the clinical efficacy of MRI-based adaptive brachytherapy (IGABT) using combined intracavitary and interstitial techniques in the curative treatment of patients with advanced cervical cancer (LACC). A retrospective analysis was conducted on 149 LACC patients treated at a single center. The therapeutic protocol included intensity-modulated external beam radiotherapy (IMRT) and IGABT. Dosimetric parameters were evaluated for relevance for local control (LC), progression-free survival (PFS), and overall survival (OS) using Kaplan–Meier estimation, Cox regression, and log-rank test. Patients predominantly presented with stage III/IV tumors (81%, FIGO 2018). The median high-risk clinical target volume (hrCTV) was 34 cm³, with a median D90% dose of 88.9 GyEQD2. At 24 months, OS, PFS, and LC rates were 86%, 57%, and 81%, respectively. FIGO stage, tumor volume, and histology were significant predictors of PFS. Higher total hrCTV doses were strongly correlated with improved LC and PFS, emphasizing the importance of precise dosimetric optimization in IGABT and confirming the critical role of IGABT in achieving very good LC rates for LACC. The reported LC rates are comparable to landmark studies, such as INTERLACE and KEYNOTE-A18. This study validates the effectiveness of MRI-guided IGABT in enhancing local tumor control in advanced-stage cervical cancer while providing insights into the prognostic implications of dosimetric parameters such as hrCTV and point A. Future research should address the persistent challenge of distant metastases by exploring the integration of novel systemic treatment options. Full article

Background: Spectroscopic MRI (sMRI) is a quantitative imaging technique that maps infiltrated tumors in the brain without contrast injections. In a previous study (NCT03137888), sMRI-guided radiation treatment extended patient survival, showing promise for clinical translation. The spectral fitting of individual voxels in an sMRI dataset generate metabolite concentration maps that guide treatment. The established spectral analysis methods use iterative least-squares fitting (FITT) that are computationally demanding. This study compares the performance of NNFit, a neural network-based, accelerated spectral fitting model, to the established FITT for metabolite quantification and radiation treatment planning. Methods: NNFit is a self-supervised deep learning model trained on 50 ms echo-time (TE) sMRI data to estimate metabolite levels of choline (Cho), creatine (Cr), and NAA. We trained the model on 30 GBM patients (56 scans) and tested it on 17 GBM patients (29 scans). NNFit’s performance was compared to the FITT using structural similarity indices (SSIM) and the Dice coefficient. Results: NNFit significantly improved processing speed while maintaining strong agreement with FITT. The radiation target volumes defined by Cho/NAA ≥ 2x were visually comparable, with fewer artifacts in NNFit. Structural similarity indices (SSIM) indicated minimal bias and high consistency across methods. Conclusions: This study highlights NNFit’s potential for rapid, accurate, and artifact-reduced metabolic imaging, enabling faster radiotherapy planning. Full article