Gad Abikhzer

Altered Hepatic Metabolic Activity in Patients With Hepatic Steatosis on FDG PET/CT

OBJECTIVE FDG PET studies frequently use the liver as an internal reference organ to assess the significance of FDG uptake in pathologic processes involving other organs. The purpose of this study was to assess whether hepatic steatosis has a significant effect on the standardized uptake value (SUV) of the liver. SUBJECTS AND METHODS This prospective case-control study analyzed FDG PET/CT scans of patients with frank hepatic steatosis on the unenhanced CT portion of the study. Maximum SUVs (corrected for both body weight [SUV(bw)] and lean body mass [SUV(lbm)]) in 37 patients with hepatic steatosis were compared with those in 37 control patients without hepatic steatosis. RESULTS Patients with hepatic steatosis had statistically significant smaller mean (± SD) values than did the control subjects for liver SUV(lbm) (1.91 ± 0.57 vs 2.17 ± 0.36), liver SUV(lbm)-mediastinum ratio (1.23 ± 0.19 vs 1.35 ± 0.19), and liver SUV(bw)-mediastinum ratio (1.24 ± 0.16 vs 1.39 ± 0.22). CONCLUSION Hepatic steatosis results in a small statistically significant decrease in hepatic metabolic activity, as measured by FDG PET. However, because the degree of change is small, compared with healthy control subjects, this decrease is unlikely to have any clinical significance on the use of the liver as an internal reference organ.

Hypertrophic pulmonary osteoarthropathy diagnosed by FDG PET-CT in a patient with lung adenocarcinoma.

A 52-year-old man had a positron emission tomography computed tomography (PET-CT) scan for staging of a biopsy proven lung adenocarcinoma. An additional acquisition of the lower extremities was performed as the patient complained of bilateral leg pain. The PET-CT scan showed a 6.5 x 5.0 cm left upper lobe lung mass invading the mediastinum with maximal standardized uptake value of 10.7, compatible with primary lung cancer. The CT portion of the PET-CT of the legs showed extensive irregular bilateral periosteal new bone formation in the long bones. The PET images showed diffuse moderately increased FDG uptake in the periostea of the long bones of the legs, with some focal sites of more intense FDG uptake in the thicker portions of the periosteum. A bone scan showed mild hyperemia surrounding the long bones of the legs and intense Tc-99m MDP uptake in the periostea. The patient was diagnosed with hypertrophic pulmonary osteoarthropathy.

Tuberculous synovitis of the hip joint diagnosed by FDG PET-CT.

A 61-year-old woman with a history of lupus had a Positron emission tomography-computed tomography (PET-CT) scan as part of a malignancy workup for new cerebellar lesions. She had presented with new onset headaches. A CT scan of the thorax, abdomen, and pelvis, done 2 months earlier, had only shown an asymptomatic left hip joint effusion that was attributed to a nonerosive synovitis, possibly caused by her lupus. The PET-CT now showed extensive left acetabular and femoral head destructive bone lesions that had progressed significantly in 2 months, with associated intense 18F-fluoro-2-deoxy-glucose (FDG) uptake (maximal SUV 8.7). The left hip joint effusion also had intense FDG uptake. The hip joint was aspirated following the PET scan, and the synovial fluid grew mycobacterium tuberculosis. The PET-CT also showed an enlarged left iliopsoas bursa, which did not have FDG uptake and was therefore probably not infected.

Incidental Early Stage Endometrial Adenocarcinoma Diagnosed by F-18 FDG PET-CT, Which Was Negative on Ultrasound and Nonspecific on MRI

A 65-year-old woman with a history of gastric adenocarcinoma was referred for a follow-up F-18 FDG PET-CT scan. Although there was no evidence of recurrence of her gastric malignancy, there was an incidental finding of mild focal FDG uptake in the mid uterus. This was considered suspicious, especially in a postmenopausal woman, and she was referred for further imaging. Ultrasound did not find any abnormalities, and MRI re- ported a nonspecific focus of mild endometrial thickening. Extensive his- topathological sampling of the endometrium revealed a focus of intramucosal endometrial adenocarcinoma; the patient was diagnosed with Stage IA disease and treated surgically. This case demonstrates the importance of alerting referring physicians to even mildly FDG-avid focal abnormalities of the endometrium of postmenopausal women, despite normal or nonspecific correlative diagnostic imaging results. (Clin Nucl Med 2010;35: 265-266)

The appearance of osseous PEComa on F-18 FDG PET/CT.

A 29-year-old male presented with a 6-month history of left hip pain. Radiography and CT demonstrated a 6-cm lytic lesion of the left acetabulum. F-18 FDG PET for staging of the biopsy-proven malignant PEComa demonstrated intense hypermetabolism corresponding to the lytic left acetabulum. The patient underwent left hemipelvectomy with reconstructive surgery. On a follow-up F-18 FDG PET scan 3 months after initial surgery, a left lung pleural-based 9-mm nodule with hypermetabolism (SUVmax 4.1) was discovered and pathologically proven to be metastases from the primary osseous PEComa.

False positive high probability V/Q scan due to malignant obstruction of both pulmonary vein and artery.

