In vitro analysis of extracted dens invaginatus using various radiographic imaging techniques.

AIM: Dens Invaginatus (DI) is a rare malformation of the teeth, showing a broad spectrum of morphologic variations. The aim of this study was to perform in vitro radiographic analyses of three extracted dens invaginatus (DI) teeth with complex root anatomy using plain radiographs, CBCT, MRI and micro CT techniques. MATERIALS AND METHODS: Study design: Three maxillary lateral incisors (A, B and C) from two patients were extracted due to poor prognosis and were radiographically analysed. Initially, conventional two dimensional digital radiographs were taken. Subsequently CBCT, micro CT and MRI analyses were performed. RESULTS: According to the Schulze and Brand system of classification, teeth A, B and C were classified as A2, B3 and B2 respectively. To detect the relationship between the invagination to the oral cavity and pulp chamber, conventional two dimensional radiographs were of no help. CBCT and MRI images were found to be complementary to each other but provided lesser structural detail than micro CT images. CONCLUSION: Reporting on these three DI teeth, normal conventional radiographs did not provide detailed structural information about the malformation due to geometric distortion and lack of information. Even though Oehlers classification system is the most widely used, classification by Schulze and Brand is more applicable in rare and deviant teeth.

Innovation in cancer imaging.

Cancer is rapidly becoming the worldwide leading cause of premature death. Iconographic techniques have traditionally provided information on tumor anatomy. The recent introduction of functional and molecular imaging techniques allows probing tumor physiology and biology in addition to mere anatomical description. In addition to the research implications, these novel imaging techniques offer early response assessment and target visualization which, in the era of personalized medicine, may offer significant advances in cancer therapy. Here, we provide an overview of the most important developments in cancer imaging, with a focus on the clinical applications.

Resolution improvement and noise reduction in human pinhole SPECT using a multi-ray approach and the SHINE method.

PURPOSE: This work aimed at quantifying the gains in spatial resolution and noise that could be achieved when using resolution modelling based on a multi-ray approach and additionally the Statistical and Heuristic Noise Extraction (SHINE) method in human pinhole single photon emission tomography (PH-SPECT). METHODS: PH-SPECT of two line phantoms and one homogeneous cylinder were recorded using parameters suited for studies of the human neck area. They were reconstructed using pinhole dedicated ordered subsets expectation maximisation algorithm including a resolution recovery technique based on 7 or 21 rays. Optionally, the SPECT data were SHINE pre-processed. Transverse and axial full widths at half-maximum (FWHM) were obtained from the line phantoms. The noise was quantified using the coefficient of variation (COV) derived from the uniform phantom. Two human PH-SPECT studies of the thyroid (a hot nodule and a very low uptake) were processed with the same algorithms. RESULTS: Depending on the number of iterations, FWHM decreased by 30 to 50% when using the multi-ray approach in the reconstruction process. The SHINE method did not affect the resolution but decreased the COV by at least 20% and by 45% when combined with the multi-ray method. The two human studies illustrated the gain in spatial resolution and the decrease in noise afforded both by the multi-ray reconstruction and the SHINE method. CONCLUSION: Iterative reconstruction with resolution modelling allows to obtain high resolution human PH-SPECT studies with reduced noise content. The SHINE method affords an additional noise reduction without compromising the resolution.

Left ventricular ejection fraction and volumes from gated blood pool tomography: comparison between two automatic algorithms that work in three-dimensional space.

