O-(2-[18F]fluorethyl)-L-tyrosine PET in the clinical evaluation of primary brain tumours

PURPOSE

The aim of this study was to evaluate the differential uptake of O-(2-[18F]fluorethyl)-L-tyrosine (FET) in suspected primary brain tumours.

METHODS

Positron emission tomography (PET) was performed in 44 patients referred for the evaluation of a suspected brain tumour. Acquisition consisted of four 10-min frames starting upon i.v. injection of FET. Tumour uptake was calculated as the ratio of maximal tumour intensity to mean activity within a reference region (FETmax).

RESULTS

FET uptake above the cortical level was observed in 35/44 lesions. All histologically confirmed gliomas and many other lesions showed FET uptake to a variable extent. No uptake was observed in nine lesions (one inflammatory lesion, one dysembryoplastic neuroepithelial tumour, one mature teratoma, six lesions without histological confirmation). An analysis of uptake dynamics was done in the patients with increased FET uptake (22 gliomas, three lymphomas, three non-neoplastic lesions, three lesions with unknown histology and four other primaries). Upon classification of tumours into low (i.e. WHO I and II) and high grade (i.e. WHO III and IV), a significant difference in FETmax between the two categories was observed only in the first image frame (0-10 min p.i.), with FETmax=2.0 in low-grade and 3.2 in high-grade tumours (p<0.05); no significant differences were found in frame 4 (30-40 min p.i.), with FETmax=2.4 vs 2.7. Similar results were obtained when the analysis was applied only to astrocytic tumours (2.0 vs 3.1 in the first frame; 2.4 vs 2.6 in the fourth frame).

CONCLUSION

These initial results indicate that FET PET is a useful method to identify malignant brain lesions. It appears that high- and low-grade brain tumours exhibit a different uptake kinetics of FET. A kinetic analysis of FET PET may provide additional information in the differentiation of suspected brain lesions.

Motion correction in PET/CT

Motion in PET/CT leads to artifacts in the reconstructed PET images due to the different acquisition times of positron emission tomography and computed tomography. The effect of motion on cardiac PET/CT images is evaluated in this study and a novel approach for motion correction based on optical flow methods is outlined. The Lukas-Kanade optical flow algorithm is used to calculate the motion vector field on both simulated phantom data as well as measured human PET data. The motion of the myocardium is corrected by non-linear registration techniques and results are compared to uncorrected images.

Guidelines on radioiodine therapy for differentiated thyroid carcinoma: impact on clinical practice

AIM

For the examination of the impact on clinical practice of the guidelines for differentiated thyroid carcinoma (DTC), treatment data from the ongoing Multicenter Study Differentiated Thyroid Carcinoma (MSDS) were analyzed.

PATIENTS, METHODS

Patients were randomized to adjuvant external beam radiotherapy (RTx) or no RTx in addition to standard therapy in TNM stages pT4 pN0/1/x M0/x (UICC, 5th ed. 1997). All patients were to receive the same treatment regimen consisting of thyroidectomy, ablative radioiodine therapy (RIT), and a diagnostic 131I whole-body scintigraphy (WBS) 3-4 months after RIT.

RESULTS

Of 339 eligible patients enrolled between January 2000 and March 2004, 273 could be analyzed. Guideline recommendations by the German Society for Nuclear Medicine from 1999 and 1992 were complied with within 28% and 82% with regard to the interval between surgery and RIT (4 vs. 4-6 weeks), in 33% and 84% with regard to 131I activity for RIT (1-3 vs. 1-4 GBq; +/- 10%), and in 16% and 60% with regard to 131I activity for WBS (100-300 vs. 100-400 MBq; +/- 10%).

CONCLUSIONS

The 1999 guideline revision appears to have had little impact on clinical practice. Further follow-up will reveal if guideline compliance had an effect on outcomes.

