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Biomedical subjects

J S Laughlin

Publications and source records attributed to J S Laughlin.

At least 37 records · Page 2Linked to original sources
PubMed1981

Quotient imaging with N-13 L-glutamate in osteogenic sarcoma: correlation with tumor viability.

An investigation was performed to correlate the regional uptake of N-13 L-glutamate with histologic changes in tumor tissue in patients undergoing adjuvant chemotherapy for osteogenic sarcoma. A parametric image was produced by calculating the ratio of N-13 uptake in the tumor in a pixel-by-pixel fashion, using the presurgical scan as the numerator and the pretherapy scan as the denominator. The change in N-13 uptake in 2 x 2-cm regions of the tumor was compared with residual cell viability as determined by microscopic examination of multiple thin sections obtained from the surgical specimens. Regions that showed decreases in N-13 uptake of more than 30% were frequently associated with areas of highly necrotic tumor, and regions that showed increasing uptake were associated with high residual cell viability and incomplete response to chemotherapy.

Adolescent↗
PubMed1981

Use of computerized tomography in dose calculations for radiation treatment planning.

The detailed anatomic information provided by CT scanners can be used to improve the accuracy of dose distribution calculations for radiation treatment planning. Commonly used methods for dose computations are described, with emphasis on their use with CT data, and measured data are presented to illustrate their relative merits. Modification of CT numbers to account for the difference in energies of diagnostic and therapeutic radiation is discussed. A description of a typical CT-based radiation treatment planning system is presented.

Humans↗
PubMed1980

Imaging of the human heart after administration of L-(N-13)glutamate.

In normal volunteers and cancer patients, studies using L-(N-13)glutamate as an imaging agent showed localization of N-13 activity in the heart. Other organs that were well visualized include the liver, pancreas, and salivary glands. In ten subjects the average myocardial uptake after intravenous injection of labeled glutamate was (5.7 +/- 0.39)% (s.e.m.) of injected dose, as determined by a quantitative scanning system. The concentration of N-13 activity in the human heart could not be predicted from previous studies involving myocardial uptake in dogs and rodents after administration of L-(N-13)glutamate.

Ammonia↗
PubMed1979

Absorbed radiation dose in mammography.

Radiation dose from mammographic techniques was determined as a function of surface exposure, beam quality, and depth. Relative exposure vs. depth was measured in tissue-substitute materials by thermoluminescent dosimetry. The f-factors were calculated from elemental compositions of mastectomy specimens. Dose at depth depends on beam quality as well as exposure and tissue composition. Analysis of data from the ACS/NCI Screening Centers shows current average midbreast doses to be 25 times lower (film/screen) and 3 times lower (Xerox) than the 2 rads previously estimated. Quantitative risk indicators other than midbreast dose are also discussed.

Adipose Tissue↗
PubMed1979

The dynamics of ammonia metabolism in man. Effects of liver disease and hyperammonemia.

The cyclotron-produced radionuclide, 13N, was used to label ammonia and to study its metabolism in a group of 5 normal subjects and 17 patients with liver disease, including 5 with portacaval shunts and 11 with encephalopathy. Arterial ammonia levels were 52-264 micron. The rate of ammonia clearance from the vascular compartment (metabolism) was a linear function of its arterial concentration: mumol/min = 4.71 [NH3]a + 3.76, r = +0.85, P less than 0.005. Quantitative body scans showed that 7.4 +/- 0.3% of the isotope was metabolized by the brain. The brain ammonia utilization rate, calculated from brain and blood activities, was a function of the arterial ammonia concentration: mumol/min per whole brain = 0.375 [NH3]a - 3.6, r = +0.93, P less than 0.005. Assuming that cerebral blood flow and brain weights were normal, 47 +/- 3% of the ammonia was extracted from arterial blood during a single pass through the normal brains. Ammonia uptake was greatest in gray matter. The ammonia utilization reaction(s) appears to take place in a compartment, perhaps in astrocytes, that includes less than 20% of all brain ammonia. In the 11 nonencephalopathic subjects the [NH3]a was 100 +/- 8 micron and the brain ammonia utilization rate was 32 +/- 3 mumol/min per whole brain; in the 11 encephalopathic subjects these were respectively elevated to 149 +/- 18 micron (P less than 0.01), and 53 +/- 7 mumol/min per whole brain (P less than 0.01). In normal subjects, approximately equal to 50% of the arterial ammonia was metabolized by skeletal muscle. In patients with portal-systemic shunting, muscle may become the most important organ for ammonia detoxification. Muscle atrophy may thereby contribute to the development of hyperammonemic encephalopathy with an associated increase in the brain ammonia utilization rate.

