Dual-head Camera Research Articles

Comparative impact of standard approach, FDG PET and FDG dual-head coincidence gamma camera imaging in preoperative staging of patients with non-small-cell lung cancer

We prospectively compared the impact of the standard approach, of fluorodeoxyglucose positron emission tomography (FDG PET) and of FDG dual-head coincidence gamma camera imaging (DHC) in preoperative staging of patients with non-small-cell lung cancer (NSCLC). In addition to traditional staging, 42 patients were studied with a PET system and a DHC system. The number of lesions detected on DHC and on PET were compared independently of the proof of a tumoural invasion. Then, for the sub-group of lesions with the proof of a tumoural invasion, the sensitivity of the different imaging modalities was compared. Finally, stagings were compared with final staging established by histopathological findings (n=28), additional imaging modalities (n=4), clinical and traditional imaging follow-up over at least 4 months. DHC detected 105 of the 145 lesions considered as pathological on PET (73%, P=0.01), with a concurrence of 89% (NS) in lesions larger than 1.5 cm, and only 17% (P=0.03) in those smaller or equal to 1 cm. Traditional staging detected 87 of the 114 verified tumoural lesions (76%), PET 110/114 (96%, P=0.01 vs traditional staging), DHC 88/114 (77%, NS vs traditional staging, P=0.01 vs PET). PET correctly predicted the N stage in 39/42 (93%) patients, DHC in 38/42 (90%), and computed tomography in 32/42 (76%). PET correctly predicted the M stage in 42/42 (100%) patients, DHC in 41/42 (98%), and traditional staging in 38/42 (90%). Identical NM staging was obtained with DHC and PET in 38/42 (90%) patients. Compared to traditional NM staging, PET correctly up-staged 9/42 (21%) patients and down-staged 3/42 (7%), with one additional false N up-staging. DHC correctly up-staged 7/42 (17%) patients and down-staged 3/42 (7%), with one additional false N down-staging. PET correctly reclassified 4/42 (9.5%) patients from resectable to unresectable and incorrectly reclassified one. DHC correctly reclassified 3/42 (7%) patients without false therapeutic reclassification. Although DHC detected fewer lesions than PET, DHC is a possible alternative to PET since the impact on staging was high as compared with traditional staging and was very similar to that of PET.

PET and SPECT performance of the Siemens HD3 E.Cam/sup duet//spl reg/: a 1" Na(I) hybrid camera

Siemens has recently developed a new PET/SPECT dual-head camera, the e.cam/sup duet//spl reg/. This camera employs two HD3 detectors with 2.54 cm (1") deep Na(I) segmented crystals. This design, relatively new for Na(I), is aimed at increasing the stopping power for 511 keV /spl gamma/ rays, while maintaining good spatial resolution for SPECT. The PET performance of this camera was evaluated using the new NEMA NU2-2001 specifications. The effect of the thicker crystal on the camera's performance in the single photon acquisition mode was assessed by comparing its resolution and sensitivity to that obtained with a standard gamma camera with a 0.9525 cm (3/8") deep crystal. The Siemens e.cam was selected for this purpose as it is a very similar dual-head variable-angle system with several hardware and software elements identical to the e.cam/sup duet//spl reg/ camera.

Optimisation of the OS-EM algorithm and comparison with FBP for image reconstruction on a dual-head camera: a phantom and a clinical 18F-FDG study

