Focus on radioiodine-131 biokinetics: the influence of methylprednisolone on intratherapeutic effective half-life of 131I during radioiodine therapy of Graves' disease.

AIM: Radioiodine therapy (RIT) may trigger the development of Graves' ophthalmopathy (GO) or exacerbate pre-existing subclinical GO. Therefore, glucocorticoid administration is recommended for patients with pre-existing GO. Aim of this study was to analyze the influence of glucocorticoid therapy with methylprednisolone on intratherapeutic effective half-life (EHL) of radioiodine-131 in patients with Graves' disease (GD) as recent studies showed an effect for prednisolone. METHODS: In a retrospective study, 264 patients with GD who underwent RIT without any additional antithyroid medication were evaluated. Intrathyroidal EHL was determined pre- and intratherapeutically. Patients with co-existing GO (n = 43) received methylprednisolone according to a fixed scheme starting 1 day prior to RIT, patients without GO (n = 221) did not receive any protective glucocorticoid medication. The ratios of EHL during RIT and during radioiodine uptake test (RIUT) were compared. RESULTS: Patients receiving methylprednisolone showed a slight decrease of the mean EHL from 5.63 d (RIUT) to 5.39 d (RIT) (p > 0.05). A comparable result was obtained in patients without glucocorticoids (5.71 d (RIUT) to 5.47 d (RIT); p > 0.05). The ratios of the EHL between RIT and RIUT failed to show a significant difference between the two groups. EHL is therefore not significantly influenced by an additional protective treatment with methylprednisolone. CONCLUSIONS: In the present study a decreased intrathyroidal EHL under glucocorticoid medication with methylprednisolone could not be detected. Therefore, co-medication with methylprednisolone in patients with GO may be preferred to avoid an intratherapeutic decrease of EHL by accompanying protective glucocorticoides.

Correction for hyperfunctioning radiation-induced stunning (CHRIS) in benign thyroid diseases.

PURPOSE: Radioiodine-131 treatment has been a well-established therapy for benign thyroid diseases for more than 75 years. However, the physiological reasons of the so-called stunning phenomenon, defined as a reduced radioiodine uptake after previous diagnostic radioiodine administration, are still discussed controversially. In a recent study, a significant dependence of thyroid stunning on the pre-therapeutically administered radiation dose could be demonstrated in patients with goiter and multifocal autonomous nodules. A release of thyroid hormones to the blood due to radiation-induced destruction of thyroid follicles leading to a temporarily reduced cell metabolism was postulated as possible reason for this indication-specific stunning effect. Therefore, the aim of this study was to develop dose-dependent correction factors to account for stunning and thereby improve precision of radioiodine treatment in these indications. METHODS: A retrospective analysis of 313 patients (135 with goiter and 178 with multifocal autonomous nodules), who underwent radioiodine uptake testing and radioiodine treatment, was performed. The previously determined indication-specific values for stunning of 8.2% per Gray in patients with multifocal autonomous nodules and 21% per Gray in patients with goiter were used to modify the Marinelli equation by the calculation of correction factors for hyperfunctioning radiation-induced stunning (CHRIS). Subsequently, the calculation of the required activity of radioiodine-131 to obtain an intra-therapeutic target dose of 150 Gy was re-evaluated in all patients. Furthermore, a calculation of the hypothetically received target dose by using the CHRIS-calculated values was performed and compared with the received target doses. RESULTS: After integrating the previously obtained results for stunning, CHRIS-modified Marinelli equations could be developed for goiter and multifocal autonomous nodules. For patients with goiter, the mean value of administered doses calculated with CHRIS was 149 Gy and did not differ from the calculation with the conventional Marinelli equation of 152 Gy with statistical significance (p = 0.60). However, the statistical comparison revealed a highly significant improvement (p < 0.000001) of the fluctuation range of the results received with CHRIS. Similar results were obtained in the subgroup of patients with multifocal autonomous nodules. The mean value of the administered dose calculated with the conventional Marinelli equation was 131 Gy and therefore significantly below the CHRIS-calculated radiation dose of 150 Gy (p < 0.05). Again, the fluctuation range of the CHRIS-calculated radiation dose in the target volume was significantly improved compared with the conventional Marinelli equation (p < 0.000001). CONCLUSIONS: With the presented CHRIS equation it is possible to calculate a required individual stunning-independent radioiodine activity for the first time by only using data from the radioiodine uptake testing. The results of this study deepen our understanding of thyroid stunning in benign thyroid diseases and improve precision of dosimetry in radioiodine-131 therapy of goiter and multifocal autonomous nodules.

