Quantitative imaging of bone-cartilage interactions in ACL-injured patients with PET-MRI.

OBJECTIVE: To investigate changes in bone metabolism by positron emission tomography (PET), as well as spatial relationships between bone metabolism and magnetic resonance imaging (MRI) quantitative markers of early cartilage degradation, in anterior cruciate ligament (ACL)-reconstructed knees. DESIGN: Both knees of 15 participants with unilateral reconstructed ACL tears and unaffected contralateral knees were scanned using a simultaneous 3.0T PET-MRI system following injection of 18F-sodium fluoride (18F-NaF). The maximum pixel standardized uptake value (SUVmax) in the subchondral bone and the average T2 relaxation time in cartilage were measured in each knee in eight knee compartments. We tested differences in SUVmax and cartilage T2 relaxation times between the ACL-injured knee and the contralateral control knee as well as spatial relationships between these bone and cartilage changes. RESULTS: Significantly increased subchondral bone 18F-NaF SUVmax and cartilage T2 times were observed in the ACL-reconstructed knees (median [inter-quartile-range (IQR)]: 5.0 [5.8], 36.8 [3.6] ms) compared to the contralateral knees (median [IQR]: 1.9 [1.4], 34.4 [3.8] ms). A spatial relationship between the two markers was also seen. Using the contralateral knee as a control, we observed a significant correlation of r = 0.59 between the difference in subchondral bone SUVmax (between injured and contralateral knees) and the adjacent cartilage T2 (between the two knees) [P < 0.001], with a slope of 0.49 ms/a.u. This correlation and slope were higher in deep layers (r = 0.73, slope = 0.60 ms/a.u.) of cartilage compared to superficial layers (r = 0.40, slope = 0.43 ms/a.u.). CONCLUSIONS: 18F-NaF PET-MR imaging enables detection of increased subchondral bone metabolism in ACL-reconstructed knees and may serve as an important marker of early osteoarthritis (OA) progression. Spatial relationships observed between early OA changes across bone and cartilage support the need to study whole-joint disease mechanisms in OA.

2-Deoxy-2-[F-18]fluoro-D-glucose positron emission tomography/computed tomography in the management of melanoma.

OBJECTIVES: 2-Deoxy-2-[F-18]fluoro-D-glucose (FDG)-positron emission tomography (PET)/computed tomography (CT) is widely available as a powerful imaging modality, combining the ability to detect active metabolic processes and their morphologic features in a single exam. The role of FDG-PET is proven in a variety of cancers, including melanoma, but the estimates of sensitivity and specificity are based in the majority of the published studies on dedicated PET, not PET/CT. Therefore, we were prompted to review our experience with FDG-PET/CT in the management of melanoma. METHODS: This is a retrospective study on 106 patients with melanoma (20-87 years old; average: 56.8 +/- 15.9), who had whole-body FDG-PET/CT at our institution from January 2003 to June 2005. Thirty-eight patients (35.9%) were women and 68 patients (64.1%) were men. Reinterpretation of the imaging studies for accuracy and data analysis from medical records were performed. RESULTS: All patients had the study for disease restaging. The primary tumor depth (Breslow's thickness) at initial diagnosis was available for 76 patients (71.7%) and ranged from 0.4 to 25 mm (average: 3.56 mm). The anatomic level of invasion in the skin (Clark's level) was determined for 70 patients (66%): 3, level II; 13, level III; 43, level IV; 11, level V. The administered dose of (18)F FDG ranged from 9.8 to 21.6 mCi (average: 15.4 +/- 1.8 mCi). FDG-PET/CT had a sensitivity of 89.3% [95% confidence interval (CI): 78.5-95] and a specificity of 88% (95% CI: 76.2-94.4) for melanoma detection. CONCLUSION: This study confirms the good results of FDG-PET/CT for residual/recurrent melanoma detection, as well as for distant metastases localization. PET/CT should be an integral part in evaluation of patients with high-risk melanoma, prior to selection of the most appropriate therapy.

Follicular dendritic sarcoma within a focus of Castleman's disease. Serial FDG PET/CT in the follow up of recurrence with histopathologic confirmation.

We report the case of a 30 year-old man with previous history of melanoma and new diagnoses of localized abdominal Castleman's disease with a focus of follicular dendritic sarcoma within the Castleman's tumor. He presented soon after with a single enlarged abdominal lymph node characterized and followed-up by FDG PET/CT as a low grade malignancy consistent with Castleman's recurrence. However, other imaging techniques raised the possibility of sarcoma/ melanoma recurrence. Final surgical resection allowed histological confirmation of the FDG PET/CT findings. To our knowledge, this is one of the few cases in the literature of Castleman's disease and follicular dendritic sarcoma association in the same focus. This is the first paper to our knowledge to use FDG PET/CT as the follow-up imaging tool for serial characterization of recurrence of Castleman's disease and follicular dendritic sarcoma. FDG PET/CT may be useful in the differentiation between Castleman's disease and malignancies associated with this disease.

