Low-power water suppression by hyperbolic secant pulses with controlled offsets and delays (WASHCODE)

A class of chemical-shift-selective (CHESS) water suppression (WS) schemes is presented in which the characteristic frequency-domain excitation profiles of "adiabatic" full-passage (AFP) RF pulses are utilized for frequency-selective excitation of the water resonance. In the proposed WS schemes, dubbed WASHCODE, hyperbolic secant (HS) pulses were used as the AFP pulses. Besides the high immunity of WS efficiency toward B(1) inhomogeneity, these sequences also exhibit extraordinary insensitivity to the dispersion of the water T(1) relaxation times. The actual performance of the proposed WS schemes was achieved in particular by optimizing the frequency offsets of WS HS pulses and the time intervals between them. To reduce the RF power requirements of these WS sequences for in vivo applications, HS pulses with the minimum possible frequency bandwidths were employed, which also substantially reduced the adverse effects on the observed proton MR spectra. The proposed WS schemes were evaluated by simulations based on the Bloch equations. Several WS sequences which looked particularly promising were verified experimentally on the human brain on a 3 T MR scanner using very short echo-time STEAM for volume selection and a standard single-loop surface coil for both signal transmission and reception. Routinely, water-suppression factors ranging from 2000 to 4000 were achieved in vivo without additional adjustment of parameters for individual subjects and without violating legal safety limits.

Validation of FDG positron emission tomography for differentiation of unknown pulmonary lesions

OBJECTIVE

The impact of the (2-(fluorine-18)-fluoro-2-2deoxy-D-glucose)-positron emission tomography ((18)F-FDG-PET) for discrimination of pulmonary lesions was evaluated in a single centre prospective study.

METHODS

In the study, 109 patients with pulmonary lesions of unknown origin verified by computed tomography were enrolled consecutively (April 1999--May 2000). They were subject to (18)F-FDG-PET diagnostics. (18)F-FDG-PET images were interpreted by two independent nuclear medicine physicians who were blinded to the results of other imaging procedures. In 87 patients, surgery was applied followed by histological investigation, which served as the gold standard. In 22 other patients, extensive tumour load or assumed benign dignity of the lesions prevented surgery.

RESULTS

Overall sensitivity of (18)F-FDG-PET in 87 resected patients was 0.86. Differentiation in malignant (n = 69) and benign lesions (n = 18) revealed sensitivities of 0.9 and 0.72, respectively. Sensitivity of (18)F-FDG-PET in inflammatory lesions was markedly lower (0.43) than in benign tumours (0.91). Standard uptake values were significantly increased in malignant tumours compared with benign lesions (9.9 and 1.6, respectively; P = 0.035). There was a clear correlation of sensitivity with tumour size with a failure rate of 27% in lesions < or = 1cm (n = 15), 10% (n = 20) in lesions between 1 and 2 cm and 12% (n = 45) above 2 cm. In primary bronchial carcinoma, a clear correlation of sensitivity was observed with regard to tumour grading (G1, three out of five; G2, 24 out of 27; G3, 26 out of 26; and G4, one out of one). Lymph node involvement was correctly suggested in 10 out of 19 (52.6%) patients. However, false positive lymph node enhancement was indicated in one out of 18 (5.5%) operated patients with benign lesions and eight out of 39 (20.5%) with bronchial carcinoma.

CONCLUSION

(18)F-FDG-PET at present does not serve as the gold standard for early detection of small and well-differentiated tumours. However, it contributes efficiently to the detection of malignancy in tumours >1cm, which are moderately or poorly differentiated. Positive lymph node imaging must not preclude surgery but requires histological proof. Discrimination of benign and malignant pulmonary tumours by (18)F-FDG-PET appears to be hampered in inflammatory lesions.

Whole-body 18F dopa PET for detection of gastrointestinal carcinoid tumors

PURPOSE

To evaluate fluorine 18 (18F) dopa positron emission tomography (PET) in comparison with established imaging procedures in gastrointestinal carcinoid tumors.

