The cost effectiveness of <Superscript>123</Superscript>I-FP-CIT SPECT imaging in patients with an uncertain clinical diagnosis of parkinsonism

PURPOSE: (123)I-N-omega-fluoropropyl-2-beta-carboxymethoxy-3beta-(4-iodophenyl)nortropane ((123)I-FP-CIT) Single-photon emission computed tomography (SPECT) has been suggested to be a useful diagnostic adjunct in patients with clinically uncertain parkinsonism. We developed a pharmaco-economic (PE) model, evaluating the cost effectiveness of adding (123)I-FP-CIT SPECT to the diagnostic workup. As the model was developed before application of the diagnostic technique in real practice, a predictive validity assessment was performed based on data from a large nationwide patient registry in these patients. METHODS: A PE model, using a Markov state transition model, was created, based on literature-derived and clinical expert panel data. Effects were expressed as adequately treated years (ATY). Key input data were compared to the real-life patterns in a nationwide multi-centre clinical setting, based on a complete national registry of 1,701 consecutive patients. The change in initial diagnosis and alteration of management of the patient after SPECT were registered. RESULTS: In the PE model, it was calculated that management would change in 48.5% of patients by SPECT and that, over a 5-year period, 1.2 ATYs could be gained at a yearly additional cost of 72. From the studied 1,701 patients, nigrostriatal degeneration was observed in 59.8%, the initial diagnosis was changed in 51.5%, management was altered in 49%, and cost effectiveness was increased to 358 per ATY. CONCLUSION: Good correspondence between assumed and observed changes in patient management was found, indicating that (123)I-FP-CIT SPECT is influential in diagnosis and management of patients with uncertain clinical diagnosis of parkinsonism. This can be achieved at a marginal added cost to the health insurance and leads to a significant gain in ATY.     

Clinical correlation of the binding potential with <Superscript>123</Superscript>I-FP-CIT in de novo idiopathic Parkinson’s disease patients

Purpose  The aim of this study was to evaluate the accuracy of different single-photon emission computed tomography (SPECT) reconstruction techniques in measuring striatal N-ω-fluoropropyl-2β-carbomethoxy-3β-4-[¹²³I]iodophenyl-nortropane (¹²³I-FP-CIT) binding in de novo Parkinson’s disease (PD) patients, in order to find a correlation with clinical scales of disease severity in the initial phases of disease. Methods  Thirty-six de novo PD patients underwent ¹²³I-FP-CIT SPECT and MRI scan. SPECT data were reconstructed with filtered back projection (FBP), with an iterative algorithm (ordered subset expected maximization, OSEM) and with a method previously developed in our institution, called least-squares (LS) method. The ratio of specific to non-specific striatal ¹²³I-FP-CIT binding (binding potential, BP) was used as the outcome measure with all the reconstruction methods (BP_FBP, BP_OSEM, BP_LS). Results  The range of values of striatal BP_LS was significantly greater than BP_FBP and BP_OSEM. For all striatal regions, estimates of BP_FBP correlated well with BP_OSEM (r = 0.84) and with BP_LS (r = 0.64); BP_OSEM correlated significantly with BP_LS (r = 0.76). A good correlation was found between putaminal BP_LS and Hoen and Yahr, Unified PD Rating Scale (UPDRS) and lateralized UPDRS motor scores (r = −0.46, r = −0.42, r = −0.39, respectively). Neither putaminal BP_FBP nor putaminal BP_OSEM correlated with any of these motor scores. Conclusions  In de novo PD patients, ¹²³I-FP-CIT BP values derived from FBP and OSEM reconstruction techniques do not permit to differentiate PD severity. The LS method instead finds a correlation between striatal BP and disease severity scores. The results of this study support the use of ¹²³I-FP-CIT BP values estimated with the LS method as a biomarker of PD severity.     

