Pustulosis exantemática aguda generalizada asociada a Epstein Barr: A propósito de un caso / Acute generalized exanthematous pustulosis associated to Epstein Barr: A propose of a case

Acute generalized exanthematous pustulosis (AGEP) is a rare skin eruption most commonly caused by medications. It is characterized by an acute eruption of sterile pustules and it is accompanied by an episode of fever, which regresses a few days after discontinuation of the drug that caused the condition. We report a case 23 year-old woman without history of psoriasis, that consults for fever and an acute generalized pustular eruption after amoxicillin, with clavulanic acid administration in a mononucleosis infection context, which resolved spontaneously. The microbiologic culture was negative for pathogenic germens.

La pustulosis exantemática aguda generalizada (PEAG) es una rara afección de hipersensibilidad, inducida principalmente por drogas y se manifiesta por una erupción aguda de pústulas estériles, acompañada de fiebre, que regresa en pocos días luego de discontinuar el fármaco causante. Se comunica el caso de una paciente de 23 años de edad, sin antecedentes de psoriasis que consulta por fiebre y una erupción pustulosa generalizada, asociada a la ingesta previa de amoxicilina y ácido clavulánico en el contexto de una mononucleosis infecciosa, con resolución espontánea del cuadro. El cultivo microbiológico no objetivó gérmenes patógenos.

Progresión a necrólisis epidérmica tóxica por uso de lamotrigina: A propósito de un caso / Progression to toxic epidermal necrolysis by using lamotrigina: In connection of a case

El Síndrome de Stevens Johnson (SSJ), el Síndrome de Superposición (SSJ/ NET) y la Necrólisis Epidérmica Tóxica (NET) son formas clínicas cutáneo-mucosas graves, desencadenadas por fármacos y muy frecuentemente por anticonvulsivantes. Comunicamos el caso de una paciente medicada por su epilepsia, quién presentó un cuadro incipiente de SSJ empeorando rápidamente hasta derivar en la NET. A pesar de la gravedad, la paciente respondió satisfactoriamente a altas dosis de corticoides sistémicos desde el comienzo y por las medidas de soporte del equipo médico multidisciplinario del hospital.

The Stevens Johnson Syndrome, the Overlape Syndrome (SSJ / NET), and the Toxic Epidermal Necrolysis are clinical cutaneous mucouse forms due to drugs administration and most frequently due caused by antiepileptic. We communicate the case of a patient treated with lamotrigina for epilepsy, who presented an incipient case of Stevens Johnson Syndrome, worsened rapidly causing a Toxic Epidermal Necrolysis. Nevertheless, the patient gained a satisfactory answer due to high doses of corticoids, which were given from the beginning as well as the measures and the support of the whole medical team of the hospital.

Inusual presentación de un Linfoma B cutáneo en un paciente joven / Unusual presentation of a cutaneous B Lymphoma in a young male

Se reporta el caso de un paciente masculino de 23 años de edad, que se presenta con una úlcera de región latero cervical, única, sin compromiso del estado general. Se solicita estudio histopatológico de la lesión e inmunomarcación, con diagnóstico de Linfoma no Hodgkin B de células grandes cutáneos primarios. Se realiza una revisión sobre los Linfomas no Hodgkin B de células grandes cutáneos primarios, siendo anecdótica la presentación en pacientes jóvenes.

We report a case of a 23 year old male with a lateral cervical ulcer, without general involvement. Histophatological study and immunomarcation were positive to non Hodgkin Difuse Primary Cutaneous Large B-Cell Lymphoma. A revision was made about Primary Cutaneous B-Cell Lymphomas, being unusual this presentation in young people.

Relation of thallium uptake to morphologic features of chronic ischemic heart disease: evidence for myocardial remodeling in noninfarcted myocardium.

