Does radiotherapy affect regional bone formation?
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Bed Rest↗
Biomedical subjects
N D Charkes
Publications and source records attributed to N D Charkes.
Comparison of left anterior oblique and geometric mean gastric emptying.
A left anterior oblique image (LAO) and the geometric mean of anterior and posterior counts have both been proposed as methods for acquiring gastric emptying data. Both approaches are used to correct for the changes in attenuation that occur as the depth of radiolabeled solids changes during gastric emptying. These two methods were compared by using a power exponential curve fit to calculate a lag phase, an equilibrium emptying rate, and a half-time for gastric emptying in 20 patients. There were no significant differences (mean +/- 1 s.e.m.) in the measured half-emptying time (115 +/- 10 versus 104 +/- 7 min) (p = 0.08) or rate of gastric emptying (0.015 +/- 0.002 versus 0.015 +/- 0.002 min-1) (p = 0.56) for LAO imaging versus the geometric mean. However, the LAO measurements of the lag phase were significantly higher (69 +/- 7 min) than the geometric mean (53 +/- 6 min) measurements (p = 0.004). This resulted in 4/20 (20%) of patients with normal geometric mean lag phase measurements who would have been reclassified as abnormal using the LAO method.
Female↗
Thallium-201 SPECT increases detectability of thyroid cancer metastases.
Thallium-201- (201Tl) chloride is known to accumulate in metastatic foci of differentiated thyroid carcinoma, but small and deep-seated lesions are generally not detectable by planar imaging. We have evaluated the use of 201Tl-chloride single-photon emission computed tomography (SPECT) in 41 post-thyroidectomy patients with differentiated thyroid carcinoma and one with medullary carcinoma; planar imaging alone was done in eight additional patients (total 50). Of 20 patients with known metastatic disease, planar 201Tl images were positive in 12 (60%) but SPECT revealed an additional 5 (25%) who had metastases (total 85%). SPECT revealed foci as small as 1.0 cm in the neck and 1.5 cm in the lungs, and was particularly useful in detection of disseminated micronodular pulmonary metastases, especially in patients whose scans were negative with diagnostic doses of 131I. Some pitfalls in interpretation of the tomographic reconstructions were found. Thallium-201 SPECT is a marked improvement over planar imaging in the detection of metastases of differentiated thyroid cancer.
Adenocarcinoma↗
The two-component stomach: effects of meal particle size on fundal and antral emptying.
Using a dual-headed gamma camera and a standardized egg test meal labeled with 99mTc-sulfur colloid, the quantitative emptying of the total, proximal and distal stomach in five normal subjects was characterized. The same egg meal was given to the volunteers in 3 different forms: homogenized, and as 2.5 mm and 5.0 mm cubes on 3 separate occasions for a total of 15 studies. For the total stomach emptying, the lag phase and half emptying time (T1/2) obtained using a power exponential model were significantly shorter for the homogenized test meal than for the 2.5 mm and 5.0 mm cubed egg particles; the lag phases were 29 +/- 19 min (mean +/- SD) vs 55 +/- 26 (P less than 0.05) and 64 +/- 24 min (P less than 0.01), the T1/2's were 71 +/- 30 min vs 91 +/- 26 (P less than 0.05) and 104 +/- 30 min (P less than 0.05), respectively. For the proximal stomach, no statistically significant difference was observed among the 3 test meals; the T1/2s for the homogenized, 2.5 mm and 5.0 mm cubed meals were 65 +/- 26 min, 53 +/- 18 min and 64 +/- 20 min, respectively. For the distal stomach, both the peak activity (%) and time to peak activity (min) were significantly higher for the 2.5 mm cubes (43%, 54 min) and the 5.0 mm cubes (38%, 60 min) than for the homogenized eggs (16.4%, 30 min) (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Scintigraphic evaluation of gastric emptying: are radiolabeled solids necessary?