A 64-year-old woman with known extensive metastatic breast cancer had a V/Q scan for suspicion of pulmonary embolism. The scan was interpreted as high probability. Due to the discordant clinical status and significant presumed clot burden, the patient underwent a pulmonary CT angiogram (CTA). No arterial embolus was seen and the perfusion defects were found to be caused by malignant obstruction of the left lower lobe pulmonary vein and right pulmonary artery. This high probability ventilation and perfusion (V/Q) scan was therefore a false positive scan for the detection of pulmonary embolus. (Clin Nucl Med 2009;34: 367–370) REFERENCES 1. Mallin WH, Silberstein EB, Shipley RT, et al. Fibrosing mediastinitis causing nonvisualization of one lung on pulmonary scintigraphy. Clin Nucl Med. 1993;18:594–596. 2. Park HM, Jay SJ, Brandt MJ, et al. Pulmonary scintigraphy in fibrosing mediastinitis due to histoplasmosis. J Nucl Med. 1981;22:349–351. 3. Bailey CL, Channick RN, Auger WR, et al. “High probability” perfusion lung scans in pulmonary venoocclusive disease. Am J Respir Crit Care Med. 2000;162:1974–1978. 4. PIOPED investigators. Value of the Ventilation/Perfusion scan in Acute Pulmonary Embolism. JAMA. 1990;263:2753–2759. 5. van Strijen MJ, de Monye W, Kieft GJ, et al. Diagnosis of pulmonary embolism with spiral CT as a second procedure following scintigraphy. Eur Radiol. 2003;13:1501–1507. 6. Mendelson S, Train J, Goldstein S, et al. Ventilation-Perfusion mismatch due to obstruction of pulmonary vein. J Nucl Med. 1981;22:1062–1063. 7. Stanley DC, Cho SR, Tisnado J, et al. Pulmonary arteriography in patients with hilar or mediastinal masses and lung scans suggesting pulmonary embolism. South Med J. 1981;74:960–964, 967. 8. Shields JJ, Cho KJ, Geisinger KR. Pulmonary artery constriction by mediastinal lymphoma simulating pulmonary embolus. AJR. 1980;135:147–150. Received for publication November 12, 2008; revision accepted February 18, 2009. From the Departments of *Nuclear Medicine, and †Radiology, Jewish General Hospital, Montréal, Québec, Canada. Reprints: Gad Abikhzer, MDCM, Department of Nuclear Medicine, Jewish General Hospital, 3755 Côte-Sainte-Catherine Road, Montréal, Québec, Canada H3T 1E2. E-mail: gad101@hotmail.com. Copyright

Whole-body bone SPECT in breast cancer patients: the future bone scan protocol?

ObjectiveThe aim of the study was to compare the detectability rate of bone metastases in breast cancer patients using whole-body single-photon emission computed tomography (WB-SPECT) performed with a half-time acquisition algorithm with that of planar±selected field-of-view SPECT [standard bone scintigraphy (BS)]. Materials and methodsNinety-two consecutive breast cancer patients (age range 35–74 years) underwent planar BS followed by WB-SPECT (acquisition time 28 min). Clinical and imaging follow-up data from BS, 18F-FDG-PET/CT and CT were used as composite reference standards. Institutional review board approval was obtained. For a review of standard BS results, data from a selected SPECT field-of-view were extracted from the WB-SPECT when requested by the readers. Diagnostic confidence of interpretation criteria were defined using a five-point level-of-confidence grading scale of lesions. ResultsBone metastases were diagnosed in 34 of 92 studies (37%). On patient-based analysis, the detectability rate of standard BS was 97% (33/34 patients) as compared with 100% for WB-SPECT (P=NS). On a lesion-based analysis, 268 foci were detected, including 124 metastases. Standard BS detected 195 lesions (73%; 99 metastases and 96 benign) and missed 73 lesions (25 metastases and 48 benign). WB-SPECT detected 266 lesions (99%; 124 metastases and 142 benign) and missed two benign foci because of SPECT reconstruction artefacts. The lesion-based detectability rate of metastases for standard BS was 80% compared with 100% for WB-SPECT (P<0.001). WB-SPECT was associated with a higher level of confidence compared with standard BS for both benign (P<0.01) and malignant lesions (P<0.05). ConclusionWB-SPECT is a useful tool for skeletal assessment, showing good performance in comparison with standard BS in breast cancer patients, and may eliminate the need for an initial planar scan.

Role of 18F-FDG PET/CT in the staging of pediatric peritoneal mesothelioma.

A 7-year-old girl with a 1-month history of diffuse abdominal pain underwent an ultrasound which showed a pelvic mass with multiple peritoneal implants and ascites. An US-guided core biopsy of one of the implants as well as a transrectal biopsy of the pelvic tumor showed pathological findings consistent with epithelioid mesothelioma. We describe the findings on (18)F-FDG PET/CT in pediatric peritoneal mesothelioma.

Submandibular salivary gland transfer: a pitfall in head and neck imaging with F-18 FDG PET/CT.

Xerostomia is a significant morbidity of radiation treatment in the management of head and neck cancers. To preserve salivary function, a surgical technique has been developed that involves the transfer of one submandibular gland to the ipsilateral submental space, where it can be shielded during radiation therapy. F-18 FDG PET/CT imaging characteristics of recently or remotely transferred submandibular glands have not been previously described in the literature. We report 2 cases of patients with surgically transferred submandibular glands, which highlight a potential pitfall in the interpretation of PET/CT of the head and neck region in oncologic patients.

Extraosseous Extension of Aggressive Vertebral Hemangioma as a Potential Pitfall on 68Ga-PSMA PET/CT

A 74-year-old man with newly diagnosed prostate cancer underwent Ga-PSMA PET/CT, which demonstrated intense uptake in and adjacent the L2 vertebral body. Subsequent MRI of the lumbar spine showed an aggressive L2 hemangioma with adjacent soft tissue extension. There was congruence of the intraosseous and extraosseous components of the hemangioma and the PSMA PET uptake. This is a rare but important potential pitfall in Ga-PSMA PET/CT-a soft tissue lesion with intense tracer uptake related not to a nodal metastasis of prostate cancer but to extraosseous extension of an aggressive vertebral body hemangioma.