[PET tumor diagnosis with modified gamma camera: gamma PET. The Danish Society of Clinical Physiology and Nuclear Medicine].
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Denmark↗
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Usefulness of dual-head coincidence gamma camera with thick NaI crystals for nuclear oncology: comparison with dedicated PET camera and conventional gamma camera with thin NaI crystals.
AIM: A comparative study of the images obtained with a dual-head coincidence gamma camera with thick NaI crystals (19 mm), a dedicated PET camera with BGO crystals and a conventional gamma camera with thin NaI crystals (9.5 mm) was conducted to clarify the clinical feasibility of a dual-head coincidence gamma camera with thick NaI crystals. METHODS: FDG images of 27 patients with malignant tumors were obtained by means of a dual-head coincidence gamma camera with thick NaI crystal and a dedicated PET camera with BGO crystals. The images of bone scintigraphy in 10 cancer patients obtained with the dual-head coincidence gamma camera were compared with those taken by a conventional dual-head gamma camera with thin NaI crystals. RESULTS: Patient-basis sensitivity in 27 patients with neoplasms and lesion-basis sensitivity of the dual-head coincidence gamma camera and the dedicated PET camera were 74.1% and 85.2% (n.s.), 66.7% and 72.2% (n.s.), respectively. The tumor to background FDG uptake ratio derived from the coincidence gamma camera was significantly lower than that derived from the dedicated PET camera (mean +/- s.d.; 3.48 +/- 3.77 vs. 8.12 +/- 8.92, p < 0.0001), but the tumor to background FDG uptake ratio obtained with both methods correlated well (r = 0.84, p < 0.001). Similar whole body bone scans were obtained with the dual-head coincidence gamma camera and the conventional dual-head gamma camera in all 10 patients. CONCLUSION: These results suggest that the dual-head coincidence gamma camera with thick NaI crystals has potentially high clinical applicability for community hospitals.
Adult↗
Dual photon absorptiometry for bone mineral measurements using a gamma camera.
A gamma camera was equipped with a special collimator and arm assembly for bone mineral measurements with dual photon absorptiometry (DPA). The system was evaluated in vitro and in vivo and compared both with a rectilinear DPA and a dual energy X-ray (DEXA) system. All 3 systems showed a linear response in measurements of 4 vials, containing different amounts of hydroxyapatite. Phantom measurements with the gamma camera system showed a precision of 1.6% to 2.8%. Results obtained in 8 healthy volunteers with rectilinear and gamma camera systems were well correlated (R2 = 0.78). With the photon beam directed from posterior to anterior, the separation of vertebrae was easy with the gamma camera system. We conclude that bone mineral measurements can be made with a gamma camera for assessment of fracture risk and in the decision process whether a patient needs treatment or not. For follow-up, the precision of DPA with a gamma camera is inadequate.
Absorptiometry, Photon↗
[Present status and evaluation of mobile gamma cameras and gamma probe system].
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Gamma Rays↗
Chest tomography by gamma camera and external gamma source: concise communication.
To obtain tomographic images of the chest, we used a large-field gamma camera to detect the 90 degrees scattered radiations (180 keV) from a linear source of Hg-203 (279 keV). The primary beam traveling across the chest is scattered according to the relative density of tissues. Chest sections can be visualized at different depths on frontal and sagittal planes. The resolution of the technic is that of the gamma camera.
Gamma Rays↗
Localization of sentinel nodes in breast cancer: novel method and device to help pen marking of active nodes during gamma camera imaging.