BACKGROUND: Two different algorithms, which are fast and automatic and which operate in 3-dimensional space, were compared in the same group of patients to compute left ventricular ejection fraction (LVEF) and volumes from gated blood pool tomography. One method, developed at Cedars-Sinai Medical Center (CS), was dependent on surface detection, whereas the other method, developed at the Free University of Brussels (UB), used image segmentation. METHODS AND RESULTS: Gated blood pool tomograms were acquired in 92 consecutive patients after injection of 740 MBq of technetium 99m-labeled human serum albumin. After reconstruction and reorientation according to the left ventricular long axis, LVEF and left ventricular volumes were measured with the CS and UB algorithms. Measurements of LVEF were validated against planar radionuclide angiocardiography (PRNA) results. The success rates of the algorithms were 87% for CS and 97% for UB. Agreement between LVEF measured with CS and UB (LVEF(CS) = 0.91. LVEF(UB) - 0.85; r = 0.87) and between LVEF measured with CS and PRNA (LVEF(CS) = 1.04. LVEF(PRNA) - 4.75; r = 0.80) and UB and PRNA (LVEF(UB) = 0.98. LVEF(PRNA) + 4.42; r = 0.82) was good. For left ventricular volumes, linear regression analysis showed good correlation between both methods with regard to end-diastolic volumes (r = 0.81) and end-systolic volumes (r = 0.91). On average, end-diastolic volumes were similar and end-systolic volumes were slightly higher with CS than with UB. Consequently, significantly lower LVEFs were observed with CS than with UB. CONCLUSIONS: Good correlation was observed between CS and UB for both left ventricular volumes and ejection fraction. In addition, measurements of LVEF obtained with both algorithms correlated fairly well with those obtained from conventional PRNA over a wide range of values.

Automatic determination of left ventricular ejection fraction from gated blood-pool tomography.

UNLABELLED: The aim of this study was to develop and validate a new algorithm to automatically compute left ventricular ejection fraction (LVEF) from gated blood-pool tomography (GBPT). The results were compared with those of conventional planar radionuclide angiocardiography (PRNA). METHODS: Fifty-three consecutive patients received an injection of 740 MBq (99m)Tc-labeled human serum albumin. PRNA and GBPT were performed consecutively in a random sequence. PRNA served as the reference, and GBPT images were processed using a new edge detection algorithm. The algorithm is fast (<45 s), fully automatic, and works in three-dimensional space. The method includes identification of the valve plane and the septum. The left ventricular cavity at end-diastole is delineated by segmentation using an iterative threshold technique. An optimal threshold is reached when the corresponding isocontour best fits the first derivative of the end-diastolic count distribution in three dimensions. This optimal threshold is then applied to delineate the left ventricular cavity on the other time bins. The data are corrected for the partial-volume effect. Left ventricular volumes are determined using a geometry-based method and are used to calculate the ejection fraction. RESULTS: The success rate of the new algorithm was 94%. LVEFs calculated from GBPT agreed well with those calculated from PRNA (r = 0.78; GBPT = 0.94 PRNA + 6.33). The systematic error was 2.8%, and the random error was 8.8%. Excellent inter- and intraobserver reproducibility was found, with average differences of 1.1% +/- 4.6% and 1.1% +/- 5.0%, respectively, between the two measurements. CONCLUSION: This new algorithm provides a fast, automated, and objective method to calculate LVEF from GBPT.

Diagnosis of recurrent head and neck squamous cell carcinoma with 3-[123I]iodo-L-alpha-methyltyrosine SPET.

The distribution of 3-[123I]iodo-L-alpha-methyltyrosine (123I-3-IMT) in the tumour region of 21 patients with clinically suspected recurrent squamous cell head and neck carcinoma was studied. Single-photon emission tomography (SPET) imaging of the head and neck region was performed 10 min after the injection of 130-170 MBq 123I-3-IMT using a dual-detector gamma camera. Images were interpreted visually and classified as positive or negative for recurrent disease. In addition, target to background ratios (T/B) were measured using semi-automated region of interest analysis. IMT-SPET results were compared with the data derived from clinicopathological follow-up. IMT-SPET detected recurrent disease in 14 of 15 patients (sensitivity 93%). T/B ratios ranged between 1.5 and 2.4 (mean 1.88). One patient with a small tumour (1.2 cm) had a false-negative result. This is attributed to the limited spatial resolution of the SPET system. Five of six patients were correctly diagnosed to be negative for tumour recurrence. T/B ratios ranged between 1.2 and 1.4 (mean 1.30). In one patient IMT-SPET was positive without evidence of recurrence based on clinicopathological follow up. This finding was probably due to uptake into inflammatory tissue. IMT-SPET appears to be a sensitive tool (93%) for the detection of recurrent head and neck squamous cell carcinoma. Further studies with 123I-3-IMT as a metabolic tracer for the detection of head and neck cancer recurrence using SPET are recommended.

Low-dose dobutamine gated single-photon emission tomography: comparison with stress echocardiography.