The basal ganglia matching tools package for striatal uptake semi-quantification: description and validation

PURPOSE: To design a novel algorithm (BasGan) for automatic segmentation of striatal (123)I-FP-CIT SPECT. METHODS: The BasGan algorithm is based on a high-definition, three-dimensional (3D) striatal template, derived from Talairach's atlas. A blurred template, obtained by convolving the former with a 3D Gaussian kernel (FWHM = 10 mm), approximates striatal activity distribution. The algorithm performs translations and scale transformation on the bicommissural aligned image to set the striatal templates with standard size in an appropriate initial position. An optimization protocol automatically performs fine adjustments in the positioning of blurred templates to best match the radioactive counts, and locates an occipital ROI for background evaluation. Partial volume effect correction is included in the process of uptake computation of caudate, putamen and background. Experimental validation was carried out by means of six acquisitions of an anthropomorphic striatal phantom. The BasGan software was applied to a first set of patients with Parkinson's disease (PD) versus patients affected by essential tremor. RESULTS: A highly significant correlation was achieved between true binding potential and measured (123)I activity from the phantom. (123)I-FP-CIT uptake was significantly lower in all basal ganglia in the PD group versus controls with both BasGan and a conventional ROI method used for comparison, but particularly with the former. Correlations with the motor UPDRS score were far more significant with the BasGan. CONCLUSION: The novel BasGan algorithm automatically performs the 3D segmentation of striata. Because co-registered MRI is not needed, it can be used by all nuclear medicine departments, since it is freely available on the Web.     

Two patients with meningioma visualized as high uptake by SPECT with N-isopropyl-p-iodo-amphetamine (I-123)

Summary It has been reported that brain tumors show decreased IMP uptake, however, we encountered two cases of meningioma which had initially increased IMP uptake. SPECT was performed at 30 min, 2 hr and 6 hr after intravenous administration of IMP (3 mCi). The delayed images (2 and 6 h) showed decreased IMP uptake. These were convexity and parasagittal meningiomas which had tumor stains at angiography. Although the mechanism of IMP uptake in brain tumor is still unclear, this finding should be considered in the interpretation of IMP-SPECT.     

Relationship between striatal [123I]β-CIT binding and four major clinical signs in Parkinson’s disease

We investigated the correlation between clinical severity and striatal [123I]-CIT binding in 12 patients with Parkinson's Disease (PD: 6 men and 6 women, age: 65 +/- 7 years, Hoehn & Yahr stage: 1 to 3). The clinical severity of PD patients was measured with the Unified Parkinson's Disease Rating Scale (UPDRS) after withdrawal of antiparkinsonian medication at least 12 hours before assessment. [123I]beta-CIT binding in the caudate and putamen was measured at 3 hours [V'3 (day 1)], and at 24 hours [V'3 (day 2)) after tracer injection with small square ROIs. The specific striatal uptake index (day 2) was calculated with large square ROIs that encompassed the whole striatum. The best correlation (r = -0.82, p < 0.0012) was between putamenal V'3 (day 2) and the motor UPDRS scores. When the motor UPDRS scores were divided into four subscales, bradykinesia was the only sign that correlated significantly with putamenal V'3 (day 2) (r = -0.81, p < 0.002). [123I]beta-CIT SPECT is a useful marker of disease severity in PD with potential utility in the serial monitoring of disease progression.     

Automated Analysis of 123I-beta-CIT SPECT Images with Statistical Probabilistic Anatomical Mapping

Background

Population-based statistical probabilistic anatomical maps have been used to generate probabilistic volumes of interest for analyzing perfusion and metabolic brain imaging. We investigated the feasibility of automated analysis for dopamine transporter images using this technique and evaluated striatal binding potentials in Parkinson’s disease and Wilson’s disease.

Materials and Methods

We analyzed 2β-Carbomethoxy-3β-(4-¹²³I-iodophenyl)tropane (¹²³I-beta-CIT) SPECT images acquired from 26 people with Parkinson’s disease (M:F = 11:15, mean age = 49 ± 12 years), 9 people with Wilson’s disease (M: F = 6:3, mean age = 26 ± 11 years) and 17 normal controls (M:F = 5:12, mean age = 39 ± 16 years). A SPECT template was created using striatal statistical probabilistic map images. All images were spatially normalized onto the template, and probability-weighted regional counts in striatal structures were estimated. The binding potential was calculated using the ratio of specific and nonspecific binding activities at equilibrium. Voxel-based comparisons between groups were also performed using statistical parametric mapping.

