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Introduction: Sentinel lymph node biopsy (SLNB) is a standard practice for staging cutaneous melanoma. High false-negative rates have an increased interest in adjunctive techniques for localizing SLNs. Mobile gamma cameras (MGCs) represent potential tools to enhance SLNB performance., Methods: An institutional review board approval was obtained for this study (ClinicalTrials.gov ID NCT01531608). After obtaining informed consent, 20 eligible melanoma patients underwent 99m Tc sulfur colloid injection and standard lymphoscintigraphy with a fixed gamma camera (FGC). A survey using a 20 cm square MGC, performed immediately preoperatively by the study surgeon, was used to establish an operative plan while blinded to the FGC results. Subsequently, SLNB was performed using a gamma probe and a novel 6 cm diameter handheld MGC., Results: A total of 24 SLN basins were detected by FGC. Prior to unblinding, all 24 basins were identified with the preoperative MGC and the operative plan established by preoperative MGC imaging was confirmed accurate by review of the FGC images. All individual sentinel lymph nodes were identified during intraoperative MGC imaging, and in 5/24 (21%) cases, surgeon-reported additional clinically useful information was obtained from the MGC., Conclusions: Preoperative MGC images provide information consistent with FGC images for planning SLNB and in some cases provide additional information that aided in surgical decision-making., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Assessment of lymphatic status via sentinel lymph node (SLN) biopsy is an integral and crucial part of melanoma surgical oncology. The most common technique for sentinel node mapping is preoperative planar scintigraphy of an injected gamma-emitting lymphatic tracer followed by intraoperative node localization using a non-imaging gamma probe with auditory feedback. In recent years, intraoperative visualization of SLNs in 3D has become possible by coupling the probe to an external system capable of tracking its location and orientation as it is read out, thereby enabling computation of the 3D distribution of the tracer (freehand SPECT). In this project, the non-imaging probe of the fhSPECT system was replaced by a unique handheld gamma camera containing an array of sodium iodide crystals optically coupled to an array of silicon photomultipliers (SiPMs). A feasibility study was performed in which preoperative SLN mapping was performed using camera fhSPECT and the number of detected nodes was compared to that visualized by lymphoscintigraphy, probe fhSPECT, and to the number ultimately excised under non-imaging probe guidance., Results: Among five subjects, SLNs were detected in nine lymphatic basins, with one to five SLNs detected per basin. A basin-by-basin comparison showed that the number of SLNs detected using camera fhSPECT exceeded that using lymphoscintigraphy and probe fhSPECT in seven of nine basins and five of five basins, respectively. (Probe fhSPECT scans were not performed for four basins.) It exceeded the number excised under non-imaging probe guidance for seven of nine basins and equaled the number excised for the other two basins., Conclusions: Freehand SPECT using a prototype SiPM-based gamma camera demonstrates high sensitivity for detection of SLNs in a preoperative setting. Camera fhSPECT is a potential means for efficiently obtaining real-time 3D activity distribution maps in applications such as image-guided percutaneous biopsy, and surgical SLN biopsy or radioguided tumor excision.

Purpose: This study investigated a novel gamma camera for molecular breast tomosynthesis (MBT), which is a nuclear breast imaging method that uses limited angle tomography. The camera is equipped with a variable angle, slant-hole (VASH) collimator that allows the camera to remain close to the breast throughout the acquisition. The goal of this study was to evaluate the spatial resolution and count sensitivity of this camera and to compare contrast and contrast-to-noise ratio (CNR) with conventional planar imaging using an experimental breast phantom., Methods: The VASH collimator mounts to a commercial gamma camera for breast imaging that uses a pixelated (3.2 mm), 15 × 20 cm NaI crystal. Spatial resolution was measured in planar images over a range of distances from the collimator (30-100 mm) and a range of slant angles (-25° to 25°) using 99m Tc line sources. Spatial resolution was also measured in reconstructed MBT images including in the depth dimension. The images were reconstructed from data acquired over the -25° to 25° angular range using an iterative algorithm adapted to the slant-hole geometry. Sensitivity was measured over the range of slant angles using a disk source. Measured spatial resolution and sensitivity were compared to theoretical values. Contrast and CNR were measured using a breast phantom containing spherical lesions (6.2 mm and 7.8 mm diameter) and positioned over a range of depths in the phantom. The MBT and planar methods had equal scan time, and the count density in the breast phantom data was similar to that in clinical nuclear breast imaging. The MBT method used an iterative reconstruction algorithm combined with a postreconstruction Metz filter., Results: The measured spatial resolution in planar images agreed well with theoretical calculations over the range of distances and slant angles. The measured FWHM was 9.7 mm at 50 mm distance. In reconstructed MBT images, the spatial resolution in the depth dimension was approximately 2.2 mm greater than the other two dimensions due to the limited angle data. The measured count sensitivity agreed closely with theory over all slant angles when using a wide energy window. At 0° slant angle, measured sensitivity was 19.7 counts sec -1 μCi -1 with the open energy window and 11.2 counts sec -1 μCi -1 with a 20% wide photopeak window (126 to 154 keV). The measured CNR in the MBT images was significantly greater than in the planar images for all but the lowest CNR cases where the lesion detectability was extremely low for both MBT and planar. The 7.8 mm lesion at 37 mm depth was marginally detectable in the planar image but easily visible in the MBT image. The improved CNR with MBT was due to a large improvement in contrast, which out-weighed the increase in image noise., Conclusion: The spatial resolution and count sensitivity measurements with the prototype MBT system matched theoretical calculations, and the measured CNR in breast phantom images was generally greater with the MBT system compared to conventional planar imaging. These results demonstrate the potential of the proposed MBT system to improve lesion detection in nuclear breast imaging., (© 2017 American Association of Physicists in Medicine.)

