Vickie Stipp

Medullary thyroid carcinoma imaged by Tc-99m MIBI SPECT and Tl-201 chloride/Tc-99m pertechnetate subtraction SPECT.

A 61-year-old man with medullary thyroid carcinoma and local invasion of the left lobe of the thyroid had Tc-99m MIBI SPECT and Tl-201 chloride/Tc-99m pertechnetate subtraction SPECT after left lobectomy of the thyroid, using a triple-headed gamma camera. Tl-201 chloride/Tc-99m pertechnetate subtraction demonstrated a large mass with high Tl-201 uptake in the left neck. Although there was intense uptake in the tumor in the left thyroid bed on Tc-99m MIBI neck SPECT, there was also uptake in both salivary glands and the right lobe of the thyroid gland. Thus, uptake in the right lobe of the thyroid gland and the salivary glands might not be differentiated from tumor invasion or metastasis from medullary cell carcinoma. Compared with MIBI SPECT, Tl-201 chloride/Tc-99m pertechnetate subtraction SPECT shows more apparent delineation of tumor uptake and may be a preferable technique.

Ring appearance on Tc-99m MIBI thoracic SPECTs and increased uptake on Tc-99m HMDP thoracic SPECTs in a pulmonary mass of small cell carcinoma

Tc-99m MIBI is taken up avidly by viable tumor tissue and does not accumulate in the necrotic carcinoma. We present a patient who underwent Tc-99m MIBI and Tc-99m HMDP thoracic SPECTs: a large area of increased MIBI uptake with central photopenia (ring appearance) in the right upper lung localizes bone imaging agent and does not localize multiple areas of intense uptake in the metastatic hilar mediastinum lymph nodes. Rapid growth of tumor cells in the lung leading to central necrosis/ischemia accounts for bone imaging agent localization in the tumor, as well as the ring-appearance of lung mass on Tc-99m MIBI imaging. These findings may reflect less viability of the lung tumor as compared with intense MIBI uptake in hilar/mediastinal lymph node uptake without bone agent localization.

Heterogenous Uptake on Brain SPECT

A 71-YEAR-OLD MAN with coronary artery disease and hypertension was admitted with a three-day history of fever, productive cough, and mental status changes. He had a past history of steroid-dependent chronic obstructive pulmonary disease (COPD) and a positive PPD with antituberculosis therapy. He had smoked three packs of cigarettes daily for 30 years and was a retired roofer who had been exposed to asbestos. Physical exam on admission revealed a lethargic individual with diffuse wheezing and an enlarged prostate. His blood pressure was 193/66 mm Hg. The chest radiograph on the day of admission showed a left-lower-lobe infiltrate with effusion. PPD was positive on the 4th hospital day. Laboratory findings included WBC 15.2 with 8 bands, Hct 43.7, sodium 130, potassium 3.4. Arterial blood gas data included pH 7.52, PCO2 40, PO2, 56, and oxygen saturation of 92%. The patient was started on Claforan and INH without alleviation of fever and confusion. A second chest radiograph, on the 7th hospital day, showed new right-and left-lower-lobe infiltrates. On the 10th hospital day, the patient developed fever, confusion, headache, nausea, and back pain. On the 12th hospital day a lumbar puncture revealed 40 WBC with 38% neutrophils, 62% monocytes, and no bacteria. For suspected bacterial meningitis the patient was treated with ampicillin and Claforan without improvement. Repeated lumbar puncture on the 16th hospital day showed 7 WBC and 128 RBC, positive for mycoplasma titers and cold agglutinins. Rheumatoid factor, ANA, lyme, legionella, RPR, and Mono TE tests, were all negative. CT studies performed on the day of admission and the 12th hospital day were also negative. Tc-99m HMPAO brain SPECT performed on the 21st hospital day showed irregular uptake throughout both cerebral hemispheres (Fig 1). Surface three-dimensional (3D) displays demon strated scattered multiple areas of hypoperfusion in both cerebral hemispheres (Fig 2). An EEG showed a generalized slowing of background activity and the presence of intermittent delta and theta activity, consistent with encephalopathy. Tc-99m DTPA brain images performed on the 24th day were negative. In addition to fever and deterioration of mcntal status, the patient developed abdominal pain. Amylase was 216, and GGT was 276; 2 days later lipase was 305 and amylase decreased to 134. Pancreatitis was suspected and cholescintigraphy suggested chronic cholecystitis. Because the patient became progressively delirious and developed meningeal symptoms, infectious encephalitis versus a toxic metabolic process was considered in the differential diagnosis. The patient died on the 35th hospital day. At autopsy, acute massive intracerebral hemorrhage and a 200-gm of blood clot in the left parieto-occipital lobe was found and considered to be the immediate cause of death. Microscopic exam confirmed cerebral necrotizing angiitis and cerebral amyloid angiopathy. Sporadic medium-to-small meningeal and parenchymal vessels exhibited fibrinoid necrosis of varied severity. Inflammatory cells, mainly lymphocytes, histiocyte, and a few multinucleate giant cells were also present. Occasional, affected vessels contained fibrin thrombi. No features of vasculitis in major basal arteries suggested generalized meningitis or encephalitis. Many of the small and medium-tosmall vessels in the leptomeninges and parenchyma displayed mildly intramural deposition of amyloid, confirmed by Congo-red strains and electron microscopic exam. Other final anatomic diagnoses included chronic microinfarctions of the caudate nucleus and left parieto-occipitai cortex, left ventricular hypertrophy, nephrosclerosis, pulmonary edema, hepatomegaly, moderate centrilobular emphysema, bronchopneumonia, and prostate adenocarcinoma. Cerebral amyloid angiopathy is characterized by the presence of amyloid in the walls of smalland medium-sized arteries and, less often, in the veins of brain parenchyma and adjacent leptomeninges. ~

