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Biomedical subjects

J S Laughlin

Publications and source records attributed to J S Laughlin.

At least 19 recordsLinked to original sources
PubMed1995

The quest for the laws governing radiations and the search for beneficial innovations.

The last few years of the 19th Century saw the initial discoveries of ionizing radiation. These seminal discoveries were followed by an era of intensive studies of the physics related to radiation and clinical applications. The quantum theory revolutionized the ideas about nuclear structure and had a major impact on the physics of radiation. The discoveries of artificial radioactivity and of the neutron and the associated nuclear research have led to the availability of a variety of labeled compounds important to the study of human metabolism. Radioimmunoassay is an example, while other labeled compounds have therapeutic significance. New concepts in the acceleration of electrons and positive ions have contributed to the ability to concentrate radiation energy. New concepts in physics have led to the development of significant and versatile forms of diagnostic imaging. An example is computed tomography. Magnetic resonance is another example of an important physical concept which, decades after its discovery, made possible important applications in imaging and spectroscopy. Unlike ionizing radiation, the less energetic radiofrequency photons can convey information about molecular bonds but do not have sufficient energy to break them. Photon and positron emission scanning and tomography provide external images of internal concentrations of radionuclides, permitting the noninvasive determination of function. Dosimetry is fundamentally important to the diagnostic and therapeutic uses of radiation at both microscopic and macroscopic levels. A variety of radiation measuring instruments have been designed and studied for different purposes, including those based on radiation chemical response. Mammography is just one of the diagnostic applications where dosimetry, detector sensitivity characteristics, the radiation energy spectrum and image resolution are all vital parameters. In radiation treatment, physical and mathematical developments and quantitative radiation biology have increasingly led to optimum conformal radiation treatment, with dosimetry as a guiding parameter.

Brachytherapy↗
PubMed1988

A comprehensive three-dimensional radiation treatment planning system.

A comprehensive software system has been developed to allow 3-dimensional planning of radiation therapy treatments using the extensive anatomical information made available by imaging modalities such as CT and MR. Biological structures of interest and tumor volumes are defined by outlines drawn on a sequence of CT slices. Beam set-ups may then be determined in three dimensions by displaying the structure contours in a beam's eye view, or in two dimensions using a single CT cut. Each beam defined may be shaped by the specification of block aperture contours, and its intensity may be modified with the use of planar compensators. 3D dose calculation algorithms are discussed. To evaluate the calculation results, dose volume histograms are provided, as well as various types of displays in two and three dimensions, including dose on arbitrarily oriented planes, dose on the surface of anatomical objects, and isodose surfaces. Computer generated beam films are also available as an aid in patient set-up verification. These tools, and others, provide the basis for a comprehensive 3D system that can be used throughout the treatment planning process.

Humans↗
PubMed1987

Imaging studies of patients with malignant fibrous histiocytoma using C-11-alpha-aminoisobutyric acid (AIB).

Alpha-aminoisobutyric acid (AIB), a synthetic, nonmetabolized amino acid which is rapidly transported into viable cells by the A-type or alanine-preferring amino acid transport system, has been labeled with the short-lived, positron-emitting radionuclide carbon-11. Carbon-11 labeled AIB is currently being evaluated as a tumor imaging agent for in vivo amino acid transport studies in patients with cancer. In this study, C-11 AIB was used to image two patients with malignant fibrous histiocytoma (MFH), a pleomorphic sarcoma. Following intravenous administration of C-11 AIB, tumors in the distal femur of one patient and in the anterior chest wall of another patient were well visualized using high energy gamma scintigraphy. Since therapy may alter the accumulation of amino acids in tumor tissue, studies using C-11 AIB in patients with MFH before and after chemotherapy are in progress.

Adult↗
PubMed1986

Tumor imaging with carbon-11 labeled alpha-aminoisobutyric acid (AIB) in a patient with advanced malignant melanoma.

A 29 year-old-man presenting with advanced metastatic malignant melanoma was successfully imaged using carbon-11 (11C) labeled alpha-aminoisobutyric acid (AIB), a synthetic, non-metabolized amino acid transported into viable cells by the A-type, or alanine-preferring, amino acid transport system. Tumor located in the hilum of the lung was well visualized with 11C-AIB prior to chemotherapy. A gallium image with liver subtraction using 99mTc-sulfur colloid demonstrated regions of increased activity in liver which correlated with regions of increased activity on the 11C-AIB liver image.

Adult↗
PubMed1986

Choice of optimum megavoltage for accelerators for photon beam treatment.

