The role of Tc-99m HMPAO functional brain imaging in detection of cerebral radionecrosis.

BACKGROUND: Cerebral radionecrosis is a possible complication of brain radiation therapy in patients with primary or metastatic tumors. This retrospective study evaluated the role of Tc-99m hexamethyl propyleneamine oxime (HMPAO) scintigraphy in monitoring the effects of radiation on the brain. METHODS: Ninety-eight patients (41 female, 57 male) with a mean age of 51 years (range, 16-82 years) underwent 128 sets of single-photon emission computed tomography studies. TI-201 and Tc-99m HMPAO single-photon emission computed tomography studies were performed for tumor localization and evaluation of the effect of radiation on the cerebral cortex. Thirty concomitant neuropsychological tests and 96 anatomic imaging (computed tomography/magnetic resonance imaging) were performed. The average radiation dose was 52 Gy delivered as 1.8 to 2 Gy/fraction. Thirty-two patients received an average dose of 160 mCi of I-125 EGFr concomitantly. The average follow-up period was 34 months. Abnormalities away from the tumor site were interpreted as positive on HMPAO studies, neuropsychological testing, or anatomic imaging; otherwise, they were classified as negative. RESULTS: There were 10/45 (22%) and 75/83 (90%) abnormal HMPAO study results before and after radiation therapy. The HMPAO studies compared with neuropsychological testing showed 3/13 (23%) and 14/17 (82%) concordant abnormalities in addition to tumor site in patients pre- versus postradiation therapy. There was better concordance of HMPAO and anatomic imaging in 22/30 (76%) patients versus 24/67 (36%) patients before radiation therapy. HMPAO imaging after radiation therapy revealed significantly more perfusion abnormalities. There were significant differences between all of the aforementioned parameters. CONCLUSION Tc-99m HMPAO imaging is useful in the evaluation of the effects of radiation therapy on the brain and is highly concordant with neuropsychological testing. It is superior to anatomic studies in identifying radiation-induced changes.

Contracted gallbladder: a cause of false-positive hepatobiliary scan in patients with cystic fibrosis.

Gallbladder nonvisualization on hepatobiliary scintigraphy in cystic fibrosis is generally secondary to cystic duct obstruction from inspissated bile, mucus, or gallstones. We report gallbladder nonvisualization on hepatobiliary imaging in two patients with cystic fibrosis who had contracted gallbladders on ultrasonography. Repeat ultrasonography at 6 months revealed persistent gallbladder contraction. A contracted gallbladder therefore is a potential cause of a false-positive hepatobiliary scan which can be treated with conservative management.

Clinical utility of technetium-99m methoxisobutylisonitrile imaging in differentiated thyroid carcinoma: comparison with thallium-201 and iodine-131 Na scintigraphy, and serum thyroglobulin quantitation.

Recently, technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) has been used to image thyroid carcinoma. A prospective study was performed to compare the efficacy of 99mTc-MIBI to thallium-201 (201Tl) scintigraphy in patients with differentiated thyroid carcinoma. The clinical utility of all radionuclide imaging modalities, i.e., 99mTc-MIBI, 201Tl, and iodine-131 Na (131I-Na), as well as serum thyroglobulin estimation, was evaluated. Thirty-four post-thyroidectomy patients (age range: 26-76 years) underwent 45 studies. Histopathologies studied included fourteen papillary, eight papillary-follicular, ten follicular, one Hürthle cell, and one medullary carcinoma of the thyroid. Following optimal stimulation of endogenous thyroid stimulating hormone (i.e, TSH 50 mU/ml), the patients underwent 201Tl and 99mTc-MIBI scintigraphy. Concomitant 131I-Na scintigraphy was performed and serum thyroglobulin levels were measured. Sixteen scan sets were performed prior to 131I-Na ablation therapy. Twenty-nine scan sets were performed following 131I-Na ablation therapy. The presence or absence of thyroid cancer was established by clinical, biochemical, radiologic, and/or biopsy findings. There was no significant difference in sensitivity and specificity of 201Tl scintigraphy versus 99mTc-MIBI scintigraphy in pre- and postablation studies. 131I-Na scintigraphy with determination of thyroglobulin level was sufficient in preablation studies. Among postablation patients, the addition of 99mTc-MIBI or 201Tl offered a higher diagnostic yield. Between the 201Tl and 99mTc-MIBI studies, there was a concordance of 69% in preablation and 97% among postablation patients (P=0.027). It is concluded that 99mTc-MIBI is a suitable alternative to 201Tl scintigraphy in thyroid carcinoma, especially following thyroidectomy and 131I-Na therapy. 131I-Na scintigraphy with serum thyroglobulin is adequate in both pre- and postablation patients. Among the post-131I-Na ablation patients, 99mTc-MIBI or 201Tl is extremely valuable for tumor localization, especially when the 131I-Na whole-body scan is negative. The combination of 99mTc-MIBI or 201Tl scintigraphy with 131I-Na and serum thyroglobulin offers the highest diagnostic yield.

Idiopathic peripheral pulmonary artery stenosis: an unusual cause of ventilation-perfusion mismatch.

