Whole-body PET Research Articles

64Cu]Cu-Albumin Clearance Imaging to Evaluate Lymphatic Efflux of Cerebrospinal Space Fluid in Mouse Model.

Clearance of brain waste in the cerebrospinal fluid (CSF) through the meningeal lymphatic vessels (mLV) has been evaluated mostly through the fluorescent imaging which has inherent limitations in the context of animal physiology and clinical translatability. The study aimed to establish molecular imaging for the evaluation of mLV clearance function. Radionuclide imaging after intrathecal (IT) injection was acquired in C57BL/6 mice of 2-9 months. The distribution of [99mTc]Tc-diethylenetriamine pentaacetate (DTPA) and [64Cu]Cu-human serum albumin (HSA) was comparatively evaluated. Evans Blue and [64Cu]Cu-HSA were used to evaluate the distribution of tracer under various speed and volume conditions. [99mTc]Tc-DTPA is not a suitable tracer for evaluation of CSF clearance via mLV as no cervical lymph node uptake was observed while it was cleared from the body. A total volume of 3 to 9 μL at an infusion rate of 300 to 500 nL/min was not sufficient for the tracer to reach the cranial subarachnoid space and clear throughout the mLV. As a result, whole-body positron emission tomography imaging using [64Cu]Cu-HSA at 700 nL/min, to deliver 6 μL of injected volume, was set for characterization of the CSF to mLV clearance. Through this protocol, the mean terminal CSF clearance half-life was measured to be 123.6 min (range 117.0-135.0) in normal mice. We established molecular imaging to evaluate CSF drainage through mLV using [64Cu]Cu-HSA. This imaging method is expected to be extended in animal models of dysfunctional meningeal lymphatic clearance and translational research for disease-modifying therapeutic approaches. The online version contains supplementary material available at 10.1007/s13139-022-00746-6.

Intramural Great Vessel Lymphoma in a Patient with Left Ventricular Assist Device

<h3>Introduction</h3> Intramural Great Vessel lymphoma (IMGVL) is an extremely rare lymphoma proliferating within the lumina of large vessels like Superior vena cava and Aorta. We present a case of an IMGVL presenting in a patient with a Left Ventricular Assist Device (LVAD). <h3>Case Report</h3> A 63-year-old male with ischemic cardiomyopathy and advanced systolic failure supported by an LVAD as a bridge to transplant, presented to the clinic complaining of claudication symptoms. He has known peripheral vascular disease and underwent Aortobifemoral stenting in the past. Coronary Tomography with Angiography (CTA) showed a large intraluminal thrombus above the iliac limbs with severe narrowing of the lumen thought to be flow-limiting (Figure 1). He underwent a mechanical thrombectomy. Intra-operatively, a large mural thrombus with near occlusion of the descending aorta was noted (Figure 2). Pathology revealed diffuse large B-cell lymphoma (DLBCL) with immunohistochemistry positive for BCL2, MYC, Ki-67 and CD20. EBV status was negative. A whole-body Positron Emission Tomography (PET) scan was negative for malignancy elsewhere. He was initiated on chemotherapy. <h3>Summary</h3> Primary IMGVL is a rare subtype of extranodal lymphoma with only 4 cases reported in literature. It is distinct from Intravascular Large B-cell Lymphoma (IVLBCL) which is limited to small vessels. Furthermore, only a single case of aortic IMGVL found on autopsy of an EBV positive patient, has been reported. DLBCL is known to be an aggressive subtype of lymphoma often requiring a combination of chemotherapy and immune therapy. Long term prognosis in our patient awaiting heart transplant is rather uncertain.

Performance Evaluation of Amplitude and Phase Respiratory Gating Methods on Continuous-Bed-Motion Whole-Body PET Studies

Positron emission tomography (PET) scanners with the feature of continuous-bed-motion (CBM) that allows efficient whole-body dynamic scans and customized imaging protocols have been made commercially available in recent years. As the bed motion has to be reasonably slow in order to achieve sufficient count statistics, the blurring effect induced by respiratory motion is inevitable, and adequate gating methods should be applied. The aim of this study is to identify a relatively reliable gating method for CBM whole-body scans with respect to breathing pattern variability. Two methods: 1) equal amplitude gating (EAG) and 2) phase gating (PG) initially developed for the single-bed imaging protocol are evaluated using CBM data for subjects with a regular breathing pattern, irregular breathing pattern with baseline shift, and irregular breathing pattern with prolonged end expiration. The potential influence of the scan duration on the performance of the applied gating methods is taken into account as well. Based on the results, we suggest that the PG method is relatively reliable for all studied breathing patterns, while the EAG method could introduce severe artifacts in the presence of the baseline shift.