This paper describes the development of a hand-held gamma camera for intraoperative surgical guidance that is based on silicon photomultiplier (SiPM) technology. The camera incorporates a cerium doped lanthanum bromide (LaBr 3 :Ce) plate scintillator, an array of 80 SiPM photodetectors and a two-layer parallel-hole collimator. The field of view is circular with a 60 mm diameter. The disk-shaped camera housing is 75 mm in diameter, approximately 40.5 mm thick and has a mass of only 1.4 kg, permitting either hand-held or arm-mounted use. All camera components are integrated on a mobile cart that allows easy transport. The camera was developed for use in surgical procedures including determination of the location and extent of primary carcinomas, detection of secondary lesions and sentinel lymph node biopsy (SLNB). Here we describe the camera design and its principal operating characteristics, including spatial resolution, energy resolution, sensitivity uniformity, and geometric linearity. The gamma camera has an intrinsic spatial resolution of 4.2 mm FWHM, an energy resolution of 21.1 % FWHM at 140 keV, and a sensitivity of 481 and 73 cps/MBq when using the single- and double-layer collimators, respectively.

Unlabelled: We have developed a SPECT imaging system, AwakeSPECT, to enable molecular brain imaging of untrained mice that are conscious, unanesthetized, and unrestrained. We accomplished this with head tracking and motion correction techniques., Methods: The capability of the system for motion-corrected imaging was demonstrated with a (99m)Tc-pertechnetate phantom, (99m)Tc-methylene diphosphonate bone imaging, and measurement of the binding potential of the dopamine transporter radioligand (123)I-ioflupane in mouse brain in the awake and anesthetized (isoflurane) states. Stress induced by imaging in the awake state was assessed through measurement of plasma corticosterone levels., Results: AwakeSPECT provided high-resolution bone images reminiscent of those obtained from CT. The binding potential of (123)I-ioflupane in the awake state was on the order of 50% of that obtained with the animal under anesthesia, consistent with previous studies in nonhuman primates. Levels of stress induced were on the order of those seen in other behavioral tasks and imaging studies of awake animals., Conclusion: These results demonstrate the feasibility of SPECT molecular brain imaging of mice in the conscious, unrestrained state and demonstrate the effects of isoflurane anesthesia on radiotracer uptake.

Several positron emitting radioisotopes such as (11)C and (13)N can be used in plant biology research. The (11)CO(2) tracer is used to facilitate plant biology research toward optimization of plant productivity, biofuel development and carbon sequestration in biomass. Positron emission tomography (PET) imaging has been used to study carbon transport in live plants using (11)CO(2). Because plants typically have very thin leaves, little medium is present for the emitted positrons to undergo an annihilation event. The emitted positrons from (11)C (maximum energy 960 keV) could require up to approximately 4 mm of water equivalent material for positron annihilation. Thus many of the positrons do not annihilate inside the leaf, resulting in limited sensitivity for PET imaging. To address this problem we have developed a compact beta-positive, beta-minus particle imager (PhytoBeta imager) for (11)CO(2) leaf imaging. The detector is based on a Hamamatsu H8500 position sensitive photomultiplier tube optically coupled via optical grease to a 0.5 mm thick Eljen EJ-212 plastic scintillator. The detector is equipped with a flexible arm to allow its placement and orientation over or under the leaf to be studied while maintaining the leaf's original orientation. To test the utility of the system the detector was used to measure carbon translocation in a leaf of the spicebush (Lindera benzoin) under two transient light conditions.