Iterative reconstruction algorithms, such as the ordered subsets expectation maximisation (OS-EM), are a promising alternative to filtered backprojection (FBP). The aims of this study were first to optimise the OS-EM algorithm in terms of iteration number and to study the usefulness of post-filtering, and second to compare OS-EM and FBP for image reconstruction on a fluorine-18 fluorodeoxyglucose ((18)F-FDG) dual-head camera (DHC). These two goals were addressed using phantom acquisitions. The performances of these algorithms were also studied in patient acquisitions performed on a DHC and a PET on the same day. Phantom experiments were performed on a DHC using a Jaszczak phantom containing six spheres filled with (18)F-FDG, two background levels (0.95, 6.80 kBq/ml) and three object contrasts (5.9, 3.7, 2.7). The reconstruction algorithms were FBP with a Gaussian filter (FWHM 0.5-2 pixel width) and OS-EM using 8-128 equivalent iterations (equivalent to the ML-EM algorithm) with and without Gaussian post-filtering [OS-EM (iterations, pixel width)]. Contrast recovery coefficient (CRC) and noise characteristics were assessed. Twenty-two patients (21 male, one female; age 55+/-15 years) with lung cancer underwent, on the same day, PET (1 h post injection of 37 MBq/kg (18)F-FDG) and DHC acquisitions (3 h post injection). DHC data were reconstructed using six methods: FBP (1), OS-EM (16), (40), (40,1), (64) and (64,1). These sets were evaluated by two observers and compared to PET reconstructed with OS-EM (16). The number of detected lesions and the visual quality were assessed. A marked improvement in CRC was observed with OS-EM as compared with FBP when more than 24 iterations were used. The CRC increased markedly from 8 to 40 iterations and then reached a plateau. The noise was stable until 40 iterations and then increased. The best compromise was obtained for OS-EM (32) and OS-EM (40,1). For the patient study, OS-EM provided images of better visual quality, but with no significant difference in detection sensitivity. OS-EM was superior to FBP in terms of contrast recovery and noise level. The optimal compromise between contrast recovery and noise was obtained for OS-EM (32) and (40,1) on the phantom study. The clinical study showed that OS-EM yielded images of better visual quality but with no improvement in terms of detection of lung cancer.

Comparison of fluorine‐18 fluorodeoxyglucose positron emission tomography and Ga‐67 scintigraphy in evaluation of lymphoma

BACKGROUND The accuracy of fluorodeoxyglucose positron emission tomography (FDG-PET; dual-head camera with attenuation correction) and Ga-67 scintigraphy was compared to identify disease sites in patients with Hodgkin disease (HD) and intermediate and high-grade non-Hodgkin lymphoma (NHL) at initial diagnosis or clinical recurrence. METHODS Fifty-one contemporaneous FDG-PET and Ga-67 scintigraphies were performed on patients with NHL (35 intermediate grade, 3 high grade) or HD (13 patients). Sites of disease were correlated on a site-by-site basis on FDG-PET and Ga-67 images. Tumor-to-background (T/B) ratios were obtained for both techniques. Discordant FDG-PET and Ga-67 findings were correlated with computed tomography findings or clinical evaluation including repeat FDG-PET scans obtained after therapy. RESULTS Fluorodeoxyglucose positron emission tomography was positive at all 158 sites in 51 patients compared with 113 sites in 41 positive studies with Ga-67 scintigraphy (single positron emission computed tomography [SPECT] and/or planar images). In 44 patients who had complete Ga-67 SPECT data on all tumor sites, FDG-PET was positive at 126 sites and Ga-67 SPECT was positive at 81 sites. Ga-67 SPECT failed to demonstrate disease at 45 sites (35.7%). In 10 of 44 patients, Ga-67 SPECT completely failed to detect any disease at 22 of 45 sites (17.5%) and partially identified disease sites at 23 of 45 sites (18.2%) in 11 patients regardless of the tumor site and histology. In these patients, the lesions measured between 0.6 and 14.0 cm by CT. Fluorodeoxyglucose positron emission tomography revealed higher stage disease in 13 patients compared with Ga-67 imaging. Tumor-to-background ratios were statistically different between the two techniques with higher ratios obtained with FDG-PET (P < 0.0001). CONCLUSIONS In imaging aggressive lymphoma and HD before therapy, FDG-PET has significantly higher site and patient sensitivity than Ga-67 scintigraphy (100% vs. 71.5% and 100% vs. 80.3%, respectively). The change in disease stage by FDG-PET may result in a change in therapy strategy. Cancer 2002;94:879–88. © 2002 American Cancer Society. DOI 10.1002/cncr.10336

Comparison of fluorine‐18 fluorodeoxyglucose positron emission tomography and Ga‐67 scintigraphy in evaluation of lymphoma