OBJECTIVES: The aim of this study was to investigate the disparity between the extent of myocardial injury as assessed by thallium and the severity of left ventricular (LV) dysfunction in chronic ischemic heart disease. BACKGROUND: Although it is believed that thallium differentiates between viable and nonviable myocardium, in some patients with chronic ischemic heart disease, viable regions by thallium may fail to improve function after revascularization. METHODS: Thirteen transplant candidates with chronic ischemic heart disease (LV ejection fraction = 14 +/- 6% at rest) were studied prospectively with stress-redistribution-reinjection thallium single-photon emission computed tomography. We examined pretransplantation quantitative thallium uptake and post-transplantation extent and the histological distribution of collagen replacement in infarcted and noninfarcted myocardium and in 13 age-matched control hearts. RESULTS: The volume fraction of collagen varied inversely with wall thickness (r = -0.70, p < 0.001) and was higher in irreversible (30.9 +/- 15.8%) compared with reversible (20.2 +/- 12.6%, p < 0.001) or normal thallium segments (15.0 +/- 8.7%, p < 0.001). The irreversible thallium segments had lower wall thickness and more severe coronary artery narrowing (9.7 +/- 2.8 mm and 95 +/- 8%) compared with reversible (11.7 +/- 2.7 mm and 87 +/- 13%, p < 0.001) and normal thallium segments (12.8 +/- 2.6 mm and 80 +/- 14%, p < 0.001). Mean volume fraction of collagen was significantly lower in noninfarcted than it was in infarcted segments (13 +/- 6% vs. 36 +/- 13%, p < 0.001) but exceeded that in the control hearts (4 +/- 2%, p < 0.001). Noninfarcted segments had predominantly interstitial fibrosis with either microscopic or patchy areas of replacement fibrosis. CONCLUSIONS: In chronic ischemic heart disease with severe LV dysfunction, patterns of normal, reversible and irreversible thallium uptake correlated with the magnitude of collagen replacement, segmental wall thickness and severity of coronary artery narrowing. The finding of scattered areas of replacement fibrosis in noninfarcted myocardium may explain the observed disparity between LV contractile dysfunction and the extent of myocardial injury assessed by thallium.

Therapeutic angiogenesis with recombinant fibroblast growth factor-2 improves stress and rest myocardial perfusion abnormalities in patients with severe symptomatic chronic coronary artery disease.

BACKGROUND: We report the effects of the administration of recombinant fibroblast growth factor-2 (rFGF-2) protein on myocardial perfusion using single photon emission computed tomography imaging in humans with advanced coronary disease. METHODS AND RESULTS: A total of 59 patients with coronary disease that was not amenable to mechanical revascularization underwent intracoronary (n=45) or intravenous (n=14) administration of rFGF-2 in ascending doses. Changes in perfusion were evaluated at baseline and again at 29, 57, and 180 days after rFGF-2 administration. In this uncontrolled study, perfusion scans were analyzed by 2 observers who were blinded to patient identity and test sequence; scans were displayed in random order, with scans from nonstudy patients randomly interspersed to enhance blinding. Combining all dose groups, a reduction occurred in the per-segment reversibility score (reflecting the magnitude of inducible ischemia) from 1.7+/-0.4 at baseline to 1.1+/-0.6 at day 29 (P:<0.001), 1.2+/-0.7 at day 57 (P:<0.001), and 1.1+/-0.7 at day 180 (P:<0.001). The 37 patients with evidence of resting hypoperfusion had evidence of improved resting perfusion: their per-segment rest perfusion score of 1.5+/-0. 5 at baseline decreased to 1.0+/-0.8 at day 29 (P:<0.001), 1.0+/-0.8 at day 57 (P:=0.003), and 1.1+/-0.9 at day 180 (P:=0.11). CONCLUSIONS: These preliminary data suggest that the administration of rFGF-2 to patients with advanced coronary disease resulted in an attenuation of stress-induced ischemia and an improvement in resting myocardial perfusion; these findings are consistent with a favorable effect of therapeutic angiogenesis.

Myocardial blood flow at rest and contractile reserve in patients with chronic coronary artery disease and left ventricular dysfunction.