Idiopathic peripheral pulmonary artery stenosis is a rare cause of ventilation-perfusion mismatch in adults. We report a 39-yr-old man with this entity. Pulmonary scintigraphy demonstrated findings indistinguishable from pulmonary embolism, and pulmonary angiography was necessary for accurate diagnosis.

The role of gallium-67-citrate in the detection of phenytoin-induced pneumonitis.

A patient with a history of cardiac transplant presented with a fever of undetermined etiology. The patient had been on multiple medications, including phenytoin, which can occasionally cause allergic or hypersensitivity pneumonitis. A chest x-ray and CT scan of the chest revealed no active disease. A 67Ga study was obtained after intravenous administration of 377.4 MBq (10.2 mCi) of 67Ga-citrate. The images showed diffuse intense lung uptake bilaterally. Bronchoscopic biopsy revealed hypersensitivity pneumonitis. Phenytoin was withdrawn and corticosteroid was started in therapeutic doses. A follow-up gallium study obtained 25 days after the baseline demonstrated marked improvement in the lungs with concurrent clinical recovery. This case illustrates the usefulness of 67Ga in the detection of drug-induced pneumonitis and in the follow-up of response to therapy.

Indium-111-labeled anti-EGFr-425 scintigraphy in the detection of malignant gliomas.

BACKGROUND: The monoclonal antibody anti-epidermal growth factor receptor (EGFr) antibody-425, against the epidermal growth factor receptor, has the potential to bind specifically to gliomas and not normal brain tissue. A prospective study was conducted (1986-1988) to evaluate the use of Indium-111 (111In)-labeled anti-EGFr-425 in the localization of gliomas before radioimmunotherapy with Iodine-125 (125I)-labeled anti-EGFr-425. METHODS: Twenty-eight patients with intracranial neoplasms were injected intravenously with an average dose of 2.2 mCi 111In-labeled anti-EGFr-425. Planar and single-photon emission computed tomography scans were performed after 48 and 72 hours. Control studies also were performed in two cases with 111In-labeled Co 17-1A (an antibody to colorectal cancer) and in one case with unlabeled 111In chloride. RESULTS: The immunoscintigraphic findings were generally in good agreement with computerized tomographic findings. The definitive diagnosis was established by biopsy findings: 23 gliomas (1 Grade I, 5 Grade II, 6 Grade III, and 11 Grade IV), 1 meningioma, and 4 metastatic lesions. The localization of gliomas with 111In-labeled anti-EGF-425 had a sensitivity of 0.96, a specificity of 0.60 and an accuracy of 0.90. CONCLUSION: Immunoscintigraphy with 111-In labeled anti-EGFr-425 can be useful in the management of malignant gliomas, especially before radioimmunotherapy with 125I-labeled anti-EGFr-425.

Paradoxical changes in iodine-131 scintigraphic findings in advanced follicular thyroid cancer.

We present the findings on iodine-131 (131I) scintigraphy, thallium-201 (201Tl) scintigraphy and quantitative thyroglobulin (QTG) estimation in two patients with follicular carcinoma of the thyroid with extensive metastases. The lesions were initially seen on 131I scintigraphs, but were not subsequently visualized with scanning doses of 131I (5 mCi), while retaining their ability to produce increasing amounts of thyroglobulin and take up 201Tl. Implications in choosing the appropriate diagnostic tests in the management of differentiated thyroid cancer are discussed.

The role of iodine-131 and thallium-201 imaging and serum thyroglobulin in the management of differentiated thyroid carcinoma.

BACKGROUND: A prospective study was conducted to evaluate the use of iodine-131 sodium scintigraphy, thallium-201 chloride scintigraphy, and quantitative serum thyroglobulin estimation in the detection of differentiated thyroid carcinoma after thyroidectomy and iodine-131 sodium ablative therapy. METHODS: Thirty-one patients with a median age of 45.6 years (range, 20-73 years) were included in the study. After optimal endogenous thyroid-stimulating hormone stimulation (> 50 mU/ml), 53 pairs of iodine-131 and thallium-201 scans were performed. Concomitant serum thyroglobulin levels were available for 32 pairs of scans. The presence or absence of thyroid cancer was established by clinical, radiologic, and/or biopsy findings. RESULTS: The concordance between iodine-131 and thallium-201 scan findings in the presence of disease (25 scan sets) was 36%. The concordance in the absence of disease (28 scan sets) was 82%. Iodine-131 scanning was found to be significantly better (P < 0.05) than thallium-201 scanning, in terms of sensitivity (0.8 versus 0.6), specificity (0.96 versus 0.82), accuracy (0.89 versus 0.72), and the predictive value of a positive test (0.95 versus 0.75). The measurement of serum thyroglobulin had a low sensitivity (0.3) in the study but had a specificity of 1.0. CONCLUSION: It was concluded that iodine-131 sodium scintigraphy is superior to thallium-201 scintigraphy and serum thyroglobulin estimation for the detection of residual or metastatic differentiated thyroid carcinoma. However, the use of combined modalities provides a higher diagnostic yield. Thallium-201 scintigraphy was especially useful in cases in which iodine-131 scintigraphy was negative and quantitative thyroglobulin levels were elevated.