Results

Qualitative assessment showed that spatial normalizations of the SPECT images were successful for all images. The striatal binding potentials of participants with Parkinson’s disease and Wilson’s disease were significantly lower than those of normal controls. Statistical parametric mapping analysis found statistically significant differences only in striatal regions in both disease groups compared to controls.

Conclusion

We successfully evaluated the regional ¹²³I-beta-CIT distribution using the SPECT template and probabilistic map data automatically. This procedure allows an objective and quantitative comparison of the binding potential, which in this case showed a significantly decreased binding potential in the striata of patients with Parkinson’s disease or Wilson’s disease.     

Single photon emission computed tomography with123I-IMP in three cases of the neuroleptic malignant syndrome

Single photon emission computed tomography (SPECT) perfusion brain scans using¹²³I-N-isopropyl-p-iodoamphetamine (¹²³I-IMP) were performed in three patients with the neuroleptic malignant syndrome (NMS). In two accumulation was increased in the left basal ganglia and decreased in the right on the early images during the active phase of NMS; this asymmetry was not seen after recovery. In the third patient two examinations were performed during the active phase; on the first, increased accumulation of¹²³I-IMP in the left basal ganglia was found on the early images, but on the second, increased accumulation of tracer was found in the right basal ganglia on the delayed images. These abnormalities disappeared after improvement of the NMS. These results suggest that a disturbance in the basal ganglia is related to the development of NMS.     

Diagnostic value of asymmetric striatal D<Subscript>2</Subscript> receptor upregulation in Parkinson’s disease: an [<Superscript>123</Superscript>I]IBZM and [<Superscript>123</Superscript>I]FP-CIT SPECT study

Introduction Striatal postsynaptic D₂ receptors in Parkinson’s disease (PD) are thought to be upregulated in the first years of the disease, especially contralateral to the clinically most affected side. The aim of this study was to evaluate whether the highest striatal D₂ binding is found contralateral to the most affected side in PD, and whether this upregulation can be used as a diagnostic tool. Methods Cross-sectional survey was undertaken of 81 patients with clinically asymmetric PD, without antiparkinsonian drugs and with a disease duration of ≤5 years and 26 age-matched controls. Striatal D₂ binding was assessed with [¹²³I]IBZM SPECT, and severity of the presynaptic dopaminergic lesion with [¹²³I]FP-CIT SPECT. Results The mean striato-occipital ratio of [¹²³I]IBZM binding was significantly higher in PD patients (1.56 ±0.09) than in controls (1.53 ±0.06). In PD patients, higher values were found contralateral to the clinically most affected side (1.57 ±0.09 vs 1.55 ±0.10 ipsilaterally), suggesting D₂ receptor upregulation, and the reverse was seen using [¹²³I]FP-CIT SPECT. However, on an individual basis only 56% of PD patients showed this upregulation. Conclusion Our study confirms asymmetric D₂ receptor upregulation in PD. However, the sensitivity of contralateral higher striatal [¹²³I]IBZM binding is only 56%. Therefore, the presence of contralateral higher striatal IBZM binding has insufficient diagnostic accuracy for PD, and PD cannot be excluded in patients with parkinsonism and no contralateral upregulation of D₂ receptors, assessed with [¹²³I]IBZM SPECT.     

Metaiodobenzylguanidine (MIBG) uptake in Parkinson’s disease also decreases at thyroid

BACKGROUND: Decreased cardiac metaiodobenzylguanidine (MIBG) uptake was reported in Parkinson's disease and this contributes to the differential diagnosis between Parkinson's disease and other forms of parkinsonism such as multiple system atrophy. However, decreased MIBG uptake of the thyroid has not been demonstrated. OBJECTIVE: To compare MIBG uptake of the thyroid among Parkinson's disease, multiple system atrophy and controls. METHODS: Twenty-six patients with Parkinson's disease, 11 patients with multiple system atrophy and 14 controls were examined in this study. Planar images were taken 15 minutes (early images) and 3 hours (late images) after intravenous injection of 111 MBq 123I-MIBG. RESULTS: MIBG uptake of the thyroid on early images decreased significantly in Parkinson's disease compared to controls (p < 0.0001) and multiple system atrophy (p = 0.018). MIBG uptake of the thyroid on early images decreased significantly also in multiple system atrophy compared to controls (p = 0.027). On late images, thyroid uptake differed significantly only between Parkinson's disease and controls (p = 0.010). CONCLUSIONS: Our study is the first to demonstrate decreased MIBG uptake of the thyroid in Parkinson's disease. Sympathetic nervous denervation of Parkinson's disease occurred not only in the heart but also in the thyroid.     