Gamma camera imaging with Tc-99m marking is a widely used method to locate sentinel lymph nodes (SNs) in breast cancer patients. Prior to SN biopsy, the anterior and lateral location of the SN is marked on the patient's skin using an ink pen. The pen marks guide the surgeon during an operation. However, in many cases the marking is difficult due to limited space under the detectors of a gamma camera. The aim of this study was to improve the pen marking method. Eleven female patients were imaged 3-4 h after injection of Tc-99m labelled Nanocol. Injection was performed to parenchyma surrounding the breast tumour. To facilitate pen marking, two polycarbonate (PC) plates with 40 x 32 holes (spacing=10 mm) were engineered for anterior and lateral side imaging and then installed on the bed of a dual-head gamma camera. Two drops of Tc-99m were placed into the top corners of both the PC plates, in order to trace the corresponding x-y coordinates first from the acquired images and then from the plates. After imaging, the x-y coordinates of the SN(s) were determined from the anterior and lateral side images. Subsequently, the location of each SN was marked with an ink pen on the skin through the small holes in the PC plates. According to the surgeon's evaluation, the distance between the marks and the true location of the SNs was 4.5+/-6.9 mm. Measurements with a custom made phantom revealed that the accuracy of the novel method was significantly (P=0.06) higher as compared with the traditional method (2.7+/-3.0 mm versus 9.2+/-3.0 mm). In addition, we were not able to mark the weakest activity (0.02 MBq) with the traditional method. Taken together, the marking process was considerably easier with the novel method, it had better accuracy and sensitivity than the traditional method and the device is simple enough to be adapted for most gamma cameras.
Adult↗
The gamma camera as an absolute measurement device: determination of glomerular filtration rate in 99mTc-DTPA renography using a dual head gamma camera.
AIM: The aim of this study was to design a general nuclear medicine method for fast, accurate and direct determination of the clearance of a radioactive indicator provided that all uptake compartments of the radioactive indicator could be included in the field of view of the gamma camera. METHODS: The data material for clearance calculation in the gamma camera method (GCM) comprises: (1) a transmission map of a part of the body using a water filled flood field phantom with a uniform distribution of the radioisotope, (2) the background corrected activity curves in the anterior and posterior views over all uptake compartments following the injection of the radioactive indicator, and (3) the activity of the radioactive indicator in at least two blood samples drawn during the examination. With a view to determining glomerular filtration rate (GFR) in 99mTc-DTPA renography the gamma camera method was tested in a group of 26 adult subjects in whom GFR was determined simultaneously using the simplified multiple samples method (MSM) with plasma samples drawn 3-5 h following the injection of 51Cr-EDTA. RESULTS: For values of GFR above 30 ml.min(-1) the regression line of GFR in the MSM versus GFR in the GCM was not significantly different from the line of identity. The reliability of the GCM alone was about 14%, 11% and 6% for GFR values of 30, 60 and 120 ml.min(-1) and, therefore, the reliability of the GCM and the simplified MSM for prediction of GFR was almost the same. CONCLUSION: Since the recording of the renal count rates in the anterior and posterior views permits an accurate determination of the split renal function, the GCM yields reliable estimates also of the single kidney GFR.
Algorithms↗
[Brain scanning using a gamma camera. (PHO-gamma 3)].
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Angiography↗
Tc-99m attenuation coefficients in water-filled phantoms determined with gamma cameras.
Quantitative imaging with gamma cameras requires compensation for attenuation of source photons. Some methods of compensation make use of a constant or average estimated attenuation coefficient mu. A value for mu of 0.15 cm-1 for 140.5-keV photons in water or tissue is commonly used. This value, however, neglects scattered photons which are detected within the energy window in gamma camera imaging. Values for mu of 0.12 cm-1 used in attenuation compensation of Tc-99m single-photon emission computed tomography scans of uniform cylindrical sources have been shown to give improved results compared with use of mu = 0.15 cm-1. In this study, gamma cameras and a multichannel pulse-height analyzer were used to determine effective values of mu for photons in water as a function of energy window. Two cylindrical water-filled phantoms, circular and elliptical, were used with a point source of Tc-99m at depths up to 18 cm. Energy data were integrated over the top half of the photopeak, and over 10%, 20%, and 30% windows centered on the photopeak. Attenuation curves were exponential for all photopeak windows with values of mu of 0.12 +/- 0.014 cm-1 for all windows up to 20% and 0.1 cm-1 for a 30% window. This study suggests that a value of mu of 0.11-0.12 cm-1 is, in fact, appropriate for use in attenuation compensations where an average is required.
