PubMed Health⌕ Search

Biomedical subjects

K Hahn

Publications and source records attributed to K Hahn.

At least 37 records · Page 2Linked to original sources
PubMed2004

[Acquisition of age- and sex-dependent patient data for the calculation of annual radiation exposure in nuclear medicine: a German pilot study].

AIM: A pilot study for estimation of radiation exposure due to diagnostic procedures in nuclear medicine using routine data of hospitals and practices in Germany. METHODS: Hospitals and practices willing to participate in the study supplied data of one year (1997), containing information on patients' identification number, age, sex, type of diagnostic procedure, radiopharmaceutical, administered activity, type of health insurance (private/public), inpatient/outpatient status, and so-called Leistungsziffer, which describes the type of medical performances in Germany. The effective dose per examination was calculated according to ICRP 80. Mean, standard deviation, median, 5th and 95th percentiles of the effective dose were calculated, stratified by type of organ system and also by sex and age, including patients of > or = 18 years. RESULTS: 82,039 examinations from patients of 9 hospitals and practices were analyzed. The median (5-95(th) percentiles) of the effective dose per examination for all patients was 2.9 mSv (0.4-8.5 mSv); 1.2 examinations per patient and year were performed on average. The three most frequent examinations were bone scans (median 3.4 mSv; 2.9-5.1), thyroid (0.9 mSv; 0.4-2.2) and cardiovascular studies (7.3 mSv; 3.8-20.2). The median effective dose for 18 to 40 years old women was 1.0 mSv (0.4-5.8), for women between 41 and 65 years 2.2 mSv (0.4-7.3) and for women older than 65 years 2.4 mSv (0.5-7.6). The corresponding values for men were 2.6 mSv (0.3-7.6); 3.3 mSv (0.4-9.1), and 3.4 mSv (0.5-8.8). CONCLUSION: It was possible to gain an accurate determination of radiation exposure of diagnostic procedures in nuclear medicine by routine data.

Adult↗
PubMed2004

Colorectal cancer patients before resection of hepatic metastases. Impact of (18)F-FDG PET on detecting extrahepatic disease.

AIM: Evaluation of the role of FDG-PET in comparison to conventional staging methods for detecting extrahepatic tumour deposits prior to resection of liver metastases. PATIENTS, METHODS: In our prospective study, 58 patients (24 women, 34 men; age 33-81 years) with liver metastases of colorectal carcinoma underwent FDG-PET. Images were acquired in 3D-mode including transmission scans and reconstructed iteratively. For conventional staging all patients underwent abdominal ultrasound, helical computed tomography (CT) of the thorax and abdomen, and colonoscopy/rectoscopy. A preliminary therapeutic decision was established without knowledge of the FDG-PET findings. Thereafter, it was revised or confirmed according to the results of FDG-PET. RESULTS: In 3/58 patients extrahepatic tumour deposits were concordantly identified with both conventional staging methods and FDG-PET. However, in one case, both conventional methods and FDG-PET were false positive regarding pulmonary metastases. In 12/58 patients, nothing but FDG-PET detected extrahepatic tumour masses, which were later confirmed either by histology or follow-up. CONCLUSION: Our study suggests that in 21% of patients exclusively FDG-PET is an appropriate diagnostic tool to reveal extrahepatic metastases or local recurrence of colorectal carcinoma. Our results demonstrate that FDG-PET provides relevant additional information for accurate therapeutic planning as compared to the conventional combination of staging methods. Therefore, FDG-PET has to exert a decisive influence on the decision for resection of hepatic metastases.

Adult↗
PubMed2003

[18F]FDG imaging of head and neck tumours: comparison of hybrid PET and morphological methods.