Perfusion scintigraphy provides important information regarding the presence of viable tissue after myocardial infarction. Defects of moderate severity, however, may represent viable myocardium, necrotic tissue or a mixture of both. In this study the presence or absence of inotropic response in the infarcted area was assessed by low-dose dobutamine tetrofosmin gated single-photon emission tomography (LDD gated SPET). Results were compared with those obtained with stress echocardiography (SE). Twenty-five patients with acute myocardial infarction were studied. Gated SPET myocardial perfusion imaging was performed 60 min after the injection of technetium-99m tetrofosmin (925 MBq) at rest using a triple-headed camera equipped with focussing collimators (Cardiofocal). Two consecutive acquisitions were performed according to a "fast" gated SPET protocol (3x20 stops, 9 s/stop, 64x64 pixel matrix, zoom 1.23) with the subjects remaining in the same position. The first acquisition was obtained at rest; the second acquisition was obtained under infusion of 10 microg kg(-1) min(-1) dobutamine. The severity of regional dysfunction, wall thickening severity (WTsev), was assessed and quantified using a method based on circumferential profile analysis. SE was performed at rest and during infusion of 5 and 10 microg kg(-1) min(-1) dobutamine. Two patients could not be analysed because of disturbing gastro-intestinal activity on the perfusion study. Under dobutamine 11 patients presented a significant change in WTsev (three showed normalisation, five an improvement and three a deterioration), while in 12 patients the WTsev score remained unchanged. The overall concordance between LDD gated SPET and SE was 83%. In patients with perfusion defects of moderate severity the concordance was 90% (9/10). It may be concluded that functional changes in infarcted areas induced by dobutamine can be detected with gated SPET. Good agreement was observed between LDD gated SPET and SE for the identification of inotropic reserve in infarcted areas.

Effect of beta-blockade on low-dose dobutamine-induced changes in left ventricular function in healthy volunteers: assessment by gated SPET myocardial perfusion scintigraphy.

Viability studies are often performed in patients receiving beta-blocking agents. However, the intake of beta-blocking agents could influence the identification of viable myocardium when low-dose dobutamine is used to demonstrate inotropic reserve. The aim of this study was to quantify the effect of beta-blockade on global and regional left ventricular function in healthy volunteers using low-dose dobutamine gated single-photon emission tomographic (SPET) myocardial perfusion scintigraphy. Ten subjects were studied once "on" and once "off" beta-blocker therapy (metoprolol succinate, 100 mg day(-1)). On each occasion four consecutive gated SPET acquisitions (of 7 min duration) were recorded after injection of 925 MBq technetium-99m tetrofosmin on a triple-headed camera equipped with focussing (Cardiofocal) collimators. Acquisitions were made at rest (baseline 1 and 2) and 5 min after the beginning of the infusion of 5 and 10 microg kg(-1) min(-1) dobutamine. Wall thickening (WT) was quantified using a method based on circumferential profile analysis. Left ventricular ejection fraction (LVEF) was obtained using the Cedars-Sinai algorithm. Blood pressure (BP) and heart rate (HR) were recorded at the end of each acquisition. At baseline LVEF, WT and systolic BP values under beta-blockade were not significantly different from those obtained in the non-beta-blocked state. The mean HR and diastolic BP at baseline were lower under beta-blockade. Dobutamine administration (at 5 and 10 microg kg(-1) min(-1)) induced a significant increase in WT, LVEF and systolic BP in all subjects both on and off beta-blockade. The increases in WT, LVEF and systolic BP in the beta-blocked state were less pronounced but not significantly different. HR increased significantly at 10 microg kg(-1) min(-1) dobutamine without beta-blocker administration, while no increase in HR was observed in the beta-blocked state. Beta-blocker therapy in healthy subjects attenuates the inotropic and chronotropic myocardial response to low-dose dobutamine. At doses of 5 and 10 microg kg(-1) min(-1) dobutamine, however, significant increases in global and regional left ventricular function can still be measured using consecutive gated SPET myocardial perfusion scintigraphy acquisitions even under beta-blocker therapy.

Assessment of perfusion, function, and myocardial metabolism after infarction with a combination of low-dose dobutamine tetrofosmin gated SPECT perfusion scintigraphy and BMIPP SPECT imaging.

