Dieter L. Munz

Recovery correction for quantitation in emission tomography: a feasibility study.

Abstract.In emission tomography, the spread of regional tracer uptake to surrounding areas caused by limited spatial resolution of the tomograph must be taken into account when quantitating activity concentrations in vivo. Assuming linearity and stationarity, the relationship between imaged activity concentration and true activity concentration is only dependent on the geometric relationship between the limited spatial resolution of the tomograph in all three dimensions and the three-dimensional size and shape of the object. In particular it is independent of the type of object studied. This concept is characterized by the term ”recovery coefficient”. Recovery effects can be corrected for by recovery coefficients determined in a calibration measurement for lesions of simple geometrical shape. This method works on anatomical structures that can be approximated to simple geometrical objects. The aim of this study was to investigate whether recovery correction of appropriate structures is feasible in a clinical setting. Measurements were done on a positron emission tomography (PET) scanner in the 2D and 3D acquisition mode and on an analogue and digital single-photon emission tomography (SPET) system using commercially available software for image reconstruction and correction of absorption and scatter effects. The results of hot spot and cold spot phantom measurements were compared to validate the assumed conditions of linearity and stationarity. It can be concluded that a recovery correction is feasible for PET scanners down to lesions measuring about 1.5×FWHM in size, whereas with simple correction schemes, which are widely available, an object-independent recovery correction for SPET cannot be performed. This result can be attributed to imperfections in the commercially available methods for attenuation and scatter correction in SPET, which are only approximate.

Peritumoural versus subareolar administration of technetium-99m nanocolloid for sentinel lymph node detection in breast cancer: preliminary results of a prospective intra-individual comparative study

The scintigraphic detection of sentinel lymph nodes (SNs) in early-stage breast cancer is a widely accepted diagnostic method. However, which radiotracer administration mode should be used is still controversial. This prospective study aimed to intra-individually compare the detection rates obtained after peritumoural versus subareolar injection with regard to SN number and localisation. Fifty-one women (age, 32–76 years) with breast cancer were investigated on two consecutive days. On day 1, 140–400xa0MBq technetium-99m nanocolloid was injected along the peripheral tumour margins. Static lymphoscintigrams of the axilla, thorax and neck were taken in various views 1 and 19xa0h p.i. On day 2, 10xa0MBq 99mTc-nanocolloid was injected subareolarly in the clock position of the tumour and dynamic and static scans were performed immediately. Thereafter, 30xa0MBq 99mTc-nanocolloid was administered peri-subareolarly and lymphoscintigrams were acquired in a dynamic and static manner. In 49/51 women, the different injection techniques disclosed the identical number and location of SNs in the axilla. In seven patients, the peritumoural injection detected additional SNs in the parasternal group. Axillary SNs were detected as early as 2–15xa0min following subareolar injection, both in the clock position and peri-subareolarly, as compared with about 1xa0h after peritumoural administration. Sixteen patients showed at least one tumour-positive SN, and nine also had tumour-positive non-SNs. One patient with a tumour-negative SN, visualised concordantly by both subareolar and peritumoural administration, demonstrated two metastatic non-SNs, yielding a false-negative rate of 5.9%. In conclusion, a simple subareolar injection in the clock position is sufficient for SN detection in breast cancer, if it is accepted that parasternal lymph node detection has no therapeutic consequences.

Imaging of low-grade bone infection with a technetium-99m labelled monoclonal anti-NCA-90 Fab' fragment in patients with previous joint surgery