BACKGROUND: The mechanisms that determine chronic left ventricular dysfunction in coronary artery disease (in particular, critical reductions in coronary artery blood flow leading to hibernating myocardium) may affect the ability of the myocardium to respond to inotropic stimulation with dobutamine. This study was designed to investigate the relationship between resting myocardial blood flow and contractile reserve in patients with coronary artery disease and chronic left ventricular dysfunction. METHODS AND RESULTS: Twenty-three patients (21 men and 2 women; age 61 +/- 9 years) underwent transesophageal echocardiography during infusion of dobutamine (2.5 microg/kg to 40 microg/kg per minute) and positron emission tomography (PET) with 150-water (9 patients) or 13N-ammonia (14 patients). Systolic wall thickening at each dose of dobutamine and resting myocardial blood flow were quantitatively analyzed in 8 anatomically matched regions at mid-ventricular level. Myocardial regions with preserved contraction had higher blood flow compared with regions with basal dyssynergy (0.99 +/- 0.3 vs 0.65 +/- 0.3 mL/min/gm; P < .0001). Among myocardial regions with preserved resting contraction, no relation was observed between blood flow and the response to dobutamine (r = 0.06). In contrast, among myocardial regions with diminished resting contraction, a significant correlation was observed between resting blood flow and contractile reserve (r = 0.53; P < .0001). The maximum increase in percent systolic wall thickening with dobutamine was 32.8% +/- 14% in regions with normal blood flow, 21.5% +/- 17% in regions with mildly to moderately reduced blood flow, and 10.7% +/- 10% in regions with severely reduced blood flow (P < .0001). CONCLUSIONS: These findings emphasize the importance of resting myocardial blood flow for the preservation of contractile reserve in patients with coronary artery disease and left ventricular dysfunction. Because a positive inotropic response to dobutamine is more likely to occur in dyssynergic regions with preserved rather than reduced myocardial blood flow, regional perfusion may determine in which circumstances dobutamine echocardiography contributes to the assessment of myocardial viability.

Segmentation of gated Tl-SPECT images and computation of ejection fraction: a different approach.

BACKGROUND: We describe a set of image processing algorithms and mathematical models that can be advantageously used in schemes for the segmentation of thallium-201-single photon emission computed tomography (SPECT) images and for computation of left ventricular ejection fraction (EF). METHODS: The system consists of two independent blocs for image segmentation and computation of function. The former is based on a multiresolution elliptical coordinate transformation and dynamic contour tracking. Computation of EF is formulated on the basis of both the endocardial and epicardial contours, and we compare this formulation with that using only the endocardial border for images with low signal-to-noise ratios. The accuracy of border detection was validated against manual border tracing on FDG-PET images, simulated Tl-201-SPECT images where the true underlying borders were known, and actual Tl-201-SPECT images. Finally, we compared EFs computed for FDG-PET, technetium-99m-SPECT and Tl-201-SPECT with those obtained from planar gated blood pool imaging. RESULTS: The automatically obtained results always were within the manual uncertainty range. Agreement between myocardial volumes from positron emission tomography and automatically obtained values from the simulated Tl-201-SPECT images was excellent (r = 0.95, n = 32). Agreement between EFs from planar gated blood pool imaging and the other image modalities was good (FDG-PET: y = 5.89 + 1.21x, r = 0.92, see = 6.24, n = 19, Tc-99m-SPECT: y = -3.86 + 1.06x, r = 0.88, see = 7.78, n = 9, Tl-201-SPECT: y = 17.8 + 0.81x, r = 0.77, see = 7.44, n = 26). For noisy input data the combined use of information from epicardial and endocardial contours gives more accurate EF values than the traditional formula on the basis of the endocardial contour only. CONCLUSIONS: Alternate approaches for segmentation and computation of function have been presented and validated. They might also be advantageously incorporated into other existing techniques.

13N-ammonia myocardial blood flow and uptake: relation to functional outcome of asynergic regions after revascularization.