Medical researchers have used structural and functional imaging techniques to study various neurological phenomena. Humans are typically conscious for both structural and functional neuroimaging studies. The use of functional neuro-imaging techniques in mouse-based animal models is typically accomplished with restrained or anesthetized mice. A system was developed to perform functional imaging with single-photon emission computed tomography of awake mice to avoid the confounding influences of anesthesia or physical restraint. This review article provides an overview of the technique and how it is presently being used. The system is designed for brain imaging and uses infrared reflectors to track the head position as a function of time. The detected photons are acquired in list mode and are time-stamped. The position of the rotating gamma camera is also recorded as a function of time. These three sets of data are integrated together in an iterative image reconstruction program that performs motion compensation. The successful performance of the system is demonstrated in moving phantom and awake animal studies. The system and methodology has the potential of being a powerful tool in behavioral neuroimaging studies involving awake, unrestrained mice.

Introduction: We describe a compact, portable dual-gamma camera system (named "MONICA" for MObile Nuclear Imaging CAmeras) for visualizing and analyzing the whole-body biodistribution of putative diagnostic and therapeutic single photon emitting radiotracers in animals the size of mice., Methods: Two identical, miniature pixelated NaI(Tl) gamma cameras were fabricated and installed "looking up" through the tabletop of a compact portable cart. Mice are placed directly on the tabletop for imaging. Camera imaging performance was evaluated with phantoms and field performance was evaluated in a weeklong In-111 imaging study performed in a mouse tumor xenograft model., Results: Tc-99m performance measurements, using a photopeak energy window of 140 keV+/-10%, yielded the following results: spatial resolution (FWHM at 1 cm), 2.2 mm; sensitivity, 149 cps (counts per seconds)/MBq (5.5 cps/microCi); energy resolution (FWHM, full width at half maximum), 10.8%; count rate linearity (count rate vs. activity), r(2)=0.99 for 0-185 MBq (0-5 mCi) in the field of view (FOV); spatial uniformity, <3% count rate variation across the FOV. Tumor and whole-body distributions of the In-111 agent were well visualized in all animals in 5-min images acquired throughout the 168-h study period., Conclusion: Performance measurements indicate that MONICA is well suited to whole-body single photon mouse imaging. The field study suggests that inter-device communications and user-oriented interfaces included in the MONICA design facilitate use of the system in practice. We believe that MONICA may be particularly useful early in the (cancer) drug development cycle where basic whole-body biodistribution data can direct future development of the agent under study and where logistical factors, e.g., limited imaging space, portability and, potentially, cost are important., (Copyright 2010 Elsevier Inc. All rights reserved.)

We have designed and built a small animal single photon emission computed tomography (SPECT) imaging system equipped with parallel-hole and multipinhole collimators and capable of circular or helical SPECT. Copper-beryllium parallel-hole collimators suitable for imaging the ~35 keV photons from the decay of (125)I have been built and installed to achieve useful spatial resolution over a range of object-detector distances and to reduce imaging time on our dual-detector array. To address the resolution limitations in the parallel-hole SPECT and the sensitivity and limited field of view of single-pinhole SPECT, we have incorporated multipinhole circular and helical SPECT in addition to expanding the parallel-hole SPECT capabilities. The pinhole SPECT system is based on a 110 mm diameter circular detector equipped with a pixellated NaI(Tl) scintillator array (1x1x5 mm(3)/pixel). The helical trajectory is accomplished by two stepping motors controlling the rotation of the detector-support gantry and displacement of the animal bed along the axis of rotation of the gantry. Results obtained in SPECT studies of various phantoms show an enlarged field of view, very good resolution and improved sensitivity using multipinhole circular or helical SPECT. Collimators with one, three and five 1 mm diameter pinholes have been implemented and compared in these tests. Our objective is to develop a system on which one may readily select a suitable mode of either parallel-hole SPECT or pinhole circular or helical SPECT for a variety of small animal imaging applications.

