Traditional gamma cameras are preferred.

Although the new solid-state dedicated cardiac cameras provide excellent spatial and energy resolution and allow for markedly reduced SPECT acquisition times and/or injected radiopharmaceutical activity, they have some distinct disadvantages compared to traditional sodium iodide SPECT cameras. They are expensive. Attenuation correction is not available. Cardio-focused collimation, advantageous to increase depth-dependent resolution and myocardial count density, accentuates diaphragmatic attenuation and scatter from subdiaphragmatic structures. Although supplemental prone imaging is therefore routinely advised, many patients cannot tolerate it. Moreover, very large patients cannot be accommodated in the solid-state camera gantries. Since data are acquired simultaneously with an arc of solid-state detectors around the chest, no temporally dependent "rotating" projection images are obtained. Therefore, patient motion can be neither detected nor corrected. In contrast, traditional sodium iodide SPECT cameras provide rotating projection images to allow technologists and physicians to detect and correct patient motion and to accurately detect the position of soft tissue attenuators and to anticipate associated artifacts. Very large patients are easily accommodated. Low-dose x-ray attenuation correction is widely available. Also, relatively inexpensive low-count density software is provided by many vendors, allowing shorter SPECT acquisition times and reduced injected activity approaching that achievable with solid-state cameras.

Gamma camera imaging for studying intestinal absorption and whole-body distribution of selenomethionine.

Se metabolism in humans is not well characterised. Currently, the estimates of Se absorption, whole-body retention and excretion are being obtained from balance and tracer studies. In the present study, we used gamma camera imaging to evaluate the whole-body retention and distribution of radiolabelled selenomethionine (SeMet), the predominant form of Se present in foods. A total of eight healthy young men participated in the study. After consumption of a meal containing 4 MBq [75Se]L-SeMet ([75Se]SeMet), whole-body gamma camera scanning was performed for 45 min every hour over a 6 h period, every second hour for the next 18 h and once on each of the subsequent 6 d. Blood, urine and faecal samples were collected to determine the plasma content of [75Se]SeMet as well as its excretion in urine and faeces. Imaging showed that 87·9 (sd 3·3)% of the administered activity of [75Se]SeMet was retained within the body after 7 d. In contrast, the measured excretion in urine and faeces for the 7 d period was 8·2 (sd 1·1)% of the activity. Time-activity curves were generated for the whole body, stomach, liver, abdomen (other than the stomach and the liver), brain and femoral muscles. Gamma camera imaging allows for the assessment of the postprandial absorption of SeMet. This technique may also permit concurrent studies of organ turnover of SeMet.

Determination of in vivo behavior of mitomycin C-loaded o/w soybean oil microemulsion and mitomycin C solution via gamma camera imaging.

In this study, a microemulsion system was evaluated for delivery of mitomycin C (MMC). To track the distribution of the formulated drug after intravenous administration, radiochemical labeling and gamma scintigraphy imaging were used. The aim was to evaluate a microemulsion system for intravenous delivery of MMC and to compare its in vivo behavior with that of the MMC solution. For microemulsion formulation, soybean oil was used as the oil phase. Lecithin and Tween 80 were surfactants and ethanol was the cosurfactant. To understand the whole body localization of MMC-loaded microemulsion, MMC was labeled with radioactive technetium and gamma scintigraphy was applied for visualization of drug distribution. Radioactivity in the bladder 30 minutes after injection of the MMC solution was observed, according to static gamma camera images. This shows that urinary excretion of the latter starts very soon. On the other hand, no radioactivity appeared in the urinary bladder during the 90 minutes following the administration of MMC-loaded microemulsion. The unabated radioactivity in the liver during the experiment shows that the localization of microemulsion formulation in the liver is stable. In the light of the foregoing, it is suggested that this microemulsion formulation may be an appropriate carrier system for anticancer agents by intravenous delivery in hepatic cancer chemotherapy.