Cardiac <Superscript>123</Superscript>I-metaiodobenzylguanidine imaging allows early identification of dementia with Lewy bodies during life

PURPOSE: Differential diagnosis between dementia with Lewy bodies (DLB) and other neurodegenerative diseases with cognitive impairment represents a clinical challenge. Due to the overlapping of symptoms, the clinical diagnosis can be modified during the prolonged follow-up of these diseases. The purpose of this study was to assess the ability of cardiac metaiodobenzylguanidine (MIBG) imaging for early identification of DLB. MATERIALS AND METHODS: Since January 2003, all patients with neurodegenerative diseases with cognitive impairment at their first visit at the Memory Unit and clinical criteria of DLB were consecutively recruited and underwent a cardiac (123)I-MIBG study. The heart-to-mediastinum ratio (HMR) and the washout rate (WR) of cardiac MIBG uptake were obtained. RESULTS: Sixty-five patients were included. After a clinical follow-up of 4 years, the progress of the disease procured a definite diagnosis in 44 (68%) patients: 19 DLB, 12 Alzheimer disease (AD), and 13 other neurodegenerative diseases with cognitive impairment. HMR was significantly decreased in DLB with respect to the other neurodegenerative diseases. WR was only significantly different between DLB and AD. The HMR cut off point of 1.36 differentiated DLB from the other dementias with a sensitivity of 94% and a specificity of 96% with an accuracy of 95%. CONCLUSIONS: Cardiac MIBG imaging performed at the time of the first clinical diagnosis of DLB can help early clinical identification or exclusion of this disease.     

Primary activity standardization of Co by sum-peak method

The sum-peak method was applied to standardize a ⁵⁷Co solution within the framework of an international comparison organized by International Atomic Energy Agency, in 2008, aimed toward international traceability of activity measurements. A planar germanium detector was used with the sources placed on top of the detector for activity determination measurements. An analytical expression for accidental summing correction was derived and the effect of the germanium characteristic KX-ray escape peak of 112 keV was taken into account. The standard uncertainty associated to the activity concentration value was 0.37% and the result was compared with other measurement methods.     

99mTc-TRODAT-1 and 123I-IBZM SPECT studies in a patient with extrapontine myelinolysis with parkinsonian features

Osmotic demyelination syndrome can result from the rapid correction of hyponatremia, and is categorized by central pontine myelinolysis and extrapontine myelinolysis (EPM). Magnetic resonance imaging (MRI) is currently the most useful modality for visualizing EPM lesions. However, MRI is unable to delineate the severity of involvement in the nigrostriatal dopaminergic pathway. The authors describe the case of a 48-year-old woman who developed isolated EPM with predominantly right-sided parkinsonian symptoms after rapid correction of hyponatremia. MRI revealed symmetrical demyelinating lesions in the bilateral striatum without central pontine involvement. ^99mTc-TRODAT-1 and ¹²³I-iodobenzamide (¹²³I-IBZM) single-photon emission computed tomography (SPECT) images showed unequally decreased uptake in the bilateral striatum. Treatment with carbidopa/levodopa improved the clinical parkinsonian symptoms. ^99mT_C-TRODAT-1 and ¹²³I-IBZM SPECT images provide presynaptic and postsynaptic molecular information of the nigrostriatal dopaminergic pathway. The lesions demonstrated in the ^99mT_C-TRODAT-1 and ¹²³I-IBZM SPECT images show higher correlation with the severity of clinical features in EPM than MRI, and the modalities may be useful in the evaluation of patients with parkinsonian symptoms.     