Combination of ultrasound guided percutaneous microwave ablation and radioiodine therapy in benign thyroid diseases. A suitable method to reduce the 131I activity and hospitalization time?

AIM: Goiters and thyroid nodules are an ongoing problem in healthcare. There has not been any treatment of goiters and thyroid nodules based on the combined therapy of microwave ablation (MWA) and radioiodine therapy (RIT) until now. In this study the potential benefit of a combined therapy versus single RIT is evaluated in order to achieve improvements concerning ¹³¹I-dose and hospitalization time. PATIENTS, MATERIAL, METHODS: Ten patients with goiter and benign thyroid nodules or Graves' disease were included. Pre-ablation assessments included sonographical imaging, functional imaging with 99mTc and FNAB to collect data of nodules and total thyroid volume and to exclude malignancy. Prior to treatment, radioiodine uptake test was performed. MWA was operated under local anesthesia with a system working in a wavelength field 902-928 MHz. Post-MWA, thyroid volume was recalculated ultrasonically. Due to reduced vital volume, changes of ¹³¹I-dose and hospitalization time could be monitored. RESULTS: Mean absolute thyroid volume reduction by MWA before applying RIT was 22 ± 11 ml, meaning a relative reduction of 24 ± 6% (p < 0.05). Thereby, administered activity could be reduced by 393 ± 188 MBq using the combined therapy, reflecting a relative reduction of 24 ± 6% (p < 0.05). Additionally, mean hospitalization time was decreased by 2.1 ± 0.8 days using MWA prior to RIT, implying a relative reduction of 28 ± 6% (p < 0.05). CONCLUSION: Depending on ablated volume by MWA, RIT-monotherapy requires on average 31.2% more ¹³¹I-activity than the combined therapy. The combined therapy remarkably decreases ¹³¹I-dose and hospitalization time. The combined MWA and RIT therapy is a considerable, effective and safer alternative to surgery for the treatment of very large benign nodular goiters.

Age and body composition influence TSH concentrations after administration of rhTSH.

AIM: Previous studies listed body surface area (BSA), lean body mass (LBM), and age as modifying factors on the TSH concentrations after administration of recombinant human thyrotropin (rhTSH). The purpose of this study was to identify the main modifying factors on serum TSH levels and to compare the stimulation via single rhTSH injection after a short thyroid hormone withdrawal (THW) with that of the standard stimulating protocol. PATIENTS, METHODS: 106 patients with differentiated thyroid cancer (DTC) undergoing radioiodine therapy (RIT) after rhTSH administration were obtained through chart review. Two groups were evaluated: Group I was treated with a single rhTSH administration after two weeks of T3 therapy followed by one week of THW. Group II was stimulated according to the international standard protocol via rhTSH injections for two consecutive days. Serum TSH concentrations were documented prior to rhTSH administration (day 1 TSH), one day after (day 3 TSH) and 3-6 days after (mean 4.2 days, day 6 TSH) the last rhTSH injection. The following data was collected: age, gender, weight, height, BMI, LBM, BSA, residual thyroid tissue, CRP, creatinine, GFR, liver enzymes, alkaline phosphatase, cholesterol, and triglycerides. RESULTS: Group I: Age combined with anthropometric factors like BMI (TSH increase and day 6 TSH), BSA (TSH decrease), and gender (day 6 TSH) are the main modifying factors on serum TSH concentrations after rhTSH administration. Group II: Age and lean body mass (LBM) showed a significant impact on day 3 TSH, TSH increase (day 3-day 1), and TSH decrease (day 6-day 3). Day 6 TSH was found to be influenced by GFR (group II). CONCLUSION: Age and anthropometric parameters have significant independent influence on TSH concentrations after rhTSH injection in both groups. Anthropometric parameters (BSA, LBM) and demographic parameters (female gender) show strong influence on TSH concentrations. Further research should be conducted to examine the influence of body compartments on TSH levels through measuring total body water.

[Colour-coded duplex-sonography versus scintigraphy. Can scintigraphy be replaced by sonography for diagnosis of functional thyroid autonomy?]. / 99mTc-Szintigraphie versus Farbduplex-Sonographie. Kann zur Diagnose der funktionellen Schilddrüsenautonomie auf die Szintigraphie verzichtet werden?