A standard, dual-isotope meal (Tc-99m-egg sandwich and In-111 DTPA in water) was administered to 14 normal volunteers and 37 patients, who had not undergone gastric surgery, to determine if the emptying characteristics of the liquid phase alone could accurately predict delayed solid emptying. Delayed gastric emptying was defined clinically as a solid half-emptying time more than two standard deviations greater than the mean for normal volunteers. Linear regression analysis was performed on the natural logarithm of liquid fractional retention at each time interval to yield a slope and y-intercept for each subject. There was no significant difference (0.6 less than P less than 0.8) between volunteers and patients with normal solid emptying for the liquid slope. In patients who exhibited delayed gastric emptying for solids, the liquid slopes were significantly different from the normal values (P less than .001). There was a high correlation of liquid slope to solid half-emptying time in all patients and volunteers (r = -0.80, P less than .001). Comparison of the liquid slope measurement to solid half-emptying time criteria revealed a sensitivity of 96%, a specificity of 100%, and a predictive value of 100% for the slope test. These results suggest that delayed gastric emptying can be accurately detected with a liquid-solid meal using only a single-liquid label.
Adult↗
Calculation of net renal uptake curves without use of a blood pool agent.
The usual method of generating net Hippuran renal uptake curves involves the administration of a blood pool agent. Two techniques are presented which permit the determination of net renal uptake curves from data intrinsic to the Hippuran study. This reduced the complexity of the procedure, as well as reducing its cost and decreasing the radiation exposure. The new procedures were tested in 9 patients and showed excellent correlation with the blood pool agent technique.
Humans↗
Myocardial infarct imaging with 99mTc-pyrophosphate and 99mTc-methylene diphosphonate: lack of correlation.
A prospective study of eight patients with recent transmural myocardial infarction was performed using 99mTc-Sn-pyrophosphate and 99mTc-Sn-methylene diphosphonate in each patient. All pyrophosphate scans were strongly positive whereas the diphosphonate scan was strongly positive in only one case. We conclude that 99mTc-Sn-pyrophosphate is preferable to 99mTc-Sn-methylene diphosphonate for myocardial imaging.
Diphosphates↗
The mode of action alginic acid compound in the reduction of gastroesophageal reflux.
This study was designed to evaluate quantitatively the mode of action of alginic acid compound (AAC) in the treatment of patients with symptomatic gastroesophageal reflux. Gastroesophageal scintigraphy using an orall administered Tc-99m sulfur colloid solution was used to demonstrate that AAC decreased significantly the gastroesophageal reflux index from (9.9 +/- 1.3) % to (6.5 +/- 0.8) % (p less than 0.05). No alteration of lower esophageal sphincter pressure was observed. After ACC was suitably labeled with Sr-87m, a dual-nuclide scintigraphic technique was used to show that most (greater than 75%) of the AAC was located in the upper half of the stomach in both normal subjects and patients with gastroesophageal reflux. In those subjects in whom reflux did occur after treatment with AAC, the Sr-87m-AAC refluxed into the esophagus preferentially compared with the liquid containing Tc-99m sulfur colloid. These findings suggest that AAC dimishes gastroesophageal reflux by means of its foaming, floating, and viscous properties.
Adult↗
Studies of skeletal tracer kinetics: II. evaluation of a five-compartment model of [18F]fluoride kinetics in rats.
We have evaluated a five-compartment model of [18F]fluoride kinetics in rats. The initial fluoride distribution was found to be similar to that of [77Br]bromide, a known extracellular-fluid (ECF) tracer, in agreement with the hypothesis underlying the model, and the measured uptake rate in rat bones compared well with the digital computer solution. Simpler models did not give a better fit. In dead rats, fluoride movement was found within the skeleton, presumably from bone ECF to bone substance, although not as rapidly as predicted or found in the live animal. Evaluation of the rate constants permitted estimates to be made of cardiac output, skeletal blood flow, and bone ECF volume, all in accord with independent measurements. It is suggested that skeletal blood flow at rest is a constant fraction of body weight, and probably subserves a hematopoietic as well as a mineralization function.
Animals↗
Studies of skeletal tracer kinetics. III. Tc-99m(Sn)methylenediphosphonate uptake in the canine tibia as a function of blood flow.