Comparison between a dual-head and a brain-dedicated SPECT system in the measurement of the loss of dopamine transporters with [<Superscript>123</Superscript>I]FP-CIT

BACKGROUND: Dual-head SPECT systems are used by many clinical departments for [(123)I]FP-CIT SPECT imaging, while triple-head or brain-dedicated systems with better imaging performance are more commonly used by research institutions. There are limited data comparing the capability of the two types of system to measure dopamine transporter (DAT) loss in vivo. PURPOSE: The aim of this study was to compare the ability of a dual-head and a brain-dedicated SPECT system to estimate the degree of DAT loss in different movement disorders with variable nigrostriatal impairment, with [(123)I]FP-CIT. MATERIALS AND METHODS: Four patients with essential tremor, 24 with Parkinson's disease (PD), six with spinocerebellar ataxia type 2 and six controls were studied with [(123)I]FP-CIT. SPECT scans were performed on a dual-head (E.CAM-Siemens) and subsequently on a brain-dedicated system (Ceraspect-DSI). RESULTS: Striatal DAT outcome measures on the E.CAM and the Ceraspect were strongly correlated and the putamen-to-caudate ratios were almost identical. Although the measured values were lower by 52 +/- 25% in caudate and by 51 +/- 31% in putamen on the E.CAM (p < 0.0001), the average striatal DAT decrease in each patient group compared with controls was similar for both systems. In PD patients, similar correlations (p < 0.05) were found between motor UPDRS or Hoehn and Yahr stage and striatal DAT density. CONCLUSIONS: Despite underestimation of striatal DAT outcome measures, the E.CAM showed similar capability as the Ceraspect in measuring the degree of nigrostriatal dopaminergic deficit and assessing the correlation between DAT outcome measures and clinical variables of PD severity and stage.     

Usefulness of rCBF analysis in diagnosing Parkinson’s disease: supplemental role with MIBG myocardial scintigraphy

(123)I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy is a useful tool for differentiating idiopathic Parkinson's disease (PD) from parkinsonism (PS) caused by other disorders. However, cardiac MIBG uptake is affected by various causes. Alternatively, hypoperfusion in the occipital lobe of PD is reported recently. OBJECTIVE: The objective is to clarify the correlation between regional cerebral blood flow (rCBF) alteration and cardiac MIBG uptake in PD. In addition, we examined whether additional brain perfusion analysis improved the differential diagnostic ability for PD from PS when compared with MIBG scintigraphy alone. METHODS: Forty-nine patients with PD (27 mild groups: Hoehn and Yahr stages I, II; 22 severe groups: Hoehn and Yahr stages III, IV) and 28 patients with PS participated. We compared absolute rCBF values between PD and PS. In addition, we determined correlation between MIBG parameters and each rCBF value. Finally, we compared the diagnostic ability for the differentiation of PD from PS between two diagnostic criteria, each MIBG index abnormality alone [heart-to-mediastinum ratio, H/M (E) < 1.9, H/E (D) < 1.7, washout rate > 40%] and each MIBG index abnormality or occipital lobe hypoperfusion (<36 ml/100 g per min). RESULTS: Absolute rCBF value of occipital lobe was significantly lower in severe PD as compared with PS or mild PD. In the correlation analysis, rCBF of occipital lobe correlated positively with MIBG parameters (H/M). Regarding the diagnostic ability, sensitivity improved by accounting for occipital hypoperfusion as compared with MIBG indices alone. In contrast, neither specificity nor accuracy improved by adding occipital lobe analysis. CONCLUSIONS: MIBG parameters (H/M) correlated positively with occipital hypoperfusion in PD. In the differential diagnosis between PD and PS, although its usefulness might be limited, analysis of rCBF in the occipital lobe added to (123)I-MIBG myocardial imaging can be recommended.     