Abnormal intracerebral thallium localization in a bacterial brain abscess.

A 56-yr-old man with a prior history of renal cell carcinoma had moderately intense abnormal localization of 201Tl-chloride in a solitary brain lesion which was discovered to be a bacterial abscess. The organisms isolated by culture included Actinomycosis odontolyticus, Peptostreptococcus and Hemophilus aphrophilus. Because of the clinical presentation, MRI characteristics and thallium scintigraphic findings, the lesion had been felt to represent either a primary or a metastatic neoplasm. This case illustrates the need for caution in the interpretation of thallium brain scintigram.

Malignant astrocytomas treated with iodine-125 labeled monoclonal antibody 425 against epidermal growth factor receptor: a phase II trial.

Twenty-five patients with primary presentation of malignant astrocytoma, astrocytoma with anaplastic foci, and glioblastoma multiforme were treated with surgical resection and definitive radiation therapy followed by intravenous or intra-arterial administration of Iodine-125 labeled monoclonal antibody-425, which binds specifically to human epidermal growth factor receptor. The patients presented with primary untreated disease, positive contrast enhanced computed tomography scans of the brain, and compatible clinical symptoms. In this Phase II clinical trial, the patients had surgical debulking or biopsy followed by definitively administered external beam radiation therapy and one or multiple doses (35 to 90 mCi per infusion) of radiolabeled antibody. The total cumulative doses ranged from 40 to 224 mCi. The administrations of the radiolabeled antibody were performed in most cases 4-6 weeks following completion of the primary surgery and radiation therapy. Ten patients had astrocytoma with anaplastic foci and 15 had glioblastoma multiforme. No significant life-threatening toxicities were observed during this trial. At 1 year 60% of the patients with astrocytoma with anaplastic foci or glioblastoma multiforme are alive. The median survival for both groups was 15.6 months.

Diagnostic significance of apparent abnormal bowel activity on Ga-67 scans in AIDS patients.

Twenty-one Ga-67 studies on 19 AIDS patients were analyzed to investigate the relationship between clinically acute gastrointestinal disease and abnormal scintigraphic bowel activity. Whole body images were obtained at times ranging from 4 to 192 hours, with most exams imaged at 48 and 72 hours. Abnormal bowel activity was observed in eight of 21 exams. Patients experienced acute GI disease during seven studies. Gallium scan results and clinical presentation agreed in 14 cases; both were abnormal in four and normal in 10. However, four exams showed abnormal activity in asymptomatic patients, while three normal studies were obtained in patients with clinically evident GI disease. Sensitivity was 57% and specificity 71%. Positive predictive value was .50 and negative predictive value .77. All true-positive cases were associated with Mycobacterium avium intracellulare (MAI) infection. This study implies that gallium imaging is unreliable for diagnosing acute bowel disease in AIDS patients, but may suggest a particular pathogen (MAI) in the symptomatic individual.

Altered biodistribution of gallium-67 in a patient with aluminum toxicity treated with desferoxamine.

Markedly altered biodistribution of [67Ga]citrate was observed in a 66-yr-old hemodialysis patient imaged at 48 hr postinjection. A review of the patient's hospital records revealed toxic serum levels of aluminum, treated with the chelating agent desferoxamine. Based on what is known about the biologic interactions between gallium, aluminum, transferrin, and desferoxamine, we believe that both toxic serum aluminum levels and desferoxamine therapy may cause altered biodistribution on [67Ga]citrate scintigraphy.

Mismatch between 99mTc-DTPA aerosol and 81mKr lung ventilation scintigraphy: a pitfall of radionuclide imaging.

Pulmonary ventilation and perfusion scintigraphies were performed using 99mTc-MAA, 81mKr, and 99mTc-DTPA aerosol in a patient with asthma. Lung perfusion scintigraphy and 99mTc-DTPA aerosol scintigraphy showed multiple matching defects, however, 81mKr ventilation scintigraphy showed mismatch with lung perfusion scintigraphy. A pitfall of this examination was discussed.

Triple-phase bone image abnormalities in Lyme arthritis.

Arthritis is a frequent manifestation of Lyme disease. Limited triple-phase Tc-99m MDP bone imaging of the wrists and hands with delayed whole-body images was performed in a patient with Lyme arthritis. This demonstrated abnormal joint uptake in the wrists and hands in all three phases, with increased activity seen in other affected joints on delayed whole-body images. These findings are nonspecific and have been previously described in a variety of rheumatologic conditions, but not in Lyme disease. Lyme disease should be considered in the differential diagnosis of articular and periarticular bone scan abnormalities.

Bone and gallium scintigraphy in a patient with bone sarcoidosis.

Periosteal reaction in bone lesions in patients with sarcoidosis is rare. We report a case with this type of bone sarcoidosis in whom bone and gallium scintigraphy were useful in detecting the lesions and making the diagnosis.

Aggressive lesion in osseous sarcoidosis.

We describe an unusual aggressive lytic bone lesion with "sunburst/hair-on-end" periosteal reaction in a patient with surgically proven osseous sarcoid and review the pertinent literature.