MATERIALS AND METHODS

After evaluation of the normal distribution of 18F dopa, 17 patients with histologically confirmed tumors were examined with 18F dopa PET. Results of 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) PET, somatostatin-receptor scintigraphy, and morphologic imaging (computed tomography and/or magnetic resonance imaging) were available for all patients. Results of the procedures were evaluated by two radiologists and two nuclear medicine specialists, whose consensus based on all available histologic, imaging, and follow-up findings was used as the reference standard.

RESULTS

Ninety-two tumors were diagnosed: eight primary tumors, 47 lymph node metastases, and 37 organ metastases. 18F dopa PET led to 60 true-positive findings (seven primary tumors, 41 lymph node metastases, 12 organ metastases); FDG PET, 27 (two primary tumors, 14 lymph node metastases, 11 organ metastases); somatostatin-receptor scintigraphy, 52 (four primary tumors, 27 lymph node metastases, 21 organ metastases); and morphologic imaging, 67 (two primary tumors, 29 lymph node metastases, 36 organ metastases). This resulted in the following overall sensitivities: 18F dopa PET, 65% (60 of 92); FDG PET, 29% (27 of 92); somatostatin-receptor scintigraphy, 57% (52 of 92); morphologic procedures, 73% (67 of 92). Although the morphologic procedures were most sensitive for organ metastases, 18F dopa PET enabled best localization of primary tumors and lymph node staging.

CONCLUSION

18F dopa PET is a promising procedure and useful supplement to morphologic methods in diagnostic imaging of gastrointestinal carcinoid tumors.

Proton T (1) and T (2) relaxation times of human brain metabolites at 3 Tesla

Longitudinal and transverse relaxation times were measured for proton MRS signals from human brain metabolites at 3 T using a short-echo STEAM protocol and a surface coil as a transmitter/receiver. Volumes of interest containing mostly grey or mostly white matter were selected in occipital lobes of healthy subjects and relaxation times for the following resonances were obtained: N-acetylaspartate at 2.01 ppm (T(1) and T(2)), glutamate at 2.35 ppm (T(1)), creatine at 3.03 and 3.92 ppm (T(1) and T(2)), choline-containing substances at 3.22 ppm (T(1) and T(2)), myo-inositol at 3.57 and 3.65 ppm (T(1)) and the overlapping signals of glutamate and glutamine at 3.75 ppm (T(1)). The T(1) relaxation times obtained range from 0.97 to 1.47 s for grey matter and from 0.87 to 1.35 s for white matter. On the other hand, T(2) relaxation times range from 116 to 247 ms and from 141 to 295 ms in grey and white matter, respectively. Generally, the T(1) values measured at 3 T are close to the previously published data found at 1.5, 2 and 4.1 T. Also, the T(2) values confirm the previously observed decrease in transverse relaxation times with increasing static magnetic field. The proton relaxation times obtained will allow improved sequence design and spectra quantitation at 3 T, currently tested for enhanced clinical applications.

Evidence for premotor cortex activity during dynamic visuospatial imagery from single-trial functional magnetic resonance imaging and event-related slow cortical potentials

A strong correspondence has been repeatedly observed between actually performed and mentally imagined object rotation. This suggests an overlap in the brain regions involved in these processes. Functional neuroimaging studies have consistently revealed parietal and occipital cortex activity during dynamic visuospatial imagery. However, results concerning the involvement of higher-order cortical motor areas have been less consistent. We investigated if and when premotor structures are active during processing of a three-dimensional cube comparison task that requires dynamic visuospatial imagery. In order to achieve a good temporal and spatial resolution, single-trial functional magnetic resonance imaging (fMRI) and scalp-recorded event-related slow cortical potentials (SCPs) were recorded from the same subjects in two separate measurement sessions. In order to reduce inter-subject variability in brain activity due to individual differences, only male subjects (n = 13) with high task-specific ability were investigated. Functional MRI revealed consistent bilateral activity in the occipital (Brodmann area BA18/19) and parietal cortex (BA7), in lateral and medial premotor areas (BA6), the dorsolateral prefrontal cortex (BA9), and the anterior insular cortex. The time-course of SCPs indicated that task-related activity in these areas commenced approximately 550-650 ms after stimulus presentation and persisted until task completion. These results provide strong and consistent evidence that the human premotor cortex is involved in dynamic visuospatial imagery.