Over three decades ago, the development of megavoltage accelerators revolutionized radiation oncology and provided the therapist with photons and electrons of any desired energy. The initial advantages cited for high energy photon therapy, listed below, have proved valid and accelerators have almost totally replaced orthovoltage units. Initially, it appeared that most of these cited advantages should continue to improve with increasing energy, and there has been an impetus for the production of ever higher megavoltage accelerators. Some of these advantages are reviewed in this paper. Also, recent investigations have indicated increasing diffuseness of the photon beam boundary with increasing energy because of lateral transport of electrons. The impact on treatment planning as a function of energy of the increase in volume dose due to the diffuseness of beam boundaries, "build-down" and "rebuild-up" effects in tissues at cavity and inhomogeneity interfaces, bone absorption, and photoneutron production are discussed. Consideration of the behavior of these parameters indicates that optimum photon energies have been achieved and that the impetus for higher megavoltages is unwarranted for most treatment. For many therapeutic applications, there are major advantages of 4 MV to 8 MV photon beams relative to 60Co gamma rays. For large lesions in the abdomen or pelvis there is an advantage to energies above those provided by 15 MV units. The various considerations above are discussed and summarized as a function of lesion site and megavoltage.

Humans↗
PubMed1986

Physical aspects of radiation treatment. Some past and present developments with implications for the future.

Some aspects of the development and initial use of high energy photons and electrons are discussed, including the initial roles of Kerst and Quastler. Analytical developments in brachytherapy are also described. Relative to orthovoltages, the availability of high energy photons and electrons have provided the opportunity for concentration of ionizing energy anywhere in the body. Computer methods became necessary to handle the number of computations required in treatment planning, and the development of computerized treatment planning over the past 3 decades is sketched, with emphasis on current multidimensional planning. Both anatomical detail and dose distributions are now displayed in any arbitrary plane with radiation beams incident at any angle. The physical advantages of high energy photons are assessed, as well as increasing limitations with increasing energy, leading to determination of optimum photon energy ranges relative to lesion sites. A recent advance in the analysis of interstitial implants is discussed, which provides a basis for quantitative evaluation of implant systems and their application to specific cases. Further anticipated developments of these current advances are summarized.

Brachytherapy↗
PubMed1986

Imaging of human tumors and organs with N-13-labeled L-methionine.

The work described herein is the first reported use of nitrogen-13-labeled L-methionine in human subjects. Three volunteers and 14 patients with a variety of solid tumors were scanned after intravenous administration of L-(N-13) methionine. In both volunteers and cancer patients, uptake of label was seen in the liver and pancreas, with smaller amounts of label detected in the heart, urinary bladder, and salivary glands. Concentration of N-13 in tumor was seen in 12 of the 14 cancer patients. Five had repeat studies after chemotherapy; in each case, the change in tumor uptake of N-13 after N-13 methionine injection paralleled the clinical response to chemotherapy. Three patients had L-(N-13) glutamate scans the same day that they were studied with N-13 methionine. Concentration of the radiolabel in the tumor was very similar for the two compounds in each case. The systemic distribution of N-13 from methionine is similar to that from glutamate, except for a much smaller myocardial uptake and a prominent accumulation in the intestinal region. It is concluded that L-(N-13) methionine is potentially useful as a biologically significant agent for tumor visualization and assessment of therapeutic response.

Adolescent↗
PubMed1984

A computerized record and verify system for radiation treatments.

We have developed a general purpose, comprehensive, and highly reliable computerized Record and Verify System to detect and prevent mistakes in the delivery of external beam radiation therapy. This system helps prevent accidental delivery of dangerous dose, improves quality control, and provides invaluable record keeping and report generating capabilities. Currently, treatment machine and couch parameter settings of four different machines are monitored by the system and compared with prescribed values. The system inhibits a machine from being turned on if the settings do not agree with the prescribed values to within specified maximum permissible deviations. The system is user-friendly and provides useful, complete, and easily accessible data. We describe many aspects of the system including hardware, software, data, and operation, and we conclude with a brief discussion of clinical experience and preliminary data.

Computers↗
PubMed1984

Development of quality assurance in radiation therapy in North America.

Although diagnostic radiology developed rapidly following Roentgen's discovery, limitations on voltage delayed penetrating external radiation therapy until after World War II. Quality assurance has developed in both the USA and Canada in many different institutions. Tolerances for implementation of the prescribed tumor dose have been established. A series of quality assurance procedures for calibration, three dimensional dose distributions, the treatment planning process, and for treatment delivery have been formulated in protocols and their development is sketched briefly. The importance of computerized tomography in treatment planning and computerized record and verify systems in treatment delivery is emphasized.