Merkel cell carcinoma: Is there a role for 2-deoxy-2-[f-18]fluoro-D-glucose-positron emission tomography/computed tomography?

PURPOSE: 2-Deoxy-2-[F-18]fluoro-D-glucose (FDG)-positron emission tomography (PET)/computed tomography (CT) is becoming widely available as a powerful imaging modality, combining the ability to detect active metabolic processes and their morphologic features in a single study. The role of FDG-PET/CT is proven in lymphoma, melanoma, colorectal carcinoma, and other cancers. However, there are rare malignancies such as Merkel cell carcinoma that can potentially be evaluated with PET/CT. We were therefore prompted to review our experience with FDG-PET/CT in the management of patients with Merkel cell carcinoma. PROCEDURES: This is a retrospective case series of six patients with Merkel cell carcinoma, 58-81 years old (average 69 +/- 8.3), who had whole-body PET/CT at our institution from January 1st, 2003 to August 31st, 2005. Two patients were women and four were men. Reinterpretation of the imaging studies for accuracy and data analysis from medical records were performed. RESULTS: Twelve examinations were acquired for the six patients (one patient had six PET/CT, one patient had two PET/CT, and four patients had one PET/CT). The injected FDG doses ranged 381.1-669.7 MBq (average 573.5 +/- 70.3). Four patients had the PET/CT as part of initial staging, and two patients had the exam for restaging (after surgery and XRT). A total of six Merkel lesions (pancreas, adrenal, lip, submandibular lymph nodes, cervical lymph nodes, and parapharyngeal soft tissue) were identified in three patients and confirmed on histopathological examination. The FDG uptake in these areas was intense, with maximum standardized uptake value (SUVmax) values of 5-14 (average 10.4 +/- 3.8). In one patient, the PET/CT scan identified abnormal focal distal sigmoid uptake that was biopsied and diagnosed as adenocarcinoma. Two patients had negative scans and had no clinical evidence of disease on follow-up office visits (up to one year after PET/CT). CONCLUSIONS: This case series suggests that FDG-PET/CT may have a promising role in the management of patients with Merkel cell carcinoma.

Follicular dendritic sarcoma within a focus of Castleman's disease. Serial FDG PET/CT in the follow up of recurrence with histopathologic confirmation

Presentamos el caso de un varón de 30 años con historia previa de melanoma y nuevo diagnóstico de enfermedad de Castleman localizada en el abdomen, con un foco de sarcoma dendrítico folicular dentro del tumor de Castleman. Poco después presentó una adenopatía caracterizada y seguida con PET/TAC con FDG con criterio de bajo grado de malignidad concordante con una recurrencia de Castleman. Sin embargo, otras técnicas de imagen sugerían la posibilidad de recurrencia de sarcoma/melanoma. Una resección quirúrgica final permitió la confirmación histológica de los hallazgos de la PET/TAC con FDG. Hasta lo que sabemos, este es uno de los pocos casos en la literatura en el que aparece una asociación de enfermedad de Castleman y sarcoma dendrítico folicular en el mismo foco. Este es el primer trabajo, que sepamos, en el que se utiliza PET/TAC con FDG como herramienta de imagen para el seguimiento y caracterización seriada de la recurrencia de la enfermedad de Castleman y sarcoma dendrítico folicular. La PET/TAC con FDG puede ser útil en la diferenciación entre la enfermedad de Castleman y tumores malignos asociados con esta enfermedad

We report the case of a 30 year-old man with previous history of melanoma and new diagnoses of localized abdominal Castleman's disease with a focus of follicular dendritic sarcoma within the Castleman's tumor. He presented soon after with a single enlarged abdominal lymph node characterized and followed-up by FDG PET/CT as a low grade malignancy consistent with Castleman's recurrence. However, other imaging techniques raised the possibility of sarcoma/ melanoma recurrence. Final surgical resection allowed histological confirmation of the FDG PET/CT findings. To our knowledge, this is one of the few cases in the literature of Castleman's disease and follicular dendritic sarcoma association in the same focus. This is the first paper to our knowledge to use FDG PET/CT as the follow-up imaging tool for serial characterization of recurrence of Castleman's disease and follicular dendritic sarcoma. FDG PET/CT may be useful in the differentiation between Castleman's disease and malignancies associated with this disease