Whole-body PET angiography on semiconductor PET/CT

Whole-body PET angiography on semiconductor PET/CT

Clinical feasibility and impact of data-driven respiratory motion compensation studied in 200 whole-body 18F-FDG PET/CT scans

BackgroundThis study examines the clinical feasibility and impact of implementing a fully automated whole-body PET protocol with data-driven respiratory gating in patients with a broad range of oncological and non-oncological pathologies 592 FDG PET/CT patients were prospectively included. 200 patients with lesions in the torso were selected for further analysis, and ungated (UG), belt gated (BG) and data-driven gating (DDG) images were reconstructed. All images were reconstructed using the same data and without prolonged acquisition time for gated images. Images were quantitatively analysed for lesion uptake and metabolic volume, complemented by a qualitative analysis of visual lesion detection. In addition, the impact of gating on treatment response evaluation was evaluated in 23 patients with malignant lymphoma.ResultsPlacement of the belt needed for BG was associated with problems in 27% of the BG scans, whereas no issues were reported using DDG imaging. For lesion quantification, DDG and BG images had significantly greater SUV values and smaller volumes than UG. The physicians reported notable image blurring in 44% of the UG images that was problematic for clinical evaluation in 4.5% of cases.ConclusionRespiratory motion compensation using DDG is readily integrated into clinical routine and produce images with more accurate and significantly greater SUV values and smaller metabolic volumes. In our broad cohort of patients, the physicians overwhelmingly preferred gated over ungated images, with a slight preference for DDG images. However, even in patients with malignant disease in the torso, no additional diagnostic information was obtained by the gated images that could not be derived from the ungated images.

Whole-body Positron Emission Tomography (WBPET) Scan in All Patients of Breast Cancer: Is This the Way Forward?

Objectives: Globally, breast cancer is the second most frequently diagnosed malignancy just behind lung cancer, accounting for over 2 million cases each year. It is the second most commonly diagnosed cancer worldwide and the most common malignancy among females in India. The role of whole-body positron emission tomography (WBPET) in all cases of breast cancer is still not clear. This pilot study was undertaken to study whether there is any change in the management of breast cancer using WBPET scan in all patients of breast cancer irrespective of the stage? Materials and Methods: We retrospectively reviewed the data of 43 patients with invasive breast cancer who were newly diagnosed at Malignant Disease Treatment Centre at a tertiary care centre in East India. The duration of the study was between June 2020 and March 2021. Patients underwent liver function test, mammography, breast ultrasound, bone scan, and tru-cut needle biopsy to confirm the presence of breast cancer and 18F-fluoro-Dglucose (FDG) positron emission tomography/computed tomography (PET/CT) was studied in all 43 patients before the initiation of any therapy. The primary objective was to find out whether doing a WBPET upstaged the disease and changed our management. The secondary objective was to determine whether hormonal status (oestrogen receptor [ER], progesterone receptor [PR] and human epidermal growth factor receptor 2 [Her2] Neu) and Breast Imaging-Reporting and Database System (BIRADS) score staging had any correlation with metastasis. Results: A total of 43 patients with newly diagnosed breast cancer were studied. The number of patients in Stage IIA (3/43), Stage IIB (4/43), Stage III A (17/43), Stage IIIB (13/43), and Stage IV was (6/33). Out of total 43 patients, in 10 (23%) patients, there was a change in treatment on doing an upfront WBPET scan. There was no correlation between ER, PR, or Her2 Neu positivity or negativity on the upstaging of the disease and change in treatment. Standardised uptake value (SUV) uptake of the primary lesion &gt;7.2 was associated with upstaging and change of treatment. Conclusion: The use of 18F-FDG PET/CT has been shown to bring change in treatment in almost 20% of patients with breast cancer. Although the role of other variables in breast cancer such as hormone status, SUV of the primary lesion, and grade of lesion on BIRADS has also shown some association with change of treatment.

Deep learning-based attenuation correction for whole-body PET - a multi-tracer study with 18F-FDG, 68Ga-DOTATATE, and 18F-Fluciclovine.