EANM Dosimetry Committee series on standard operational procedures for pre-therapeutic dosimetry II. Dosimetry prior to radioiodine therapy of benign thyroid diseases.

The EANM Dosimetry Committee Series "Standard Operational Procedures for Pre-Therapeutic Dosimetry" (SOP) provides advice to scientists and clinicians on how to perform patient-specific absorbed dose assessments. This particular SOP describes how to tailor the therapeutic activity to be administered for radioiodine therapy of benign thyroid diseases such as Graves' disease or hyperthyroidism. Pretherapeutic dosimetry is based on the assessment of the individual (131)I kinetics in the target tissue after the administration of a tracer activity. The present SOP makes proposals on the equipment to be used and guides the user through the measurements. Time schedules for the measurement of the fractional (131)I uptake in the diseased tissue are recommended and it is shown how to calculate from these datasets the therapeutic activity necessary to administer a predefined target dose in the subsequent therapy. Potential sources of error are pointed out and the inherent uncertainties of the procedures depending on the number of measurements are discussed. The theoretical background and the derivation of the listed equations from compartment models of the iodine kinetics are explained in a supplementary file published online only.

Comparison between stress myocardial perfusion SPECT recorded with cadmium-zinc-telluride and Anger cameras in various study protocols.

PURPOSE: The results of stress myocardial perfusion SPECT could be enhanced by new cadmium-zinc-telluride (CZT) cameras, although differences compared to the results with conventional Anger cameras remain poorly known for most study protocols. This study was aimed at comparing the results of CZT and Anger SPECT according to various study protocols while taking into account the influence of obesity. METHODS: The study population, which was from three different institutions equipped with identical CZT cameras, comprised 276 patients referred for study using protocols involving (201)Tl (n = 120) or (99m)Tc-sestamibi injected at low dose at stress ((99m)Tc-Low; stress/rest 1-day protocol; n = 110) or at high dose at stress ((99m)Tc-High; rest/stress 1-day or 2-day protocol; n = 46). Each Anger SPECT scan was followed by a high-speed CZT SPECT scan (2 to 4 min). RESULTS: Agreement rates between CZT and Anger SPECT were good irrespective of the study protocol (for abnormal SPECT, (201)Tl 92 %, (99m)Tc-Low 86 %, (99m)Tc-High 98 %), although quality scores were much higher for CZT SPECT with all study protocols. Overall correlations were high for the extent of myocardial infarction (r = 0.80) and a little lower for ischaemic areas (r = 0.72), the latter being larger on Anger SPECT (p < 0.001). This larger extent was mainly observed in 50 obese patients who were in the (201)Tl or (99m)Tc-Low group and in whom stress myocardial counts were particularly low with Anger SPECT (228 ± 101 kcounts) and dramatically enhanced with CZT SPECT (+279 ± 251 %). CONCLUSION: Concordance between the results of CZT and Anger SPECT is good regardless of study protocol and especially when excluding obese patients who have low-count Anger SPECT and for whom myocardial counts are dramatically enhanced on CZT SPECT.

SPECT/CT and a portable gamma-camera for image-guided laparoscopic sentinel node biopsy in testicular cancer.

