Jacqueline Jerushalmi

Physiologic Thymic Uptake of 18F-FDG in Children and Young Adults: A PET/CT Evaluation of Incidence, Patterns, and Relationship to Treatment

18F-FDG uptake in the thymus, mainly related to hyperplasia after chemotherapy, has been described. Thymic uptake can challenge the accurate assessment of cancer patients by 18F-FDG imaging. The present study defines the incidence, patterns, and intensity of thymic 18F-FDG uptake in relationship to age and time after treatment in a large cohort of patients. Methods: A total of 559 consecutive 18F-FDG PET/CT studies in 160 patients (86 men, 74 women; age, 3–40 y) performed at baseline, during treatment, at the end of treatment, and during follow-up were retrospectively reviewed. PET/CT studies were assessed for the presence or absence (T+ or T−, respectively), pattern, and intensity (SUVmax) of increased 18F-FDG uptake in the anterior mediastinum, localized by the CT component to the thymus. The overall incidence of 18F-FDG avidity in the thymus in relationship to the patients age and time after treatment administration were statistically evaluated. Results: There were 137 of 559 T+ studies (25%), with equal sex distribution. T+ studies were found in significantly younger patients (20.6 ± 9.3 y vs. 27.4 ± 8.4 y, P < 0.001). Most T+ patients (60%) showed an inverted V pattern of thymic uptake, with additional unilateral mediastinal extension in 24% and focal midline uptake in 16% of studies. T+ studies were encountered in 80% of patients younger than 10 y, compared with 8% of patients in the 31- to 40-y age group. There were 17% T+ studies at baseline, 6% during treatment, 8% at the end of treatment, and 27%–40% during follow-up. The average SUVmax of thymic 18F-FDG uptake was 3.73 ± 1.22. Conclusion: Thymic 18F-FDG uptake was found in 28% of the present study population, more frequently after treatment. T+ patients were significantly younger. Thymic uptake was found in 73% of untreated patients up to the age of 13 y and in 8% of patients in the fourth decade of life. Knowledge of this age- and treatment-related incidence of physiologic thymic 18F-FDG avidity can reduce the number of potential pitfalls in reporting PET/CT studies in cancer patients.

Spectrum of scintigraphic appearance of liver hemangiomas.

Two hundred and twenty five liver hemangiomas in 166 patients were studied with Tc-99m labeled RBC and are the basis for this atlas. All hemangiomas showed various presentations of the perfusion blood pool mismatch, which is the basis for diagnosis. The size of the hemangiomas was the factor that determined the mixing of the Tc-99m RBC with the blood and, hence, the sequence of visualization of the lesion. Hemangiomas may appear as multiple lesions on liver scan and imitate metastases. Ninety-five hemangiomas appeared in 36 patients as multiple local abnormalities. Hemangiomas are extremely variable in size. They may be huge (31 hemangiomas) and sometimes occupy most of the abdomen. Or they can be very small and are then detected only by SPECT (two cases). Thrombosed large hemangiomas appear as focal defects on Tc-99m RBC.

Normal and abnormal Ga-67 SPECT anatomy in patients with lymphoma

The appearance of normal Ga-67 SPECT images in the coronal, sagittal and transaxial planes is described. The normal tomographic appearance of bone, liver, spleen, and gut is shown and compared with disease involvement above and below the diaphragm.

Kohler disease: diagnoses and assessment by bone scintigraphy.

Limping is a frequent occurrence in children and may be caused by various conditions, including trauma, inflammation, infection, and malignancy. Nontraumatic avascular necrosis of the tarsal bones should be included in the differential diagnosis. Accumulated data have supported the superiority of bone scans to radiography in the early diagnosis of avascular necrosis. Bone scintigraphy is a useful tool for investigating pain when symptoms, laboratory examinations, and radiography do not point to a specific diagnosis. In the early phase of disease, bone scans may demonstrate decreased tracer uptake (photopenic region), subsequently a hot area is seen during the reparative process. Although magnetic resonance imaging has important implications in the diagnosis of avascular necrosis, bone scintigraphy with its ready availability has a significant role as a primary tool in the evaluation of a limping child.

