Lymphoma Masquerading as Lung Cancer.

ABSTRACT: Lymphoma typically manifests as lymphadenopathy, with or without solid organ involvement. Lymphomatous masses tend to respect anatomical structures, encasing rather than invading them. Tumor thrombus formation is a rare presentation in lymphoma that has been previously described in the liver and kidneys. We report an unusual presentation of B-cell lymphoma with imaging findings suggestive of metastatic lung cancer with tumor thrombus in the pulmonary vein and left atrium.

Restaging of rectal cancer with hybrid positron emission tomography magnetic resonance imaging after preoperative chemoradiotherapy.

Introduction: This study determines the sensitivity and specificity of positron emission tomography/magnetic resonance imaging (PET/MRI) parameters in predicting treatment response in patients with localised rectal cancer who have undergone preoperative chemoradiotherapy (CRT). Method: Patients with stage I-III adenocarcinoma of the rectum planned for preoperative CRT followed by surgery were recruited. Patients had PET/MRI scans at baseline and 6-8 weeks post-CRT. Functional MRI and PET parameters were assessed for their diagnostic accuracy for tumour regression grade (TRG). Nonparametric receiver operating characteristic analysis was employed to determine the area under the ROC curve (AUC), and the sensitivity and specificity of each quantile cut-off. Results: A total of 31 patients were recruited, of whom 20 completed study protocol. All patients included had mid or lower rectal tumours. There were 16 patients (80%) with node-positive disease at presentation. The median time to surgery was 75.5 days (range 52-106 days). Histopathological assessment revealed 20% good responders (TRG 1/2), and the remaining 80% of patients had a poor response (TRG 3/4). When predicting good responders, the AUC values for percent maximum thickness reduction and percent apparent diffusion coefficient (ADC) change were 0.82 and 0.73, respectively. A maximum thickness reduction cut-off of >47% and a percent ADC change of >20% yielded a sensitivity and specificity of 75%/95% and 75%/73%, respectively. Conclusion: Parameters such as percent maximum thickness reduction and percent ADC change may be useful for predicting good responders in patients undergoing preoperative CRT for rectal cancer. Larger studies are warranted to establish the utility of PET/MRI in rectal cancer staging.

An ex vivo platform to guide drug combination treatment in relapsed/refractory lymphoma.

Although combination therapy is the standard of care for relapsed/refractory non-Hodgkin's lymphoma (RR-NHL), combination treatment chosen for an individual patient is empirical, and response rates remain poor in individuals with chemotherapy-resistant disease. Here, we evaluate an experimental-analytic method, quadratic phenotypic optimization platform (QPOP), for prediction of patient-specific drug combination efficacy from a limited quantity of biopsied tumor samples. In this prospective study, we enrolled 71 patients with RR-NHL (39 B cell NHL and 32 NK/T cell NHL) with a median of two prior lines of treatment, at two academic hospitals in Singapore from November 2017 to August 2021. Fresh biopsies underwent ex vivo testing using a panel of 12 drugs with known efficacy against NHL to identify effective single and combination treatments. Individualized QPOP reports were generated for 67 of 75 patient samples, with a median turnaround time of 6 days from sample collection to report generation. Doublet drug combinations containing copanlisib or romidepsin were most effective against B cell NHL and NK/T cell NHL samples, respectively. Off-label QPOP-guided therapy offered at physician discretion in the absence of standard options (n = 17) resulted in five complete responses. Among patients with more than two prior lines of therapy, the rates of progressive disease were lower with QPOP-guided treatments than with conventional chemotherapy. Overall, this study shows that the identification of patient-specific drug combinations through ex vivo analysis was achievable for RR-NHL in a clinically applicable time frame. These data provide the basis for a prospective clinical trial evaluating ex vivo-guided combination therapy in RR-NHL.

Comparison of the performances of machine learning and deep learning in improving the quality of low dose lung cancer PET images.

PURPOSE: To compare the performances of machine learning (ML) and deep learning (DL) in improving the quality of low dose (LD) lung cancer PET images and the minimum counts required. MATERIALS AND METHODS: 33 standard dose (SD) PET images, were used to simulate LD PET images at seven-count levels of 0.25, 0.5, 1, 2, 5, 7.5 and 10 million (M) counts. Image quality transfer (IQT), a ML algorithm that uses decision tree and patch-sampling was compared to two DL networks-HighResNet (HRN) and deep-boosted regression (DBR). Supervised training was performed by training the ML and DL algorithms with matched-pair SD and LD images. Image quality evaluation and clinical lesion detection tasks were performed by three readers. Bias in 53 radiomic features, including mean SUV, was evaluated for all lesions. RESULTS: ML- and DL-estimated images showed higher signal and smaller error than LD images with optimal image quality recovery achieved using LD down to 5 M counts. True positive rate and false discovery rate were fairly stable beyond 5 M counts for the detection of small and large true lesions. Readers rated average or higher ratings to images estimated from LD images of count levels above 5 M only, with higher confidence in detecting true lesions. CONCLUSION: LD images with a minimum of 5 M counts (8.72 MBq for 10 min scan or 25 MBq for 3 min scan) are required for optimal clinical use of ML and DL, with slightly better but more varied performance shown by DL.