OBJECTIVES: In this study we determined whether 13N-ammonia uptake measured late after injection provides additional insight into myocardial viability beyond its value as a myocardial blood flow tracer. BACKGROUND: Myocardial accumulation of 13N-ammonia is dependent on both regional blood flow and metabolic trapping. METHODS: Twenty-six patients with chronic coronary artery disease and left ventricular dysfunction underwent prerevascularization 13N-ammonia and 18F-deoxyglucose (FDG) positron emission tomography, and thallium single-photon emission computed tomography. Pre- and postrevascularization wall-motion abnormalities were assessed using gated cardiac magnetic resonance imaging or gated radionuclide angiography. RESULTS: Wall motion improved in 61 of 107 (57%) initially asynergic regions and remained abnormal in 46 after revascularization. Mean absolute myocardial blood flow was significantly higher in regions that improved compared to regions that did not improve after revascularization (0.63+/-0.27 vs. 0.52+/-0.25 ml/min/g, p < 0.04). Similarly, the magnitude of late 13N-ammonia uptake and FDG uptake was significantly higher in regions that improved (90+/-20% and 94+/-25%, respectively) compared to regions that did not improve after revascularization (67+/-24% and 71+/-25%, p < 0.001 for both, respectively). However, late 13N-ammonia uptake was a significantly better predictor of functional improvement after revascularization (area under the receiver operating characteristic [ROC] curve = 0.79) when compared to absolute blood flow (area under the ROC curve = 0.63, p < 0.05). In addition, there was a linear relationship between late 13N-ammonia uptake and FDG uptake (r = 0.68, p < 0.001) as well as thallium uptake (r = 0.76, p < 0.001) in all asynergic regions. CONCLUSIONS: These data suggest that beyond its value as a perfusion tracer, late 13N-ammonia uptake provides useful information regarding functional recovery after revascularization. The parallel relationship among 13N-ammonia, FDG, and thallium uptake supports the concept that uptake of 13N-ammonia as measured from the late images may provide important insight regarding cell membrane integrity and myocardial viability.

What is new in nuclear medicine imaging?

Modern nuclear medicine tests can be of great help to today's surgical oncologists. The new techniques of positron emission tomography (PET) and single photon emission computed tomography (SPECT), and the availability of new radiopharmaceuticals for localization of tumors and assessment of organ function provide information vital to the management of oncology patients.

Thallium scintigraphy compared with 18F-fluorodeoxyglucose positron emission tomography for assessing myocardial viability in patients with moderate versus severe left ventricular dysfunction.

Thallium-201 reinjection imaging and positron emission tomography provide concordant information regarding myocardial viability in many patients with coronary artery disease and left ventricular (LV) dysfunction. It is unclear whether this concordance applies to patients with severe, as well as those with moderate, LV dysfunction. We studied 44 patients with chronic coronary artery disease and LV dysfunction, subgrouped on the basis of severity of dysfunction: 23 patients had moderate and 21 had severe dysfunction (ejection fractions 34 +/- 6% and 19 +/- 6%). Patients underwent exercise thallium single-photon emission computed tomography (SPECT) with 3- to 4-hour redistribution and reinjection imaging, as well as positron emission tomography (PET) imaging with 18fluorodeoxyglucose and 15O-water. Data were analyzed quantitatively in aligned transaxial PET and SPECT tomograms. A myocardial region was considered nonviable by PET if 18fluorodeoxyglucose activity was <50% of that in a normal region, associated with proportional reduction in blood flow. Similarly, regions were considered nonviable by thallium if activity was <50% of activity in normal regions on redistribution and reinjection studies. Thallium SPECT and PET data were concordant regarding viability in 98% and 93% of myocardial regions, respectively, in patients with moderate and with severe LV dysfunction. Lower concordance was observed only when regions with severe irreversible thallium perfusion defects on redistribution images were considered in both groups: 86% and 78%, respectively (p <0.01). Thus, thallium SPECT with reinjection yields information regarding regional myocardial viability that is similar to that provided by PET in patients with severe as well as moderate LV dysfunction. However, there is discordance in >20% of regions manifesting severe irreversible thallium defects in patients with severely reduced LV function.