BACKGROUND: Tetrofosmin gated single photon emission computed tomography (SPECT) allows simultaneous assessment of regional myocardial perfusion, global and regional left ventricular function, and function at rest and during pharmacologic intervention. SPECT with fatty acid analogues, such as beta-methyl-iodophenyl-pentadecanoic acid (BMIPP), can be used to monitor metabolic changes induced by myocardial ischemia. In this work, the results of both studies obtained in patients with recent myocardial infarction are integrated. METHODS: Twenty patients underwent tetrofosmin and BMIPP scintigraphy with a 3-head camera. Two consecutive tetrofosmin gated SPECT acquisitions were performed 60 minutes after administration of technetium-99m tetrofosmin (925 MBq) at rest (3x20 stops of 9 s; matrix 64x64 over 360 degrees . One acquisition was made at rest, and the second was made during dobutamine infusion (10 microg/kg/min). Regional functional abnormalities were quantified and expressed as wall thickening severity (WTsev) in arbitrary units. Left ventricular ejection fraction and volumes were assessed with the Cedars Sinai algorithm. BMIPP imaging started 20 minutes after iodine 123-BMIPP (150 MBq) administration at rest (3x32 stops of 60 s; matrix 64x64 over 360 degrees; medium energy collimators). Tracer uptake was scored according to a 25-segment model. RESULTS: Sixteen of 18 patients had regional functional abnormalities at baseline (average WTsev 13.7 units). The WTsev score at baseline correlated well with the degree of residual perfusion. During dobutamine infusion, WTsev did not change (from 23.4 to 23.6 units) in 5 patients; it decreased (from 16.1 to 5.9 units) in 11 patients; and it increased (from 13.0 to 22.3 units) in 3 patients. An increase or decrease in WTsev during dobutamine infusion was associated with the presence of a considerable amount of BMIPP mismatched myocardium, whereas no change in WTsev was preferentially associated with a BMIPP matched pattern and perfusion defects with a higher severity score. CONCLUSION: Immediately after infarction, the severity of regional dysfunction at rest correlated well with the perfusion defect severity. Improvement in regional function during dobutamine administration is associated with less severe perfusion defects and a considerable amount of BMIPP mismatched myocardium, both suggesting viability.

Interest of the ordered subsets expectation maximization (OS-EM) algorithm in pinhole single-photon emission tomography reconstruction: a phantom study.

Pinhole single-photon emission tomography (SPET) has been proposed to improve the trade-off between sensitivity and resolution for small organs located in close proximity to the pinhole aperture. This technique is hampered by artefacts in the non-central slices. These artefacts are caused by truncation and by the fact that the pinhole SPET data collected in a circular orbit do not contain sufficient information for exact reconstruction. The ordered subsets expectation maximization (OS-EM) algorithm is a potential solution to these problems. In this study a three-dimensional OS-EM algorithm was implemented for data acquired on a single-head gamma camera equipped with a pinhole collimator (PH OS-EM). The aim of this study was to compare the PH OS-EM algorithm with the filtered back-projection algorithm of Feldkamp, Davis and Kress (FDK) and with the conventional parallel-hole geometry as a whole, using a line source phantom, Picker's thyroid phantom and a phantom mimicking the human cervical column. Correction for the angular dependency of the sensitivity in the pinhole geometry was based on a uniform flood acquisition. The projection data were shifted according to the measured centre of rotation. No correction was made for attenuation, scatter or distance-dependent camera resolution. The resolution measured with the line source phantom showed a significant improvement with PH OS-EM as compared with FDK, especially in the axial direction. Using Picker's thyroid phantom, one iteration with eight subsets was sufficient to obtain images with similar noise levels in uniform regions of interest to those obtained with the FDK algorithm. With these parameters the reconstruction time was 2.5 times longer than for the FDK method. Furthermore, there was a reduction in the artefacts caused by the circular orbit SPET acquisition. The images obtained from the phantom mimicking the human cervical column indicated that the improvement in image quality with PH OS-EM is relevant for future clinical use and that the improvements obtained using the OS-EM algorithm are more significant for the pinhole geometry than for the conventional parallel-hole geometry. We conclude that PH OS-EM is a practical and promising alternative for pinhole SPET reconstruction.

Effects of low-dose dobutamine on left ventricular function in normal subjects as assessed by gated single-photon emission tomography myocardial perfusion studies.