Utility and pitfalls of the electrocardiogram in the evaluation of cardiac amyloidosis.

BACKGROUND: Cardiac amyloidosis is a protein misfolding disorder involving deposition of amyloid fibril proteins in the heart. The associated fibrosis of the conduction tissue results in conduction abnormalities and arrhythmias. "Classical" electrocardiogram (ECG) findings in cardiac amyloidosis include that of low voltage complexes with increased left ventricular wall thickness on echocardiography. However, this "classical" finding is neither sensitive nor specific. As cardiac amyloidosis is associated with a generally poor prognosis, the need for early recognition of this disease is important given the availability of new treatment options. In this review, we highlight 3 cases of patients with cardiac amyloidosis. Although presenting with typical clinical signs and symptoms, ECG for all 3 patients was not consistent with the classical findings described. They underwent further diagnostic tests which clinched the diagnosis of cardiac amyloidosis, allowing patients to receive targeted treatment. Through the review of the literature, we will highlight the different ECG patterns in patients with different types of cardiac amyloidosis and clinical scenarios, as well as the pitfalls of using ECG to identify the condition. Lastly, we also emphasize the current paradigms in diagnosing cardiac amyloidosis through the non-invasive methods of echocardiography, cardiac magnetic resonance imaging, and nuclear technetium-pyrophosphate imaging. CONCLUSIONS: Electrocardiogram is often the first investigation used in evaluating many cardiac disorders, including cardiac amyloidosis. However, classical features of cardiac amyloidosis on ECG are often not present. A keen understanding on the ECG features of cardiac amyloidosis and knowledge of the diagnostic workflow is important to diagnose this condition.

"Hot Cord" Sign on 18F-FDG PET/CT in a Patient With Acute Myelitis Due to Neuromyelitis Optica Spectrum Disorder.

A 44-year-old woman presented with prolonged low-grade fever, bilateral upper limb weakness, and hyperesthesia. MRI showed hyperintense T2 signal and enhancement of the cervicothoracic spinal cord. F-FDG PET/CT was requested to investigate pyrexia of unknown origin. It demonstrated diffusely increased FDG uptake along the entire spinal cord, suggestive of extensive acute myelitis. Initial blood work was positive for antinuclear antibodies and anti-Ro/SSA antibodies. Cerebrospinal fluid analysis revealed lymphocytosis and detected the presence of neuromyelitis optica aquaporin-4-immunoglobulin G antibodies, fulfilling the criteria for diagnosis of neuromyelitis optica spectrum disorder.

Lymphoma Recurrence Along the Lymphatic Tract on 18F-FDG PET/CT Presenting as Lower Limb Swelling.

A 66-year-old woman with a known history of diffuse large B-cell lymphoma presented with left lower limb swelling following recent long-distance air travel. Ultrasound Doppler showed no evidence of deep vein thrombosis. In view of her medical history, an F-FDG PET/CT was ordered that found a soft tissue mass following the course of the femoral neurovascular bundle along the anteromedial aspect of the left thigh down to the popliteal fossa and the lateral calf muscle. This was confirmed to be tumor recurrence.

(68)Ga-DOTA-peptide: A novel molecular biomarker for nasopharyngeal carcinoma.

BACKGROUND: Increased somatostatin receptor (SSTR) expression in patients with undifferentiated nasopharyngeal carcinoma (NPC) has been demonstrated with receptor autoradiography, (111) In-Octreotide scintigraphy, and (68) Ga-DOTA-TOC positron emission tomography (PET)/CT imaging. We sought to compare and correlate the uptake of fluorodeoxyglucose (FDG) and DOTA-NOC in undifferentiated NPC to ascertain the possible role of (68) Ga-DOTA-NOC PET/CT as a new imaging biomarker and to assess whether targeted peptide receptor radionuclide therapy is a feasible treatment option. METHODS: After obtaining approval from our institutional review board, 4 patients with biopsy proven nonkeratinizing undifferentiated NPC who had just undergone routine staging/restaging (18) F-FDG PET/CT imaging were prospectively and consecutively recruited for (68) Ga-DOTA-NOC PET/CT imaging. Of these 4 patients, 3 were newly diagnosed with untreated NPC, whereas 1 patient was diagnosed with a case of recurrent NPC with previous treatment. These patients subsequently underwent (68) Ga-DOTA-NOC PET/CT within 10 days from the (18) F-FDG PET/CT to ensure lesion comparability. Tracer uptake in tumor lesions were assessed visually and semiquantitatively by measuring maximum standardized uptake values (SUVmax). RESULTS: There were 12 FDG-avid lesions of which 7 showed avid uptake of DOTA-NOC greater than liver uptake, whereas 5 showed low uptake of DOTA-NOC less than liver uptake. Subset analysis of the FDG-avid lesions at the primary and recurrent sites showed that all the FDG-avid primary tumors in the nasopharynx showed avid uptake of DOTA-NOC. On the contrary, the case of recurrent NPC showed avid FDG uptake but low DOTA-NOC uptake. Subset analysis of the suspicious FDG-avid cervical lymph nodes showed that 50% of them demonstrated avid DOTA-NOC uptake greater than liver uptake, whereas the remaining demonstrated low-grade DOTA-NOC uptake less than liver uptake. The 2 subcentimeter cervical lymph nodes that showed low-grade uptake of FDG lower than mediastinal blood pool activity were deemed to be reactive/inflammatory and showed low-grade uptake of DOTA-NOC. CONCLUSION: This study highlights the potential of (68) Ga-DOTA-peptide PET/CT as a new molecular biomarker for newly diagnosed undifferentiated NPC, and less so for recurrent NPC and metastatic nodes. This potentially opens up new diagnostic and therapeutic options in the management of undifferentiated NPC.