The aim of this study was to evaluate fluorine-18 fluorodeoxyglucose ([(18)F]FDG) imaging of head and neck tumours using a second- or third-generation hybrid PET device. Results were compared with the findings of spiral computed tomography (CT) and magnetic resonance imaging (MRI), and, as regards lymph node metastasis, the ultrasound findings. A total of 116 patients with head and neck tumours (83 males and 33 females aged 27-88 years) were examined using a hybrid PET scanner after injection of 185-350 MBq of [(18)F]FDG (Picker Prism 2000 XP-PCD, Marconi Axis gamma-PET(2) AZ). Hybrid PET examinations were performed in list mode using an axial filter. Reconstruction of data was performed iteratively. Ninety-six patients underwent CT using a multislice technique (Siemens Somatom Plus 4, Marconi MX 8000), 18 patients underwent MRI and 100 patients were examined by ultrasound. All findings were verified by histology, which was considered the gold standard, or, in the event of negative histology, by follow-up. Correct diagnosis of the primary or recurrent lesion was made in 73 of 85 patients using the hybrid PET scanner, in 50 of 76 patients on CT and in 7 of 10 patients on MRI. Hybrid PET successfully visualised metastatic disease in cervical lymph nodes in 28 of 34 patients, while 23 of 31 were correctly diagnosed with CT, 3 of 4 with MRI and 30 of 33 with ultrasound. False positive results regarding lymph node metastasis were seen in three patients with hybrid PET, in 14 patients with CT and in 13 patients with ultrasound. MRI yielded no false positive results concerning lymph node metastasis. In one patient, unrecognised metastatic lesions were seen on hybrid PET elsewhere in the body (lung: n=1; bone: n=1). Additional malignant lesions at sites other than the head and neck tumour were found in three patients (one patient with lung cancer, one patient with pelvic metastasis due to a carcinoma of the prostate and one patient with pulmonary metastasis due to breast cancer). It is concluded that [(18)F]FDG PET with hybrid PET scanners is superior to CT and MRI in the diagnosis of primary or recurrent lesions as well as in the assessment of lymph node involvement, whereas it is inferior to ultrasound in the detection of cervical lymph node metastasis.

Adult↗
PubMed2003

[Planning and monitoring of autologous lymph vessel transplantation by means of nuclear medicine lymphoscintigraphy].

Autologous lymph vessel transplantation significantly improves the lymph drainage in patients with primary and secondary lymphedema. The aim of the present study was to prove whether scintigraphic long-term follow-up could demonstrate the function of autologous lymph vessels and the persisting success of this microsurgical technique respectively. In this study, visual and semiquantitative lymphoscintigraphy was used to prove the function of lymphatic vessel grafts in 20 patients comparing a preoperative baseline study with postoperative follow-up investigations once a year for a period of seven years. The reason for microsurgical lymph vessel transplantation was a primary (n = 4) or a secondary (n = 16) lymphedema. In 12 cases the transplantation site was at the upper extremity, in eight cases at the lower limb. In 17/20 patients lymphatic function significantly improved after autologous lymph vessel transplantation compared to the preoperative findings, as verified by visual improvement of lymph drainage and decrease of a numeric transport index. In 5/20 cases the vessel graft could be visualized directly. In these patients with scintigraphic visualization of the vessel graft, the transport index decreased to a significantly greater extent compared to the preoperative baseline study. 3/20 patients did not benefit from microsurgical treatment. Lymphoscintigraphy has shown to be an easy, reliable and readily available technique to assess lymphatic function on the long run. Scintigraphic visualization of the vessel graft showed a significantly better postoperative outcome than those without. The scintigraphic visualization of the vessel graft therefore seems to indicate a favourable prognosis regarding lymph drainage.

Adult↗
PubMed2003

Staging of recurrent and advanced lung cancer with 18F-FDG PET in a coincidence technique (hybrid PET).