UNLABELLED: The purpose of this study was to evaluate the utility of SPECT/CT and real-time intraoperative imaging with a portable γ-camera for laparoscopic sentinel node (SN) localization in stage I testicular cancer. METHODS: Ten patients with clinical stage I testicular cancer were studied between November 2006 and November 2010. Their mean age was 37 y (range, 25-50 y). The primary tumors were situated on the right side in 5 patients and on the left side in 5. After a funicular block with 2% lidocaine, an average dose of 80 MBq (range, 59-98 MBq) of (99m)Tc-nanocolloid in a volume of 0.2 mL was injected into the testicular parenchyma. Shortly after injection, a 10-min dynamic study was performed, followed by the acquisition of static planar images at 15 min and 2 h. SPECT/CT was performed at 2 h. After image fusion, SNs were visualized, and their exact anatomic location was determined. The SPECT/CT images were displayed in the operation room to guide SN detection using a laparoscopic γ-ray probe and a portable γ-camera. RESULTS: Lymphatic drainage to the retroperitoneum was seen in all patients. SPECT/CT identified interaortocaval or paracaval SNs in the 5 patients with right-sided tumors, one of whom had an additional SN adjacent to the testicular vessels. In all 5 patients with left-sided tumors, paraaortic SNs were visualized; a node along the testicular vessels was visualized in 2 of these 5. Twenty-six SNs were laparoscopically removed (range, 1-4 per patient). An SN contained metastases in 1 case. No recurrences developed in the 9 patients with a tumor-free SN during a median follow-up of 21 mo (range, 2-50 mo). CONCLUSION: SPECT/CT enables accurate anatomic localization of retroperitoneal SNs in patients with testicular cancer, facilitating their laparoscopic retrieval. Real-time image guidance by a portable γ-camera improves intraoperative SN detection and appears to identify (20%) additional SNs.

Nuclear myocardial perfusion imaging with a cadmium-zinc-telluride detector technique: optimized protocol for scan time reduction.

UNLABELLED: We aimed at establishing the optimal scan time for nuclear myocardial perfusion imaging (MPI) on an ultrafast cardiac gamma-camera using a novel cadmium-zinc-telluride (CZT) solid-state detector technology. METHODS: Twenty patients (17 male; BMI range, 21.7-35.5 kg/m(2)) underwent 1-d (99m)Tc-tetrofosmin adenosine stress and rest MPI protocols, each with a 15-min acquisition on a standard dual-detector SPECT camera. All scans were immediately repeated on an ultrafast CZT camera over a 6-min acquisition time and reconstructed from list-mode raw data to obtain scan durations of 1 min, 2 min, etc., up to a maximum of 6 min. For each of the scan durations, the segmental tracer uptake value (percentage of maximum myocardial uptake) from the CZT camera was compared by intraclass correlation with standard SPECT camera data using a 20-segment model, and clinical agreement was assessed per coronary territory. Scan durations above which no further relevant improvement in uptake correlation was found were defined as minimal required scan times, for which Bland-Altman limits of agreement were calculated. RESULTS: Minimal required scan times were 3 min for low dose (r = 0.81; P < 0.001; Bland-Altman, -11.4% to 12.2%) and 2 min for high dose (r = 0.80; P < 0.001; Bland-Altman, -7.6% to 12.9%), yielding a clinical agreement of 95% and 97%, respectively. CONCLUSION: We have established the minimal scan time for a CZT solid-state detector system, which allows 1-d stress/rest MPI with a substantially reduced acquisition time resulting in excellent agreement with regard to uptake and clinical findings, compared with MPI from a standard dual-head SPECT gamma-camera.

Intraoperative real-time (99m)Tc-sestamibi scintigraphy with miniature gamma camera allows minimally invasive parathyroidectomy without ioPTH determination in primary hyperparathyroidism.

BACKGROUND: Minimally invasive parathyroidectomy (MIP) is being widely accepted as the procedure of choice for the treatment of primary hyperparathyroidism (PHPT), which is caused by a parathyroid single adenoma in more than 80% of cases in some series. Preoperative location studies, like sestamibi scans, allow the proper identification of pathologic gland and intraoperative parathormone (ioPTH) assay is used to confirm the removal of the adenoma. We have studied the feasibility of a new miniature gamma camera (MGC) used intraoperatively to locate parathyroid adenomas and confirm its correct excision. MATERIALS AND METHODS: Twenty patients with PHPT positively diagnosed by preoperative sestamibi scans underwent a MIP. In the first five patients, both ioPTH assay and the new hand-held MGC were used consecutively to locate and confirm the excision of the pathologic gland. For the next 15 cases, PTH was measured but not used intraoperatively for diagnosis and the MGC was the only diagnostic tool employed to perform the operation. Concordance between preoperative and intraoperative scintigraphy, surgical time, success rate, and complications are analyzed. RESULTS: All cases were operated on successfully by a MIP. After 1 year follow-up, the drop of PTH and the normalization of calcium levels confirmed the excision of all pathologic tissue. The MGC proved its usefulness in all patients offering accurate real-time intraoperative images for location and confirming the success of the procedure. CONCLUSIONS: The MGC is a useful instrument in MIP for PHPT. It may be used as complementary to the standard tools used to date, or even replace them, at least in selected cases of single adenomas.