Electrocardiography gated single-photon emission tomography (gated SPET) allows the assessment of regional perfusion and function simultaneously and in full spatial congruency. In this study changes in global and regional left ventricular function in response to dobutamine infusion were assessed in ten healthy volunteers using sequential gated SPET myocardial perfusion acquisitions. Four consecutive gated SPET images were recorded 60 min after injection of 925 MBq technetium-99m tetrofosmin on a three-head camera equipped with focussing collimators. Two acquisitions were made at rest (baseline 1 and 2), and the third and fourth acquisitions were started 5 min after the beginning of the infusion of 5 and 10 microg kg(-1) min(-1) dobutamine, respectively. Systolic wall thickening (WT) was quantified using a method based on circumferential profile analysis. Left ventricular ejection fraction (LVEF) and volumes were calculated automatically using the Cedars-Sinai program. Nine of the ten subjects presented a definite increase in WT during dobutamine infusion. WT increased on average from 46%+/-14% at baseline to 71%+/-23% (range: 37%-106%; P<0.05) during 5 microg kg(-1) min(-1) dobutamine infusion and to 85%+/-25% (range: 62%-123%; P<0.05 with respect to WT at 5 microg kg(-1) min(-1)) during 10 microg kg(-1) min(-1) dobutamine infusion. Apical segments showed the largest WT at baseline. The average WT response to dobutamine was similar for all parts of the myocardium. It is concluded that changes in WT induced by infusion of low-dose dobutamine can be assessed by sequential gated SPET myocardial perfusion studies. The "stress gated SPET" protocol proposed in this study might be helpful to distinguish viable from scar tissue in patients with coronary artery disease, by demonstrating a preserved inotropic response in hypoperfused myocardium.

Quantitative assessment of regional dysfunction from gated single photon emission tomography myocardial perfusion studies: a non-segmental approach.

We present a modified (non-segmental) method for quantification of regional left ventricular dysfunction using gated myocardial perfusion SPET. Gated SPET is increasingly used to obtain complementary information on local perfusion and to assess the relevance of deficits in segmental count densities (attenuation vs perfusion deficit). The non-segmental approach was motivated by a hypothetical limitation regarding the validity of commonly used methods of quantitative wall thickening (WT) analysis. These methods are all based on segmental analysis, which could cause underestimation of 'true' contractile dysfunction in perfusion defects that do not have a strict segmental distribution. SPET images gated in eight time bins 60 min after the injection of 740 MBq 99Tcm-tetrofosmin or 99Tcm-sestamibi were recorded on a triple-headed camera in 20 normal subjects and in 16 patients within 2 weeks and again 3 months after myocardial infarction. Normal limits of wall thickening, calculated from pooled wall thickening profiles obtained in normal subjects, were used to identify and quantify areas with abnormal wall thickening in patients with coronary artery disease. The method was validated against data obtained from contrast ventriculography (CVG) and tested for reproducibility. The reproducibility of the method was excellent: r = 0.98 (WTsev measure 1 = 1.03WTsev measure 2 - 0.01). The localization of wall thickening abnormalities detected by gated SPET correlated well with the localization of regions with abnormal wall motion (WM) identified by CVG. The severity of the regional myocardial dysfunction assessed by gated SPET was closely correlated with the severity of the regional myocardial dysfunction derived from CVG: r = 0.85 (WMsev = 2.55WTsev + 2.30). Furthermore, a good correlation between the total wall thickening severity score and the global left ventricular ejection fraction (LVEF) was observed early and late after myocardial infarction: r = 0.80 (WTsev = -0.4LVEF + 0.46). We conclude that quantitative analysis of regional wall thickening assessed from gated SPET myocardial perfusion scintigraphy is a reliable parameter for regional ventricular function. Categorizing wall thickening abnormalities quantitatively may be helpful in assessing small changes in regional function that may occur between sequential gated SPET images.

Gated SPET myocardial perfusion acquisition within 5 minutes using focussing collimators and a three-head gamma camera.