Autocorrelation analysis of bone structure

We propose a method called spatial autocorrelation analysis (SACA) to determine the spatial anisotropy of the trabecular bone in order to investigate osteoporosis. For demonstrating the potential of SACA we first evaluate the method on rectangular, simulated test patterns as a simple model for the anisotropic pore structure of the bone. As a next step towards biomedical application, photographic reference images of human vertebral bone were investigated by SACA. Osteoporotic bone structure could be clearly differentiated from non-osteoporotic sample images. Moreover, for demonstration of the applicability and potential of the method for in vivo characterization of osteoporosis, the microstructure of the human calcaneus was investigated by MR-microimaging on a young healthy male subject and an osteoporotic female. The measurements were performed using a high-field (3T) whole-body MR tomograph equipped with a special, strong head gradient system. The signal was acquired with a surface coil mounted on an in-house-built device for convenient immobilization of the subject's foot. Using a 3D gradient echo sequence a resolution of 0.254 x 0.254 x 2.188 mm3 was achieved in vivo. Selected images were inverted, gradient corrected for the inhomogeneous but sensitive detection by the surface coil, and subsequently analyzed by SACA. The anisotropy of bone structure detected by SACA is a possible candidate for noninvasive determination of the osteoporotic status, potentially complementing standard bone mineral density measurements.

Depressive state and regional cerebral activity in cancer patients - a preliminary study

BACKGROUND

The aim of this study was to investigate influences of depressive states, chemotherapy and existence of remaining tumors on the regional brain activity of cancer patients.

MATERIAL AND METHODS

Positron emission tomography with 18F-fluorodeoxyglucose was performed on 21 patients with various types of cancer. Their brain images were compared to 10 age- and gender-matched control data using statistical parametric mapping (SPM). The patients were subgrouped into the with and without depression based on the scores on Zung's self-rating depression scale (SDS), with and without previous chemotherapy, and with and without existence of remaining tumors.

RESULTS

Significant metabolic reduction was detected in the cingulate gyrus, prefrontal, dorsolateral prefrontal, temporoparietal cortices and basal ganglia in cancer patients. These findings were close to known lesions of major depression. Intra-group comparisons showed that these hypometabolic findings were associated with the depth of depressive state. Influences of chemotherapy and remaining tumors on the cerebral cortex seemed to be weaker than that of psychological factors.

CONCLUSIONS

The present pilot study suggests that frontal hypoactivity commonly seen in cancer patients is likely to be associated with depression rather than chemotherapy or remaining tumors. A brain mapping technique might be useful in evaluating neuropsychiatric problems in cancer patients.

Spatial distribution of prostate cancers undetected on initial needle biopsies

OBJECTIVES

The spatial distribution of cancer foci of prostate carcinomas with negative initial biopsies was compared to that of prostate carcinomas with positive initial biopsies to detect areas in which carcinomas were more frequently located when the initial biopsy was negative.

METHODS

Twenty patients with prostate cancer and a negative initial biopsy trial were detected among 218 patients with preceding systematic biopsies (9.2%) in our hospital. Analysis of the prostatectomy specimens regarding cancer distribution, multifocality, tumour size, Gleason score, and stage was performed using pathohistological techniques and three-dimensional computer reconstruction.

RESULTS

Prostatectomy specimens with negative initial biopsies showed more frequently cancer foci in apical (p<0.0001) and dorsal (p<0.02) prostatic compartments, higher incidence of multifocality (p<0.01), and smaller size of carcinoma foci (p<0.00003) compared to carcinomas in 81 stage-matched prostatectomy specimens with positive initial biopsies. Comparing both groups, no significant differences were noted in Gleason score of preoperative biopsies and prostatectomies, prostate weight, prostate-specific antigen (PSA) level, digital rectal examination, and patients age.

