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Biomedical subjects

R S Hellman

Publications and source records attributed to R S Hellman.

At least 55 records · Page 3Linked to original sources
PubMed1989

False-negative radionuclide cisternography in massive communicating hydrocephalus: value of the vertex view and CT correlation.

Radionuclide cisternography evaluates cerebrospinal fluid dynamics, while CT and magnetic resonance imaging provide better information about central nervous system anatomy. This article describes two cases of patients with hydrocephalus. Their radionuclide cysternography studies were initially felt to be normal. After correlation with CT scans, massively enlarged ventricles were discovered. Tracer activity had refluxed into the ventricles, simulating normal cerebrospinal fluid rise over the convexities. When radionuclide cisternography studies in patients with excessively enlarged ventricles are interpreted, correlation with other anatomic imaging studies, such as CT and magnetic resonance imaging, is essential. A vertex view acquired during cisternography may also be helpful in correlation with transaxial plane images obtained by CT and magnetic resonance imaging.

Adult↗
PubMed1989

Alzheimer disease: quantitative analysis of I-123-iodoamphetamine SPECT brain imaging.

To enable a more quantitative diagnosis of senile dementia of the Alzheimer type (SDAT), the authors developed and tested a semiautomated method to define regions of interest (ROIs) to be used in quantitating results from single photon emission computed tomography (SPECT) of regional cerebral blood flow performed with N-isopropyl iodine-123-iodoamphetamine. SPECT/IMP imaging was performed in ten patients with probable SDAT and seven healthy subjects. Multiple ROIs were manually and semiautomatically generated, and uptake was quantitated for each ROI. Mean cortical activity was estimated as the average of the mean activity in 24 semiautomatically generated ROIs; mean cerebellar activity was determined from the mean activity in separate ROIs. A ratio of parietal to cerebellar activity less than 0.60 and a ratio of parietal to mean cortical activity less than 0.90 allowed correct categorization of nine of ten and eight of ten patients, respectively, with SDAT and all control subjects. The degree of diminished mental status observed in patients with SDAT correlated with both global and regional changes in IMP uptake.

Adult↗
PubMed1989

Technetium-99m ECD: a new brain imaging agent: in vivo kinetics and biodistribution studies in normal human subjects.

Lipophilic neutral 99mTc complexes of diaminedithiol (DADT) ligands cross the brain-blood barrier. A new derivative of DADT family, 99mTc ethyl cysteinate dimer (ECD) showed high brain uptake in nonhuman primates. We report here the in vivo kinetics and biodistribution results in 16 normal human subjects. Dynamic images of brain obtained for 10 min following an i.v. administration of [99mTc]ECD showed that the maximum 99mTc brain activity reached within 1 min and remained near that level for the next 10 min. The blood clearance of the tracer was very rapid and the activity remaining in blood after 5 min was less than 10%. Within 2 hr 50% of 99mTc activity was excreted in urine. Anterior and posterior total-body images were obtained at 5, 30, 60 min, 2, 4, 24, and 48 hr using a moving table at 20 cm/min. Percent injected dose was calculated for different organs and tissues. The brain uptake was 6.5 +/- 1.9% at 5 min postinjection and remained relatively constant over several hours. Two-compartment analysis of brain time-activity curve showed that 40% of brain activity washed out faster (T 1/2 = 1.3 hr) while the remaining 60% had a slower clearance rate (T 1/2 = 42.3 hr). Some of the tracer was excreted through the hepatobiliary system. Lung uptake and retention of [99mTc]ECD was negligible. Radiation dosimetry is favorable for the administration of up to 20-40 mCi of [99mTc]ECD. These results show that [99mTc]ECD is rapidly extracted and retained by the brain providing favorable conditions for single photon emission computed tomography imaging.

Adult↗
PubMed1989

Biodistribution, dosimetry, and clinical evaluation of technetium-99m ethyl cysteinate dimer in normal subjects and in patients with chronic cerebral infarction.

Technetium-99m ethyl cysteinate dimer (ECD) has high initial cerebral uptake with slow clearance in nonhuman primates suggesting ideal characteristics for single photon emission computer tomography (SPECT) imaging. We evaluated the biodistribution, dosimetry and scintigraphic pattern of [99mTc]ECD in normal subjects and the accuracy of SPECT imaging in patients with chronic cerebral infarction. Sixteen normal subjects were injected with approximately 10 mCi of [99mTc]ECD. Anterior and posterior single-pass whole-body images were obtained at multiple times after injection. Blood clearance of the radiotracer was rapid, falling to 10.0 +/- 6.6% and 4.9 +/- 1.1% of the injected dose at 2 and 60 min, respectively. Brain uptake was 6.4 +/- 2.1% of the injected dose 5 min after injection. The critical organ was the urinary bladder. Technetium-99m ECD SPECT was performed with a rotating gamma camera in ten of the 16 normal subjects and 34 patients with clinical and CT evidence of chronic stroke. Thirty-three of the thirty-four patients had focal [99mTc]ECD abnormalities on SPECT (97.1%) based on visual inspection of the SPECT images. In summary, we obtained high quality SPECT images as a result of the optimal physical and biologic characteristics of the tracer. Technetium-99m ECD SPECT shows promise for the evaluation of patients with stroke.