Multi-modality imaging (such as PET-CT) is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET, fused with anatomical images created by MRI, allow the correlation of form with function. Perhaps more exciting than the combination of anatomical MRI with PET, is the melding of PET with MR spectroscopy (MRS). Thus, two aspects of physiology could be combined in novel ways to produce new insights into the physiology of normal and pathological processes. Our team is developing a system to acquire MRI images and MRS spectra, and PET images contemporaneously. The prototype MR-compatible PET system consists of two opposed detector heads (appropriate in size for small animal imaging), operating in coincidence mode with an active field-of-view of approximately 14 cm in diameter. Each detector consists of an array of LSO detector elements coupled through a 2-m long fiber optic light guide to a single position-sensitive photomultiplier tube. The use of light guides allows these magnetic field-sensitive elements of the PET imager to be positioned outside the strong magnetic field of our 3T MRI scanner. The PET scanner imager was integrated with a 12-cm diameter, 12-leg custom, birdcage coil. Simultaneous MRS spectra and PET images were successfully acquired from a multi-modality phantom consisting of a sphere filled with 17 brain relevant substances and a positron-emitting radionuclide. There were no significant changes in MRI or PET scanner performance when both were present in the MRI magnet bore. This successful initial test demonstrates the potential for using such a multi-modality to obtain complementary MRS and PET data.

The protection of the thyroid against radioiodine uptake has been an important safety concern for decades. After several studies examined potassium iodide blockade efficacy in the 1960's and 1970's, a standard dosage was prescribed by both the World Health Organization and the U.S. Food and Drug Administration. In this paper, we tested the effectiveness of a scaled version of that standard dosage in comparison to higher doses in mice. A novel gamma camera was employed with a high spatial resolution for precisely quantifying activity within the thyroid and a field of view large enough to image the entire mouse body. Thyroid and whole-body 125I biodistribution was analyzed immediately after exposure and 1 and 7 days later. It was found that 1 h after exposure five times the scaled human dose blocked thyroid uptake about 40% more effectively than the 1X scaled dose. Even after 1 d and 7 d, five times the recommended scaled human dose blocked approximately 10% more effectively than the 1X dose. These data suggest the need for continued evaluation of the effectiveness of KI as a blocking agent and the application of novel, non-invasive technologies to this important human health issue.

Multi-modality imaging is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET fused with anatomical structure images created by MRI will allow the correlation of form with function. Our group is developing a system to acquire MRI and PET images contemporaneously. The prototype device consists of two opposed detector heads, operating in coincidence mode. Each MRI-PET detector module consists of an array of LSO detector elements coupled through a long fibre optic light guide to a single Hamamatsu flat panel position-sensitive photomultiplier tube (PSPMT). The use of light guides allows the PSPMTs to be positioned outside the bore of a 3T MRI scanner where the magnetic field is relatively small. To test the device, simultaneous MRI and PET images of the brain of a male Sprague Dawley rat injected with FDG were successfully obtained. The images revealed no noticeable artefacts in either image set. Future work includes the construction of a full ring PET scanner, improved light guides and construction of a specialized MRI coil to permit higher quality MRI imaging.

Positron emission mammography (PEM) with tomographic acquisition using dual planar detectors rotating about the breast can obtain complete angular sampling and has the potential to improve activity estimation compared with PEM using stationary detectors. PEM tomography (PEMT) was compared with stationary PEM for point source and compressed breast phantom studies performed with a compact dual detector system. The acquisition geometries were appropriate for the target application of PEM guidance of stereotactic core biopsy. Images were reconstructed with a three-dimensional iterative maximum likelihood expectation maximization algorithm. PEMT eliminated blurring normal to the detectors seen with stationary PEM. Depth of interaction effects distorted the shape of the point spread functions for PEMT as the angular range from normal incidence of lines of response used in image reconstruction increased. Streak artefacts in PEMT for large detector rotation increments led to the development of an expression for the maximum rotation increment that maintains complete angular sampling. Studies with a compressed breast phantom were used to investigate contrast and signal-to-noise ratio (SNR) trade-offs for different sized spherical tumour models. PEMT and PEM both had advantages depending on lesion size and detector separation. The most appropriate acquisition method for specific detection or quantitation tasks requires additional investigation.