The accuracy of fluorodeoxyglucose positron emission tomography (FDG-PET; dual-head camera with attenuation correction) and Ga-67 scintigraphy was compared to identify disease sites in patients with Hodgkin disease (HD) and intermediate and high-grade non-Hodgkin lymphoma (NHL) at initial diagnosis or clinical recurrence. Fifty-one contemporaneous FDG-PET and Ga-67 scintigraphies were performed on patients with NHL (35 intermediate grade, 3 high grade) or HD (13 patients). Sites of disease were correlated on a site-by-site basis on FDG-PET and Ga-67 images. Tumor-to-background (T/B) ratios were obtained for both techniques. Discordant FDG-PET and Ga-67 findings were correlated with computed tomography findings or clinical evaluation including repeat FDG-PET scans obtained after therapy. Fluorodeoxyglucose positron emission tomography was positive at all 158 sites in 51 patients compared with 113 sites in 41 positive studies with Ga-67 scintigraphy (single positron emission computed tomography [SPECT] and/or planar images). In 44 patients who had complete Ga-67 SPECT data on all tumor sites, FDG-PET was positive at 126 sites and Ga-67 SPECT was positive at 81 sites. Ga-67 SPECT failed to demonstrate disease at 45 sites (35.7%). In 10 of 44 patients, Ga-67 SPECT completely failed to detect any disease at 22 of 45 sites (17.5%) and partially identified disease sites at 23 of 45 sites (18.2%) in 11 patients regardless of the tumor site and histology. In these patients, the lesions measured between 0.6 and 14.0 cm by CT. Fluorodeoxyglucose positron emission tomography revealed higher stage disease in 13 patients compared with Ga-67 imaging. Tumor-to-background ratios were statistically different between the two techniques with higher ratios obtained with FDG-PET (P < 0.0001). In imaging aggressive lymphoma and HD before therapy, FDG-PET has significantly higher site and patient sensitivity than Ga-67 scintigraphy (100% vs. 71.5% and 100% vs. 80.3%, respectively). The change in disease stage by FDG-PET may result in a change in therapy strategy.

F-18-FDG-hybrid-camera-PET in patients with postoperative fever

Evaluation of F-18-FDG-hybrid-camera-PET imaging in patients with undetermined postoperative fever (POF). Prospective study of 18 patients (9 women, 9 men; age 23-85 years) suffering from POF with 2-fluoro-2'-deoxyglucose (F-18-FDG) using a dual headed coincidence camera (DHCC). Surgery had been performed 5-94 days prior to our investigation. 13 of the 18 patients received antibiotic therapy during the time of evaluation. Ten (55%) had an infectious and eight (45%) a non infectious cause of fever. Increased F-18-FDG-uptake outside the surgical wound occurred in 13 regions (infection n = 11, malignancy n = 2). The sensitivity of F-18-FDG-hybrid-camera-PET in imaging infection in areas outside the surgical wound was 86% and the specificity 100%, respectively. Antibiotic therapy did not negatively influence the results of F-18-FDG-scanning. Increased F-18-FDG-uptake within the surgical wound was seen in 8 of 18 patients. The sensitivity of F-18-FDG-hybrid-camera-PET in imaging infection within the surgical wound was 100% and the specificity 56%, respectively. The interval between surgery and F-18-FDG-scanning was significantly shorter in patients with false positive results compared with patients showing true negative results (median 34 vs. 54 days; p = 0.038). In POF-Patients, F-18-FDG transaxial tomography performed with a F-18-FDG-hybrid-camera-PET is sensitive in the diagnosis of inflammation and malignant disease within and outside the surgical wound. Because of the accumulation of the tracer both in granulation tissue and infection, the specificity in detecting the focus of fever within the surgical wound is poor.

A depth-encoding Anger detector using scintillating fibers

Parallax error during coincidence imaging with dual-head cameras causes infidelity in tomographic images, worsening as one increases crystal thickness to combat poor detection efficiency. The authors are integrating wavelength-shifting (WLS) scintillating fibers onto a thick NaI(Tl) crystal to create an Anger detector capable of measuring depth-of-interaction (DOI). Our studies target eventual implementation on the large-area detectors of commercial multihead coincidence imaging systems. The prototype detector uses a 127/spl times/127/spl times/25.4 mm/sup 3/ NaI(Tl) crystal. The crystal is sealed in a two-windowed aluminum enclosure-both faces of the crystal are coupled optically to glass windows. A ribbon of 125 square 1-mm WLS fibers is coupled lengthwise to the entrance window; enhanced-green- response photomultiplier tubes (PMTs) detect the light from the fibers. The number of fibers exhibiting signals above a threshold value determines the DOI. For interactions near the ribbon, light localizes in only a few fibers; light from distant interactions illuminates many fibers. Four PMTs, for position centroid calculation and energy windowing, are coupled through a light-guide to the exit window of the detector. This paper summarizes the concept of the depth-encoding Anger detector, describes the design of the detector prototype, and details on-going feasibility testing and optimization of the detector.