Direct imaging of radionuclide-produced electrons and positrons with an ultrathin phosphor.

UNLABELLED: Current electron detectors are either unable to image in vivo or lack sufficient spatial resolution because of electron scattering in thick detector materials. This study was aimed at developing a sensitive high-resolution system capable of detecting electron-emitting isotopes in vivo. METHODS: The system uses a lens-coupled charge-coupled-device camera to capture the scintillation light excited by an electron-emitting object near an ultrathin phosphor. The spatial resolution and sensitivity of the system were measured with a 3.7-kBq (90)Y/(90)Sr beta-source and a 70-microm resin bead labeled with (99m)Tc. Finally, we imaged the (99m)Tc-pertechnetate concentration in the mandibular gland of a mouse in vivo. RESULTS: Useful images were obtained with only a few hundred emitted beta particles from the (90)Y/(90)Sr source or conversion electrons from the (99m)Tc bead source. The in vivo image showed a clear profile of the mandibular gland and many fine details with exposures of as low as 30 s. All measurements were consistent with a spatial resolution of about 50 microm, corresponding to 2.5 detector pixels with the current camera. CONCLUSION: Our new electron-imaging system can image electron-emitting isotope distributions at high resolution and sensitivity. The system is useful for in vivo imaging of small animals and small, exposed regions on humans. The ability to image beta particles, positrons, and conversion electrons makes the system applicable to most isotopes.

Non-invasive screening method for simultaneous evaluation of in vivo growth factor release profiles from multiple ectopic bone tissue engineering implants.

The purpose of this study was to develop and validate a screening method based on scintillation probes for the simultaneous evaluation of in vivo growth factor release profiles of multiple implants in the same animal. First, we characterized the scintillation probes in a series of in vitro experiments to optimize the accuracy of the measurement setup. The scintillation probes were found to have a strong geometric dependence and experience saturation effects at high activities. In vitro simulation of 4 subcutaneous limb implants in a rat showed minimal interference of surrounding implants on local measurements at close to parallel positioning of the probes. These characteristics were taken into consideration for the design of the probe setup and in vivo experiment. The measurement setup was then validated in a rat subcutaneous implantation model using 4 different sustained release carriers loaded with (125)I-BMP-2 per animal. The implants were removed after 42 or 84 days of implantation, for comparison of the non-invasive method to ex vivo radioisotope counting. The non-invasive method demonstrated a good correlation with the ex vivo counting method at both time-points of all 4 carriers. Overall, this study showed that scintillation probes could be successfully used for paired measurement of 4 release profiles with minimal interference of the surrounding implants, and may find use as non-invasive screening tools for various drug delivery applications.

Predictive value of the preablation serum thyroglobulin level after thyroidectomy is combined with postablation 131I whole body scintigraphy for successful ablation in patients with differentiated thyroid carcinoma.