UNLABELLED: Since the development of colour coded duplex-sonography (ccds), several attempts have been made to implement this technique for diagnosis of focal lesions in the thyroid. There are controversial discussions on whether ccds might replace thyroid scintigraphy in diagnosis of hyperfunctional thyroid nodules. Aim of this study was the comparison of ccds and thyroid scintigraphy in diagnosis of functional thyroid autonomy. PATIENTS, MATERIAL AND METHODS: 192 patients with thyroid nodules > 10mm detected by conventional sonography underwent thyroid scintigraphy. Additionally, these patients were subjected to ccds of the thyroid. In total, 286 thyroid nodules were examined by scintigraphy, ccds and blood tests. RESULTS: Thyroid scintigraphy showed 67% of thyroid nodules as hyperfunctional, 19% indifferent and 14% as hypofunctional. Mean 99mTc uptake of hyperfunctional nodules was 2.19%, of indifferent nodules 1.12% and of hypofunctional nodules 1.06% respectively. The ccds allowed perinodular measurement of flow speed (hyperfunctional: 0.23 ± 0.1 m/s; hypofunctional: 0.22 ± 0.1; indifferent: 0.21 ± 0.09), resistance index (hyperfunctional: 1.21 ± 1.16; hypofunctional: 0.62 ± 0.48; indifferent: 0.93 ± 1.02) and pulsatility index (hyperfunctional: 0.97 ± 0.45; hypofunctional: 0.84 ± 0.4; indifferent: 1.04 ± 0.6) in all nodules as well as intranodular measurement in some of the nodules (24% in hyperfunctional, 2% in indifferent and 15% in hypofunctional nodules). Statistic analysis of the obtained ccds data did not show any practically relevant correlations (p>0.05) with 99mTc uptake, basal TSH, fT3 or fT4. CONCLUSION: Thyroid scintigraphy cannot be replaced by ccds for diagnosis of functional thyroid autonomy. Reliable diagnostics still require a combination of thyroid scintigraphy, sonography and blood tests.

[Incorporation monitoring of employees of a radioiodine therapy ward. Is incorporation monitoring required for routine?]. / Überwachung der Mitarbeiter einer Radioiodtherapiestation mittels Ausscheidungsmessungen. Ist im Routinebetrieb eine Inkorporationsüberwachung erforderlich?

UNLABELLED: Aim of the study was to determine the annual incorporation of staff on a radioiodine therapy ward and the resulting annual effective dose (aed). Following the German incorporation guideline (gig), incorporation monitoring is not necessary for potential aed below 0.5 mSv/a. For aed > 0.5 mSv/a adherence to the 1 mSv dose limit must be verified. For doses > 1 mSv/a incorporation has to be monitored by the authority. Furthermore, the (131)I incorporation factor from the gig should be verified. METHODS: To determine the actual work related incorporation, the (131)I activity concentration in urine samples (collection over 24 h) of 14 employees of different professions were examined over a period of 27 months. RESULTS: Measured activity concentrations were related to the individual time of exposure. A constant activity supply for at least three days was assumed. The mean annual effective doses were 2.4 · 10⁻¹ mSv/a (nursing staff; n = 3), 5.6 · 10⁻² mSv/a (cleaning staff; n = 2), 2.8 · 10⁻³ mSv/a (technical staff; n = 2) and 5.2 · 10⁻³ mSv/a (physicians; n = 7). All aed were below the dose limits of the gig. The calculated mean incorporation factors ranged from 3.0 · 10⁻8 for the nursing staff to 3.6 · 10⁻¹° for the technical staff (cleaning staff: 7 · 10⁻9; physicians: 6.5 · 10⁻¹°) and were therefore well below the (131)I incorporation factor defined by the gig. CONCLUSIONS: To estimate the aed caused by incorporation of (131)I it has to be subdivided for the different requirements in the diverse fields of activity of the employees. Regarding those who spend most of their time nearby the patient an incorporation monitoring by the authority might be required. The (131)I incorporation factor from the guideline (10⁻6) can be reduced by a factor of 10. For (99m)Tc and (18)F an incorporation factor of 10⁻7 is accepted.