NEMA NU 2-2000+ performance measurements on an ADAC MCD camera

The clinically oriented NEMA NU-2 2000+ performance standards have been performed on an ADAC molecular coincidence detection dual-head camera. At 1 cm radius, the transverse resolution full-width at half-maximum was measured to be 5.2 (10.0) mm and the axial was 5.0 (10.6) mm. At 10 cm radius, the transverse radial resolution was 4.7 (7.4) mm and the transverse tangential was 8.5 (20.9) mm. The axial resolution was 14.0 (41.1) mm. The peak true count rate was 4370 counts/s at a concentration of 4.3 kBq/ml. The peak noise equivalent count rate (NECR) was 1620 counts/s at 2.9 kBq/ml. The system scatter fraction was 48%, The maximum relative count rate error observed at the NECR peak was -42%. The sensitivity was 1010 counts/sm/rSq in the center and 870 counts/s/MBq at an offset of 10 cm. The contrast for the hot spheres ranged from 18.5 (11.6)% to 11.6 (7.9)% for a contrast ratio of 8:1 (4:1). For the cold spheres, it ranged from 41% to 25% with an overall background variability of 7%. The residual error in scatter and attenuation correction was approximately 50%. All measurements were performed at the maximum allowed crystal-to-crystal distance of 810 mm.

27. Quantitative planar organ uptake measurement using attenuation correction with a scanning 153Gd line source and a dual head camera

s of the Twenty-Ninth Annual Meeting of The British Nuclear Medicine Society. Brighton Conference Centre, 9-11 April 2001. Tuesday 10 April: PHYSICS II Hall A

Transfer of normal 99mTc-ECD brain SPET databases between different gamma cameras.

A stereotactic, normal perfusion database is imperative for optimal clinical brain single-photon emission tomography (SPET). However, interdepartmental use of normal data necessitates accurate transferability of these data sets. The aim of this study was to investigate transfer of three normal perfusion databases obtained in the same large population of healthy volunteers who underwent sequential scanning using multihead gamma cameras with different resolution. Eighty-nine healthy adults (46 females, 43 males; aged 20-81 years) were thoroughly screened by history, biochemistry, physical and full neurological examination, neuropsychological testing and magnetic resonance imaging. After injection of 925 MBq technetium-99m labelled ethyl cysteinate dimer (ECD) under standard conditions, 101 scans were acquired from all subjects (12 repeat studies) on a triple-head Toshiba GCA-9300A (measured average FWHM 8.1 mm). Ninety-one sequential scans were performed on a dual-head Elscint Helix camera (FWHM 9.6 mm) and 22 subjects also underwent imaging on a triple-head Prism 3000 (FWHM 9.6 mm). Images were transferred to the same processing platform and reconstructed by filtered back-projection with the same Butterworth filter (order 8, cut-off 0.9 cycles/cm) and uniform Sorensen attenuation correction (mu = 0.09). After automated rigid intrasubject registration, all subjects were automatically reoriented to a stereotactic template by a nine-parameter affine transformation. The databases were analysed using 35 predefined volumes of interest (VOIs) with normalisation on total VOI counts. For comparison, the high-resolution data were smoothed with a 3D Gaussian kernel to achieve more similar spatial resolution. Hoffman phantom measurements were conducted on all cameras. Partial volume effects after smoothing varied between -6.5% and 10%, depending on VOI size. Between-camera reproducibility was 2.5% and 2.7% for the Toshiba camera versus the Helix and the Prism database, respectively. The highest reduction in between-camera variability was achieved by resolution adjustment in combination with linear washout correction and a Hoffman phantom-based correction. In conclusion, transfer of normal perfusion data between multihead gamma cameras can be accurately achieved, thereby enabling widespread interdepartmental use, which is likely to have a positive impact on the diagnostic capabilities of clinical brain perfusion SPET.

Evaluation of the E.CAM+, dual-head coincidence camera: a phantom study

Evaluation of the E.CAM+, dual-head coincidence camera: a phantom study

A positron floodlight for PET attenuation measurements

A new technique to image the patient surface has been developed to assist in the segmented attenuation correction, currently finding favor in positron emission tomography (PET). The goals of this approach are to outline the body's contours quickly, with an inherent surface enhancement that would permit transmission scanning after the emission scan. To achieve this, an orbiting, thin-windowed source, mounted out of the detector plane, illuminates the patient's skin with a soft positron flux, while a static emission scan quickly delineates the patient outline. The ability to visualize internal structures is a welcome, if unexpected, windfall. The measurements of resolution and sensitivity cover a grid of three positron radionuclides and two source assemblies imaging several phantoms to challenge four commercial scanners. Currently mounted on a CTI 933/04, the positron floodlight is well suited to virtually any ring-array PET scanner, with the potential for adaptation to the dual-headed camera instruments emerging on the market today.