Canada↗
PubMed1983

PET tomographic imaging of the human heart, pancreas, and liver with nitrogen-13 derived from [13N]-L-glutamate.

The first commercial version of the Massachusetts General Hospital (MGH) positron camera was used to image the relative distributions of 13N (T1/2 = 9.96 min) in the human heart, pancreas, and liver after intravenous administration of [13N]-L-glutamate. The instrument was operated in two imaging modes. Conventional 2-dimensional (2-D) focal-plane images showed high concentrations of 13N in the heart and pancreas, and lower levels in the liver. Five PET tomographic transverse section (3-D) images were made through the heart and three through the pancreas. Our results suggest that further studies designed to gain an improved understanding of the biochemistry of [13N]-L-glutamate aided by PET imaging, especially with newer instrumentation, are worthy of further investigation.

Aged↗
PubMed1983

Quantitative scanning of soft-tissue sarcomas with nitrogen-13-labeled L-glutamate.

Nitrogen-13-L-glutamate, a labeled amino acid enzymatically synthesized from cyclotron-produced N-13 ammonia and alpha-ketoglutaric acid, was used as an imaging agent in 14 patients with soft-tissue sarcomas. Concentration of nitrogen-13 label within the sarcoma was seen in 11 of the 14 patients; in some cases, clinically inapparent metastatic tumor lesions could also be detected. In eight patients, the tumor response to chemotherapy was evaluated by serial studies with this agent. In each case, the change in uptake of N-13 label by the sarcoma after therapy paralleled the clinical response to treatment. N-13-labeled L-glutamate may thus be of value as an imaging agent in the management of patients with soft-tissue sarcomas.

Adolescent↗
PubMed1982

Evaluation of the response to xenon-133 radiations by thermoluminescent dosimeters used during the accident at Three Mile Island.

An evaluation is presented of the accuracy and sensitivity of three types of TLD's used during the accident at the Three Mile Island Nuclear Station. This evaluation indicated that, due to the method of calibration, all the dosimeters over-responded to 133Xe radiations. The response ranged from slightly above unity to almost two. Exposures of the TLD's were of two types, namely, the characteristic X-rays either were or were not filtered from the beam. The angular sensitivity of the dosimeters is also reported.

Accidents↗
PubMed1982

Imaging of primary Ewing sarcoma with 13N-L-glutamate.

Eleven patients with untreated primary Ewing sarcoma were studied with intravenously administered 13N-labeled L-glutamate. Seven were repeatedly scanned during chemotherapy using this agent and 99mTc-methylene diphosphonate (99mTc-MDP). The untreated primary tumor was distinctly visualized with 13N-L-glutamate in all cases; the distribution of 13N label in the tumor sometimes differed from that of 99mTc. A kinetic study showed rapid uptake of 13N by tumor tissue. Repeat scans following therapy indicated that 13N-L-glutamate and 99mTc-MDP uptake showed changes consistent with histological findings following subsequent surgery. 13N uptake often decreased more markedly than 99mTc uptake during chemotherapy, but metastatic lesions were not visualized with 13N-L-glutamate. Tumor imaging with this labeled amino acid may be of value in assessing the response of primary Ewing sarcoma to chemotherapy.

Adolescent↗
PubMed1982

Scanning with L-(13 N) glutamate: Assessment of the response to chemotherapy of a patient with embryonal rhabdomyosarcoma.

The use of (13) N-labeled L-glutamate as an imaging agent in a patient with embryonal rhabdomyosarcoma is described. Localization of (13)N in a large, poorly defined tumor of the left pectoral region was seen, and clinically occult right axilliary metastases were also detected. A marked reduction in uptake in these areas occurred after chemotherapy, paralleling the clinical disappearance of tumor. These changes were verified on gallium scan. (13)N-labeled glutamate may be useful as an imaging agent, especially in patients with soft-tissue sarcomas.

Adult↗
PubMed1982

Imaging of brain tumors after administration of L-(N-13)glutamate: concise communication.

Cyclotron-produced L-(N-13)glutamate was used to visualize malignant intracranial tumors in 12 pediatric patients who had evidence of recurrent disease as documented by computed transaxial tomography (TCT). Imaging was performed using a rectilinear scanner, gamma camera, or a positron-emission tomograph (PET). The results indicate that N-13 is rapidly taken up by a majority of brain tumors following the administration of L-(N-13)glutamate, and that N-13 uptake is correlated with breakdown of the blood-brain barrier as demonstrated by contrast TCT or pertechnetate (Tc-99m) studies. The feasibility of using this agent in conjunction with PET is established.

Adolescent↗