[The influence of cardiopulmonary bypass operation on the biodistribution of 99mTc-HMPAO-labelled granulocytes - Evaluation in pigs by planar scintigraphy and section-analyses]. / Einfluss der extrakorporalen Perfusion auf die Biodistribution 99mTc-HMPAO-markierter Granulozyten. Evaluierung im Schwein mittels planarer Szintigraphie und Sektionsanalytik.

AIM: of the study was to evaluate the influence of an extra corporal perfusion (cardiopulmonary bypass operation - cpb) on activation and biodistribution of (99m)Tc labelled granulocytes in pigs with and without inhibition of the granulocytes by a leukocyte inhibition module (LIM). The cpb is often related to an activation of granulocytes resulting in an inflammatory answer. The biological mechanisms are unsolved yet. First trials of our group showed that LIM may inhibit the activation of neutrophils and therefore antagonize a cpb-caused impairment of cardiac function. This study is the continuation of these experiments with a higher number of animals and the focus on scintigraphic imaging. ANIMALS, MATERIAL, METHODS: 39 German landrace pigs were subdivided into three groups: group A (control) median sternotomy without cpb, group B with cpb, group C with LIM in addition to cpb. After labelling with (99m)Tc-HMPAO autologues granulocytes were reinjected. Subsequently to cpb, the animals underwent scintigraphic imaging. Quantification was performed with ROI evaluation and with tissue samples (section analysis) examined in a well counter. RESULTS: A high uptake of (99m)Tc-HMPAO was found in the liver. The count rates in brain, heart, lung, spleen and kidneys were far below. The amount of 99mTc-activity in the organ related to the half life corrected administered activity [%] was for the tissue samples (group A/B/C): brain 0.01/0.02/0.03; lung 12.1/8.3/11.5; heart 0.35/0.54/0.42; kidney 1.24/0.87/1.02; spleen 4.0/4.0/4.5, liver 16.8/20.9/19.6. The count rates determined by ROI-evaluation of the scintigraphic images related to the total count rate in the image [%] were (group A/B/C): brain 1.1/0.9/1.0; lung 15.6/10.4/12.2; heart 4.0/3.5/3.4; kidney 4.0/2.9/3.2; spleen 7.6/7.7/9.5, liver 23.1/36.7/31.4. A significant difference in the tracer uptake between the groups could neither be detected by scintigraphic imaging nor evaluation of tissue samples. CONCLUSION: Scintigraphic imaging as well as section analysis showed a comparable biodistribution of the tracer. Therefore, the initial results of our group were not confirmed with a considerably higher number of animals. Neither cpb nor the use of the LIM influenced distribution of 99mTc-labelled granulocytes in pigs significantly.

Comparison of positron emission tomography with [(18)F]FDG and [(68)Ga]DOTATOC in recurrent differentiated thyroid cancer: preliminary data.

AIM: The aim of this study was to retrospectively analyse the value of positron emission tomography (PET) with a radiolabelled somatostatin analogue, [(68)Ga]DOTATOC, in recurrent radioiodine positive and negative differentiated thyroid cancer (DTC) compared to [(18)F]FDG PET. METHODS: Seventeen patients with known or suspected recurrent DTC were enrolled in this study. All patients underwent PET with [(68)Ga]DOTATOC and [(18)F]FDG under TSH suppressive therapy and whole-body scintigraphy (WBS) after administration of [(131)I] following TSH stimulation. The total number of tumour lesions was defined as the sum of the lesions detected by at least one of these three imaging techniques. Pathologic findings were confirmed histopathologically or by follow-up and conventional radiological imaging. RESULTS: Both PET tracers consistently detected metastases in 12 patients. In two cases, only [(131)I] WBS and computed tomography revealed metastatic disease; in the remaining three patients with an increased thyroglobulin no correlate could be found. From a total of 104 tumour lesions, [(18)F]FDG PET showed only slightly higher detection rate than [(68)Ga]DOTATOC PET in radioiodine positive patients (28/31 versus 25/31), whereas significant differences were seen in the group with negative [(131)I] WBS (70/73 versus 26/73, P<0.01). Three out of 104 lesions were only visible using [(68)Ga]DOTATOC PET. CONCLUSIONS: [(68)Ga]DOTATOC and [(18)F]FDG PET showed comparable diagnostic performance in recurrent, radioiodine positive DTC. Due to much higher lesion detection rates, [(18)F]FDG PET should be preferred to [(68)Ga]DOTATOC PET in the work-up of radioiodine negative DTC relapse. These preliminary results have to be confirmed by more extensive data in further studies.