Models, Structural↗
Low-level internal radionuclide contamination: use of gamma camera for detection.
The uncollimated gamma camera was evaluated as a screening tool for the detection of low levels of internal radionuclide contamination. The minimum detectable activity (MDA) is on the order of 1-4 nCi (37-148 Bq) for a 3-min sample and background counting time. Identification of unknown radionuclides at these low levels involves a systematic search and hence requires a more careful peaking method than organ imaging. Most gamma cameras are capable both of detecting a wide range (35 keV to 1.332 MeV) of gamma-ray energies in the presence of three to four radionuclides and also of distinguishing principal gamma-ray energies from Compton scatter. The differences in MDAs among gamma cameras are small, and vary primarily with the background activity. The actual contaminant activities lie between the calculated values based on measurements when the source is 10 cm away from the uncollimated detector head and using point sources both in air and with the tissue-equivalent scatter medium. The widely available gamma camera is capable of screening a large population, either suspected or actually contaminated, in the event of an emergency.
Environmental Exposure↗
[Performance of a multispect 2 gamma camera for imaging 511-keV gamma rays].
The performance of a modified Multispect 2 gamma camera, which was supplied with two pairs of collimators constructed for imaging positron emitters was tested. The measurements involved the determination of sensitivity and of spatial resolution. The septal penetration was calculated approximately using two different methods. The spatial resolution determined by FWHM as measured by planar imaging in water at 10 cm distance from the collimator was evaluated as 14.0 mm with collimator 511-A and 12.5 mm with collimator 511-B. Using a Gaussian fit of the line-spread function septal penetrations of 12% with collimator 511-A and of 36% with collimator 511-B were calculated. The absolute system sensitivity measured with 18F was 66 cpm with collimator 511-A and 98.7 cpm/37 kBq with collimator 511-B. The high sensitivity with collimator 511-B may be explained, at least partially, by the high septal penetration.
Deoxyglucose↗
Clinical impact of fluorine-18 fluorodeoxyglucose positron emission tomography in cancer patients. A comparative study between dedicated camera and dual-head coincidence gamma camera.
AIM: Positron emission tomography (PET) using fluorine-18 fluorodeoxyglucose (FDG) can be performed using a dedicated PET scanner (PET-I) or a dual-head coincidence gamma camera (CGC-I). The aim of this study was to comparatively assess the impact of PET-I and CGC-I on clinical management in cancer patients. METHODS: From November 2000 to November 2002, PET-I and CGC-I were performed at an interval of 2 days in 151 patients with colorectal cancer (n=40), breast cancer (n=28), thyroid cancer (n=23), lung tumors (n=22), germ cell tumors (n=14), unknown primary cancer (n=7) and other cancers (n=17). PET-I and CGC-I were interpreted independently with knowledge of conventional imaging (CI). In June 2003, theoretical management, e.g. treatment modality/ies and treatment intent (curative or palliative), after CI, PET-I and CGC-I were stated during multidisciplinary sessions and were a posteriori considered as appropriate or inappropriate using pathological and follow-up data. RESULTS: The theoretical management proposed after PET-I and after CGC-I was similar in 112/151 (74%; 95% CI: 66-81%) patients. In 125 assessable patients, theoretical management after PET-I was appropriate in 86% (95% CI: 79-92%), significantly higher (P=0.0033) than after CGC-I (70%; 95% CI: 62-78%). Both proportions were also higher than after CI (46%; 95% CI: 37-56%), (P<0.0001). A similar trend for higher proportions of appropriate management after PET-I than after CGC-I was observed for each tumor localization. CONCLUSIONS: The clinical impact of PET-I is superior to that of CGC-I in a large series of cancer patients. Although CGC-I could be considered as an acceptable alternative, PET-I remains the standard and should preferably equip nuclear medicine departments.
