Barry McCook

Combined positron emission tomography/computed tomography imaging of recurrent thyroid cancer.

OBJECTIVE: The study goal was to evaluate the use of combined positron emission tomography/computed tomography (PET/CT) imaging for localization of recurrent disease in thyroid cancer patients. STUDY DESIGN AND SETTING: Eight patients with suspected recurrence of thyroid cancer on the basis of elevated serum thyroglobulin or calcitonin levels underwent combined PET/CT imaging on a prototype device. All 8 patients had previously undergone total thyroidectomy and 131I ablation for thyroid carcinoma. Patients with papillary carcinoma had negative 131I scans. RESULTS: Eight patients underwent combined PET/CT scanning. Four (50%) of 8 patients underwent PET/CT indicating recurrence in the head and neck. A total of 11 lesions in these 4 patients were suspicious for recurrence on combined PET/CT imaging. Three patients with 8 lesions suspicious for recurrence on PET/CT underwent surgical removal of disease. All 3 patients had pathologic confirmation of recurrence, with 6 (75.0%) of 8 lesions being positive. CONCLUSION: Combined PET/CT imaging is a valuable tool for the diagnosis and anatomic localization of recurrent thyroid cancer.

Physiologic uterine uptake of FDG during menstruation demonstrated with serial combined positron emission tomography and computed tomography.

F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has been used extensively to stage, restage, and follow neoplastic disease. However, focal accumulation of FDG may cause false-positive results in certain physiologic conditions. In this report, a unique PET and computed tomography (CT) combination scan helped define physiologic accumulation of FDG in the uterus during menstruation in a 40-year-old woman with a history of rectal melanoma and possible recurrent disease. An initial PET study, performed during menstruation, was followed immediately by a PET-CT scan, which showed marked accumulation of FDG in the posterior pelvis, localized to a retroverted uterus. An FDG PET-CT scan repeated 2 weeks later confirmed resolution of this “lesion.” Thus, combined PET-CT correctly differentiated physiologic FDG uptake in a retroverted uterus from recurrent rectal melanoma. This case shows that physiologic FDG accumulation in the uterus should be considered when focal FDG accumulation is observed in the pelvis in women of reproductive age.

Diffuse bone marrow uptake on whole-body F-18 fluorodeoxyglucose positron emission tomography in a patient taking recombinant erythropoietin.

F-18 fluorodeoxyglucose (FDG)–positron emission tomography (PET) is used extensively in oncology to diagnose, stage, and restage patients with various malignancies. Many patients treated for malignancies develop neutropenia secondary to marrow suppressive chemotherapy and are subsequently treated with synthetic hematopoietic growth factors (HGF), both granulocyte–macrophage colony-stimulating factor (GM-CSF) and granulocyte–colony-stimulating factor (G-CSF). Patients taking HGF can present a diagnostic challenge for those interpreting PET because they can demonstrate diffuse marrow uptake on FDG-PET scans, mimicking diffuse bone marrow metastases. It has not been reported whether bone marrow uptake is affected on PET scans in patients taking erythropoietin, the erythroid-specific cell-line stimulator. We report a case of extensive diffuse bone marrow uptake in a 77-year-old man with a history of colon cancer who began taking erythropoietin 3 weeks before his PET scan. This case demonstrates the need to consider erythropoietin in the differential diagnosis of possible etiologies causing diffuse bone marrow uptake on PET scans.

Full-Dose 90Y Ibritumomab Tiuxetan Therapy Is Safe in Patients with Prior Myeloablative Chemotherapy

Purpose: Targeted radioimmunotherapy with yttrium-90 (90Y)–labeled ibritumomab tiuxetan (Zevalin, IDEC-Biogen, San Diego, CA) has shown significant activity in the treatment of relapsed or refractory CD20+ non–Hodgkins lymphoma. Eligibility criteria used in phase I trials, and adopted in phase II and III trials, excluded patients with prior myeloablative therapy. We treated eight patients with 90Y ibritumomab tiuxetan who had prior autologous stem cell transplant, but met all other treatment criteria. Experimental Design: Eight patients with CD20+ non–Hodgkins lymphoma had extensive prior therapy including myeloablative chemotherapy but did not receive total body irradiation. Each had bone marrow cellularity of >15%, platelet count of >100,000/mm3, and one had documented lymphomatous bone marrow involvement of <25%. The standard course of 0.3 to 0.4 mCi/kg of 90Y ibritumomab tiuxetan was administered to patients at full dose. 18-Flouro-deoxyglucose positron emission tomography/computed tomography scans were done at pretreatment and ∼12 weeks after treatment to assess patient response. Maximum toxicities were monitored and classified according to the Common Terminology Criteria for Adverse Events (ver. 3.0). Results: Toxicities observed included grade 4 thrombocytopenia in three of eight evaluable patients and grade 4 neutropenia in one of eight evaluable patients. One patient had a neutropenic fever; all patients were off blood product support 12 weeks post-zevalin. Complete response by 18-flouro-deoxyglucose positron emission tomography/computed tomography imaging occurred in one of seven evaluable patients and one patient treated as consolidation had no evidence of disease. Conclusion: Our experience suggests that 90Y ibritumomab tiuxetan treatment is safe for use in patients with prior myeloablative therapy when the general inclusion criteria are fulfilled. In this small series, the response rates, however, are limited. Nevertheless, 90Y ibritumomab tiuxetan treatment may provide clinical benefit in carefully selected extensively pretreated patients.