Instrumentation for coincidence imaging with multihead scintillation cameras

Positron emission tomography (PET) has been used as a tool by investigators for many years to study metabolic processes in the body primarily with the radiopharmaceutical 18-fluordeoxyglucose. However, use of this technology has not been widespread because of the high expense of the equipment and its limitation to the imaging of positron emitters only. Recent improvements in scintillation camera technology have now made it possible to produce hybrid multihead cameras that can function in a coincidence mode for the detection of the annihilation radiation from positron emitters and in the normal mode for routine single-photon imaging. Although still limited in sensitivity, these camera systems continue to be improved and the recent addition of iterative reconstruction algorithms and attenuation correction capability have resulted in significant improvements in image quality. The integration of a low resolution computed tomography (CT) scanner with a dualhead camera by 1 manufacturer now makes it possible to perform attenuation correction and image fusion of anatomy and function into 1 image to improve the anatomic localization of abnormalities detected with coincidence imaging. Investigators continue to work on improved electronics and new types of detectors to further improve the sensitivity of these systems. These developments coupled with continued improvements in PET technology have resulted in the availability of a broad spectrum of systems for the investigator to consider when purchasing a system with positron imaging capability.

Effect of shielding the radioactivity outside the field of view on image quality in a dual head coincidence [PET camera

Limited count rate ability and open geometry make the image quality obtained from dual head cameras very sensitive to radioactivity outside the camera field of view. The spatial distribution of non true events, scatter and randoms, originating from radioactivity outside the FOV was investigated. The image quality quantified with the noise equivalent count rate, improved by up to 58% as a consequence of shielding. Radioactivity in the first 10 cm outside the FOV was found to contribute most significantly to the detected events. A modular and easily movable patient body shield was designed.

Impaired dopaminergic neurotransmission in patients with traumatic brain injury: a SPET study using 123I-β-CIT and 123I-IBZM

Structural imaging suggests that traumatic brain injury (TBI) may be associated with disruption of neuronal networks, including the nigrostriatal dopaminergic pathway. However, to date deficits in pre- and/or postsynaptic dopaminergic neurotransmission have not been demonstrated in TBI using functional imaging. We therefore assessed dopaminergic function in ten TBI patients using [123I]2-beta-carbomethoxy-3-beta-(4-iodophenyl)tropane (beta-CIT) and [123I]iodobenzamide (IBZM) single-photon emission tomography (SPET). Average Glasgow Coma Scale score (+/-SD) at the time of head trauma was 5.8+/-4.2. SPET was performed on average 141 days (SD +/-92) after TBI. The SPET images were compared with structural images using cranial computerised tomography (CCT) and magnetic resonance imaging (MRI). SPET was performed with an ADAC Vertex dual-head camera. The activity ratios of striatal to cerebellar uptake were used as a semiquantitative parameter of striatal dopamine transporter (DAT) and D2 receptor (D2R) binding. Compared with age-matched controls, patients with TBI had significantly lower striatal/cerebellar beta-CIT and IBZM binding ratios (P< or =0.01). Overall, the DAT deficit was more marked than the D2R loss. CCT and MRI studies revealed varying cortical and subcortical lesions, with the frontal lobe being most frequently affected whereas the striatum appeared structurally normal in all but one patient. Our findings suggest that nigrostriatal dysfunction may be detected using SPET following TBI despite relative structural preservation of the striatum. Further investigations of possible clinical correlates and efficacy of dopaminergic therapy in patients with TBI seem justified.

Clinical value of FDG Hybrid-PET in staging and restaging of malignant lymphoma – compared with conventional diagnostic methods