Clinical whole-body PET/CT datasets of 18F-FDG (N = 113), 68Ga-DOTATATE (N = 76), and 18F-Fluciclovine (N = 90) were used to train and test tracer-specific neural networks. For each tracer, forty subjects were used to train the neural network to predict attenuation maps (µ-DL). µ-DL and µ-MLAA were compared to the gold-standard µ-CT. PET images reconstructed using the OSEM algorithm with µ-DL (OSEMDL) and µ-MLAA (OSEMMLAA) were compared to the CT-based reconstruction (OSEMCT). Tumor regions of interest were segmented by two radiologists and tumor SUV and volume measures were reported, as well as evaluation using conventional image analysis metrics. µ-DL yielded high resolution and fine detail recovery of the attenuation map, which was superior in quality as compared to µ-MLAA in all metrics for all tracers. Using OSEMCT as the gold-standard, OSEMDL provided more accurate tumor quantification than OSEMMLAA for all three tracers, e.g., error in SUVmax for OSEMMLAA vs. OSEMDL: - 3.6 ± 4.4% vs. - 1.7 ± 4.5% for 18F-FDG (N = 152), - 4.3 ± 5.1% vs. 0.4 ± 2.8% for 68Ga-DOTATATE (N = 70), and - 7.3 ± 2.9% vs. - 2.8 ± 2.3% for 18F-Fluciclovine (N = 44). OSEMDL also yielded more accurate tumor volume measures than OSEMMLAA, i.e., - 8.4 ± 14.5% (OSEMMLAA) vs. - 3.0 ± 15.0% for 18F-FDG, - 14.1 ± 19.7% vs. 1.8 ± 11.6% for 68Ga-DOTATATE, and - 15.9 ± 9.1% vs. - 6.4 ± 6.4% for 18F-Fluciclovine. The proposed framework provides accurate and robust attenuation correction for whole-body 18F-FDG, 68Ga-DOTATATE and 18F-Fluciclovine in tumor SUV measures as well as tumor volume estimation. The proposed method provides clinically equivalent quality as compared to CT in attenuation correction for the three tracers.

Primary appendiceal diffuse large B-cell lymphoma initially presenting as acute appendicitis: A case report.

IntroductionDiffuse large B-cell lymphoma (DLBCL) is the most common histologic subtype of non-Hodgkin lymphoma (NHL), accounting for approximately 25% of all NHL cases. Primary appendiceal lymphomas (PAL) presenting as acute appendicitis are very rare, occurring in only 0.015% of all cases of gastrointestinal lymphoma.Case presentationA 57-year-old man who was initially presented as acute appendicitis and subsequently underwent interval laparoscopic appendectomy. Pathological examination revealed diffuse large B cell lymphoma with cut end involvement. Whole-body positron emission tomography (PET) scan revealed enlarged right palatine tonsil and raised a suspicion of lymphoma involvement in two right cervical lymph nodes (level II and III); biopsy, however, showed that the lymph nodes were benign, with non-specific cellular changes. Bone marrow biopsy of the iliac crest also did not show lymphoma involvement. Subsequently, a diagnosis of primary appendiceal diffuse large B cell lymphoma (Ann Arbor Stage II) was established. After six courses of definite chemotherapy with cyclophosphamide, doxorubicin HCl, vincristine, and rituximab (R-CHOP), PET/CT showed complete remission of the prior FDG-avid malignancy of appendiceal DLBCL. The patient continued to be stable with no recurrence for fifteen months of regular outpatient department follow-ups.ConclusionsPAL is rare, and it clinically manifests the signs and symptoms of acute appendicitis. Specific characteristics of lymphoma in CT scans may lead to a more confirmative diagnosis. PET/CT is important for staging the lymphoma. Patients with PAL should be managed with surgical resection followed by R-CHOP-21 for 6 cycles regardless of whether they have localized disease or disseminated disease.