[Guideline for radioiodine therapy for benign thyroid diseases (version 3)]

The version 3 of the guideline for radioiodine therapy for benign thyroid diseases presents first of all a revision of the version 2. The chapter indication for radioiodine therapy, surgical treatment or antithyroid drugs bases on an interdisciplinary consensus. The manifold criteria for decision making consider the entity of thyroid disease (autonomy, Graves' disease, goitre, goitre recurrence), the thyroid volume, suspicion of malignancy, cystic nodules, risk of surgery and co-morbidity, history of subtotal thyroidectomy, persistent or recurrent thyrotoxicosis caused by Graves' disease including known risk factors for relapse, compression of the trachea caused by goitre, requirement of direct therapeutic effect as well as the patient's preference. Because often some of these criteria are relevant, the guideline offers the necessary flexibility for individual decisions. Further topics are patients' preparation, counseling, dosage concepts, procedural details, results, side effects and follow-up care. The prophylactic use of glucocorticoids during radioiodine therapy in patients without preexisting ophthalmopathy as well as dosage and duration of glucocorticoid medication in patients with preexisting ophthalmopathy need to be clarified in further studies. The pragmatic recommendations for the combined use of radioiodine and glucocorticoids remained unchanged in the 3rd version.

Synthesis and preliminary biological evaluation of new radioiodinated MMP inhibitors for imaging MMP activity in vivo

Non-invasive measurement of matrix metalloproteinase (MMP) activity in vivo is a clinical challenge in many disease processes such as inflammation, tumor metastasis and atherosclerosis. Therefore, radioiodinated analogues of the non-peptidyl broad-spectrum MMP inhibitor (MMPI) CGS 27023A 1a were synthesized for non-invasive detection of MMP activity in vivo using single photon emission computed tomography (SPECT). The compounds Br-CGS 27023A 1b and HO-CGS 27023A 1d were synthesized from the amino acid D-valine and used as precursors for radioiodinated derivatives of CGS 27023A and their non-radioactive references I-CGS 27023A 1c and HO-I-CGS 27023A 1e. Radioiodination of the precursors with [(123)I]NaI or [(125)I]NaI produced the no-carrier-added MMP inhibitors [(123)I]I-CGS 27023A 1f, [(125)I]I-CGS 27023A 1g, HO-[(123)I]I-CGS27023A 1h, and HO-[(125)I]I-CGS 27023A 1i. In vitro studies showed that the non-radioactive analogues of the MMP inhibitors exhibited affinities against gelatinase A (MMP-2) and gelatinase B (MMP-9) in the nanomolar range, comparable to the parent compound CGS 27023A. In vivo biodistribution using HO-[(125)I]I-CGS 27023A 1i in CL57 Bl6 mice showed rapid blood and plasma clearance and low retention in normal tissues. The preliminary biological evaluation warrant further studies of these radioiodinated MMP inhibitors as potential new radiotracers for imaging MMP activity in vivo.

High-density lipoprotein stimulates myocardial perfusion in vivo

BACKGROUND

Several clinical studies have demonstrated a close association between plasma HDL cholesterol levels and endothelium-dependent vasodilation in peripheral arteries. In isolated arteries, HDL has been shown to mediate vasodilation via NO release. In vivo, administration of reconstituted HDL restored abnormal endothelial function of the brachial artery in hypercholesterolemic patients. However, no data are currently available on the effect of HDL on myocardial perfusion.

METHODS AND RESULTS

In this study, administration of human HDL enhanced incorporation of the perfusion tracer 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) into the murine heart in vivo by approximately 18%. This increase was completely abolished in mice deficient for endothelial NO synthase. Because we have recently identified sphingosine 1-phosphate (S1P) as an important vasoactive component contained in HDL, we measured myocardial perfusion after administration of S1P in vivo. We observed an approximately 25% decrease in myocardial MIBI uptake, which was abolished in mice deficient for the S1P receptor S1P3. In S1P3-/- mice, the stimulatory effect of HDL on myocardial perfusion was preserved.

CONCLUSIONS

HDL increased myocardial perfusion under basal conditions in vivo via NO-dependent mechanisms, whereas S1P inhibited myocardial perfusion through the S1P3 receptor. Thus, HDL may reduce coronary risk via direct NO-mediated vasodilatory effects on the coronary circulation.