Significance of<Superscript>123</Superscript>I-MIBG scintigraphy as a pathophysiological indicator in the assessment of Parkinson’s disease and related disorders: It can be a specific marker for Lewy body disease

Recently, reliable and clear evidence for the usefulness of 123I-MIBG scintigraphy in the diagnosis of Parkinson's disease (PD) has been accumulated and it has become increasingly popular as one of the most accurate means of diagnosing the disease. PD, one of the most common neurodegenerative disorders, is characterized by resting tremor, rigidity, bradykinesia or akinesia, and postural instability. The disease is characterized pathologically by distinctive neuronal inclusions called Lewy bodies in many surviving cells of dopaminergic neurons of the substantia nigra pars compacta and other specific brain regions. Furthermore Lewy body type degeneration in the cardiac plexus has been observed in PD. In PD, cardiac MIBG uptake is reduced markedly even in the early disease stages; therefore, MIBG imaging can be used as an indicator of the presence of PD rather than disease severity. Other parkinsonian syndromes such as multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration demonstrate normal cardiac MIBG uptake or only mild reduction of MIBG uptake, indicating that MIBG imaging is a powerful method to differentiate PD from other parkinsonian syndromes. Dementia with Lewy bodies (DLB) also shows severe reduction of MIBG uptake, whereas Alzheimer's disease (AD) demonstrates normal MIBG uptake, permitting differentiation of DLB from AD using MIBG scintigraphy. In pure autonomic failure, which shares similar pathological findings with PD and is thought to be associated with diffuse loss of sympathetic terminal innervation, cardiac MIBG uptake also decreases markedly. Considering all the data together, marked reduction of cardiac MIBG uptake seems to be a specific marker of Lewy body disease and thus extremely useful in the differentiation from other diseases with similar symptoms without Lewy bodies.     

A case of primary malignant lymphoma of the brain with high uptake of 123I-IMP

Summary In general the ¹²³I-IMP SPECT image of a brain tumor is visualized as a defect. Tumor case with high IMP uptake have been rarely reported. We encountered a case of primary malignant lymphoma of the brain with high IMP uptake on both early and late scans corresponding to the CT lesions. Previously reported positive cases seemed to be confined to the early scan. For the present the exact behaviour of IMP is incompletely understood, but the mechanism of high uptake has been accounted for by increased extraction and increased amine receptors at the tumor sites. We need further information to establish whether these SPECT findings were specific for primary malignant lymphoma of the brain.     

Early and delayed single photon emission CT in various cerebral diseases using N-isopropyl-p-(123I)iodoamphetamine

Summary Early and delayed single photon emission computed tomography (SPECT) using N-isopropyl-p-(¹²³I)iodoamphetamine (IMP) was performed on 28 subjects (2 normal, 12 with cerebrovascular diseases and 14 with brain tumors) to evaluate the reversibility of the cerebral abnormality and cerebral viability. The results were compared with X-ray CT, ^99mTc brain scintigraphy and rCBF by ¹³³Xe inhalation method. Three types of IMP kinetics were observed. Initial hypoactivity that changed over 4 to 6 hours approaching a normal pattern suggests a hypofunctional parenchyma without significant tissue damage: long-lasting abnormalities on IMP SPECT indicates cellular damage.     

[123I]FP-CIT binding in rat brain after acute and sub-chronic administration of dopaminergic medication

The recently developed radioligand [¹²³I]FP-CIT is suitable for clinical single-photon emission tomography (SPET) imaging of the dopamine (DA) transporter in vivo. To date it has remained unclear whether dopaminergic medication influences the striatal [¹²³I]FP-CIT binding. The purpose of this study was to investigate the influence of this medication on [¹²³I]FP-CIT binding in the brain. We used an animal model in which we administered dopaminomimetics, antipsychotics and an antidepressant. In vivo [¹²³I]FP-CIT binding to the DA and serotonin transporters was evaluated after sub-chronic and acute administration of the drugs. The administered medication induced small changes in striatal [¹²³I]FP-CIT binding which were not statistically significant. As expected, the DA reuptake blocker GBR 12,909 induced a significant decrease in [¹²³I]FP-CIT binding. [¹²³I]FP-CIT binding in the serotonin-rich hypothalamus was decreased only after acute administration of fluvoxamine. The results of this study suggest that dopaminergic medication will not affect the results of DA transporter SPET imaging with [¹²³I]FP-CIT. Received 15 August and in revised form 15 October 1999     