Target occupancy study and whole-body dosimetry with a MAGL PET ligand [11C]PF-06809247 in non-human primates

BackgroundMonoacylglycerol lipase (MAGL) is a key serine hydrolase which terminates endocannabinoid signaling and regulates arachidonic acid driven inflammatory responses within the central nervous system. To develop [11C]PF-06809247 into a clinically usable MAGL positron emission tomography (PET) radioligand, we assessed the occupancy of MAGL by an inhibitor in the non-human primate (NHP) brain. Additionally, we measured the whole-body distribution of [11C]PF-06809247 in NHP and estimated human effective radiation doses.MethodsSeven cynomolgus monkeys were enrolled for brain PET measurements. Two PET measurements along with arterial blood sampling were performed in each NHP: one baseline and one pretreatment condition with intravenous administration of PF-06818883, a pro-drug of a selective MAGL inhibitor (total of seven doses between 0.01 and 1.27 mg/kg). Kinetic parameters K1, k2 and k3 were estimated by a two tissue compartment (2TC) model using metabolite corrected plasma radioactivity as the input function. k4 was set as 0 according to the irreversible binding of [11C]PF-06809247. Ki by 2TC and Patlak analysis were calculated as the influx constant. The target occupancy was calculated using Ki at baseline and pretreatment conditions. Two cynomolgus monkeys were enrolled for whole-body PET measurements. Estimates of the absorbed radiation dose in humans were calculated with OLINDA/EXM 1.1 using the adult male reference model.ResultsRadioactivity retention was decreased in all brain regions following pretreatment with PF-06818883. Occupancy was measured as 25.4–100.5% in a dose dependent manner. Whole-body PET showed high radioactivity uptake values in the liver, small intestine, kidney, and brain. The effective dose of [11C]PF-06809247 was calculated as 4.3 μSv/MBq.Conclusions[11C]PF-06809247 is a promising PET ligand for further studies of MAGL in the human brain.

D1 MTE1 Case 1: Steroid refractory insulin autoimmune syndrome treated with rituximab and continuous glucose monitoring

A 67-year-old female presented with severe hypoglycaemia with a blood glucose of 34mg/dl 5 hours after having dinner. She did not have diabetes and had no access to oral hypoglycaemic agents, insulin, or any other drug known to cause hypoglycaemia. She was a known case of primary hypothyroidism euthyroid on treatment. The physical examination was unremarkable. Her liver, renal functions, thyroid, and adrenal functions were normal. At blood sugar of 23 mg/dl, her serum insulin was 24000uU/ml (normal<3uU/ml) and c-peptide was 16.2 ng/ml (normal 0-0.6ng/ml) which were very high. As the serum insulin levels were very high insulin autoimmune syndrome was suspected. Insulin autoantibodies were positive 87.2 units/ml (normal<12). Imaging with contrast-enhanced computerized tomography (CECT Abdomen), endoscopic ultrasonography, 68 gallium octreotide dotanoc whole-body PET -CT scan did not reveal any pancreatic or extra-pancreatic tumour. Autoimmune insulin syndrome (IAS) was diagnosed. She was started on high dose prednisolone, diazoxide and octreotide in addition to low carbohydrate meals. Hypoglycaemic episodes continued for 1 month despite this therapy. Remission was achieved only after 2 doses of Rituximab 1 gram infusion were given. Serum insulin levels were reduced to 230uU units from 24000uU/ml, and the patient's hypoglycaemic and hyperglycaemic episodes were normalized. We used continuous glucose monitoring using the Freestyle Libre glucose monitoring system, and the management of the patient was greatly facilitated with this.

Evidence of a Gastro-Duodenal Effect on Adipose Tissue and Brain Metabolism, Potentially Mediated by Gut-Liver Inflammation: A Study with Positron Emission Tomography and Oral 18FDG in Mice.

Interventions affecting gastrointestinal (GI) physiology suggest that the GI tract plays an important role in modulating the uptake of ingested glucose by body tissues. We aimed at validating the use of positron emission tomography (PET) with oral 18FDG administration in mice, and to examine GI effects on glucose metabolism in adipose tissues, brain, heart, muscle, and liver, and interfering actions of oral lipid co-administration. We performed sequential whole-body PET studies in 3 groups of 10 mice, receiving i.p. glucose and 18FDG or oral glucose and 18FDG ± lipids, to measure tissue glucose uptake (GU) and GI transit, and compute the absorption lumped constant (LCa) as ratio of oral 18FDG-to-glucose incremental blood levels. GI and liver histology and circulating hormones were tested to generate explanatory hypothesis. Median LCa was 1.18, constant over time and not significantly affected by lipid co-ingestion. Compared to the i.p. route, the oral route (GI effect) resulted in lower GU rates in adipose tissues and brain, and a greater steatohepatitis score (+17%, p = 0.03). Lipid co-administration accelerated GI transit, in relation to the suppression in GIP, GLP1, glucagon, PP, and PYY (GI motility regulators), abolishing GI effects on subcutaneous fat GU. Duodenal crypt size, gastric wall 18FDG uptake, and macro-vesicular steatosis were inversely related to adipose tissue GU, and positively associated with liver GU. We conclude that 18FDG-PET is a suitable tool to examine the role of the GI tract on glucose transit, absorption, and bio-distribution. The GI effect consists in the suppression of glucose metabolism selectively in organs responsible for energy intake and storage, and is blunted by lipid ingestion. Modulation of gut and liver inflammation, as reflected by high GU, may be involved in the acute signalling of the energy status.