Abnormal Myocardial Presynaptic Norepinephrine Recycling in Patients With Brugada Syndrome

Background— Life-threatening ventricular tachyarrhythmias can occur in young patients without structural heart disease (idiopathic forms). In many patients, these are typically triggered by an increased sympathetic tone, eg, by physical or mental stress. In contrast, in Brugada syndrome, ventricular tachyarrhythmias more often occur during rest or sleep when the vagal tone is predominant. Furthermore, adrenergic agonists can reduce the level of ST-segment elevation, whereas it is increased by parasympathetic agonists or adrenergic antagonists. The aim of this study was to investigate presynaptic and postsynaptic myocardial sympathetic function in patients with Brugada syndrome.

Methods and Results— Nine patients with Brugada syndrome (6 male, 3 female; age, 41±13 years) were enrolled in this study. The cardiac autonomic nervous system was assessed noninvasively, quantifying myocardial presynaptic and postsynaptic sympathetic function by means of positron emission tomography with the norepinephrine analogue 11 C-Hydroxyephedrine ( 11 C-HED) and the nonselective β-blocker 11 C-CGP 12177 ( 11 C-CGP). Presynaptic sympathetic norepinephrine recycling, assessed by 11 C-HED, was globally increased in patients with Brugada syndrome compared with a group of age-matched healthy control subjects (92.9±16.2 mL/g versus 69.1±14.2 mL/g; P <0.05), whereas postsynaptic β-adrenoceptor density, assessed by 11 C-CGP, was similar in patients and control subjects (10.4±6.7 pmol/g versus 10.2±2.9 pmol/g; P =NS).

Conclusions— The present study on autonomic innervation in Brugada syndrome describes an enhanced presynaptic norepinephrine recycling with preserved β-adrenoceptor density, further supporting the hypothesis of an autonomic dysfunction in Brugada syndrome. This is a further step toward the understanding of the pathophysiology of the disease with potential future impact on therapeutic strategies.

PET-CT in der Strahlentherapie

Combining positron emission tomography (PET) and X-ray computed tomography (CT) with simultaneous acquisition may improve diagnostic accuracy in oncology. Moreover this combination holds considerable promise in radiotherapy. Metabolic information may be used in decision making in radiotherapy and in planning target volumes. Furthermore early evaluation of treatment efficacy becomes possible. New tracers for the assessment of tumour hypoxia or apoptosis in clinical routine are currently being developed. These tracers may yield high relevance in radiotherapy. Hybrid scanners facilitate patient handling and shorten the duration of acquisition. Furthermore fusion accuracy is optimal. Prospective studies have to be conducted to show that the new technology improves patient care in terms of efficiency and quality.

Functional changes after partial left ventriculectomy and mitral valve repair assessed by gated perfusion SPECT

A myocardial remodeling in dilated cardiomyopathy (DCM) after partial left ventriculectomy (PLV) has been previously discussed. The aim of this study was to investigate the functional changes in the follow-up of patients with DCM undergoing PLV using electrocardiographically triggered perfusion SPECT (gated SPECT).

METHODS

Twelve DCM patients (10 men, 2 women; 56 +/- 9 y [mean +/- SD]), after successful PLV and mitral valve repair (PLV-MVR), were monitored by gated SPECT and echocardiography. Gated SPECT quantified end-diastolic volumes (EDV), end-systolic volumes (ESV), myocardial and scar volumes, as well as ejection fraction (EF) preoperatively, early (38 +/- 28 d), and late (296 +/- 130 d) after PLV-MVR.

RESULTS

EDV and ESV showed an immediate reduction after PLV-MVR (EDV from 542 +/- 90 mL to 350 +/- 81 mL, P < 0.001; ESV from 452 +/- 91 mL to 254 +/- 79 mL, P < 0.001) with no significant change in the late follow-up (EDV late, 316 +/- 63 mL; ESV late, 207 +/- 63 mL; both P = not significant vs. early follow-up). PLV-MVR immediately improved EF (preoperative, 16.8% +/- 5.5%; early, 28.8% +/- 7.6%; P = 0.003) with no significant change in the late follow-up (36.0% +/- 9.4%; P = not significant vs. early follow-up).