The aim of this study was to evaluate [18F]fluorodeoxyglucose ( F-FDG) imaging of recurrent or inoperable lung cancer using a hybrid positron emission tomography (PET) device of the third generation. Examinations were compared with the results of conventional staging. Thirty-six patients suffering from recurrent or primarily inoperable lung cancer (29 men, seven women; age 64.8+/-12.0 years) were examined using hybrid PET (Marconi Axis gamma-PET ) 60 min after injection of 370 MBq F-FDG. The data obtained were reconstructed iteratively. All patients received a computed tomography (CT) scan using either the spiral or multislice technique. All lesions suspicious for primary or recurrent tumour were verified by biopsy; mediastinal lymph nodes were considered as malignant, when positive histology or a small axis diameter of greater than 1 cm measured with CT in addition to progression of clinical course was found. Distant metastases were diagnosed by CT and bone scintigraphy. Using hybrid PET all lesions showed a focally elevated glucose metabolism. Lymph node involvement of the ipsilateral peribronchial and hilar station (N1) was identified in 24/26 cases (92%), in 26/29 cases (90%) of ipsilateral central manifestation (N2) and in 11/13 (85%) cases of central contralateral or supraclavicular lymphatic infestation (N3). Pulmonary spread in hybrid PET was found in 4/8 cases (50%), whereas mainly lung metastases with a diameter of 1.5 cm and smaller were missed. Pleural involvement diagnosed by CT was verified in 4/5 patients. All four patients with bony metastases in conventional staging also presented with positive findings in hybrid PET (8/9 lesions). Concordance with conventional staging was found in 28/36 of patients (78%). In 4/36 patients (11%) unknown sites of tumour were detected leading to therapeutic consequences in three patients after radiological confirmation. Hybrid PET would have led to an understaging in four cases (11%), resulting theoretically in inefficient treatment in two patients. Hybrid PET for F-FDG imaging in the staging of recurrent or primarily inoperable lung cancer supplied equal (78%) or more information (11%) compared to conventional staging procedures. Using the information of hybrid PET alone, 11% of the patients would have been understaged. We conclude that hybrid PET has the potential for use as an additional staging tool in this subgroup of patients, providing supplementary information compared to conventional staging modalities.

Adenocarcinoma↗
PubMed2003

Breast cancer: monitoring response to neoadjuvant chemotherapy using Tc-99m sestamibi scintimammography.

BACKGROUND: Aim of the study was to assess the value of scintimammography using Tc-99m sestamibi in the evaluation of tumor response to neoadjuvant chemotherapy. MATERIAL ANS METHODS: Results were calculated for 9 patients undergoing neoadjuvant chemotherapy. Scintimammography using 740 MBq Tc-99m sestamibi was performed before, during and after chemotherapy, and sestamibi uptake was scored visually and semiquantitatively to evaluate tumor response. RESULTS: In the case of complete response (n = 3) sestamibi uptake decreased 8 days after beginning neoadjuvant chemotherapy and normalized in the following course. Focal uptake decreased more slowly in patients with partial response (n = 3), who showed clear, persisting tracer accumulation after therapy. The patients without response (n = 3) showed a persisting high tumor activity even after chemotherapy was completed. CONCLUSIONS: The preliminary data suggest that in contrast to other imaging modalities scintimammography appears to yield early information regarding tumor response to neoadjuvant chemotherapy.

Breast↗
PubMed2003

[Stunning effects in radioiodine therapy of thyroid carcinoma: existence, clinical effects and ways out].

In radioiodine therapy for malignant thyroid disease, the pre-therapeutically administered iodine-131-dose can reduce the potential of thyroid or thyroid carcinoma cells to absorb the following therapeutic iodine-131-dose, possibly leading to its failure. This so called stunning effect is controversially discussed in the scientific community. Here we summarize and evaluate publications with regard to the existence and the effects of stunning as well as possible countermeasures.

Humans↗
PubMed2002

Methionine homozygosity at codon 129 in the prion protein is associated with white matter reduction and enlargement of CSF compartments in healthy volunteers and schizophrenic patients.