Abstract. Low-grade bone infection represents a serious clinical problem. Diagnostic options are often insufficient, yet the therapeutic implications of proven disease are important, especially in patients with prosthetic joint replacement. Technetium-99m labelled monoclonal anti-NCA-90 granulocyte antibody Fab fragment (MN3 Fab) has been shown to be useful in bone and joint infection, but there are no data specifically referring to low-grade bone infection. We therefore analysed 38 scans in 30 consecutive patients (age range, 30–85 years; median age, 62 years) referred for suspected low-grade bone infection. There were 17 patients (21 scans) with total hip arthroplasty (THA), six with total knee arthroplasty (TKA), three who had undergone hip or knee surgery for trauma and five (seven scans) with resected hips and no endoprostheses (Girdlestone situations); one of these five patients had been investigated before with THA in situ and another prior to surgery for low-grade coxitis. There were no patients with rheumatoid arthritis as the underlying disease. Results were verified by means of bacteriological cultures, histopathological findings and/or follow-up and compared with the respective Zimmerli scores, which were used for clinical assessment of inflammatory activity. In one patient, the final diagnosis could not be established. One, 5 and 24xa0h after intravenous injection of up to 1.1xa0GBq of MN3 Fab, whole-body and planar scans were performed using a dual-head gamma camera. Scans were analysed visually and semiquantitatively adopting an arbitrary score ranging from 0 to 3. There were 13 true positive, 14 true negative and 10 false positive outcomes, yielding an overall sensitivity of 100%, an overall specificity of 58%, an accuracy of 73% and positive and negative predictive values of 57% and 100%, respectively. In patients with THA or TKA, accuracy was 81% and 80%, respectively, while it dropped to 43% in patients with Girdlestone situations owing to a high proportion of false positive findings (4/7) in this subgroup. Scintigraphic score was 1 in all of the false positive and in 11/13 true positive findings. The two remaining true positive findings displayed scintigraphic scores of 2 and 3, respectively. Scintigraphic and Zimmerli scores were loosely correlated (Spearman ρ=0.38, P<0.05). Infection was excluded in 22/24 investigations with Zimmerli scores of <6. In this group, there were 13 scintigraphically true negative, nine false positive outcomes, and just two true positive outcomes. In 11/12 investigations with Zimmerli scores of 6 or 7, infection was verified and scintigraphic outcome was accordingly true positive, while the remaining patient was true negative. In conclusion, MN3 Fab scintigraphy proved to be highly sensitive but not specific in diagnosing low-grade infections of the hip and knee regions in patients with previous joint surgery. The method seems reliable in excluding but not in proving the presence of infection. MN3 Fab scintigraphy should not be applied in patients with Girdlestone situations. Assessment of infection using the Zimmerli score was more reliable than MN3 Fab scintigraphy in this group of patients without rheumatoid arthritis as the underlying disease. Considering results from the literature concerning leucocyte scintigraphy, MN3 Fab scintigraphy may be clinically useful in evaluating low-grade bone infection in THA and TKA patients with Zimmerli scores above 5 and concomitant rheumatoid arthritis or other inflammatory diseases.

Influence of fast lymphatic drainage on metastatic spread in cutaneous malignant melanoma: a prospective feasibility study

The concept of sentinel lymph node biopsy in cutaneous malignant melanoma is widely established. Preoperative cutaneous lymphoscintigraphic mapping is a reliable method for identifying the nodal basins at risk of metastases in melanomas. In this prospective study we investigated the correlation between the scintigraphic appearance time and the metastatic involvement of sentinel lymph nodes. In 276 malignant melanoma patients (137 women, 139 men; age 16–93 years), dynamic and static lymphoscintigraphy was performed after strict intracutaneous application of technetium-99m nanocolloid (40–150xa0MBq; 0.05xa0ml/deposit) around the tumour or biopsy scar. Analysis of dynamic scans primarily focussed on the appearance time of sentinel lymph nodes. Sentinel lymph node visualisation ≤20xa0min post injection was defined as fast drainage, and visualisation >20xa0min as slow drainage. Fast lymphatic drainage was found in 236 patients, of whom 34 (14.4%) had sentinel lymph node metastases. Twenty-two patients showed hybrid (fast and slow) lymphatic drainage, and eight (36.4%) of them had sentinel lymph node metastases. Seven of the latter demonstrated fast lymphatic drainage, while one showed one positive sentinel lymph node with fast and another with slow drainage. The melanomas of 18 patients demonstrated exclusively slow lymphatic drainage, in all cases without sentinel lymph node metastases. This prospective study indicates that the scintigraphic appearance time of sentinel lymph nodes seems to be a clinically relevant factor for prediction of metastatic spread of cutaneous malignant melanoma. Larger numbers of patients need to be examined to truly assess the benefit of the scintigraphic appearance time compared with other predictors of sentinel lymph node tumour positivity.