Short acquisition protocols for gated single-photon emission tomography (SPET) myocardial perfusion imaging are desirable for sequential imaging to evaluate the myocardial response during pharmacological intervention. In this study a less than 5 min gated SPET acquisition protocol is proposed. Perfusion characteristics (defect severity) and left ventricular ejection fraction (LVEF), end-diastolic and end-systolic volumes (EDV, ESV), wall motion (WM) and wall thickening (WT) were calculated, checked for reproducibility and compared with data obtained using a standard gated SPET acquisition protocol. Gated SPET images were recorded in 20 patients starting 60 min after the administration of 925 MBq technetium-99m tetrofosmin at rest. The 5 min gated SPET studies were acquired with a three-head camera equipped with Cardiofocal collimators. This protocol was repeated twice. In addition gated SPET studies were acquired according to a standard protocol using parallel-hole collimators. The severity of perfusion defects was quantified on polar maps using the non-gated image data and a normal database. LVEF, EDV, ESV, WM and WT were calculated from the gated images. The agreement between 5-min and standard gated SPET acquisitions was excellent for all investigated parameters. The reproducibility of repeated 5-min acquisitions for the quantification of perfusion defect severity was excellent (r=0.97). The agreement for segmental WT scores between repeated 5-min gated SPET acquisitions was good: kappa=0.71; major differences in segmental classification were observed in 2.5%. For WM a good agreement was found for segments with a tracer uptake >/=30% of the maximum: kappa=0.65, major differences =7.7%. Excellent reproducibility was found for LVEF, EDV and ESV measurements: r=0.97, 0.99 and 0.99, respectively. It is concluded that fast gated SPET perfusion studies acquired in less than 5 min yield accurate and reproducible measurements of myocardial perfusion and function (global and regional). In addition the results obtained with the 5-min gated SPET protocol correlate well with those obtained using a standard acquisition protocol.

Cardiofocal collimators for gated single-photon emission tomographic myocardial perfusion imaging.

Cardiofocal collimators (CFCs) are more sensitive than parallel-hole collimators (PHCs) of the same resolution because the rays converge in the centre of the field of view. After reconstruction a useful field of view with a 10 cm radius in which both sensitivity and resolution are homogeneous is obtained. In this article the feasibility and accuracy of gated single-photon emission tomographic (gated SPET) myocardial perfusion imaging using a triple-head camera equipped with CFC, is evaluated. Twenty patients with a history of myocardial infarction were studied. SPET myocardial perfusion images, gated in eight time bins, were acquired in a random sequence with a PHC and a CFC for each patient. Imaging was started 60 min after the injection of 925 MBq of technetium-99m tetrofosmin at rest. Ninety-six projections over 360 degrees were acquired, with 32 stops of 40 s for the PHC and 20 s for the CFC in order to obtain similar count densities. The extent (EXT) and severity (SEV) of perfusion defects were quantified on polar maps using the non-gated data. Left ventricular volumes [end-diastolic volume (EDV), end-systolic volume (ESV)] and ejection fraction (LVEF) were calculated from gated data using the Cedars-Sinai program. In 17 of 20 patients the complete left ventricle was positioned within the useful field of view of the CFC. The results in respect of perfusion, volumes and ejection fraction were almost identical to those obtained with the PHC. The mean difference+/-SD between the CFC and the PHC was -2.30+/-7.16 (% of LV area) for EXT, -0.48+/-2.90 for SEV (arbitrary units), -1,50+/-5.25 (ml) for EDV and 0.53+/-4.10 (%) for LVEF. The largest differences in EXT and LV volumes were observed in patients in whom a part of the LV was not positioned within the useful field of view. We conclude that, for the majority of patients, identical information with regard to both perfusion and function can be derived from gated SPET myocardial perfusion studies obtained with PHCs or with CFCs. Because of the greater sensitivity, however, a much shorter acquisition time is required with CFCs.

Adrenal cortical carcinoma: a case report.

We present a case of adrenocortical carcinoma. Excretory urography and sonography revealed a left adrenal mass, which was confirmed by computer tomography and further delineated by arteriography. Complete surgical resection was possible. A summary of the clinical and radiological data is included.

Primary nonspecific ulcers of the small intestine: an unsolved diagnostic problem.

Two patients with nonspecific small intestinal ulceration were observed. In the two cases, the ulceration was responsible for (sub)obstruction. The medical history, the gastrointestinal roentgenographic examination and the pathologic anatomy were remarkably similar. Some aspects of these quite rare lesions are discussed.