Twin studies point toward a substantial heritability in individual variations in the size of the human brain. However, the etiology is largely unknown. The prion protein (gene name: PRNP) aids cellular resistance to oxidative stress and neurodegeneration and is involved in neurodevelopment. This study examines the influence of a polymorphism in the PRNP gene on brain morphology in 47 healthy males and 43 male schizophrenic patients. All subjects underwent identical MRI scanning sessions followed by segmentation in cerebrospinal fluid (CSF), gray and white matter tissue, and genotyping for a biallelic polymorphism in PRNP (Met129Val). Genotype and allele frequencies did not differ between schizophrenic patients and controls but the polymorphism was associated with white matter tissue reduction (P = 0.024) and enlargement of CSF compartments (P = 0.039). These findings suggest that homozygosity for methionine at codon 129 is associated with decreased white matter tissue and larger CSF volume in right-handed male healthy volunteers and schizophrenic patients. This, however, being a novel finding, should warrant further investigation.

Adolescent↗
PubMed2002

[Correlation of FDG-PET and MRI/CT with histopathology in primary diagnosis, lymph node staging and diagnosis of recurrency of head and neck cancer].

AIM: Correct staging of head and neck cancer is important for the patient's prognosis and further therapeutic strategies. Aim of the present study was to investigate the diagnostic value of FDG-PET regarding the pre-surgical diagnosis of primary tumor and cervical lymph node metastases, the diagnosis of tumour recurrence, and the localisation of unknown primary, further to compare the results to those of morphological imaging modalities (CT/MRI) and to correlate the results of both methods with histopathological findings. PATIENTS/METHODS: 115 patients (pts) (72 x primary diagnosis, 37 x recurrence, and 6 x unknown primary) underwent FDG-PET (ECAT EXACT HR+) and CT or MRI. Results were correlated with histopathological findings in terms of detection of primary and recurrent tumors as well as lymph node metastases. RESULTS: Regarding the pre-surgical diagnosis, sensitivity and specificity for identifying primary tumors were 85 % and 100 % for PET and 88 % and 75 % for CT/MRI, respectively. Accuracy was 86 % for PET and 87 % for CT/MRI. Sensitivity and specificity for detecting primary lymph node involvement were 71 %/86 % for PET and 74 %/57 % for CT/MRI, resulting in an accuracy of 77 % with PET and 68 % with morphological imaging. In 23 pts histopathology revealed pT1 stages with tumor diameters < 12 mm. In 8 pts CT/MRI and in 10 pts PET failed to identify these small primary lesions. Detecting tumor recurrence (n = 37) PET showed a higher sensitivity (83 %), specificity (76 %) and accuracy (78 %) compared to CT/MRI (sensitivity: 67 %; specificity: 52 %; accuracy: 57 %). In 4/6 pts with unknown primary, imaging was able to identify a primary lesion (3/4 in FDG-PET, 2/4 in CT/MRI), in 2/6 patients even in the follow-up no primary tumor was found. CONCLUSIONS: FDG-PET provides only minor additional information to morphological imaging concerning diagnosis of primary tumors. At a similar level of sensitivity, however, it seems to be more specific regarding the lymph node involvement. PET seems to be superior to CT/MRI in detecting tumor recurrence as well as occult primary tumors in pts with known cervical lymph node metastases.

Adult↗
PubMed2002

The use of [18 F]fluorodeoxyglucose positron emission tomography to differentiate between synovitis, loosening and infection of hip and knee prostheses.

Pain is a common unspecific symptom in orthopaedic prosthetics. The accurate differentiation between synovitis, loosening or infection is often difficult with conventional X-rays, arthrography or bone scintigraphy. Because of the high glucose uptake of inflammatory cells, [18F]fluorodeoxyglucose (18F-FDG) is an appropriate tracer for the evaluation of suspected inflammation or infection. In this preliminary study we describe 18F-FDG PET findings in patients referred for evaluation of painful hip or knee prostheses. We studied 23 patients with 28 prostheses, 14 hip and 14 knee prostheses, who had a complete operative or clinical follow-up. 18F-FDG PET scans were obtained with an ECAT EXACT HR+ PET scanner. High glucose uptake in the bone prostheses interface was considered as positive for infection, an intermediate uptake as suspect for loosening, and uptake only in the synovia was considered as synovitis. The imaging results were compared with operative findings or clinical outcome. PET correctly identified three hip and one knee prostheses as infected, two hip and two knee prostheses as loosening, four hip and nine knee prostheses as synovitis, and two hip and one knee prostheses as unsuspected for loosening or infection. In three patients covered with an expander after explantation of an infected prosthesis PET revealed no further evidence of infection in concordance with the clinical follow-up. PET was false negative for loosening in one case. Our preliminary results suggest that FDG PET could be a useful tool for differentiating between infected and loose orthopaedic prostheses as well as for detecting only inflammatory tissue such as synovitis.