CONCLUSION

In this highly selected DCM patient group, gated perfusion SPECT assessed early responses in volumes and EF after PLV-MVR. However, although statistically nonsignificant in the small patient group, ESV and EDV were further decreased, whereas EF improved toward 1 y, coinciding with the improvement of clinical symptoms (New York Heart Association), potentially indicating a functional remodeling after PLV-MVR. Further studies in larger patient cohorts and longer follow-up are warranted.

[Overtherapy or undertherapy for papillary thyroid microcarcinoma? Therapeutic considerations for radioiodine ablation]

Papillary thyroid microcarcinomas </=1 cm have an excellent prognosis both in terms of overall and relapse-free survival. Their high prevalence in autopsy series suggests that most papillary microcarcinomas do not progress to clinically relevant cancer. The extent of surgery is still controversial. Lobectomy or subtotal resection are standard procedures, but multifocal microcarcinomas or lymph node metastases might be overlooked. The pros and cons of completion thyroidectomy and ablative radioiodine therapy are based on limited evidence due to heterogenous inclusion criteria in published series. The retrospective data analyses included subgroups with infiltration of the thyroid capsule, lymph node metastases or multifocal microcarcinomas at the primary staging. The local relapse rate reached approximately 7% after different therapeutic regimes. Radioiodine ablation decreased the recurrence rate in some retrospective studies, but data are inconsistent. Successful radioiodine ablation is possible also after less radical surgery without complete thyroidectomy with postoperative (131)I uptake of 10 to 20% or remnants of 3-8 ml. This concept was evaluated successfully in a monocentric series of patients with multifocal microcarcinomas. The therapeutic consideration should include the diameter of the carcinoma, neighbourhood to the thyroid capsule, histopathologic sub-groups, age, familiar occurrence, patient's informed consent and in future moleculargenetic tests, too. There-fore, limited surgical procedures for small papillary carcinomas as therapeutic standard, respectively thyroidectomy, lymph node dissection in the central compartment of the neck and ablative radioiodine therapy for individual cases are options for experienced surgeons and specialized tumour centers.

[Procedure guidelines for radioiodine therapy of differentiated thyroid cancer (version 2)]

The procedure guidelines for radioiodine therapy (RIT) of differentiated thyroid cancer (version 2) are the counter-part to the procedure guidelines for (131)I whole-body scintigraphy (version 2) and specify the interdisciplinary guidelines for thyroid cancer of the Deutsche Krebsgesellschaft and the Deutsche Gesellschaft für Chirurgie concerning the nuclear medicine part. Compared with version 1 facultative options for RIT can be chosen in special cases: ablative RIT for papillary microcarcinoma </=1 cm, ablative RIT for mixed forms of anaplastic and differentiated thyroid cancer, and RIT in patients with a measurable or increasing thyroglobulin concentration but without detectable metastases by imaging. The description of the pretherapeutic dosimetry now includes the isotopes (123)I and (124)I as well as a broader range of the activity of (131)I. Activities of 2-5 GBq (131)I are recommended for the first ablative RIT. If high accumulative activities of (131)I are expected, men who have not yet finished their family planning should be advised to the option of sperm cryoconservation. An interdisciplinary consensus is necessary whether the new TNM-classification (UICC, 6(th) edition, 2002) will lead to modified recommendations for surgical or nuclear medicine therapy, especially for the surgical completeness and for the ablative RIT of pT1 papillary cancer.

Scintigraphic imaging of matrix metalloproteinase activity in the arterial wall in vivo

BACKGROUND

Matrix metalloproteinases (MMPs) are enzymes involved in the proteolytic degradation of extracellular matrix. They play an important role in several disease processes, such as inflammation, cancer, and atherosclerosis.

METHODS AND RESULTS

In this study, we have used the broad-spectrum MMP inhibitor CGS 27023A to develop the radioligand [123I]I-HO-CGS 27023A for in vivo imaging of MMP activity. Using this radioligand, we were able to specifically image MMP activity by scintigraphy in vivo in the MMP-rich vascular lesions that develop after carotid artery ligation and cholesterol-rich diet in apolipoprotein E-deficient mice. These results were confirmed by gamma counting of lesional tissue (counts per minute per milligram).