Cerebral Infarction↗
PubMed1989

Prospective comparison of radionuclide, computed tomographic, sonographic, and magnetic resonance localization of parathyroid tumors.

The appropriate choice of imaging techniques to localize parathyroid tumors preoperatively remains controversial. We report the first prospective, blinded study to compare the efficacy of four imaging modalities in 100 patients with primary hyperparathyroidism (pHPT). Patients were examined by computer-assisted thallium 201/technetium 99m subtraction scintigraphy (TTS), computed tomography (CT), ultrasonography (US), and magnetic resonance (MR). Each study was performed and interpreted independently. Subsequent neck exploration and "curative" parathyroidectomy allowed correlation of surgical findings with imaging reports to score their accuracy. Overall sensitivities of the four imaging modalities were TTS, 73%, CT, 68%, US, 55%; and MR, 57%; with respective specificities of 94%, 92%, 95%, and 87%. Sensitivities for lesions located below the thyroid gland (thymic tongue and mediastinum) were TTS, 90%; CT, 46%; US, 44%; and MR, 50%; with respective specificities of 100%, 99%, 100%, and 94%. There was a significant increase in overall sensitivity when TTS and CT (90%, p less than 0.01) or TTS and US (85%, p less than 0.05) were used together; however, the combination of any three or even four imaging modalities did not increase sensitivity further. For small parathyroid tumors (less than or equal to 250 mg), no imaging technique had a sensitivity of more than 50%. None of the imaging studies accurately localized small hyperplastic parathyroid glands found in patients with multiple gland disease. Preoperative parathyroid imaging may not be indicated in pHPT patients undergoing first-time neck exploration because surgeons experienced in parathyroid surgery have a 93% to 96% cure rate.

Adult↗
PubMed1989

The use of radionuclide cisternography in the diagnosis of pleural cerebrospinal fluid fistulae.

Radionuclide cisternography (RNC) is an excellent method of studying cerebrospinal fluid (CSF) dynamics and fistulous communications. Two patients are described in which pleural cerebrospinal fluid fistulae were found by this technique. In addition, marking the area presurgically reduced operating room time in one patient. Such communications are important to locate since they can cause significant loss of CSF as well as provide a pathway for pathogens to enter the central nervous system.

Adolescent↗
PubMed1988

False-negative bone imaging due to etidronate disodium therapy.

A 77-year-old man with prostate cancer was serially evaluated for bone metastases using Tc-99m methylene disphosphonate (Tc-99m MDP) both on and off treatment with etidronate disodium (EHDP). While the patient was receiving the medication only minimal bony uptake of the tracer was seen with the majority remaining in the soft tissues. The similarly structured EHDP probably saturated the binding sites that the radioactive MDP usually adheres to. Physicians should be aware of this interaction and may have to wait until the EHDP has been discontinued for several months before performing bone imaging on these patients.

Aged↗
PubMed1988

Accurate diagnosis of renal transplant rejection by indium-111 platelet imaging despite postoperative cyclosporin therapy.

Previous reports indicate that In-111 platelet scintigraphy (IPS) is a reliable test for the early diagnosis of acute post-operative renal transplant rejection (TR). However, the recent introduction of cyclosporin for post-transplantation immunosuppression requires that the diagnostic efficacy of IPS once again be established. Therefore, a prospective IPS study of 73 post-operative renal transplant recipients was conducted. Fourty-nine patients received cyclosporin and 24 patients did not receive this drug. Between these two patient groups, there were no significant differences in the diagnostic sensitivities (0.86 vs 0.80) and specificities (0.93 vs 0.84) with which TR was identified. We conclude that during the first two weeks following renal transplantation the cyclosporin treatment regimen used at our institution does not limit the reliability of IPS as a test for TR.

Adult↗
PubMed1988

Dipyridamole thallium-201 myocardial imaging. Complications associated with oral and intravenous routes of administration.