Adolescent↗
Test of a versatile on-line distortion corrector for a gamma-camera.
A gamma-camera on-line distortion corrector, based on a fast microprocessor, has been tested on two cameras. The original electronic design and the software algorithm are described. Performance measurements on phantoms and clinical results show an improvement of the pictures.
Computers↗
Cadmium telluride matrix gamma camera.
An experimental gamma camera that has significant performance has been designed, constructed, and tested. The new camera has a matrix of cadmium telluride semiconductors as the detecting medium. The detectors are located within the collimating holes (rather than behind them). Coincident outputs from each row and column are used to digitally identify the individual detector in which the energy deposition occurred. Direct digital localization of detected events and the attenuation of scatter radiation between matrix elements by the collimator septa that separate detectors, contribute to reasonable resolution and imaging time. The superior radiation detection characteristics of cadmium telluride (in comparison to sodium iodide) could provide superior discrimination against scattered radiation that contributes only spurious information to the image. Detector reliability and uniformity limit the camera's performance; however, the availability of large numbers of small cadmium telluride detectors that have uniform radiation detection properties would make a clinical camera viable.
Cadmium↗
Usefulness of a solid-state gamma camera for sentinel node identification in patients with breast cancer.
BACKGROUND: A solid-state gamma camera was recently developed. This tool may enable intra-operative imaging of sentinel nodes in breast cancer. The aim of the present study was to evaluate the usefulness of a solid-state gamma camera for the pre- and intra-operative identification of sentinel nodes in patients with breast cancer. METHODS: Breast cancer patients with clinically negative nodes underwent sentinel node biopsy using dye and radioisotopes. Lymphoscintigraphy using both the conventional Anger camera and the solid-state gamma camera was performed the day before surgery. Sentinel nodes were intra-operatively identified using the gamma probe and imaged with a solid-state gamma camera, and then excised. When several sentinel nodes were present, these steps were repeated. RESULTS: Twenty-nine patients (30 basins) were enrolled in the study. The mean patient age was 54 years and the mean tumor size was 16 mm. A total of 41 sentinel nodes were identified using the Anger camera or the solid-state gamma camera pre-operatively. Thirty-eight sentinel nodes (92.7%) were identified using both the Anger camera and the solid-state gamma camera, 1 sentinel node (2.4%) was identified using the Anger camera alone, and 2 sentinel nodes (4.9%) were identified using the solid-state gamma camera alone. A total of 63 sentinel nodes were identified using the gamma probe or the solid-state gamma camera intra-operatively, and were excised. Fifty-seven sentinel nodes (90.5%) were identified using both the gamma probe and the solid-state gamma camera, 3 sentinel nodes (4.8%) were identified using the gamma probe alone, and 3 sentinel nodes (4.8%) were identified using the solid-state gamma camera alone. CONCLUSIONS: The solid-state gamma camera is useful for pre- and intra-operative identification of sentinel nodes in breast cancer. The significance of the solid-state gamma camera could be that it compensates for the gamma probe when the gamma probe cannot identify some sentinel nodes because of the shine through effect, and avoids leaving the residual sentinel nodes behind the axilla intra-operatively.
Adult↗
Assessment of left ventricular function using solid-state gamma camera equipped with a highly-sensitive collimator.
PURPOSE: The solid-state gamma camera 2020tc Imager (Digirad, CA) is now commercially available and has been clinically applied. The present study evaluates the feasibility of equilibrium radionuclide ventriculography (ERNV) within a 3 min period using this camera equipped with a highly sensitive collimator. MATERIALS AND METHODS: ERNV was performed from the best septal position (left anterior oblique view) in 20 patients with cardiac disease using a single detector anger-type gamma camera equipped with a low-energy, high-resolution collimator. Immediately thereafter, we performed a second ERNV using the solid-state gamma camera equipped with a highly sensitive collimator. Acquisition periods were 10 and 3 min, respectively. RESULTS: Significantly more counts were collected from over the left ventricle with the solid-state gamma camera over 3 min than those with the anger-type gamma camera over 10 min (817.1 +/- 387.8 k counts vs. 668.2 +/- 327.4 k counts, p < 0.01). The left ventricular ejection fraction obtained from ERNV data using the solid-state gamma camera correlated closely with those acquired by the anger-type gamma camera (r = 0.94, p < 0.0001, SEE = 5.93%). CONCLUSION: The results showed that the solid-state gamma camera could assess left ventricular function with excellent data collection efficiency and high reliability.