CONCLUSIONS

Missing the cancer in clinically significant prostate carcinomas by current systematic biopsy techniques may also be due to an apico-dorsal cancer location, particularly in combination with multifocality and small size of carcinoma foci in large prostates. In case of reasonable clinical suspicion of prostate cancer and negative initial biopsy, an early repeat biopsy with special emphasis on the apico-dorsal peripheral zone should be envisaged.

Finger Somatotopy in Human Motor Cortex

Although qualitative reports about somatotopic representation of fingers in the human motor cortex exist, up to now no study could provide clear statistical evidence. The goal of the present study was to reinvestigate finger motor somatotopy by means of a thorough investigation of standardized movements of the index and little finger of the right hand. Using high resolution fMRI at 3 Tesla, blood oxygenation level-dependent (BOLD) responses in a group of 26 subjects were repeatedly measured to achieve reliable statistical results. The center of mass of all activated voxels within the primary motor cortex was calculated for each finger and each run. Results of all runs were averaged to yield an individual index and little finger representation for each subject. The mean center of mass localizations for all subjects were then submitted to a paired t test. Results show a highly significant though small scale somatotopy of fingerspecific activation patterns in the order indicated by Penfields motor homunculus. In addition, considerable overlap of finger specific BOLD responses was found. Comparing various methods of analysis, the mean center of mass distance for the two fingers was 2--3 mm with overlapping voxels included and 4--5 mm with overlapping voxels excluded. Our data may be best understood in the context of the work of Schieber (1999) who recently described overlapping somatotopic gradients in lesion studies with humans.

[Clinical PET activities in European and Asia-Oceanian countries]

Clinical diagnosis using positron emission tomography (PET) requires high costs. Therefore, sociomedical evaluation is very important for spread of clinical PET. In this report, sociomedical situation in European and Asia-Oceanian countries, especially concerning transportation of 18F-FDG and reimbursement of medical costs for clinical PET indications, is reported. It seems that UK, Germany and Belgium are the most advanced in clinical PET in Europe. In these countries, many PET investigations are reimbursed though systems are different among the countries. In UK, both public and private insurance gives authorization for clinical PET to some extent. In Germany, private health insurance companies give authorization but public insurance has not. In Belgium, private health insurance does not exist and public insurance gives authorization for clinical PET. Other European countries seem to be in transitional stages. Transportation of 18F-FDG has been already started in almost every country in Europe and Asia-Oceania. In Japan, neither transportation of FDG nor full reimbursement of clinical PET has not started yet and this situation seems to be exceptional. To promote clinical PET in Japan, there is the need of at least establishing a list of clinical indications for PET investigations and establishing commercial-based 18F-FDG supplying system. They could be regarded as a kind of infrastructure for spread of clinical PET.

High-resolution polymer gel dosimetry by parameter selective MR-microimaging on a whole body scanner at 3T

High dose variations across small spatial distances, as present in brachytherapeutic applications or radiosurgery and especially gamma-knife therapy, are difficult to quantify by standard dosimetry. We demonstrate the possibility to obtain planar spatial resolutions for dose imaging at pixel sizes below 200 microm within multislice parameter selective MR imaging on polymer gels. The sensitivity of the transversal and longitudinal relaxation time as well as diffusivity on dose is shown. High spatial resolution is achieved by parameter selective microimaging of polymer gels on a high-field (3 T) whole-body MR system equipped with a dedicated strong gradient system and a small probe head matched to the sample size. In addition to the spin-spin relaxation rate R2 = 1/T2 we investigate the sensitivity of the longitudinal relaxation rate R1 = 1/T1 and the diffusivity Dapp in acrylic polymer gels on irradiation up to dose levels of about 20 Gy. Dose images are obtained after calibration of the corresponding MR parameters by known dose levels of gamma irradiation. Also the MR-parameter T1 may be used for dose imaging. The impact of all of the three parameters T1, T2, and diffusivity on obtained signal intensities in irradiated regions has to be taken into account in nonoptimized pulse sequences. Further, very high spatial resolution imposes several restrictions on the evaluation of R2, which have to be considered for quantitative dosimetry. These restrictions are discussed in detail. We also demonstrate the importance of such a high spatial resolution in case of a set of differently sized gamma-knife stereotactic irradiation schemes. Gel dosimetry based on MR parameter selective microimaging represents a potent alternative for the detection of dose distributions characterized by steep dose gradients, typical in brachytherapeutic and radiosurgical applications.