OBJECTIVES: To investigate the clinical importance of the combined use of serum thyroglobulin (Tg) levels measured just before ablation (ablation-Tg) and postablation 131I whole body scintigraphy (WBS) patterns for predicting ablation success in patients with differentiated thyroid carcinoma who received total thyroidectomy and 131I ablation therapy. METHODS: We retrospectively studied the early clinical outcomes for 81 differentiated thyroid carcinoma patients treated with total thyroidectomy and high-dose 131I ablation therapy between June 2001 and July 2004. RESULTS: Ablation success was achieved in 42 (97.7%) of the 43 patients with uptake in the thyroid bed only and ablation-Tg levels less than 10 ng/mL, whereas successful ablation was achieved in 9 (75.0%) of the 12 patients with uptake in the thyroid bed only and ablation-Tg levels equal to or greater than 10 ng/mL (P = 0.029). Among 15 patients with uptake including a lymph node and ablation-Tg levels less than 10 ng/mL, 14 patients (93.3%) showed ablation success, whereas successful ablation was achieved in only 2 (18.2%) of the 11 patients with uptake including a lymph node and ablation-Tg levels equal to or greater than 10 ng/mL (P < 0.001). CONCLUSIONS: These data indicate that the combined use of serum Tg levels measured just before ablation and the 131I WBS patterns after ablation may be an early predictor of ablation success in patients with differentiated thyroid carcinoma who received total thyroidectomy and high-dose 131I ablation therapy.

A quantitative lymphoscintigraphic evaluation of lymphatic function in the swollen hands of women with lymphoedema following breast cancer treatment.

In BCRL (breast cancer-related lymphoedema), arm swelling is unevenly distributed and some regions are partly or entirely spared. In particular, the hand may or not be swollen, but when involved functional impairment can be substantial. We have found previously that, when the ipsilateral hand is spared of swelling (in a limb with swelling proximal to the hand), the local lymph drainage rate constant (k) is at least as high as in the contralateral hand, contrary to the traditional 'stopcock' concept of reduced lymph drainage from the whole limb. In the light of this finding, we have investigated lymph drainage in the hands of eight women with BCRL and moderate-to-severe hand swelling, using gamma-camera quantitative lymphoscintigraphy. Images showed pronounced superficial activity in the ipsilateral swollen arms of most patients, indicating dermal backflow. k for 99mTc-labelled hIgG (human IgG) measured over 5 h in the subcutis of the ipsilateral swollen hand was 34+/-24% less than in the contralateral hand (P=0.013). Activity measured in the ipsilateral swollen forearm increased progressively, but there was very little increase in the contralateral forearm, indicating retention of 99mTc-labelled hIgG in the swollen forearm. It is concluded that lymphatic function in the swollen hand is impaired, and that there appears to be two populations of women with BCRL, i.e. spared-hand and swollen-hand, irrespective of the cancer treatment received.

Evaluation of [123I]IBZM pinhole SPECT for the detection of striatal dopamine D2 receptor availability in rats.

Single photon emission computed tomography (SPECT) and MRI coregistration have been assessed to characterize striatal dopamine D2/D3 receptor (D2/D3R) availability in rats following injection of the D2 and D3R radioligand [123I] iodobenzamide ([123I]IBZM). High-resolution SPECT data were obtained with a pinhole collimator. In order to precisely estimate brain regions of low radioligand uptake, SPECT images were coregistered onto a MRI template with high accuracy (maximum mismatch 1.1 mm). To evaluate an adequate dose of radioligand to be administered without exceeding the radioligand-to-receptor occupancy >5% and to define an appropriate time period for image acquisition, three untreated groups of animals received 29.6, 37, and 44.4 MBq of [123I]IBZM and underwent five consecutive SPECT acquisitions lasting 64 min each. Ratio calculations between specific striatal radioligand uptake and nondisplaceable cerebellar uptake revealed a secular equilibrium between 75 and 355 min post-tracer application in all three animal groups. Consequently, since the highest regional uptake values were obtained in the animal group receiving 44.4 MBq [123I]IBZM, this injection dose was considered to be appropriate. Finally, the capacity of the imaging method to detect distinct severity levels of striatal dopamine D2/D3 receptor loss was tested in a low, medium, and high dose quinolinic acid (QA) animal model of Huntington's disease. Motor impairment indicative of striatal dysfunction was monitored using amphetamine-induced rotational behavior and locomotor activity. Loss of striatal D2/D3R bearing medium-sized spiny neurons was assessed by DARPP-32 immunohistochemistry and compared to [123I]IBZM binding. Optical density measures of DARPP-32 immunohistochemistry demonstrated QA dose-dependent mild to subtotal unilateral striatal lesions ranging from 29.4% to 96.9% when compared to the nonlesioned side. Linear regression analysis showed that measurements of striatal DARPP-32 optical density and striatal [123I]IBZM uptake of the lesioned side were highly correlated (r2=0.83; P<0.001) whereas correlation with locomotor activity was less tight (r2=0.23; P<0.05; amphetamine-induced rotational behavior was not significantly correlated). This is the first study to demonstrate that in vivo [123I]IBZM SPECT and MRI coregistration are highly sensitive and, in contrast to behavioral measures, accurately detect mild to subtotal striatal lesions by measuring loss of D2/D3R availability. SPECT-MRI-based estimation of regional [123I]IBZM uptake provides a cost effective and widely available in vivo imaging technique for assessing striatal integrity in animal studies.