Impact of Image Reconstruction Settings on Texture Features in 18F-FDG PET.

UNLABELLED: Evaluation of tumor heterogeneity based on texture parameters has recently attracted much interest in the PET imaging community. However, the impact of reconstruction settings on texture parameters is unclear, especially relating to time-of-flight and point-spread function modeling. Their effects on 55 texture features (TFs) and 6 features based on first-order statistics (FOS) were investigated. Standardized uptake value (SUV) measures were also evaluated as peak SUV (SUVpeak), maximum SUV, and mean SUV (SUVmean). METHODS: This study retrospectively recruited 20 patients with lesions in the lung who underwent whole-body (18)F-FDG PET/CT. The coefficient of variation (COV) of each feature across different reconstructions was calculated. RESULTS: SUVpeak, SUVmean, 18 TFs, and 1 FOS were the most robust (COV ≤ 5%) whereas skewness, cluster shade, and zone percentage were the least robust (COV > 20%) with respect to reconstruction algorithms using default settings. Heterogeneity parameters had different sensitivities to iteration number. Twenty-four parameters including SUVpeak and SUVmean exhibited variation with a COV less than 5%; 28 parameters, including maximum SUV, showed variation with a COV in the range of 5%-10%. In addition, skewness, cluster shade, and zone percentage were the most sensitive to iteration number. In terms of sensitivity to full width at half maximum (FWHM), 15 TFs and 1 FOS had the best performance with a COV less than 5%, whereas SUVpeak and SUVmean had a COV between 5% and 10%. Grid size had the largest impact on image features, which was demonstrated by only 11 features, including SUVpeak and SUVmean, having a COV less than 10%. CONCLUSION: Different image features have different sensitivities to reconstruction settings. Iteration number and FWHM of the gaussian filter have a similar impact on the image features. Grid size has a larger impact on the features than iteration number and FWHM. The features that exhibited large variations such as skewness in FOS, cluster shade, and zone percentage should be used with caution. The entropy in FOS, difference entropy, inverse difference normalized, inverse difference moment normalized, low gray-level run emphasis, high gray-level run emphasis, and low gray-level zone emphasis are the most robust features.

Incidental possible diagnosis by 18F-fluorocholine PET/CT of Meckel's diverticulum and potential pitfalls.

UNLABELLED: A 61 years old man with a history of prostate cancer Gleason 3+4, treated with radical prostatectomy, underwent fluorine-18-fluorocholine positron emission tomography/computed tomography ((18)F-FCH PET/CT) imaging to investigate rising serum prostate specific antigen (PSA) levels. (18)F-FCH PET/CT showed a focus of linear increased uptake by a possible Meckel's diverticulum in the right hemi-pelvis, which was an incidental finding in this asymptomatic patient. Uptake of (18)F-FCH by Meckel's diverticulum has not been reported before and thus the mechanism of uptake has not been established. Two postulations may explain this uptake. First, since Meckel's diverticulum is a true diverticulum containing all layers of the intestinal wall, the uptake may be related to physiological bowel-related uptake. Second, the uptake may be due to heterotopic pancreatic tissue in Meckel's diverticulum, especially since the intensity of uptake we have noticed was similar to that of physiological pancreatic uptake. As (18)F-FCH PET/CT scan is often used for evaluating prostate cancer, (18)F-FCH uptake by Meckel's diverticulum in the pelvis or lower abdomen may be mistaken for tumor involvement/recurrence. The identification by imaging of Meckel's diverticulum relies on the identification of a blind ending tubular structure, arising from the distal ileum. The identification of this structure may be best appreciated on the axial, coronal or sagittal plane. CONCLUSION: In this particular case, we managed to clearly demonstrate the presence of a tubular blind ending structure arising from the distal ileum on the sagittal images. The careful identification of this structure indicated that tracer uptake was in a Meckel's diverticulum and not within a pelvic lymph node or pelvic organ hence excluding recurrent disease.

Asymptomatic metastasis to cricoid from prostate carcinoma: an incidental finding detected on 18F-choline PET/CT.

Metastases to the larynx from prostate carcinoma are rare. We describe a case of asymptomatic prostate carcinoma metastasis to the right cricoid cartilage detected on 18F-fluorocholine PET/CT. This was histologically proven on open biopsy and the patient was offered local radiotherapy.