2-(fluorine-18)fluoro-2-deoxy-D-glucose positron emission tomography in the detection and staging of malignant lymphoma. A bicenter trial

BACKGROUND

The authors undertook a prospective evaluation of the clinical value of 2-fluoro [18-]-2-deoxyglucose positron emission tomography (FDG-PET) in the detection and staging of malignant lymphoma compared with computed tomography (CT) and bone marrow biopsy (BMB).

METHODS

Fifty-two consecutive patients with untreated malignant lymphoma were evaluated prospectively in a bicenter study. FDG-PET, CT, and BMB were performed for investigating lymph node/extranodal manifestations and bone marrow infiltration. Thirty-three percnt of the discrepant results were verified by biopsy, magnetic resonance imaging, or clinical follow-up (range, 4-24 month).

RESULTS

Altogether, 1297 anatomic regions (lymph nodes, organs, and bone marrow) were evaluated. FDG-PET and CT scans were compared by receiver operating characteristic (ROC) curve analysis. The area under the ROC curve were as follows: lymph nodes, 0.996 (PET) and 0.916 (CT); extranodal, 0.999 (PET) and 0.916 (CT); supradiaphragmatic, 0.996 (PET) and 0.905 (CT); and infradiaphragmatic, 0.999 (PET) and 0.952 (CT). In these analyses, FDG-PET was significantly superior to CT (P < 0.05), except in infradiaphragmatic regions, in which the two methods produced equivalent results. In detecting bone marrow infiltration, FDG-PET was superior to CT and was equivalent to BMB. In 4 of 52 patients (8%), FDG-PET led to an upstaging and a change of therapy.

CONCLUSIONS

Noninvasive FDG-PET is very accurate in the staging of malignant lymphoma. Compared with standard staging modalities (CT and BMB), PET was significantly superior and led to changes in the therapy regimen for 8% of patients.

Radioisotope albumin flux measurement of microvascular lung permeability: an independent parameter in acute respiratory failure?

AIM

To evaluate the extent to which single measurements of microvascular lung permeability may be relevant as an additional parameter in a heterogenous clinical patient collective with Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS).

METHODS

In 36 patients with pneumonia (13), non pneumogenic sepsis (9) or trauma (14) meeting the consensus conference criteria of ALI or ARDS double-isotope protein flux measurements (51Cr erythrocytes as intravascular tracer, Tc-99m human albumin as diffusible tracer) of microvascular lung permeability were performed using the Normalized Slope Index (NSI). The examination was to determine whether there is a relationship between the clinical diagnosis of ALI/ARDS, impaired permeability and clinical parameters, that is the underlying disease, oxygenation, duration of mechanical ventilation and mean pulmonary-artery pressure (PAP).

RESULTS

At the time of study, 25 patients presented with increased permeability (NSI > 1 x 10(-3) min-1) indicating on exudative stage of disease, and 11 patients with normal permeability. The permeability impairment correlated with the underlying disease (p > 0.05). With respect to survival, there was a negative correlation to PAP (p < 0.01). Apart from that no correlations between the individual parameters were found. Especially no correlation was found between permeability impairment and oxygenation, duration of disease or PAP.

CONCLUSION

In ALI and ARDS, pulmonary capillary permeability is a diagnostic parameter which is independent from clinical variables. Permeability measurement makes a stage classification (exudative versus non exudative phase) of ALI/ARDS possible based on a measurable pathophysiological correlate.