Experiments were performed in 14 dogs to study the effect of changes in bone blood flow on the tibial uptake of the skeletal tracer Tc-99m(Sn)methylenediphosphonate (Tc-99m MDP). Aortic blood was diverted through a pulsatile-flow pump in order to monitor and control femoral arterial blood flow. Tibial nutrient perfusion, as measured with labeled microspheres, paralleled the changes in arterial flow. We found that increments in bone blood flow up to four times normal produced only minimal augmentation of Tc-99m MDP uptake (mean = 33%), a markedly nonproportional relationship. The data points clustered about a predicted curve produced by perturbing the rate constants of a seven-compartment model obtained in normal dogs. These findings indicate that bone uptake of Tc-99m MDP is diffusion-limited, and they therefore cast doubt upon the validity of a method used for many years for estimating bone blood flow, the so-called skeletal tracer clearance technique. Nerve section, performed in 14 other dogs, augmented Tc-99m MDP uptake by about 50% at supranormal flows, suggesting a parallel-flow model of the microcirculation in bone, under sympathetic control. Such a model satisfactorily explains many scintigraphic findings in disease states.
Animals↗
The bone scan in thyroid cancer.
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Bone and Bones↗
Mechanisms of skeletal tracer uptake.
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Bone Diseases↗
Studies of skeletal tracer kinetics. I. Digital-computer solution of a five-compartment model of [18F] fluoride kinetics in humans.
We have developed a new model of short-term fluoride kinetics in humans and have solved the model on a digital computer using the SAAM-25 program. The solution accords well with available data. About 60% of intravenously administered [18F] fluoride is taken up by bone. Evaluation of the rate constants of tracer egress from blood indicates that about 17% of the cardiac output is distributed to the skeleton. When the model was perturbed to simulate changes in systemic or skeletal blood flow, we found that the system behaves in a nonlinear manner; even a five-fold increase in systemic or skeletal blood flow did not appreciably increase the amount of fluoride taken up by bone 1--2 hr later, the time when scans are usually made. A simulated increase in bone extraction rate, however, had a marked effect on bone-fluoride uptake. These findings suggest an important homeostatic role for bone in the regulation of blood calcium concentration and have considerable bearing on the interpretation of bone scans.
Bone and Bones↗
Nuclear medicine in motion.
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Decision Making↗
Preoperative bone scans. Use in women with early breast cancer.
Strontium nitrate Sr 87m bone scans were made preoperatively in a group of women with suspected breast cancer, 35 of whom subsequently underwent radical mastectomy. In 3 of the 35 (9%), the scans were abnormal despite the absence of clinical or roentgenographic evidence of metastatic disease. All three patients has extensive axillary lymph node involvement by tumor, and went on to have additional bone metastases, from which one died. Roentgenograms failed to detect the metastases in all three. Occult bone metastases account in part for the failure of radical mastectomy to cure some patients with breast cancer. It is recommended that all candidates for radical mastectomy have a preoperative bone scan.
Adult↗
Ultrasound evaluation of the thyroid.
Ultrasound provides a safe noninvasive means of imaging the thyroid gland. It affords a reliable method of distinguishing cystic masses from other types of hypofunctioning thyroid nodules that might require surgical exploration. Due to the reported small frequency of false positive ultrasonic diagnoses (i.e., solid or complex masses being misdiagnosed as cysts), all cystic masses should be confirmed by aspiration. With gray-scale two-dimensional imaging, high-frequency transducers, and careful attention to technique, a reduction in the number of incorrect diagnoses can be expected.
Cysts↗
Bone scanning: principles, technique and interpretation.
Bone scanning is most useful in the detection of bone metastases. The recent introduction of new radiopharmaceuticals and instrumentation has reduced the time needed to perform the study and its relative cost, while increasing the usefulness of the study in detecting roentgenographically occult diseases. Metastatic disease is used as the pathophysiologic model for understanding the principles of bone scanning. When a tumor invades bone, in addition to causing bone destruction, it also causes reactive bone formation or repair. It is here that radioisotopes are of considerable value, since some radionuclides are incorporated into the hydroxyapatite crystals of reactive bone. Bone repair is described as occurring in three phases. In Phase I, the roentgenogram shows no change in bone density, but the scan is abnormal. In Phase II, both scintigraphic and roentgenographic abnormalities increase, and in Phase III, when the osteoid has calcified completely, the roentgenogram shows radiodensities and the scan appears almost normal. Fewer than 5 per cent of patients have a normal scan in the presence of an abnormal roentgenogram. Presently, most bone scans are performed with phosphate compounds labeled with -99m-Tc. In the past, 85-Sr, 87M-Sr, and 18-F were more broadly used. Scanning may be performed on either a rectilinear scanner or a scintophoto (gamma) camera. Areas which are abnormal on bone scan should be interpreted with current roentgenograms in the light of clinical findings.
Autopsy↗