An amorphous selenium based positron emission mammography camera with avalanche gain.

Early diagnosis of breast cancer is crucial for effective treatment, and the need exists for greater detection ability and specificity than possible by screening x-ray mammography (currently the primary imaging technique for the detection of breast lesions). Positron Emission Tomography (PET) using the radiotracer 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) offers a noninvasive, highly sensitive method for the diagnosis of breast cancer. Images from PET contain unique metabolic information that is not available from anatomical imaging techniques. We propose a Positron Emission Mammography (PEM) imaging system that maintains the established high specificity of FDG PET while providing improved collection efficiency for the radiotracer signal and the potential for images with better spatial resolution. This PEM system will enable detection of lesions that are considerably smaller than those that can be visualized using whole body PET imaging. The compact dual-head PEM camera will be based on an amorphous selenium (a-Se) avalanche photodetector and the scintillator lutetium oxyorthosilicate (LSO). The camera promises high collection efficiency by combining the fast scintillation light decay and high light yield of LSO with the excellent quantum efficiency, large avalanche gain, and rapid response time of a-Se. We have measured the gain and readout time of an 8 microm a-Se layer and demonstrated the feasibility of the proposed PEM camera.

Effect of denture base surface pretreatment on microleakage of a silicone-based resilient liner.

STATEMENT OF PROBLEM: Microleakage between resilient liner and denture base resins is a significant clinical problem, often responsible for debonding of the resilient liner from the denture base resin. PURPOSE: This study investigated the effect of 2 surface treatments, airborne-particle abrasion (APA) and wetting with methyl methacrylate monomer (MMA), on microleakage between a silicone-based resilient liner and denture base resin using a gamma camera imaging technique. MATERIAL AND METHODS: Thirty-three specimens, each having 2 plates measuring 40 x 40 x 2 mm, were prepared by packing and processing an acrylic denture base resin (QC-20) into square plates following manufacturer's instructions. Specimens were divided into 3 groups (n=11) as APA-, MMA-, and control-treatment groups. For the APA group, the inner surfaces of both plates were airborne-particle abraded with 250-microm Al 2 O 3 particles and, for the MMA group, surfaces were treated with monomer (QC-20). Control specimens were not surface treated. Following application of an adhesive (Ufi Gel P-specific), a silicone lining material (Ufi Gel P) was prepared and applied to the inner surfaces of all 33 specimens. Eleven size-matched polymethyl methacrylate (PMMA) specimen blocks (40 x 40 x 6 mm) were prepared to calculate the level of residual radioactivity for the denture base itself, the entire outer surface count (OSC). All specimens and PMMA blocks were immersed in a radioactive solution (thallium-201 chloride) for 24 hours. Specimen activities (gamma-ray cts/sec, representing thallium-201 concentration) were then measured using a high-resolution gamma camera. The amount of OSC-subtracted total specimen counts was a direct indicator of the quantity of inward diffusing tracer. The subtracted values were analyzed using a 1-way analysis of variance (ANOVA) and Bonferroni multiple comparison tests (alpha=.05). RESULTS: OSC levels averaged 754 +/- 110 gamma-ray cts/sec. OSC-subtracted APA, control, and MMA values were 5,546 +/- 1,534, 3,392 +/- 738, and 1,405 +/- 392 gamma-ray cts/sec, respectively. All 3 groups were significantly different ( P <.05) from each other. Surface wetting with MMA showed the lowest microleakage values among all specimen groups. CONCLUSION: In terms of microleakage, surface treatment with MMA monomer preceding the adhesive application demonstrated lower values than adhesive application alone. APA pretreatment resulted in 4 times the microleakage found in MMA-treated specimens, and 1.5 times the microleakage of the untreated control. None of the surface pretreatments completely prevented microleakage. Microleakage between the silicone-based resilient liner and denture base resin can be quantitatively determined using the gamma camera imaging technique.