Equipment Failure Analysis↗
Reproducibility and action levels for gamma camera uniformity.
Deciding on the action level for gamma camera non-uniformity is difficult because the reproducibilities of quality control measurements and service adjustments are usually unknown. This work evaluated the reproducibilities of integral uniformity (IU), differential uniformity (DU) and the corrected relative standard deviation (CRSD). The latter was calculated by removing from the relative standard deviation of the pixel counts the component due to statistical fluctuations. The reproducibility of each parameter was evaluated by analysing 10 intrinsic flood acquisitions with total counts of 2, 5, 10 and 30 million. All three parameters were less reproducible at the lower count densities, but as expected IU and DU also showed higher mean values. CRSD was consistent and highly reproducible, at all count densities. At 10 million counts CRSD had a coefficient of variation (COV) of 1.3% which was a five-fold improvement over the 6.6% and 6.1% found for IU and DU, respectively. The relative sensitivity of IU, DU and CRSD was compared in monthly measurements on 10 gamma cameras over one year. No significant difference in relative sensitivity was demonstrated: a change in camera performance produced about the same percentage change in each parameter. The precision with which service engineers adjust gamma cameras was also assessed by measuring the uniformity of 10 gamma cameras immediately after service adjustment at monthly intervals over one year. Finally, general action levels were defined for IU, DU and CRSD at 7%, 5% and 2.5% respectively.
Gamma Cameras↗
Comparison of dual-head coincidence gamma camera FDG imaging with FDG PET in detection of breast cancer and axillary lymph node metastasis.
UNLABELLED: Dual-head coincidence gamma camera 18F-fluorodeoxyglucose (FDG) imaging was compared with FDG PET in the detection of breast cancer and axillary lymph node metastasis. METHODS: Both coincidence gamma camera FDG imaging and FDG PET were performed in a cylindrical phantom containing spheres of different sizes and activity ratios (5:1, 10:1 and 15:1) and in 30 women (age range 32-78 y) with suspected breast cancer. Biopsies or mastectomies were performed in all patients. Images were visually assessed, and the count ratio between tumor and normal tissue (T/N ratio) was calculated. RESULTS: In the phantom studies, coincidence gamma camera imaging visualized the smallest sphere (1.0 cm) at a ratio of 15:1 but not at ratios of 5:1 and 10:1. Coincidence gamma camera imaging visualized the other spheres (> or =1.3 cm) at all ratios. PET visualized all spheres at all ratios. In the clinical studies, 22 of 26 breast carcinomas detected by PET were also detected by coincidence gamma camera imaging.. Coincidence gamma camera imaging detected all of the carcinomas > or =2 cm in diameter (n = 10) and 12 of 16 carcinomas <2 cm. In breast carcinomas detected by both PET and coincidence gamma camera imaging, the T/N ratio in non-attenuation-corrected PET (7.12 +/- 7.13) was significantly higher than in coincidence gamma camera imaging (2.90 +/- 1.47, P < 0.005). Four of 8 axillary lymph node metastases detected by PET were detected by coincidence gamma camera imaging. Of 9 axillary lymph node metastases <1.0 cm in diameter, 7 and 3 were detected by PET and coincidence gamma camera imaging, respectively. CONCLUSION: Coincidence gamma camera imaging is useful in detecting breast carcinoma > or =2 cm in diameter but is not reliable for breast carcinoma <2 cm in diameter. Coincidence gamma camera imaging may be useless or even dangerous in the detection of axillary lymph node metastasis.
Adult↗