Stress-induced reversible and mild-to-moderate irreversible thallium defects: are they equally accurate for predicting recovery of regional left ventricular function after revascularization?

BACKGROUND: In patients with coronary artery disease, stress-redistribution-reinjection thallium scintigraphy provides important information regarding myocardial ischemia and viability. Although both reversible and mild-to-moderate irreversible thallium defects retain metabolically active, viable myocardium, we hypothesized that stress-induced reversible thallium defects may better differentiate reversible from irreversible regional left ventricular dysfunction after revascularization. METHODS AND RESULTS: Twenty-four patients with chronic coronary artery disease underwent prerevascularization and postrevascularization exercise-redistribution-reinjection thallium single photon emission CT, gated MRI, and radionuclide angiography. After revascularization, mean left ventricular ejection fraction increased from 30+/-9% to 37+/-13% at rest (P<0.001). Before revascularization, abnormal contraction at rest was observed in 56 of 110 reversible and 20 of 37 mild-to-moderate irreversible thallium defects (51% and 54%, respectively). After revascularization, regional contraction improved in 44 of 56 reversible compared with 6 of 20 mild-to-moderate irreversible thallium defects (79% and 30%, respectively; P<0.001). The final thallium content (maximum tracer uptake on redistribution-reinjection images) was significantly higher in regions with reversible defects that improved than in those that did not improve after revascularization (86+/-16% versus 66+/-9%, P<0.001). In contrast, final thallium content was similar in regions with mild-to-moderate irreversible defects that improved and in those that did not improve after revascularization (69+/-9% versus 65+/-10%, P=NS). Furthermore, when asynergic regions were grouped according to the final thallium content, at 60% threshold value, functional recovery was observed in 83% of regions with reversible defects compared with 33% of regions with mild-to-moderate irreversible defects (P<0.001). CONCLUSIONS: These findings suggest that although both reversible and mild-to-moderate irreversible thallium defects after stress retain viable myocardium, the identification of reversible thallium defect on stress in an asynergic region more accurately predicts recovery of function after revascularization. Even at a similar mass of viable myocardial tissue (as reflected by the final thallium content), the presence of inducible ischemia is associated with an increased likelihood of functional recovery.

[18F]fluorodeoxyglucose single photon emission computed tomography: can it replace PET and thallium SPECT for the assessment of myocardial viability?

BACKGROUND: New high-energy collimators for single photon emission computed tomography (SPECT) cameras have made imaging of positron-emitting tracers, such as [18F]fluorodeoxyglucose (18FDG), possible. We examined differences between SPECT and PET technologies and between 18FDG and thallium tracers to determine whether 18FDG SPECT could be adopted for assessment of myocardial viability. METHODS AND RESULTS: Twenty-eight patients with chronic coronary artery disease (mean left ventricular ejection fraction [LVEF]=33+/-15% at rest) underwent 18FDG SPECT, 18FDG PET, and thallium SPECT studies. Receiver operating characteristic curves showed overall good concordance between SPECT and PET technologies and thallium and 18FDG tracers for assessing viability regardless of the level of 18FDG PET cutoff used (40% to 60%). However, in the subgroup of patients with LVEF< or =25%, at 60% 18FDG PET threshold value, thallium tended to underestimate myocardial viability. In a subgroup of regions with severe asynergy, there were considerably more thallium/18FDG discordances in the inferior wall than elsewhere (73% versus 27%, P<.001), supporting attenuation of thallium as a potential explanation for the discordant observations. When uptake of 18FDG by SPECT and PET was compared in 137 segments exhibiting severely irreversible thallium defects (scarred by thallium), 59 (43%) were viable by 18FDG PET, of which 52 (88%) were also viable by 18FDG SPECT. However, of the 78 segments confirmed to be nonviable by 18FDG PET, 57 (73%) were nonviable by 18FDG SPECT (P<.001). CONCLUSIONS: Although 18FDG SPECT significantly increases the sensitivity for detection of viable myocardium in tissue declared nonviable by thallium (to 88% of the sensitivity achievable by PET), it will occasionally (27% of the time) result in falsely identifying as viable tissue that has been identified as nonviable by both PET and thallium.