Sequential FDG PET/CT in 90Y microsphere treatment of unresectable colorectal liver metastases.

The intra-arterial administration of Ymicrospheres (SIRSpheres, Sirtex Medical Ltd., Sydney, Australia) is a new palliative treatment option for unresectable colorectal liver metastases [1–4]. The Y-imprinted resin-based microspheres inducemicroembolisation of the hepatic and neovascular arterioles, thus delivering selective internal radiation. The figure shows transaxial PET/CT images of the upper abdomen with multiple liver metastases on CT and PET in both lobes of the liver (a: prior to treatment with Y microspheres). The right lobe was treated with 930 MBq (25.1 mCi) Y microspheres, resulting in a radiation dose of approximately 47 Gy. Two months after the treatment (b), the liver metastases in segment VI/VII demonstrated a marked reduction of FDG uptake to background level. The response on CT was less apparent, with partial improvement of the hypodense right lobe lesions. The dominant hypodense lesion in segment VI, which appears to have less response, is centrally hypometabolic on FDG-PET, likely secondary to tumour necrosis. The untreated metastases in the left lobe increased inmetabolic activity and tumour size. PET appears to reflect treatment response more accurately than does CT. References

Indium-111 pentetreotide imaging of carcinoid tumor of the thymus

Introduction: Carcinoid tumors are relatively rare and can occur in the thorax, abdomen, or pelvis. Indium-111 pentetreotide scanning is useful for the identification of these tumors. In this report, we present imaging findings and discussion pertaining to a 43-year-old man who presented with Cushings syndrome resulting from a thymic carcinoid tumor. The imaging is of interest because there is not only marked uptake of In-111 pentetreotide in the thymic carcinoid tumor, but also within the adrenal glands attributable to elevated tumor-derived ACTH. Method: Planar and single-photon emission computed tomography (SPECT) images of the chest and abdomen were obtained 15 minutes after the injection of 6.6 mCi of In-111 pentetreotide. Further planar and SPECT images were obtained approximately 4 and 24 hours after injection of the radiopharmaceutical. Correlation of In-111 pentetreotide SPECT was made with laboratory results and CT evaluation of the chest and abdomen. Results: Initial clinical workup for Cushings syndrome included a contrast-enhanced brain magnetic resonance image that showed a small pituitary lesion thought to represent a microadenoma. Normal inferior petrosal venous sinus sampling for ACTH suggested there was an ectopic ACTH source. Subsequent CT of the chest identified a 3 × 3-cm enhancing mediastinal mass. Avid uptake within the mass on In-111 pentetreotide images suggested that the underlying cause of Cushings syndrome was ACTH production from a thymic carcinoid. Increased uptake of In-111 pentetreotide was also noted within hyperplastic adrenal glands. Surgical resection and histologic evaluation established the diagnosis of a moderately differentiated thymic carcinoid tumor. Conclusion: This case illustrates the complementary ability of In-111 pentetreotide planar and SPECT imaging and CT to diagnose an ACTH-producing thymic carcinoid tumor leading to adrenal hyperplasia and Cushings syndrome.

Serendipitous detection of urothelial carcinoma with F-18 FDG PET/CT: usefulness of low intensity PET window setting in areas of high physiologic FDG distribution.

FDG PET/CT is widely accepted in diagnosing and staging various malignancies. However, the usefulness of PET in detecting urothelial tumors has been disputed because of high physiologic FDG excretion into the urinary bladder. Various techniques like bladder irrigation and furosemide administration have been employed to improve the diagnostic yield of PET. We report a patient who underwent PET/CT for staging or non-small cell lung cancer. Initial review of PET images in the pelvis was unremarkable, whereas the CT images revealed an exophytic lesion in the urinary bladder. Re-examination of the PET images under a low intensity window setting revealed intense FDG uptake in the lesion. Careful review of PET in different window settings in conjunction with CT images, especially in regions of high physiologic FDG distribution could facilitate detection of possible lesions.

PET/CT Protocols and Artifacts in the Head and Neck

Combined PET/CT has been in existence clinically for nearly 7 years since development and initial evaluation from 1998 to 2001. Combined PET/CT offers advantages over PET and CT acquired on separate devices, including consolidation of imaging studies, more accurate data coregistration, improved lesion localization, and benefits related to radiation therapy planning. This article discusses CT and PET protocols pertinent to PET/CT imaging in patients who have head and neck cancer, including a discussion of how the CT portion of a PET/CT scan can be performed and a description of common PET/CT artifacts that may be encountered secondary to CT protocols.