Scintimammography, or single gamma nuclear imaging of the breast, has shown promise as a way of characterizing certain biological properties of suspicious breast masses. Conventional scintimammography, performed using large clinical gamma cameras and prone patient positioning suffers from several drawbacks including poor sensitivity for small (> 1 cm) lesions and no reliable method for correlating scintigraphic findings with those of other imaging modalities. We are developing a system designed to overcome some of these problems. The system combines x-ray mammography with scintimammography on a common gantry. The x-ray and gamma ray images are obtained in quick succession, with the breast in a common configuration under mild compression. A digital x-ray detector is used, permitting rapid assessment of lesion location prior to gamma imaging, and enabling fusion of the x-ray transmission and gamma emission information in a single digital image. In a pilot clinical diagnostic study, the system has demonstrated high pathology-proven accuracy in differentiating benign and malignant masses.

Unlabelled: Positron emission mammography (PEM) is a technique to obtain planar images of the breast for detection of potentially cancerous, radiotracer-avid tumors. To increase the diagnostic accuracy of this method, use of minimally invasive methods (e.g., core biopsy) may be desirable for obtaining tissue samples from lesions detected with PEM. The purpose of this study was to test the capabilities of a novel method for performing PEM-guided stereotactic breast biopsies., Methods: The PEM system consisted of 2 square (10 x 10 cm) arrays of discrete scintillator crystals. The detectors were mounted on a stereotactic biopsy table. The stereotactic technique used 2 PEM images acquired at +/-15 degrees and a new trigonometric algorithm. The accuracy and precision of the guidance method was tested by placement of small point sources of (18)F at known locations within the field of view of the imager. The calculated positions of the sources were compared with the known locations. In addition, simulated stereotactic biopsies of a breast phantom consisting of a 10-mm-diameter gelatin sphere containing a concentration of (18)F-FDG consistent with that reported for breast cancer were performed. The simulated lesion was embedded in a 4-cm-thick slab of gelatin containing a commonly reported concentration of FDG, simulating a compressed breast (target-to-background ratio, approximately 8.5:1). An anthropomorphic torso phantom was used to simulate tracer uptake in the organs of a patient 1 h after a 370-MBq injection of FDG. Five trials of the biopsy procedure were performed to assess repeatability. Finally, a method for verifying needle positioning was tested., Results: The positions of the point sources were successfully calculated to within 0.6 mm of their true positions with a mean error of +/-0.4 mm. The biopsy procedures, including the method for verification of needle position, were successful in all 5 trials in acquiring samples from the simulated lesions., Conclusion: The success of this new technique shows its potential for guiding the biopsy of breast lesions optimally detected with PEM.

Positron emission mammography (PEM) is a new, specialized imaging modality utilizing PET radiopharmaceuticals to detect breast cancer. The capabilities and limitations of PEM in detecting breast tumors were investigated with a series of phantom experiments. The PEM imager was mounted on a standard Lorad biopsy table (separated by 18 cm). In the initial phase of the investigation, basic scanner parameters (resolution, sensitivity, and scatter fraction) were measured. The effects of a number of breast imaging parameters (length of acquisition, breast thickness, and breast density) on detection of breast lesions were then explored utilizing special phantoms. Moderately compressed breasts were simulated with a block of gelatin containing amounts of FDG consistent with 370 MBq injections. Lesions were simulated with four hollow spheres (inner diameters=5 mm, 8 mm, 12 mm, and 15 mm) filled with amounts of FDG representative of uptake in malignant breast tumors (target-to-background concentration ratio=8.5:1). Resolution at the center of the imager was 3.9 mm, sensitivity was 0.059 kcps/kBq/ml and the Compton scatter fraction was approximately 12%. Objects as small as 8 mm in diameter could be detected after 30 s of data acquisition; 5 mm spheres were detectable after 300 s. Object detection capabilities were reduced with increasing breast thickness. In thin compressed breasts (2 cm) even the smallest sphere (5 mm in diameter) could be detected; increasing breast thickness increased the minimum detectable sphere diameter to 8 mm. Increased background activity caused by FDG uptake in metabolically active normal tissue more prevalent in radiodense breasts compared to "fatty" breasts was simulated and shown to reduce the minimum detectable lesion size to 12 mm for the densest breasts. These results demonstrate the potential of PEM for the detection of breast lesions. The addition of the system to a standard biopsy apparatus indicates its potential for use to guide some core biopsies of breast cancers.