Use of recovery coefficients as a test of system linearity of response in positron emission tomography (PET).

Quantitative determination of activity concentration has always been regarded as a goal of PET scanner design. Therefore, a linear response with respect to activity concentration is essential. To prove system linearity of response a test is proposed based on the determination of recovery coefficients (RC) for different object geometries. If all degrading effects, especially scatter and attenuation, are corrected to a sufficient degree of accuracy, the system behaves linearly resulting in a theoretical relationship between hot (HSRC) and cold spot recovery coefficients (CSRC). Therefore this relationship, applied to appropriate phantom data containing hot or cold spheres, combined with the constraints on asymptotic behaviour of RC can be used as a test of system linearity of response. After applying the systems standard corrections RC were determined using both 2D and 3D data acquisition modes. For both 2D and 3D data, HSRC directly measured showed an excellent agreement with the HSRC calculated from the CSRC. The analysis was extended to radionuclides of different positron ranges, to the effect of data smoothing, and to that of iterative reconstruction. The agreement between the RC determined under varying border conditions demonstrates the effectiveness of the corrections used in constituting system linearity. Therefore, the method proposed is used as a test of system linearity of response.

Endoscopic sentinel node detection with a gamma probe combined with minimally invasive axillary lymph node dissection : A preliminary study

OBJECTIVEnTo investigate the efficacy of videoendoscopic axillary lymph node dissection combined with endoscopic sentinel node detection by gamma probe and preoperative sentinel node imaging.nnnDESIGNnOpen study.nnnSETTINGnUniversity hospital, Germany.nnnSUBJECTSnFour patients with breast cancer.nnnINTERVENTIONnInjection of 99mTc-nanocolloid around the tumour.nnnRESULTSnIn three patients axillary sentinel nodes were detected both before and after operation. In the remaining one it was not found. In two patients the minimally invasive approach had to be converted to conventional open surgery because of anatomical restrictions.nnnCONCLUSIONnWe describe a new approach that uses a minimally invasive technique and endoscopic radioguided sentinel node biopsy in patients with breast cancer. The results of this preliminary study warrant further investigation.

Temporary shielding of hot spots in the drainage areas of cutaneous melanoma improves accuracy of lymphoscintigraphic sentinel lymph node diagnostics

Abstract. Detection of the true sentinel lymph nodes, permitting correct staging of regional lymph nodes, is essential for management and prognostic assessment in malignant melanoma. In this study, it was prospectively evaluated whether simple temporary shielding of hot spots in lymphatic drainage areas could improve the accuracy of sentinel lymph node diagnostics. In 100 consecutive malignant melanoma patients (45 women, 55 men; age 11–91 years), dynamic and static lymphoscintigraphy in various views was performed after strict intracutaneous application of technetium-99m nanocolloid (40–150xa0MBq; 0.05xa0ml/deposit) around the tumour (31 patients) or the biopsy scar (69 patients, safety distance 1xa0cm). The images were acquired with and without temporary lead shielding of the most prominent hot spots in the drainage area. In 33/100 patients, one or two additional sentinel lymph nodes that showed less tracer accumulation or were smaller (<1.5xa0cm) were detected after shielding. Four of these patients had metastases in the sentinel lymph nodes; the non-sentinel lymph nodes were tumour negative. In 3/100 patients, hot spots in the drainage area proved to be lymph vessels, lymph vessel intersections or lymph vessel ectasias after temporary shielding; hence, a node interpreted as a non-sentinel lymph node at first glance proved to be the real sentinel lymph node. In two of these patients, lymph node metastasis was histologically confirmed; the non-sentinel lymph nodes were tumour free. In 7/100 patients the exact course of lymph vessels could be mapped after shielding. In one of these patients, two additional sentinel lymph nodes (with metastasis) were detected. Overall, in 43/100 patients the temporary shielding yielded additional information, with sentinel lymph node metastases in 7%. In conclusion, when used in combination with dynamic acquisition in various views, temporary shielding of prominent hot spots in the drainage area of a malignant melanoma of the skin leads to an improvement in the accuracy of identification and localisation of sentinel lymph nodes by lymphoscintigraphy.