FDG uptake after intraarterial chemotherapy in head and neck cancer.

AIM: The intraarterial chemotherapy (i.a.CHT) using high dose cisplatin combined with systemic neutralization in patients with head and neck cancer (HNSCC) is used to reduce the tumor volume preoperatively. Aim of the study is the evaluation of the influence of i.a.CHT on the metabolism of fluor-18-deoxyglucose (FDG) in the primary and lymph nodes (LN). The value of FDG positron emission tomography (PET) preoperative and as follow-up method after i.a.CHT is examined. PATIENTS, METHODS: Altogether 16 patients with HNSCC underwent two preoperative FDG PET examinations: the baseline examination one week before and the follow-up three weeks after i.a.CHT. The SUVmax values of the primary and the LN and LN metastases were evaluated and compared with each other and the histopathology. RESULTS: The SUVmax value of the primary decreased after i.a.CHT significantly from a median (25 (th) percentile/75 (th) percentile) of 6.4 (4.1/7.8) to 3.6 (2.4/6.7) (p = 0.01). In 11 out of 16 patients cervical LN metastases were detected. The cervical LN metastases showed a decrease of the SUVmax value from 3.6 (2.3/4.8) in the pretreatment examination to 2.3 (1.7/3.6) after i.a.CHT (p = 0.008). Only in one patient with LN metastases the SUVmax of the nodes increased. The histopathologically measured size of the LN metastases ranged from 2 to 30 mm. Non malignant LN did not reveal a significant SUVmax decrease after i.a.CHT (p = 0.13). CONCLUSIONS: As expected, primaries of HNSCC showed a significant reduction of SUV after i.a.CHT. Compared to the primary the SUVmax decrease in LN metastases was less, but also significant. Since cytotoxic levels of cisplatin do not occur systemic, postinflammatory reactions of the LN or a lymphatic drainage of the chemotherapeutic drug into the LN could be an explanation. PET for staging of HNSCC must thus be performed prior to i.a.CHT.

Atypical thoracic and supraclavicular FDG-uptake in patients with Hodgkin's and non-Hodgkin's lymphoma.

AIM: In FDG-PET imaging abnormal supraclavicular and paravertebral FDG uptake is a frequent finding which recently could be demonstrated to partly represent brown fat tissue. This study was carried out to further investigate causes for this phenomenon. Patients variables such as age, gender, body mass index (BMI) and the value of sedation and delayed imaging were compared with the presence of atypical uptake in 2 distinct groups of diseases, Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). METHODS: PET images of 81 patients (53 HD and 28 NHL) were evaluated for atypical uptake. In 5 patients additional delayed images were acquired. Sedatives were used in anxious patients (n=45). RESULTS: Twelve out of 53 patients with HD and 2 out of 28 patients with NHL showed an atypical uptake. The BMI of patients with atypical uptake (median, 21 kg/m2 versus 24 kg/m2; p<0.05) and the age (median, 25 y versus 44 y; p<0.05) were significantly lower compared with patients without atypical uptake. In nearly 50% of all women with HD= or <30 y and 20% of all male patients with HD= or <30 y an atypical uptake was observed. Delayed images showed a SUVmax decrease in 4 patients and an increase in 1 patient. All patients with atypical uptake received sedatives which had an anxiolytic effect in all patients, but did not prevent atypical uptake. CONCLUSION: Abnormal supraclavicular and paravertebral FDG accumulation occurs particularly in younger patients and those with lower BMI values. The use of sedatives or delayed acquisition does not increase the diagnostic information in these cases.

Case report: drug interference with MIBG uptake in a patient with metastatic paraganglioma.

Metaiodobenzylguanidine (MIBG) labelled with iodine-131 ((131)I) has become a well established therapeutic tool for inoperable metastastic tumours of paraganglioma. There are different pharmacological substances known to interfere with MIBG-uptake which may result in a false negative MIBG scan. We present the case of a 26-year-old male polytoxicomanic patient with metastatic paraganglioma, who underwent MIBG therapy. During earlier therapies, MIBG uptake in the metastatic lesions was very high. A post-therapeutic whole-body scan subsequent to recent (131)I-MIBG therapy failed to detect the vast majority of metastatic lesions-except for two. (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) showed metastases with a similar distribution to the initial MIBG scan. The possible reasons for the discrepancy in the findings of the MIBG scans and the (18)F-FDG-PET scan are discussed with special emphasis on drug intake prior to MIBG administration, increased MIBG turn-over and unknown drug mixture interference with MIBG uptake.