In breast scintigraphy, compact detectors with high intrinsic spatial resolution and small inactive peripheries can provide improvements in extrinsic spatial resolution, efficiency and contrast for small lesions relative to larger conventional cameras. We are developing a pixelated small field-of-view gamma camera for scintimammography. Extensive measurements of the imaging properties of a prototype system have been made, including spatial resolution, sensitivity, uniformity of response, geometric linearity and energy resolution. An anthropomorphic torso phantom providing a realistic breast exit gamma spectrum has been used in a qualitative study of lesion detectability. A new type of breast imaging system that combines scintimammography and digital mammography in a single upright unit has also been developed. The system provides automatic co-registration between the scintigram and the digital mammogram, obtained with the breast in a single configuration. Intrinsic spatial resolution was evaluated via calculation of the phase-dependent modulation transfer function (MTF). Measurements of extrinsic spatial resolution, sensitivity and uniformity of response were made for two types of parallel hole collimator using NEMA (National Electrical Manufacturers Association) protocols. Geometric linearity was quantified using a line input and least squares analysis of the measured line shape. Energy resolution was measured for seven different crystal types, and the effectiveness of optical grease coupling was assessed. Exit gamma spectra were obtained using a cadmium zinc telluride based spectrometer. These were used to identify appropriate radioisotope concentrations for the various regions of an anthropomorphic torso phantom, such that realistic scatter conditions could be obtained during phantom measurements. For prone scintimammography, a special imaging table was constructed that permits simultaneous imaging of both breasts, as well as craniocaudal views. A dedicated breast imaging system was also developed that permits simultaneous acquisition and superposition of planar gamma images and digital x-ray images. The intrinsic MTF is nonstationary, and is dependent on the phase relationship between the signal and the crystal array matrix. Averaged over all phases, the MTF is approximately 0.75, 0.57 and 0.40 at spatial frequencies of 1.0, 1.5 and 2.0 cycles per cm, respectively. The phase averaged line spread function (LSF) has a FWHM value of 2.6 mm. Following uniformity corrections, the RMS deviations in flood images are only slightly greater than is predicted from counting statistics. Across an 80 mm section of the active area, the differential linearity is 0.83 mm and the absolute linearity 2.0 mm. Using an anthropomorphic torso phantom with detachable breasts, scatter radiation similar to that observed exiting the breast of scintimammography patients was observed. It was observed that scattered gamma rays can constitute the majority of the radiation incident on the detector, but that the scatter-to-primary ratio varies significantly across the field of view, being greatest in the caudal portion of the breast, where scatter from the liver is high. Using a lesion-to-breast concentration ratio of 6:1, a 1.0 cm3 simulated breast lesion was detectable in lateral images obtained with both the developmental camera and with a clinical camera, while a 0.35 cm3 lesion was detectable in neither. Utilization of the dual x-ray transmission, gamma emission breast imaging system greatly increases the conspicuity of scintimammographic lesions relative to prone imaging, as well as greatly facilitating the localization and identification of structures in the gamma image. The prototype imaging gamma detector exhibits spatial resolution superior to that of conventional cameras, and comparable uniformity of response and geometric linearity. Because of light losses in the crystals, the energy resolution is inferior to that of single crystal NaI(Tl) came

The Shuttle Activation Monitor (SAM) experiment was flown on the Space Shuttle Columbia (STS-28) from 8-13 August, 1989 in a 57 degrees, 300 km orbit. One objective of the SAM experiment was to determine the relative effect of different amounts of shielding on the gamma-ray backgrounds measured with similarly configured sodium iodide (NaI) and bismuth germante (BGO) detectors. To achieve this objective twenty-four hours of data were taken with each detector in the middeck of the Shuttle on the ceiling of the airlock (a high-shielding location) as well as on the sleep station wall (a low-shielding location). For the cosmic-ray induced background the results indicate an increased overall count rate in the 0.2 to 10 MeV energy range at the more highly shielded location, while in regions of trapped radiation the low shielding configuration gives higher rates at the low energy end of the spectrum.

An X2/2B level solar flare occurred on 12 August, 1989, during the last day of the flight of the Space Shuttle Columbia (STS-28). Detectors on the GOES 7 satellite observed increased X-ray fluxes at approximately 1400 GMT and a solar particle event (SPE) at approximately 1600 GMT. Measurements with the bismuth germanate (BGO) detector of the Shuttle Activation Monitor (SAM) experiment on STS-28 showed factors of two to three increases in count rates at high latitudes comparable to those seen during South Atlantic Anomaly (SAA) passages beginning at about 1100 GMT. That increased activity was observed at both north and south high latitudes in the 57 degrees, 300 kilometer orbit and continued until the detector was turned off at 1800 GMT. Measurements made earlier in the flight over the same geographic coordinates did not produce the same levels of activity. This increase in activity may not be entirely accounted for by observed geomagnetic phenomena which were not related to the solar flare.