Value of 18FDG PET scan in staging of ocular adnexal lymphomas: a large single-center experience.

Fluorine 18 deoxyglucose positron emission tomography ((18)FDG PET) is widely used in staging of non-Hodgkin's lymphomas (NHL), but very few studies have focused on its role in the initial staging of patients with ocular adnexal lymphoma (OAL). The aim of this study was therefore to evaluate the role of (18)FDG PET in the diagnosis of ophthalmologic lymphoma. A retrospective review of all imaging records, including computed tomography (CT), magnetic resonance imaging (MRI), and FDG PET, was performed. Forty-one OAL patients were included in the study. A pathologic review according to the World Health Organization classification showed 32 low-grade lymphoma patients (78%), including 26 mucosa-associated lymphoid tissue lymphomas (63%). Ophthalmologic sites were intra-orbital + lacrimal gland in 24 patients (59%), conjunctival in 13 patients (32%), multiple in 4 cases, and bilateral in 6 patients. (18)FDG PET was positive in orbital and conjunctival sites in 68 and 35% of cases, respectively. (18)FDG PET positivity was correlated with pathologic sites detected by MRI in 22/30 patients (73%); (18)FDG PET positivity was correlated with pathologic sites detected by CT in 25/34 patients (73%). This study shows that (18)FDG PET has a lower sensitivity than MRI to detect ophthalmologic lymphoma, particularly in non-conjunctival sites.

(18)F-FDG PET/CT bone/bone marrow findings in Hodgkin's lymphoma may circumvent the use of bone marrow trephine biopsy at diagnosis staging.

PURPOSE: Accurate staging of Hodgkin's lymphoma (HL) is necessary in selecting appropriate treatment. Bone marrow trephine biopsy (BMB) is the standard procedure for depicting bone marrow involvement. BMB is invasive and explores a limited part of the bone marrow. (18)F-FDG PET/CT is now widely used for assessing response to therapy in HL and a baseline study is obtained to improve accuracy. The aim of this retrospective analysis was to assess whether routine BMB remains necessary with concomitant (18)F-FDG PET/CT. METHODS: Data from 83 patients (newly diagnosed HL) were reviewed. All patients had received contrast-enhanced CT, BMB and (18)F-FDG PET/CT. Results of BMB were not available at the time of (18)F-FDG PET/CT imaging. RESULTS: Seven patients had lymphomatous involvement on BMB. Four patients had bone involvement on conventional CT (two with negative BMB). All patients with bone marrow and/or bone lesions at conventional staging were also diagnosed on (18)F-FDG PET/CT scan. PET/CT depicted FDG-avid bone/bone marrow foci in nine additional patients. Four of them had only one or two foci, while the other had multiple foci. However, the iliac crest, site of the BMB, was not involved on (18)F-FDG PET/CT. Osteolytic/sclerotic lesions matching FDG-avid foci were visible on the CT part of PET/CT in three patients. MRI ordered in three other patients suggested bone marrow involvement. Interim and/or end-therapy (18)F-FDG PET/CT documented response of FDG-avid bone/bone marrow foci to chemotherapy in every patient. CONCLUSION: (18)F-FDG PET/CT highly improves sensitivity for diagnosis of bone/bone marrow lesions in HL compared to conventional staging.

PET versus PET-CT in patient with suspicion of non-Hodgkin lymphoma recurrence.

We present the case of a 62-year-old patient with a history of non-Hodgkin lymphoma (stage III) in complete remission after 6 cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone with rituximab (CHOP-R) in 2006. The patient was referred for a PET-CT scan because of suspicion of recurrence. On PET there were multiple lung lesions, a submandibular lesion (right side) and an impressive retroperitoneal mass with a hypermetabolic wall, and central necrosis invading all retroperitoneal structures (aorta). There was also an additional lesion in the anterior abdominal wall below the liver. It was concluded that it was recurrent non-Hodgkin lymphoma (stage IV). Contrast enhanced CT demonstrated a large, rupturing abdominal aortic aneurysm (AAA) with saccular ectasia of the posterior wall compatible with a mycotic aneurysm. The other sites of hypermetabolism corresponded to metastatic infectious lesions. Histopathology confirmed the mycotic infection. The patient underwent urgent surgery including bilateral axillofemoral stenting and removing a clot from the AAA twice. Intravenous antibiotics were started. This case clearly denotes the importance of contrast enhanced hybrid PET-CT systems in which the CT information is relevant for PET interpretation and not only for anatomic repair. With PET alone, the diagnosis would have been completely different.

Non-invasive grading of brain tumours using dynamic amino acid PET imaging: does it work for 11C-methionine?

BACKGROUND: Static imaging of amino acids does not allow differentiation of low versus high grade brain tumours. It has been shown that dynamic imaging of the amino acid analogue (18)F-fluoroethyltyrosine (FET) can achieve this goal. In many centres, (11)C-methionine (MET) is used for tumour imaging, but no clinical studies on the use of dynamic scanning for grading have been performed. METHODS: Thirty-four patients with primary brain glioma and histopathological confirmation were retrospectively studied using 40 min dynamic MET-PET with 220 MBq 11C-methionine. In relation to histopathological grading, various metabolic indices and temporal parameters as documented by Poepperl et al. (JNM 2006;47:393-403) were analyzed. RESULTS: None of the evaluated static or temporal parameters allowed discrimination between high and low grade tumours. On average, low grade tumours showed washout after the initial uptake maximum, while both increases and decreases were seen for high grade tumours. Only the relative early versus late uptake ratio showed a trend towards significance (-0.16 +/- 0.17 for low grade versus 0.01 +/- 0.25 for high grade; p = 0.07). CONCLUSION: Unlike FET-PET, the uptake characteristics of MET-PET do not allow classification of low and high grade tumours on an individual patient basis. Since literature data indicate that both tracers have a similar performance regarding biopsy location, tumour delineation, and detection of recurrence, FET-PET should be advocated over MET-PET as its uptake mechanism also allows noninvasive grading in glioma.