Previous reports have shown that TI-201 myocardial imaging with either an oral or intravenous administration of dipyridamole is a suitable diagnostic examination for patients at risk for coronary artery disease who cannot perform treadmill exercise. To compare the incidence of complications associated with these two routes of drug administration, the records of 78 oral and 97 intravenous dipyridamole TI-201 imaging studies were reviewed. The oral administration is associated with a significantly higher incidence of nausea (15% vs. 4%). Despite the higher incidence of nausea, the percentage of patients having one or more dipyridamole-induced symptoms was no greater for the oral (29%) than for the intravenous (37%) administration. Intravenous administration produced both a significantly higher incidence of atypical angina (14% vs. 4%) and a significantly greater increase in heart rate (16.6 vs. 10.2 beats per minute). No patient in either the oral or intravenous dipyridamole protocols had life-threatening arrhythmias or myocardial infarctions. In clinical practice, the difference in complications associated with the oral and intravenous administration of dipyridamole for TI-201 imaging is not significant.

Administration, Oral↗
PubMed1988

Comparison of technetium-99m pyrophosphate and technetium-99m DTPA aerosols for SPECT ventilation lung imaging.

Although [99mTc] diethylenetriaminepentaacetic acid (DTPA) is currently the most widely used radioaerosol, rapid alveolar clearance limits its usefulness for single photon emission computed tomography (SPECT) ventilation lung imaging. Previous research has shown that [99mTc]phosphate compounds have high alveolar deposition and slow clearance and thus provide suitable aerosols for pulmonary ventilation studies. We have compared the pulmonary retention and blood levels of [99mTc]pyrophosphate (PYP) and [99mTc]DTPA in eight normal nonsmoking male volunteers. These two radioaerosols have comparable pulmonary deposition. Technetium-99m PYP, however, has a much slower pulmonary clearance which allows sufficient time (20 or more minutes) for SPECT data acquisition using a single-headed rotating gamma camera. While the radiation absorbed dose to the lungs for [99mTc]PYP (0.31 rad/mCi) is greater than for [99mTc]DTPA (0.11 rad/mCi), it is at a clinically acceptable and safe level.

Administration, Inhalation↗
PubMed1987

Painful pseudarthrosis following lumbar spinal fusion: detection by combined SPECT and planar bone scintigraphy.

Twenty-six adult patients more than 6-months post-lumbar spinal fusion were studied. Flexion and extension radiographs showing motion or bone scintigrams showing focal areas of increased activity within the fusion mass were considered positive for pseudarthrosis. Patients were classified as either symptomatic or asymptomatic. Among the 15 symptomatic patients, scintigraphy had a sensitivity of 0.78 and a specificity of 0.83 which was superior to the 0.43 sensitivity and 0.50 specificity of radiography. Six of the 11 asymptomatic patients had focal areas of increased activity in the bony fusion mass, possibly reflecting painless pseudarthrosis. Planar imaging was substantially enhanced by SPECT in 14 of the 26 cases. It is concluded that for the patient who remains symptomatic after lumbar spinal fusion, bone scintigraphy with SPECT is of significant value in detecting painful pseudarthrosis.

Adult↗
PubMed1987

Bone SPECT.

Single photon emission computed tomography (SPECT) is a valuable addition to bone scintigraphy. SPECT removes from the diagnostic image unwanted activity which originates from in front and behind the tomographic plane of medical interest. This tomographic procedure allows one to examine with greater contrast and anatomic clarity such structures as the spine, hips, knees, and temporomandibular joints (TMJ). Abnormalities also seen on planar bone scintigrams often are more convincingly identified and better localized by SPECT. SPECT may even detect skeletal abnormalities not evident on planar views. These advantages of SPECT must be weighed against the superior resolution of planar bone scintigraphy. For this reason, SPECT complements, but does not replace planar bone scintigraphy. Including SPECT as an additional component of the skeletal examination does not place excessive demands on either gamma camera use or technologist time. Those nuclear medicine facilities offering bone SPECT for the evaluation of back, hip, knee, and TMJ pain should anticipate a larger volume of patient referrals.

Bone Diseases↗
PubMed1987

Use of SPECT to distinguish recurrent brain tumor from persistent activity at a craniotomy site.

A 50-year-old male underwent extensive left frontal lobe resection for a Grade II astrocytoma. Resection margins were free of tumor, and the patient suffered no significant postoperative neurologic deficits. One month later the patient was referred to radiation therapy for further evaluation and possible treatment. Unenhanced and enhanced transmission computed tomograms (CT) were interpreted as suspicious for recurrent tumor. However, using CT, which is essentially an anatomic technique, may not allow one to distinguish between surgical changes and the morbid anatomic findings of recurrent tumor. Because Tc-99m DTPA will cross the blood-brain barrier at sites of active intercranial disease, brain scintigraphy frequently is of value in distinguishing between recurrent tumor with an unstable blood-brain barrier and healed surgical changes with a stabilized blood-brain barrier. Therefore, clinicians requested that a Tc-99m DTPA brain scintigram be performed so as to distinguish between active disease and healed surgical changes.

Brain Neoplasms↗