Myocardial contrast echocardiography for predicting functional recovery after acute myocardial infarction.

Myocardial contrast echocardiography (MCE) is a promising diagnostic tool for detecting microvascular integrity. The aim of the study was to investigate the comparative specificity and sensitivity of intravenous MCE, technetium-99m Sestamibi single-photon emission computed tomography (SPECT) and dipyridamole–dobutamine (DIDO) stress echocardiography for predicting functional recovery after coronary revascularization in patients with acute myocardial infarction (AMI). Methods: In a prospective, observational study, 17 consecutive patients short after AMI who received successful treatment with primary percutaneous coronary angioplasty (PTCA) plus stent-implantation were examined with DIDO (dipyridamole with 0.28 mg/kg over 4 min plus dobutamine up to 10 mcg/kg/min), MCE (10 ml 4 g, 400 mg/ml Levovist® intravenously; second harmonic power imaging) within 12–24 h and resting perfusion SPECT within 48–72 h after PTCA. Functional recovery of regional contractile function after 6-month follow-up was the gold standard to assess viability. Results: The rate of agreement between SPECT and MCE was 69% and between SPECT and a positive response to stress echo was 76% for combined DIDO. MCE showed a higher sensitivity (96%) in the identification of viability than SPECT (77%) and combined DIDO alone (79%). Specificity was lower for viability recognition with MCE (58%) compared with SPECT (93%) and DIDO (87%). Conclusions: The wall motion response during DIDO echocardiography is useful in the prediction of recovery of regional and global ventricular function after revascularization in patients after AMI. Combined intravenous MCE and DIDO is more accurate in the diagnosis of stunned myocardium than Tc-99m-MIBI SPECT alone.

Intraindividual Comparison of F-18-Fluorodeoxyglucose and Tc-99m-Tetrofosmin in Planar Scintimammography and SPECT.

Since the comparative value of several nuclear medicine investigations for breast cancer has not been established, the rationale of this study was to examine the diagnostic performances of F-18-fluorodeoxyglucose (FDG) and Tc-99m-tetrofosmin both in single photon emission computed tomography (SPECT) and planar technique in an intraindividual comparative study.A total of 54 patients with suspected breast cancer (48 malignant and 9 benign lesions) was investigated by planar and SPECT imaging with both FDG and tetrofosmin within the last preoperative week. Pathohistological confirmation of the diagnosis was obtained in all patients.2 cm 81%/67%, 92%/67%, 75%/50%, and 75%/100%. Sensitivity was higher with FDG SPECT than with the other imaging modalities and significantly lower for tumors </=2 cm with all the techniques investigated. In 20 out of 21 patients with diverging scintigraphic findings, FDG SPECT was either true positive or true negative. In 15 patients with axillary lymph node metastases, sensitivities were 33%, 73%, 36%, and 50%, respectively.2 cm, if dedicated PET is not available.

Überprüfung der Kreuzkalibrierung von Positronen-Emissions-Tomographen zu ihren peripheren Geräten

The aim of this study was to evaluate the cross-calibration of positron emission tomographs and their peripheral devices prior to a multicenter study. The instrumentation of 22 sites (including 24 dedicated PET scanners), including 21 that could be operated in 2D mode and 20 in 3D mode, was investigated according to standardized acquisition and reconstruction protocols, and the cross-calibration was checked against the dose calibrators (22 instruments) and the sample changer (20 instruments). The deviation of the cross-calibration to the dose calibrators was below 5% for 10 of 21 PET scanners (2D mode) and 6 of 20 (3D mode). For 6 (2D mode) and 6 (3D mode) scanners, the corresponding error was up to 10%. In turn, the deviation between dose calibrator and standard was less than 8% for 19 devices, and even less than 5% for 14 devices. In most of the well counters evaluated, the cross-calibration error was less than 10%. Although required in general, the cross-calibration between positron emission tomographs and their peripheral devices becomes even more critical when pooling data in the framework of quantitative clinical multicenter studies.