Imaging of primary sternal osteomyelitis in a patient with Crohn's disease

A 41-year-old man with known Crohns disease presented with chest pain and fever. Plain film and CT of the chest were normal, but bone scan and gallium scans showed intense sternal uptake. Surgery revealed staphylococcal osteomyelitis of the sternum. Following appropriate antibiotic treatment, the patients symptoms resolved and follow-up gallium scans became normal. This is the first report of the association of sternal osteomyelitis and Crohns disease, although other sites have been described. Sternal osteomyelitis has a high morbidity and the index of suspicion for this condition must be high even in the face of initially negative imaging.

Super scan leading to definitive diagnosis in a patient with recurrent syncope.

A “super scan” pattern detected on bone scintigraphy usually indicates either metabolic bone disease or diffuse metastases. We report a rare case of a 45-year-old man with recurrent episodes of syncope of 10 years’ duration in whom bone scintigraphy showed a super scan with an axial skeleton distribution of uptake. Bone marrow biopsy established the diagnosis of systemic mastocytosis. The few reports in the literature of super scans associated with systemic mastocytosis showed diffuse axial and appendicular increased uptake. The present case shows a super scan involving the axial skeleton, which led to the diagnosis of systemic mastocytosis.

Shoulder pain in a young break-dancer evaluated with bone scintigraphy.

We report the case of an 18-year-old male breakdancer evaluated with bone scintigraphy for shoulder pain. Bone scintigraphy showed intense tracer uptake in both sholders. Dance-related injury is well described in the literature, and classically involves the feet and ankles, but breakdance injuries, which may involve any part of the body, have been reported only infrequently. We report here a case of shoulder injury related to breakdance demonstrated on bone scintigraphy.

Contracted gallbladder in hepatitis. Value of postprandial examination.

A completely contracted gallbladder is occasionally seen in patients with acute hepatitis. We have observed that postprandial examination in these patients shows the gallbladder filling with bile to a degree that permits an adequate diagnostic examination. This simple procedure may prevent having to recall the patient for follow-up examination.

Calcifying fibrous pseudotumor: a rare benign tumor detected on bone scintigraphy.

Calcifying fibrous pseudotumor (CFP) is a rare and recently recognized benign tumor of the soft tissue. It occurs most commonly in children and young adults. It is usually asymptomatic and may be detected incidentally. It is important to recognize CFP because it may be easily mistaken for a primary or metastatic tumor. Dense calcium deposition is a histologic finding that characterizes this tumor. Bone scintigraphy could be a useful imaging method in the assessment of these patients, because avid uptake of Tc-99m MDP would be expected. The authors report a case of abdominal wall CFP detected on bone scintigraphy in an adult. The lesion was initially thought to be a metastasis, but its true nature was revealed after excisional biopsy. This is the first report of the findings of CFP on bone scintigraphy.

Post-radiation vesicocolonic fistula demonstrated on bone scintigraphy

An 81-year-old man with prostate carcinoma and known lung and bone metastases underwent prostatectomy followed by radiotherapy 8 years previously. Whole-body bone scintigraphy demonstrated unexpected diffuse colonic uptake (a). The patient had suffered from recurrent urinary tract infection, haematuria, faecaluria and recurrent diarrhoea during the previous several months. Therefore, cystography was performed that revealed a fistulous communication between the bladder and the caecum (b). Most likely the fistula is related to the radiation therapy the patient had received in years past. Its presence explains the radionuclide flow from the bladder to the intestine as well as the low radionuclide concentration in the urinary bladder. A urinary fistula should always be considered when a communication between the gastrointestinal tract and the genitourinary system is detected or when the radionuclide is demonstrated in the surrounding tissue of the bladder. Most fistulas occur as a complication of abdominal surgery or trauma. A spontaneous fistula is usually the result of intra-abdominal inflammation or infection and is associated with higher mortality and morbidity rates as well as increased health care costs for diagnosis and treatment. [1–4]. It is of utmost importance to correlate this prominent imaging finding with patient history. References