CONCLUSIONS

Imaging of MMP activity in vivo is feasible using radiolabeled MMP inhibitors. Additional studies are needed to test the potential of this approach as a novel noninvasive clinical diagnostic tool for the management of human MMP-related diseases.

Acute toxicity of adjuvant radiotherapy in locally advanced differentiated thyroid carcinoma. First results of the multicenter study differentiated thyroid carcinoma (MSDS)

BACKGROUND AND PURPOSE

The indication for adjuvant postoperative radiotherapy in patients with differentiated thyroid carcinoma (DTC) extending beyond the thyroid capsule has been an issue of controversy during the past 2 decades. No randomized studies evaluating the benefit of radiotherapy have been published so far. In the Multicenter Study Differentiated Thyroid Carcinoma (MSDS), a randomization has been performed concerning external-beam radiotherapy in patients with DTC extending beyond the thyroid capsule (pT4 pN0/1/x cM0, TNM classification, 5th edition, 1997) following surgery and radioiodine therapy. Radiation-associated toxicity has been prospectively evaluated.

PATIENTS AND METHODS

Radiotherapy was performed with 50.4 Gy (pN0) or 54.0 Gy (pN1/x) to the cervical, supraclavicular and upper mediastinal lymph nodes. A total dose of 59.4 Gy (R0 resection) or 66.6 Gy (R1) was used to treat the tumor bed. Conventional fractionation was used with 1.8 Gy/d. At the time of the analysis, 36 patients were randomized or allocated to treatment arm A (with external-beam radiotherapy). Of these, 22 were treated with radiotherapy, and documentation of acute toxicity was available. Toxicity was evaluated prospectively according to the RTOG/EORTC criteria.

RESULTS

The maximal acute toxicity observed during radiotherapy was grade I in four patients, grade II in 16 patients, and grade III in two patients (9.1%; 95% confidence interval [95% CI] 1.1-29.2%). Toxicity was mainly observed at the pharynx, larynx, and skin. In 19 patients, residual toxicity within 100 days following radiotherapy was evaluated. No residual toxicity was observed in two patients. Maximal residual toxicity was grade I in 13 patients and grade II in four. No further grade III toxicity could be observed.

CONCLUSION

The majority of patients experience mild to moderate side effects from adjuvant external-beam radiotherapy. At the first follow-up examination, most side effects have subsided. Acute toxicity is tolerable in these patients.

Direct epicardial mapping predicts the recovery of left ventricular dysfunction in chronic ischaemic myocardium

AIMS

This study investigated the hypothesis that direct epicardial bipolar mapping is able to predict the recovery of left ventricular (LV) dysfunction in ischaemic myocardium.

METHODS AND RESULTS

In 34 patients with CAD, a maximum of 102 bipolar epicardial electrograms per patient (n=3468 electrograms) were simultaneously recorded with a ventricular jacket array intraoperatively immediately prior to revascularization. Only LV electrograms with good myocardial contact (n=1813, 52+/-14 per patient, mean+/-SD) were analyzed. In accordance to the position of each electrode, segmental myocardial function was assessed by transthoracic echocardiography before and 7+/-2 months (mean+/-SD; range 3-10 months) after CABG using a wall motion score. Preoperatively dysfunctional segments (n=700) were classified as viable (improvement in wall motion score of at least 20% following CABG, n=424) or non-viable (no improvement, n=276). Bipolar voltage was significantly lower in non-viable when compared to viable myocardium (P<0.001, ANOVA) At a cut-off value of 5.9mV, ROC-curve analysis for bipolar voltage (to discriminate between viable and non-viable myocardium) revealed a sensitivity of 83% at a specificity of 83% (area under the ROC-curve of 0.92+/-0.01, mean+/-SE).

CONCLUSIONS

Direct epicardial mapping is able to predict the recovery of chronically ischaemic dysfunctional myocardium and thereby proves the presence of myocardial viability.