IVC thrombectomy in a patient with adrenal tumour with IVC thrombus.

IntroductionAdrenocortical carcinoma (ACC) is a rare malignancy with a poor prognosis, and the association with tumour thrombus into the inferior vena cava (IVC) is infrequent. Radical surgery is the best treatment.Case ReportWe herein report a case of a large ACC of the left adrenal gland extending into the IVC through the left renal vein in a 68-year-old male patient. He presented with pain in the left side of the abdomen for one month and significant weight loss (7 kilograms). On examination, a hard irregular non-ballotable lump was palpable in the left lumbar region. Ultrasonography, computedtomography, and whole-body PET CT all revealed a large mass over the upper pole of the left kidney with tumour thrombus in the IVC. Laboratory tests showed creatinine levels of 0.9 mg/dl (normal range: 0.5–1.2 mg/dl) while plasma levels of cortisol, free metanephrines were normal. A midline laparotomy was performed, and the tumour was completely excised with regionallymphadenectomy, ipsilateral radical nephrectomy and IVC thrombectomy.Results And DiscussionWe emphasize that adrenal cortical carcinoma is a rare tumour and can have tumour thrombi invading the IVC. Such cases do not represent a contraindication to surgery, and we suggest radical surgical removal of cancer with the thrombus.

Cost-Effectiveness of PET/CT Surveillance Schedules to Detect Distant Recurrence of Resected Stage III Melanoma.

Objective: To estimate the cost-effectiveness of three surveillance imaging strategies using whole-body positron emission tomography (PET) with computed tomography (CT) (PET/CT) in a follow-up program for adults with resected stage III melanoma. Methods: An analytic decision model was constructed to estimate the costs and benefits of PET/CT surveillance imaging performed 3-monthly, 6-monthly, or 12-monthly compared with no surveillance imaging. Results: At 5 years, 3-monthly PET/CT surveillance imaging incurred a total cost of AUD 88,387 per patient, versus AUD 77,998 for 6-monthly, AUD 52,560 for 12-monthly imaging, and AUD 51,149 for no surveillance imaging. When compared with no surveillance imaging, 12-monthly PET/CT imaging was associated with a 4% increase in correctly diagnosed and treated distant disease; a 0.5% increase with 6-monthly imaging and 1% increase with 3-monthly imaging. The incremental cost-effectiveness ratio (ICER) of 12-monthly PET/CT surveillance imaging was AUD 34,362 for each additional distant recurrence correctly diagnosed and treated, compared with no surveillance imaging. For the outcome of cost per diagnostic error avoided, the no surveillance imaging strategy was the least costly and most effective. Conclusion: With the ICER for this strategy less than AUD 50,000 per unit of health benefit, the 12-monthly surveillance imaging strategy is considered good value for money.

Intraductal Papilloma With Carcinoma of the Breast Described by Dedicated Breast 18F-FDG PET.

Intraductal papilloma (IDP) is a benign tumor of the breast. However, IDP has been reported to show high uptake of 18F-FDG using whole-body PET. We experienced IDP with low-grade ductal carcinoma in situ using dedicated breast PET, which is more sensitive than whole-body PET. The 18F-FDG uptake of the whole tumor was high, and differentiation between the carcinoma and the residual benign lesion was difficult. This is the first report of IDP detected with dedicated breast PET. Diagnosis of IDP is sometimes controversial; papilloma may show glucose uptake similar to that of low-grade carcinoma.

68Ga-DOTA-DiPSMA PET/CT Imaging: Biodistribution, Dosimetry, and Preliminary Application in Prostate Cancer.