Summary Aim of the present retrospective study was to validate the clinical value of F-18-FDG PET imaging in lymphoma patients with a dual head camera modified for coincidence detection. Staging before and after oncological treatment was compared with a conservative diagnostic approach. Methods: 48 patients (28 non-Hodgkin lymphoma, 20 Hodgkin’s disease) received FDG-Hybrid-PET scans. Pretherapeutic staging was realized in 28 patients, 9 of them had control studies after they had completed therapy. Totally 29 persons were examined for posttherapeutic restaging. Computed tomography imaging and lymph node sonography was performed in all cases. Results were validated by clinical follow-up, in three cases a récidivé was proven by biopsy. Results: CT and ultrasound detected 77 lesions in 28 patients compared with 100 visualized by PET, but this difference in pretherapeutic staging did not reach significance at p &gt;0.05 by Fisher’s t-test. Hybrid-PET obtained a sensitivity of 93%, a specifity of 79%, a positive of 82% and a negative predictive value of 92% for detection of residual disease. The values for CT + US were 87%, 64%, 72% and 88% respectively. Conclusion: FDG Hybrid-PET is as or even more accurate than standard morphologic diagnostic methods for prestaging in malignant lymphoma. Additionally, there is a substancial benefit for therapy monitoring of residual disease using coincidence detection PET with a ¾-inch crystal gamma camera.

Multimodality SPET and PET dual head camera

Multimodality SPET and PET dual head camera

67Ga whole-body scintigraphy in the evaluation of head and neck squamous cell carcinoma.

The diagnostic accuracy of 67Ga-citrate whole-body scintigraphy for the evaluation of primary tumours, local recurrences, cervical node metastases and distant metastases was investigated in patients with head and neck squamous cell carcinoma (SCC). Altogether, 102 67Ga-citrate whole-body scans were performed on 83 patients with head and neck SCC using a dual-headed gamma camera. The results were compared with those of computed tomography (CT) and final diagnosis. 67Ga scintigraphy correctly diagnosed 28 of 29 primary lesions, a sensitivity of 97% (CT = 97%). For tumour recurrence, 67Ga scintigraphy correctly diagnosed 13 of 15 recurrences and 53 of 58 instances of no recurrence, giving a sensitivity of 87% and a specificity of 91% (CT = 80 and 62%, respectively). Scintigraphy correctly diagnosed 23 of 31 metastatic sides of the neck and all 173 negative sides of the neck, giving a sensitivity of 74% and a specificity of 100% (CT = 90 and 84%, respectively). Finally, scintigraphy correctly diagnosed all 12 distant metastases as well as 86 of 90 cases of no metastasis, resulting in a sensitivity of 100% and a specificity of 96%. Furthermore, in five patients, distant metastases were initially detected on 67Ga scintigraphy. In conclusion, 67Ga whole-body scintigraphy with a dual-headed camera resulted in a high sensitivity and specificity for the detection of primary lesions, recurrences and distant metastases of head and neck SCC. Although the sensitivity for detecting neck node metastases was relatively low, the specificity was high. Thus, 67Ga scintigraphy is an effective technique for the evaluation of head and neck SCC, especially tumour recurrence and distant metastases.

Influence of arm positioning on rest/stress technetium-99m labeled sestamibi tomographic myocardial perfusion imaging

Background. Single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is routinely performed with patients' arms positioned above their heads to avoid potential attenuation artifact and reduced image quality. Currently no data are available to support the use of this practice using 99mTc SPECT MPI. Methods and Results. Forty-one patients referred for routine rest/stress MPI were imaged using the standard protocol with arms positioned above their heads and again with their arms at their sides. The patients were injected with 10 to 45 mCi (370 to 1665 MBq) of 99mTc-labeled sestamibi ( 99mTc-sestamibi), and SPECT images were acquired 30 to 90 minutes later. Thirty patients were imaged on an ADAC Vertex dual-head camera and 11 patients on an ADAC Cirrus single-head camera. Images were interpreted by 3 nuclear cardiologists without knowledge of patient identity, arm position, or camera type using a 17-segment scoring model. No significant differences were noted in the percentage of abnormal study results, reversibility extent, or location of MPI defects between the 2 arm positions in the same patients. Image quality was also similar. Conclusion. Arm positioning does not influence the interpretation of 99mTc-sestamibi SPECT myocardial perfusion imaging with regard to image quality or defect location and extent.

PET imaging using dual-headed gamma cameras: an update.

Interest in clinical fluorodeoxyglucose (FDG) imaging with dual-headed gamma cameras continues to grow. In 1996, Jarritt and Acton published a review article of the use of gamma-camera systems for FDG imaging [1]. Since that article was published, considerable progress has been made in the adaptation of dual-headed camera systems for coincidence imaging. We review the basic principles of dual-headed coincidence imaging and some of the major limitations and challenges in the development of such technology. Since much of the current clinical experience with FDG imaging is based on the use of dedicated position emission tomographic (PET) systems, some comparisons of the performance limitations between dual-headed gamma-camera and dedicated PET systems are provided.