Adolescent↗
PubMed1979

Quantitative scanning of osteogenic sarcoma with nitrogen-13-labeled L-glutamate.

N-13 L-glutamate was used to image an osteogenic sarcoma in a 9-year-old patient. Serial quantitative measurements of the amount of N-13 taken up by the primary tumor showed a decrease of 40% after 10 wk of chemotherapy. Blood-clearance data obtained from normal subjects indicate that more than 90% of the N-13 activity had left the blood before scanning of the tumor was begun. It appears that the N-13 label concentrated in the soft-tissue portion of this osteogenic sarcoma, whereas Tc-99m diphosphonate uptake was greatest in the regions where calcification was occurring.

Child↗
PubMed1977

Radiation treatment planning.

Radiation treatment planning has developed into a substantial and effective component of the entire radiation treatment approach. Over the last 2 decades, with the development of high energy electron and x-ray sources, and also with the availability of new radionuclides and techniques for internally applied radiation, all of which permit a high degree of concentration of radiation, treatment planning has been developed to make best use of these modalities. The use of automatic computation has proved necessary in order to handle the large amounts of radiation data involved in treatment dose calculation. Tumor and anatomical localization has been carried out with increasing precision. Several cases are described which illustrate planning and in particular the use of computerized transverse tomography. The use of moving shadow-shields is also described. For internally applied radiation, the features of iodine-125 are illustrated.

Adult↗
PubMed1977

Imaging of spontaneous canine tumours with ammonia and L-glutamine labeled with N-13.

Ammonia and 6-glutamine, labeled with N-13, were tested as imaging agents for a variety of spontaneous canine tumors. The imaging capabilities of these compounds were compared with each other, with other scanning agents, and with radiologic and pathologic procedures. Good agreement between positive gamma images and postmortem findings occurred in 11 of 15 cases with [13N] ammonia as the localizing agent. Eight of the nine scans using [13N] glutamine as the imaging agent showed positive correlation with postmortem findings. In cases where both ammonia and glutamine were used to image the same lesion, no qualitative differences in tumor uptake were found between the two.

Ammonia↗
PubMed1976

Imaging of tumors involving bone with 13N-glutamic acid.

Nitrogen-13 labeled L-glutamic acid was evaluated as an imaging agent for tumors involving bone. The enzymatically prepared labeled compound was administered intravenously to dogs with spontaneous tumors, and tumor uptake was determined with a gamma camera and rectilinear scanner. These tumors were well visualized with 13N-glutamic acid, and the results compared favorably with uptake studies performed on the same animals with 99mTc-diphosphonate.

Animals↗
PubMed1976

Distribution and retention of 35S-sodium sulfate in man.

Measurements were made of the 35S content of tissues obtained from biopsies and autopsies made during and up to 6 months after treatment of chondrosarcoma or chordoma with carrier-free Na235SO4. Usually 70--90% of an intravenous dose was excreted in the urine during the first 3 days. The major component of the blood concentration had a biologic half-time of 0.4--0.7 days. The initial uptakes in chondrosarcoma, chordoma, and red bone marrow were high and nearly equal, but the rates of loss differed greatly. Uptake in epiphyseal cartilage was comparable to that in chondrosarcoma; uptake in other types of cartilage was lower, but subsequent loss was very slow. For an administered dose of 1 mCi per kilogram of body weight, the integrated radiation doses were 2.4 rads for blood, 33 rads for red bone marrow, 155 rads for chondrosarcoma, 49 rads for chordoma, and 135 rads for normal cartilage. Doses to muscle, skin, and fibrous tissue were 7--15 rads.

Adolescent↗
PubMed1976

Radiation dosimetry of 204Bi- and 206Bi-citrates.

The absorbed-radiation doses from 204Bi- and 206Bi-citrates to humans are calculated from available nuclear and biologic data in order to evaluate the relative radiation risk of these radionuclides. The calculations reveal that the radiation dose to the kidneys is reduced by a factor of 8 if 204Bi replaces 206Bi. This reduction suggests that 204Bi should be investigated further as a possible soft-tissue scanning agent.

Animals↗