A large photon-deficient area in the right thorax on Tc-99m MIBI thoracic SPECT resulting from a rapidly enlarging leiomyosarcoma.

A 64-year-old man with a history of leiomyosarcoma of the left eyebrow and the parotid gland, status postoperative irradiation, developed a rapidly enlarging mass in the right anterior thorax and was referred for Tc-99m MIBI SPECT. SPECT imaging showed a large photon-deficient area in the right mediastinum. Tc-99m RBC blood pool imaging also showed a large photon-deficient mass; CT of the thorax showed a huge necrotic mass. Aspiration biopsy of the mass yielded brownish necrotic fluid and spindle-type tumor cells were found in the necrotic fluid consistent with leiomyosarcoma. Rapia growth of the tumor led to bleeding and necrosis that resulted in a large photon-deficient area in the right anterior thorax on Tc-99m MIBI thoracic SPECT as well as on Tc-99m RBC images.

Bilateral perfusion defect/hypoperfusion in temporal and parietal regions on brain SPECT

T HE PATIENT was a 74-year-old man with dementia consistent with Alzheimers Disease for 8 years. He was provided complete supportive care at a local health and rehabilitation center. The patient underwent Tc-99m ECD brain single photon emission tomography (SPECT) on 4/25/95, surface three-dimensional (3D) display showed multiple perfusion defects in the posterior temporal, parietal, and frontal lobes (Fig 1) compatible with Alzheimers Disease. The patients last hospitalization was 7.5 months after the brain SPECT was performed for dysphagia, dehydration, hypokalemia, hypernatremia, and urinary tract infection. He died 8 months after the brain SPECT, and autopsy confirmed the diagnosis of Alzheimers Disease revealing characteristic neurofibrillary plaques and tangles in quantity sufficient for the pathologic diagnosis. Surface or volume 3D displays easily delineate the extension of cerebral cortical involvement, the displays view the brain from all angles and enhance and simplify SPECT images interpretation. 17 This image interpretation has been applied in stroke patients, 3,8 normal pressure hydrocephalus, 6 noncommunicating hydrocephalus] seizure, 8 depression, 9 and slow progressive apraxia) ~ Compared with baseline brain SPECTs, surface 3D images display an expanded perfusion defect with Diamox8,1~ the expanded defect represents the areas of failed vasodilatation. 1~ Three-dimensional displays can be applied to characteristic perfusion defects of Alzheimers Disease, such as in our patient. Bilateral posterior cortical defects, a pattern highly predictive of AD, may not be pathognomic for Alzheimers Disease. Other possibilities of such cortical perfusion defects are listed.

A mural thrombus of an infrarenal aortic aneurysm demonstrated as photon deficiency in a radionuclide study

Radionuclide angiogram (RNA) and aortogram may underestimate external aneurysmal diameter. Photon deficient areas are not uncommon along the abdominal aortic aneurysm (AAA) on RNA. To determine whether or not photon deficient areas along the aneurysm could represent a large thrombus, we studied radionuclide aortic angiography in thirty-eight patients during a preoperative cardiac gated study. All the patients (men, ages from 60 to 78) had CT, US, and/or aortogram for comparison. The presence of a thrombus was determined by CT, US, and/or surgical findings. Twelve of 38 (32%) patients’ RNA and blood pool images showed photon deficient areas along the aneurysmal walls having a large concentric or eccentric thrombus of the AAA. A large photon deficient area could be detected along the narrowing calibre of the aorta lumen. This finding results from a large mural thrombus being interposed between the left or right bowel/mesentery activity and the activity of the aneurysms functioning patent lumen. We concluded that a photon deficient area along an inferorenal aortic aneurysm may indicate a large thrombus of either eccentric or concentric type within an AAA.