Increased metabolic activity in the thymus gland studied with 18F-FDG PET: age dependency and frequency after chemotherapy

This study was designed to evaluate the age dependency of 18F-FDG uptake in the thymus and the frequency of PET confirmation of thymus hyperplasia after chemotherapy in cancer patients.

METHODS

Whole-body FDG PET recordings of 168 patients were retrospectively examined for a retrosternal lesion in the anterior mediastinum that was attributable to the thymus. The patients were assigned to the following four groups: children with malignant lesions before the first therapy (group Ia; n = 15; mean age +/- SD, 11.9 +/- 3.7 y), children with malignant disease after chemotherapy (group Ib; n = 12; mean age, 10.3 +/- 5.0 y), adults with histologically confirmed malignant lymphoma before the first therapy (group IIa; n = 37; mean age, 43.9 +/- 16.7 y), and adult lymphoma patients 3 wk to 4 mo after chemotherapy (group IIb; n = 104; mean age, 40.9 +/- 14.6 y).

RESULTS

Increased FDG accumulation in the thymus was seen in 11 patients (73%) of group Ia and 9 patients (75%) of group Ib. Thymus hyperplasia was found in 5 patients (5%) of group IIb. The eldest of these 5 patients was 25 y old. No increased FDG accumulation in the thymus was observed in any of the group IIa patients. In cases of visible FDG uptake in the thymus, standardized uptake values did not exceed 4.

CONCLUSION

FDG accumulation in the thymus is a common finding in children and can occasionally be observed in young adults after chemotherapy. Knowledge of the characteristics of a typical retrosternal lesion in conjunction with the clinical history allows avoidance of diagnostic uncertainty and unnecessary procedures.

High-resolution blood flow velocity measurements in the human finger

MR phase contrast blood flow velocity measurements in the human index finger were performed with triggered, nontriggered, and cine acquisition schemes. A strong (G(max) = 200 mT/m), small bore (inner diameter 12 cm) gradient system inserted in a whole body 3 Tesla MR scanner allowed high-resolution imaging at short echo times, which decreases partial volume effects and flow artifacts. Arterial blood flow velocities ranging from 4.9-19 cm/sec were measured, while venous blood flow was significantly slower at 1.5-7.1 cm/sec. Taking into account the corresponding vessel diameters ranging from 800 microm to 1.8 mm, blood flow rates of 3.0-26 ml/min in arteries and 1.2-4.8 ml/min in veins are obtained. The results were compared to ultrasound measurements, resulting in comparable blood flow velocities in the same subjects. Magn Reson Med 45:716-719, 2001.

Metastatic lymph nodes in patients with cervical cancer: detection with MR imaging and FDG PET

PURPOSE

To compare the diagnostic accuracy of magnetic resonance (MR) imaging with that of positron emission tomography (PET) with 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) for detecting metastatic lymph nodes in patients with cervical cancer.

MATERIALS AND METHODS

Before radical hysterectomy and pelvic lymphadenectomy in 35 patients with International Federation of Gynecology and Obstetrics stage IB or II cervical cancer, abdominal FDG-PET and MR imaging were performed. Malignancy criteria were a lymph node diameter of 1 cm or more at MR imaging and a focally increased FDG uptake at PET. The findings of FDG-PET and MR imaging were compared with histologic findings.

RESULTS

Histologic examination revealed pN0-stage cancer in 24 patients and pN1-stage cancer in 11 patients. On a patient basis, node staging resulted in sensitivities of 0.91 with FDG-PET and 0.73 with MR imaging and specificities of 1.00 with FDG-PET and 0.83 with MR imaging. The positive predictive value (PPV) of FDG-PET was 1.00 and that of MR imaging, 0.67 (not significant). The metastatic involvement of lymph node sites was identified at FDG-PET with a PPV of 0.90; at MR imaging, 0.64 (P <.05, Fisher exact test).

CONCLUSION

Metabolic imaging with FDG-PET is an alternative to morphologic MR imaging for detecting metastatic lymph nodes in patients with cervical cancer.