Pinhole imaging of 131I-metaiodobenzylguanidine (131I-MIBG) in an animal model of neuroblastoma.

PURPOSE: To evaluate (131)I-MIBG scintigraphic localization of xenotransplanted and spontaneously arising neuroblastomas in murine models of high-risk neuroblastoma. METHODS: Neuroblastoma xenografts were created by inoculation of human neuroblastoma cell suspensions into the subcutaneous flanks of athymic nude mice. In addition, spontaneous paraspinal neuroblastomas were detected by direct palpation in MYCN transgenic mice. After measured tumor volumes exceeded 200 mm(3), each mouse received an intraperitoneal injection of 18 muCi/g (131)I-metaiodobenzylguanidine ((131)I-MIBG). Pinhole scintigraphy was performed to evaluate the MIBG biodistribution and to attempt to visualize the tumors. Each mouse was imaged on a gamma camera equipped with a 3-mm pinhole on one head and an HEGP collimator on the other. RESULTS: Images demonstrated absorption of radiolabeled MIBG and visualization of tumors. Analysis of the images allowed for quantification of relative MIBG uptake and for determination of linear and area measurements of the tumors. CONCLUSION: High-energy pinhole imaging effectively demonstrates uptake of radiolabeled MIBG by human neuroblastoma tumors in murine laboratory models. This technique allows for in vivo assessment of tumor burden. In the future, we plan to use this method to evaluate sensitivity for detecting metastatic spread as well as investigating the therapeutic efficacy of high-dose (131)I-MIBG in combination with radiosensitizing agents.

[Neurological explorations in Nuclear Medicine. A Spanish survey]. / Exploraciones neurológicas en Medicina Nuclear. Encuesta española.

A representative Nuclear Medicine Service in Spain has two or three gammacameras. It performs neurologic studies one or two days at week wich account 2,1% of total workload. Brain Perfusion SPECT, specially in cognitive disorders, is the most frequent application. Neurooncology has a lower but established relevance. Neuroreceptors imaging are increasing in the last months. Emission tomography is obtained using a double-headed camera fitted with high-resolution parallel hole collimators and a half an hour total acquisition time. Datasets are reconstructed by filtered backprojection with Butterworth or Metz filtres. Images are visually interpreted with comparison to MRI and/or CT findings.

Frequency of diagnostic dilemmas in 131I whole body scanning.