Purpose: This prospective trial aimed to evaluate the safety, dosimetry, and biodistribution of a novel theranostic probe 68Ga-DOTA-DiPSMA. Also, we have performed the first preliminary application with 68Ga-DOTA-DiPSMA in prostate cancer (PCa) patients. Methods: Five healthy volunteers and ten PCa patients were injected with an intravenous bolus of 68Ga-DOTA-DiPSMA. They received serial whole-body PET scans from the time of injection up to 60 min post-injection, with a second PET/CT scanning at 120 min post-injection. In PCa patients, low-dose CT scan and whole-body PET were performed with 2 min per bed position in 40 min post-injection. Absorbed organ doses and effective doses were calculated using OLINDA/EXM. Normal organ uptake and tumor lesion uptake were measured. A lesion-by-lesion analysis was performed. Results: 68Ga-DOTA-DiPSMA administration was safe and well-tolerated. The kidneys received the highest absorbed dose (114.46 ± 29.28 μSv/MBq), followed by the urinary bladder wall (100.82 ± 46.22 μSv/MBq) in accordance with the expected Prostate-Specific Membrane Antigen (PSMA) renal excretion of the tracer. The mean effective dose was 19.46 ± 1.73 μSv/MBq. The SUVmax of 68Ga-DOTA-DiPSMA PET/CT for PCa lesions, bone metastases, and lymph node metastases was 4.41 ± 2.72, 2.95 ± 1.11, and 3.26 ± 1.20, respectively. Conclusion: Injection of 68Ga-DOTA-DiPSMA is safe and associated with low absorbed and effective doses. 68Ga-DOTA-DiPSMA shows favorable kinetics and imaging characteristics in patients who warrant further head-to-head comparison to validate 68Ga-DOTA-DiPSMA as an alternative for gallium-68-labeled PSMA clinical PET. Low nonspecific uptake in normal organs of 68Ga-DOTA-DiPSMA indicates potential radioligand therapy (RLT) application when labeled with 177Lu, 90Y, or 225Ac.

MCP-Net: Inter-frame Motion Correction with Patlak Regularization for Whole-body Dynamic PET.

Inter-frame patient motion introduces spatial misalignment and degrades parametric imaging in whole-body dynamic positron emission tomography (PET). Most current deep learning inter-frame motion correction works consider only the image registration problem, ignoring tracer kinetics. We propose an inter-frame Motion Correction framework with Patlak regularization (MCP-Net) to directly optimize the Patlak fitting error and further improve model performance. The MCP-Net contains three modules: a motion estimation module consisting of a multiple-frame 3-D U-Net with a convolutional long short-term memory layer combined at the bottleneck; an image warping module that performs spatial transformation; and an analytical Patlak module that estimates Patlak fitting with the motion-corrected frames and the individual input function. A Patlak loss penalization term using mean squared percentage fitting error is introduced to the loss function in addition to image similarity measurement and displacement gradient loss. Following motion correction, the parametric images were generated by standard Patlak analysis. Compared with both traditional and deep learning benchmarks, our network further corrected the residual spatial mismatch in the dynamic frames, improved the spatial alignment of Patlak Ki/Vb images, and reduced normalized fitting error. With the utilization of tracer dynamics and enhanced network performance, MCP-Net has the potential for further improving the quantitative accuracy of dynamic PET. Our code is released at https://github.com/gxq1998/MCP-Net.

IgG4-related disease presenting with renal injury and obstructive nephropathy discovered incidentally: a case report with literature review

IgG-4 related disease (IgG4-RD) is a chronic inflammatory condition characterized by tissues infiltration with lymphocytes and IgG4 secreting plasma cells, significant fibrosis and response well to steroids. It is typically a systemic disease that involves various organs. We are presenting a 57-year-old female who was found to have elevated serum creatinine, Proteinuria. An ultrasound scan revealed bilateral hydronephrosis and an abdominal computed tomography (CT) scan illustrated a large retroperitoneal mass. Further evaluation of the mass with whole-body positron emission tomography (PET CT) scan was suggestive of retroperitoneal fibrosis or lymphoma. A CT guided biopsy was done, and results were consistent with fibrosis in the context of IgG-4 related disease. IgG-4 serum levels were elevated. The patient was treated with oral steroids. Azathioprine and Rituximab. Renal function improved significantly and was stable upon 3 months follow up with a decrease in IgG-4 levels and with a significant reduction in the mass lesion.