Gated metabolic positron emission tomography (GAPET) of the myocardium: 18F-FDG-PET to optimize recognition of myocardial hibernation.

The aim of this study was to test the feasibility of the direct measurement of global and regional metabolic wall thickening with 18F-FDG-gated positron emission tomography (PET) in patients with coronary artery disease (CAD). Based on non-invasive (ECG, echocardiography) and invasive [cineventriculography (CVG), coronary angiography] investigations, 12 patients with CAD underwent gated metabolic PET studies with 18F-FDG. Myocardial wall thickening and wall motion analysis from short-axis horizontal and vertical long-axis slices were studied. PET-derived global ejection fraction correlated with CVG-derived global ejection fraction (r = 0.75). Forty-eight of 72 segments investigated were normal (66.7%); 24 of 72 segments were abnormal (33.3%), of which 10 (41.7%) were considered to be hibernating. Four segments were classified as partially fibrotic (16.7%) and 10 (41.7%) as entirely scar-like. Gated PET (8 gates, tail drop corrected) allows quantification of global and regional ejection fraction to detect metabolic wall thickening in left ventricular segments with dyskinesia on CVG due to critical CAD stenoses. By improving data analysis methods, our approach may enhance the detection of viable, hibernating myocardium before revascularization.

Validation of a dual-isotope technique using 123I-MIBG and 201Tl in the assessment of sympathetic reinnervation following heart transplantation: phantom and patient studies.

Dual-isotope studies using 123I and 201Tl allow the assessment of sympathetic reinnervation in patients following heart transplantation. 123I-meta-iodobenzyl guanidine (123I-MIBG) serves as a tracer of the integrity of the sympathetic nervous system. 201Tl is used for landmarking to allow better delineation of the myocardium due to faint 123I-MIBG accumulation in heart transplants. The aim of this study was to evaluate the influence of parameters such as crossover, attenuation and the 123I/201TI activity ratio on the assessment of the myocardial 123I-MIBG uptake ratio using phantom and patient studies. Crossover was calculated using the ratio: 201TI counts in the 123I energy window/201Tl counts in the 201Tl window. Phantom studies were performed using a rectangular phantom (RP) and a cardiac phantom (CP). The mean crossover from the 201Tl to the 123I energy window was 11.48% (RP) and 11.13% (CP). Depending on attenuation in water (depth of water 0-5 cm), crossover increased from 10.92 to 15.85% (RP) and from 11.05 to 15.79% (CP). In order to confirm that the experimental crossover results were equivalent to those obtained in patient studies, 15 patients underwent myocardial scintigraphy. After injection of 201Tl, a simultaneous dual-window acquisition was performed to assess crossover from the 201Tl to the 123I window. The mean crossover was 15.35%, as high as the crossover assessed in phantom studies, taking into account attenuation and scatter caused by the chest wall. In order to reduce 201Tl crossover, the 123I activities were six times as high as the 201Tl activities.(ABSTRACT TRUNCATED AT 250 WORDS)

[Sympathetic reinnervation following heart transplantation--a double-tracer study with 123I-MIBG and 201Tl]. / Sympathische Reinnervation nach Herztransplantation--Doppelnuklidstudie mit 123J-MIBG und 201Tl.

Sympathetic reinnervation was evaluated in 15 patients 2-69 months after heart transplantation using a double-tracer technique with 123I-MIBG and 201Tl. Since MIBG is accumulated in the same manner as norepinephrine it may serve as a tracer of the integrity and function of the sympathetic nervous system. 201Tl was used for landmarking. Planar anterior imaging was performed 15 min and 4 h after i.v. injection of 220 MBq 123I-MIBG and 37 MBq 201Tl. Image quantitation was based on the ratio of myocardial to mediastinal MIBG-uptake. Cardiac regions of interest were defined according to the 201Tl uptake. There was no evidence of sympathetic reinnervation in 8 patients 2-34 months after transplantation. Increased MIBG-uptake could be observed in the anterior basal region in 6 long-term cardiac transplants (37-69 months). One patient with a 59-month-old transplanted heart did not reinnervate. Increased MIBG-uptake in the anterior basal region indicating partial sympathetic reinnervation could be shown in 40% of the investigated patients with an average organ age of 51 months.