<Superscript>18</Superscript>p-FDG PET is superior to<Superscript>67</Superscript>Ga SPECT in the staging of non-Hodgkin’s lymphoma

OBJECTIVE: Our study aims to compare diagnostic accuracy between 18F-FDG PET and 67Ga SPECT in the staging of non-Hodgkin's lymphoma. METHODS: Twenty-eight patients with non-Hodgkin's lymphoma, underwent 18F-FDG PET, 67Ga SPECT and CT for the pretreatment staging of malignant lymphoma between August 1999 and March 2002. 18F-FDG PET imaging was obtained 60 minutes after the intravenous administration of 185 MBq of 18F-FDG. 67Ga SPECT imaging was obtained 2 days after the intravenous administration of 148 MBq of 67Ga. 18F-FDG PET and 67Ga SPECT were performed within one month. Both imagings were performed on the area from the neck to the pelvis. The 18F-FDG PET and 67Ga SPECT findings were compared with the CT findings and the clinical course. RESULTS: Sixty-six nodal lesions were clinically confirmed. Of these, 32 were identified by both 18F-FDG PET and 67Ga SPECT. The remaining 34 lesions were identified only by 18F-FDG PET. The mean (+/- SD) sizes' of the nodes were 34.7 +/- 32.4 mm for 18F-FDG-positive and 67Ga-positive lesions and 15.7 +/- 8.3 mm for 18F-FDG-positive and 67Ga-negative lesions (p < 0.001). Of the 23 extranodal lesions, 12 were identified by both 18F-FDG PET and 67Ga SPECT, whereas 6 lesions were identified by only 18F-FDG PET. Five lesions were not identified by either technique. No 18F-FDG-negative but 67Ga-positive nodal or extranodal lesions were observed. The difference in findings between the two studies is related to the difference in the size but not in the histology or site of the lesions. CONCLUSION: 18F-FDG PET detected significantly more lesions particularly small lesions than 67Ga SPECT. Thus, 18F-FDG PET is considered to be superior to 67Ga SPECT in the staging of non-Hodgkin' s lymphoma.     

Logistic discriminant parametric mapping: a novel method for the pixel-based differential diagnosis of Parkinson’s disease

Positron emission tomography (PET) and single-photon emission tomography (SPET) imaging of the dopaminergic system is a powerful tool for distinguishing groups of patients with neurodegenerative disorders, such as Parkinson’s disease (PD). However, the differential diagnosis of individual subjects presenting early in the progress of the disease is much more difficult, particularly using region-of-interest analysis where small localized differences between subjects are diluted. In this paper we present a novel pixel-based technique using logistic discriminant analysis to distinguish between a group of PD patients and age-matched healthy controls. Simulated images of an anthropomorphic head phantom were used to test the sensitivity of the technique to striatal lesions of known size. The methodology was applied to real clinical SPET images of binding of technetium-99m labelled TRODAT-1 to dopamine transporters in PD patients (n=42) and age-matched controls (n=23). The discriminant model was trained on a subset (n=17) of patients for whom the diagnosis was unequivocal. Logistic discriminant parametric maps were obtained for all subjects, showing the probability distribution of pixels classified as being consistent with PD. The probability maps were corrected for correlated multiple comparisons assuming an isotropic Gaussian point spread function. Simulated lesion sizes measured by logistic discriminant parametric mapping (LDPM) gave strong correlations with the known data (r ²=0.985, P<0.001). LDPM correctly classified all PD patients (sensitivity 100%) and only misclassified one control (specificity 95%). All patients who had equivocal clinical symptoms associated with early onset PD (n=4) were correctly assigned to the patient group. Statistical parametric mapping (SPM) had a sensitivity of only 24% on the same patient group. LDPM is a powerful pixel-based tool for the differential diagnosis of patients with PD and healthy controls. The diagnosis of disease even before clinical symptoms become apparent may be possible, and ultimately this technique could be most useful in differentiating between several neurodegenerative disorders, incorporating images of multiple neuroreceptor systems. Received 8 April and in revised form 23 June 1999