Primary Testicular Lymphoma: A Case Report and Review of the Literature

Background and Aim: Primary testicular lymphoma (PTL) is a rare form of extranodal non-Hodgkin’s lymphoma. It represents for 1% - 2% of non-Hodgkin’s lymphoma, and mostly affects the elderly. We describe an interesting case of PTL managed by a combined multimodal approach with a review of the literature. Case Presentation: Patient aged 56 years, consulted for an increase in the volume of the right testicle without associated pain, all evolving in the context of a slight decline in general condition. Clinical examination revealed a large painless mass in the right scrotal bursa. A scrotal ultrasound showed a right intra-testicular mass. The patient had undergone inguinal orchiectomy. Pathological analysis showed diffuse large B-cell lymphoma of the testis. Whole-body 18-fluorodeoxyglucose positron emission tomography (18-FDG-PET-CT) showed no suspicious hypermetabolism. Lumbar puncture did not reveal malignant cells in the cerebrospinal fluid (CSF). The patient then received 6 cycles of chemotherapy according to the R-CHOP protocol (Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone) and 2 cycles of intrathecal methotrexate. After chemotherapy, scrotal radiotherapy at a dose of 30 Gy was delivered. The evolution was marked by the death of the patient six months after the end of the scrotal radiotherapy following a diffuse lymph node relapse with a profound alteration of the general state. Conclusion: The treatment depends imperatively on the stage of the disease. The therapeutic approach is multimodal and combined based on orchiectomy, systemic and intrathecal treatment and scrotal radiotherapy. PTL is an aggressive malignant with a poor prognosis. Randomized trials are needed to define a better therapeutic strategy.

Cross Attention Transformers for Multi-modal Unsupervised Whole-Body PET Anomaly Detection.

Cancers can have highly heterogeneous uptake patterns best visualised in positron emission tomography. These patterns are essential to detect, diagnose, stage and predict the evolution of cancer. Due to this heterogeneity, a general-purpose cancer detection model can be built using unsupervised learning anomaly detection models; these models learn a healthy representation of tissue and detect cancer by predicting deviations from healthy appearances. This task alone requires models capable of accurately learning long-range interactions between organs, imaging patterns, and other abstract features with high levels of expressivity. Such characteristics are suitably satisfied by transformers, and have been shown to generate state-of-the-art results in unsupervised anomaly detection by training on healthy data. This work expands upon such approaches by introducing multi-modal conditioning of the transformer via cross-attention, i.e. supplying anatomical reference information from paired CT images to aid the PET anomaly detection task. Using 83 whole-body PET/CT samples containing various cancer types, we show that our anomaly detection method is robust and capable of achieving accurate cancer localisation results even in cases where healthy training data is unavailable. Furthermore, the proposed model uncertainty, in conjunction with a kernel density estimation approach, is shown to provide a statistically robust alternative to residual-based anomaly maps. Overall, a superior performance is demonstrated against leading alternatives, drawing attention to the potential of these approaches.

Noninvasive estimation of human radiation dosimetry of 18F-FDG by whole-body small animal PET imaging in rats

PurposeSmall animal PET provides the biodistribution of administrated radiotracer in vivo and have a potential to contribute on dosimetry study. The aim of this study is to investigate the effect of region-of-interest (ROI)-delineation in whole-body rat PET image toward non-invasive estimation of human dosimetry of 18F-FDG. MethodAfter administration of 18F-FDG (averaged 11.7 MBq), 3.5-h PET and 20-min CT scans were sequentially performed for three rats by Clairvivo PET/CT system. Seven source organs, and the remainder of the body, were studied to extrapolate %ID(t) and estimate time-integrated activity coefficients [kBq-h/MBq] in human. The mean absorbed dose in each target organ and the effective dose were estimated by MIRD method. Effects of ROI-definitions on both extrapolated %ID(t) in human and estimated doses were also investigated by using (i) small ROIs of high uptake region and (ii) whole organ ROIs. ResultsAveraged effective doses of 18F-FDG in human by using high-uptake and whole-organ ROIs were 27.8 ± 6.54 and 19.3 ± 2.72 μSv/MBq, respectively. ConclusionThe use of small animal PET scanner, which allows repeatedly PET scans, have a potential to contribute on the reduction of the number of experimental animals. However, the ways of ROI drawing influences on the estimated effective dose and safe-side ROI definition may be preferred.