Improved specificity of transesophageal dobutamine stress echocardiography compared to standard tests for evaluation of coronary artery disease in women presenting with chest pain.

The detection of coronary artery disease (CAD) by noninvasive methods has been hindered in women by the high rate of false-positive results. To determine the feasibility and accuracy of transesophageal dobutamine stress echocardiography for identification of CAD in women, we studied 84 patients (age 51 +/- 11 years) who underwent symptom-limited exercise treadmill testing, exercise thallium-201 scintigraphy, and coronary angiography for evaluation of anginal chest pain. Of the 84 patients, 62 had normal coronary arteries or nonsignificant coronary lesions, and 22 had significant stenosis of > or = 1 major coronary artery. During treadmill exercise, repolarization changes were observed in 16 of 21 patients with CAD and in 19 of 60 patients with normal coronary arteries. With thallium scintigraphy, a reversible defect was observed in 19 of 22 patients with CAD and in 12 of 60 patients with normal coronary arteries. Regional wall motion abnormalities during dobutamine infusion developed in 18 of 22 patients with CAD and in none of the 62 patients with normal coronary arteries. All 3 tests had similar sensitivity for detection of CAD (76% for exercise treadmill test, 86% for thallium scintigraphy, and 82% for transesophageal dobutamine stress echocardiography). However, transesophageal dobutamine stress echocardiography had significantly higher specificity than the other 2 tests (100% vs 68% for exercise treadmill test and 80% for thallium scintigraphy; p = 0.0001). Thus, transesophageal dobutamine stress echocardiography is accurate for evaluation of CAD among women presenting with chest pain; its use should be considered when more conventional tests are equivocal or technically suboptimal.

A "hybrid" method for measuring myocardial wall thickening from gated PET/SPECT images.

UNLABELLED: We introduce a hybrid index, HYB, which combines counts with geometric information to measure wall thickening from PET/SPECT gated images. Its accuracy is compared with that of a count-based index (MAX) and a geometric index (FWHM). METHODS: For each index, the index values versus thickness and the estimated thickening values versus true thickening were investigated using theoretical analyses, realistic simulated data obtained from clinical gated MR scans, phantom measurements and preliminary gated MRI and PET patient studies. Each index was studied for different spatial resolutions and noise and background conditions. The performance of each index was quantified using a parameter "Q" reflecting bias and variability of thickening estimates. RESULTS: HYB varied more linearly with thickness than MAX and FWHM, resulting in a better Q value than with MAX and FWHM for all noise, background and spatial resolutions. ROC analysis confirmed that HYB significantly increases the sensitivity and specificity for detection of wall thickening abnormalities (sensitivity = 100%; specificity = 85% for HYB, 95% and 50% for MAX and 100% and 0% for FWHM, respectively). CONCLUSION: Use of the hybrid index instead of conventional count-based or geometric indices should improve the classification of normal/abnormal wall thickening values in gated SPECT and PET.

Investigation of the mechanism of chest pain in patients with angiographically normal coronary arteries using transesophageal dobutamine stress echocardiography.