Assessment of left ventricular function and volumes by myocardial perfusion scintigraphy - comparison of two algorithms

Aim: Left ventricular volume and function can be computed from gated SPECT myocardial perfusion imaging using Emory Cardiac Toolbox (ECT) or Gated SPECT Quantification (GS-Quant). The aim of this study was to compare both programs with respect to their practical application, stability and precision on heart-models as well as in clinical use. Methods: The volumes of five cardiac models were calculated by ECT and GS-Quant. 48 patients (13 female, 35 male) underwent a one day stress-rest protocol and gated SPECT. From these 96 gated SPECT images, left ventricular ejection fraction (LVEF), end-diastolic volume (EDV) and end-systolic volume (ESV) were estimated by ECT and GS-Quant. For 42 patients LVEF was also determined by echocardiography. Results: For the cardiac models the computed volumes showed high correlation with the model-volumes as well as high correlation between ECT and GS-Quant (r ≥ 0.99). Both programs underestimated the volume by approximately 20-30% independent of the ventricle-size. Calculating LVEF, EDV and ESV, GS-Quant and ECT correlated well to each other and to the LVEF estimated by echocardiography (r ≥ 0.86). LVEF values determined with ECT were about 10% higher than values determined with GS-Quant or echocardiography. The incorrect surfaces calculated by the automatic algorithm of GS-Quant for three examinations could not be corrected manually. 34 of the ECT studies were optimized by the operator. Conclusion: GS-Quant and ECT are two reliable programs in estimating LVEF. Both seem to underestimate the cardiac volume. In practical application GS-Quant was faster and easier to use. ECT allows the user to define the contour of the ventricle and thus is less susceptible to artifacts.

18F-DOPA positron emission tomography for tumour detection in patients with medullary thyroid carcinoma and elevated calcitonin levels

In spite of the availability of numerous procedures, diagnostic imaging of tumour manifestations in patients with medullary thyroid carcinoma and elevated calcitonin levels is often difficult. In the present study, the new procedure of fluorine-18 dihydroxyphenylalanine positron emission tomography (18F-DOPA PET) was compared with the established functional and morphological imaging methods. After evaluation of the normal distribution of 18F-DOPA, 11 patients with medullary thyroid carcinoma were examined using 18F-DOPA PET. Results of 18F-fluorodeoxyglucose (18F-FDG) PET, somatostatin receptor scintigraphy (SRS) and morphological tomographic imaging (CT/MRI) were available for all patients. All individual procedures were evaluated without reference to prior information. Data assessment for each patient was based on cooperation between experienced radiologists and specialists in nuclear medicine, who considered all the available findings (histological results, imaging, follow-up studies). This cooperation served as the gold standard against which the results of the individual procedures were evaluated. A total of 27 tumours were studied [three primary tumours (PT)/local recurrence (LR), 16 lymph node metastases (LNM) and eight organ metastases (OM)]. 18F-DOPA PET produced 17 true-positive findings (2 PT/LR, 14 LNM, 1 OM), 18F-FDG PET 12 (2 PT/LR, 7 LNM, 3 OM), SRS 14 (2 PT/LR, 8 LNM, 4 OM) and morphological imaging 22 (3 PT/LR, 11 LNM, 8 OM). The following sensitivities were calculated with respect to total tumour manifestations: 18F-DOPA PET 63%, 18F-FDG PET 44%, SRS 52%, morphological imaging 81%. Thus, the morphological imaging procedures produce the best overall sensitivity, but the specificity for PT/LR (55%) and LNM (57%) was low. With respect to lymph node staging, the best results were obtained with 18F-DOPA PET. 18F-DOPA PET is a new functional imaging procedure for medullary thyroid carcinoma that seems to provide better results than SRS and 18F-FDG PET. Moreover, the data indicate that no single procedure provides adequate diagnostic certainty. Therefore, 18F-DOPA PET is a useful supplement to morphological diagnostic imaging, improving lymph node staging and enabling a more specific diagnosis of primary tumour and local recurrence.