AIM: The specific excretion pathways of iodine may cause several diagnostic pitfalls. Information concerning their relative frequency and possible consequences in daily routine is scarce. METHODS: A total of 500 (131)I whole-body scans from 300 consecutive patients with differentiated thyroid cancer of two centers were analyzed. The reports were validated with other diagnostic findings during follow-up for 12 to 85 months. 126 scans (25.2%) were performed at the time of discharge after high dose (131)I therapy (2960-11100 MBq). Residual activity was approximately 185 MBq (131)I at the time of imaging. 374 scans (74.8%) were performed in ambulatory patients 48 h after oral administration of 74 MBq (131)I. All patients revealed TSH concentrations >35 micro U/ml. RESULTS: A computerized literature search revealed 74 entities that may cause a false-positive whole body scan, from which 12 were present in our cohort. The uptake patterns could be epitomized into nine clinical settings. Apart from the significantly higher frequency of cervical activity in residual thyroid tissue in patients after high dose therapy no statistically significant difference was found between high and low dose patients. The most frequent combination was stomach and colon activity, which was seen in 15.3% of all scans. Additional images or diagnostic procedures were necessary in 59.3%. Only one patient with a kidney metastasis was initially misinterpreted. The major clinical problems included: contamination, superimposed intestinal retention, hot nose, isolated peripheral metastasis, unexpected breast activity and kidney metastasis. CONCLUSION: (131)I whole-body scanning has to be performed with painstaking precision and full awareness of even the rarest pitfalls in order to remain a sensitive and specific technique for diagnosing metastases from differentiated thyroid carcinoma.

Lack of impact of radioiodine therapy in tg-positive, diagnostic whole-body scan-negative patients with follicular cell-derived thyroid cancer.

Several reports have suggested a benefit from radioactive iodine (RAI) therapy in Tg-positive, whole-body scan-negative patients with follicular cell-derived thyroid cancer, who were said to have high rates of visualization of uptake in metastases after therapeutic doses of RAI. We sought to evaluate the rate of visualization of RAI uptake in these patients and determine the effect of such therapy on tumor progression and Tg levels. We studied 24 consecutive patients who had been treated with high-dose RAI, four of whom had no evidence of metastasis or persistent cancer. Our results showed that four patients had some uptake in posttherapy scans: in the neck, lung, and mediastinal metastases in one patient, in the thyroid remnant in two, and in a possible neck microrecurrence in one. In 13 patients with macrometastases-tumors 1 cm or greater-tumors progressed and serum Tg increased; five have died of thyroid cancer. The disease remained stable in the seven patients with micrometastases. We concluded that in high-risk patients with follicular cell-derived thyroid cancer with high Tg levels and negative diagnostic whole-body scans, only a small number showed meaningful uptake after high doses of RAI. Therefore, widespread use of empiric RAI therapy for such patients who have a large tumor burden should not be encouraged.

Preoperative functional assessment of auditory cortex in adult cochlear implant users.

OBJECTIVES: To explore functional neuroanatomical responses to auditory stimulation before and after implantation. STUDY DESIGN: A prospective study of three cochlear implant candidates (pure-tone averages of 90 dB HL or greater bilaterally and hearing in noise test [HINT] performances of <40%) in which regional cerebral blood flow (rCBF) was assessed using single photon emission computed tomography (SPECT). METHODS: Candidates watched a 15-minute videotaped story under four conditions: audio presented monaurally in the right and left ears (aided), audio presented binaurally (aided), and visual-only presentation of the story. Five minutes into each story, 20 to 25 mCi of technetium 99m (99mTc) hexamethyl-propyleneamine-oxime (HMPAO) (Ceratec; Nycomed Amersham, Princeton, NJ, U.SA) was injected over a 30-second period to ensure that subjects were unaware of tracer administration. Subjects were scanned for 20 minutes using a PRISM 3000 gamma camera (Picker International, Cleveland, OH, U.S.A.). Data were normalized and co-registered, and subtraction images were compiled. Subtraction images contrasted activation patterns generated under the visual-only control condition to the auditory activation states acquired monaurally and binaurally. RESULTS: Right and left ear monaural stimulation in normal hearing subjects resulted in significant bilateral activation of Brodmann areas 41, 42, 21, 22, and 38. Although substantial intersubject response variability was noted, subjects generally failed to bilaterally activate these areas under monaural hearing aid presentations; however, bilateral activation of areas 41 and 22 was noted under binaural presentations. CONCLUSIONS: Despite relatively similar hearing losses in each ear, significant differences in preoperative auditory cortex activation were observed between ears. These data suggest that functional brain imaging provides a useful tool for exploring the responsiveness of the auditory cortex in cochlear implant candidates.