OBJECTIVES: The present study sought to determine whether myocardial contractile abnormalities accompany the development of chest pain in patients with normal coronary angiograms. BACKGROUND: The mechanism of chest pain in patients with angina despite a normal coronary arteriogram is controversial. Although previous studies postulated the existence of coronary microvascular dysfunction, others failed to find evidence of myocardial ischemia, and recent studies have demonstrated abnormal cardiac sensitivity in these patients that can lead to chest pain on a nonischemic basis. METHODS: Seventy patients (26 men and 44 women, mean age 49 +/- 10 years) with angina-like chest pain and angiographically normal coronary arteries underwent exercise treadmill testing, radionuclide angiography at rest and during exercise, thallium stress testing and transesophageal dobutamine stress echocardiography. The results of exercise treadmill testing and stress echocardiography were compared with those obtained in 26 normal control subjects (19 men and 7 women, mean age 56 +/- 7 years). RESULTS: Abnormalities consistent with myocardial ischemia were noted in 31% of the patients during exercise treadmill testing, in 16% during exercise radionuclide angiography and in 18% during thallium stress testing. The findings of the radionuclide studies were not concordant with one another and were not related to the presence of repolarization changes during exercise testing. During infusion of dobutamine, chest pain developed in 59 patients (84%) and in none of the control subjects (p < 0.0001); repolarization changes occurred in 22 patients (34%) and in 2 control subjects (8%) (p < 0.04). None of the patients or the control subjects developed regional wall motion abnormalities with dobutamine. The quantitative myocardial contractile response to dobutamine was similar in patients and control subjects, with an 80% power to detect a 25% difference in systolic wall thickening at the maximal dose of dobutamine. CONCLUSIONS: There was no agreement in the results of noninvasive tests in our patients. Despite the frequent provocation of chest pain and electrocardiographic abnormalities with dobutamine, the patients demonstrated a quantitatively normal myocardial contractile response without development of wall motion abnormalities. These observations strongly suggest that myocardial ischemia is not the cause of chest pain in patients with a normal coronary arteriogram.

Left ventricular ejection fraction: comparison of results from planar and SPECT gated blood-pool studies.

UNLABELLED: Global ejection fraction (EF) from planar gated blood-pool (GBP) imaging is a widely accepted measure of cardiac function. It has been suggested that planar GBP could be replaced by SPECT. In this article, we compare counts-based global EF measured from SPECT and planar images and investigate reasons for discrepancies between the two. METHODS: Twenty-three subjects were imaged with both planar and SPECT GBP. SPECT short-axis slices were projected to create reprojected images. Reprojected SPECT (rSPECT) images were created in both the true long-axis view and also in a view typical of planar studies (found to be 60 degrees from the true long-axis). Thus, angle of view effects on global EF could be investigated. In addition, we studied the effects of background and attenuation. RESULTS: Long-axis rSPECT EF correlated well with planar EF (r = 0.89) but EF values were significantly higher for rSPECT than for planar (slope = 1.4, intercept = -8 EF units; p < 0.001). We found that background correction may not be necessary with rSPECT, but neither background nor attenuation explained the observed discrepancy between rSPECT and planar EFs. This discrepancy was found to be caused by atrial overlap in the planar image and disappeared when the SPECT slices were reprojected at the same angle of view as the planar images. CONCLUSION: Global EF can be easily measured from rSPECT GBP images. Long-axis rSPECT EFs are, however, greater than planar EFs by a factor of 1.4 because atrial overlap causes a significant drop in planar EF in planar images. These results suggest that (long-axis) rSPECT EFs may be more accurate than planar EFs.

Realignment of emission contaminated attenuation maps with uncontaminated attenuation maps for attenuation correction in PET.

PURPOSE: We investigated aligning a transmission (T) scan with a subsequent emission contaminated transmission (T+E) scan. This would permit correction for patient motion and thereby use of a single T scan to correct E scans taken hours or days apart. METHOD: Scans from 15 patients were used to produce 200 T scans contaminated with two levels of either [18F]fluorodeoxyglucose or [13N]ammonia E data. Known misalignments were introduced between each T+E scan and the corresponding T scan, and each pair was subsequently realigned. Realignment errors were compared with those obtained for uncontaminated T scans. RESULTS: The realignment errors increase with the contamination level and depend slightly on the contaminant. However, even at the highest level of contamination studied, the mean absolute translation errors remained less than the voxel size and the mean absolute rotation errors were < 2.5 degrees. CONCLUSION: AT+E scan can be accurately realigned with a T scan. This suggests that attenuation correction could be performed by using a high quality T scan taken days or hours earlier and aligning this T scan with a short T scan taken immediately after E imaging.