Adult↗
PubMed2002

Striatal dopamine D2 receptor binding of risperidone in schizophrenic patients as assessed by 123I-iodobenzamide SPECT: a comparative study with olanzapine.

The aim of this investigation was to compare the degree of striatal dopamine-(D2) receptor blockade by two atypical antipsychotic drugs, risperidone and olanzapine. The percentage of D2 receptor occupancy during treatment was calculated by comparing the results of 123I-iodobenzamide SPECT with those from healthy control subjects. Twenty inpatients suffering from schizophrenia or schizoaffective psychosis according to DSM IV/ICD-10 criteria were treated with clinically recommended doses of risperidone and compared with 13 inpatients treated with up to 20 mg olanzapine. Neuroleptic dose and D2 receptor blockade correlated strongly for both risperidone (Pearson r = -0.86, p = 0.0001) and olanzapine (Pearson r = -0.77, p = 0.002). There was no significant difference between the D2 receptor occupancy of the two substances when given in the clinically recommended dose range (unpaired t-test, t = -0.112, p = 0.911).

Adult↗
PubMed2002

[Initial experiences with adjuvant locoregional radioimmunotherapy using 131I-labeled monoclonal antibodies against tenascin (BC-4) for treatment of glioma (WHO III and IV)].

AIM: None of the established treatments (surgery, radiotherapy, chemotherapy) for malignant glioma has improved its very poor prognosis. Adjuvant locoregional radio-immunotherapy (RIT) represents a new therapeutic approach. We present our initial experience with this therapeutic tool with respect to adverse effects, biokinetics and clinical follow-up. METHODS: Following surgery and radiotherapy, 12 patients with glioma (4, WHO stage III; 8, WHO stage IV) underwent 1-5 RIT-cycles (average dose 1100 MBq 131labelled monoclonal BC-4 antibodies) at six week intervals. Follow-up included serial FDG-PET and MRI investigations. Evaluation of biokinetics included whole body scans, together with analysis of blood, urine and fluid from the tumor cavity. RESULTS: Following RIT, four patients experienced temporary seizures, which, in one case, were associated with temporary aphasia. Eight patients developed HAMA (human anti-mouse antibodies) during follow-up. Mean biologic half-life of the radiopharmaceutical in the resection cavity was 3.9 d (range: 1.0-10.2 d) and remained stable intraindividually during further RIT-cycles. The antibody/radionuclide conjugate remained stable in the tumor cavity for at least 5 d. Median survival presently stands at 18.5 months compared to 9.7 months in a historical patient group (n = 89) undergoing conventional therapeutic strategies. Five patients show no signs of recurrence. In three patients with post-surgical evidence of residual tumor, one patient showed partial remission, one stable disease, and one progressive disease during RIT. Four patients without evidence of residual tumor mass at the beginning of RIT developed recurrence during therapy. CONCLUSIONS: Initial experience demonstrates that locoregional RIT is a well tolerated treatment modality that may represent a promising new approach in the management of patients with malignant glioma. Advantages of local application include passage of the blood-brain barrier, high concentration of activity within the resection cavity and low systemic toxicity.

Adult↗
PubMed2002

[Diagnosis of initial changes in the hand of patients with rheumatoid arthritis--comparison between low-field magnetic resonance imaging, 3-phase bone scintigraphy and conventional x-ray].

UNLABELLED: Besides conventional X-rays, in the diagnostic work up of initial changes in patients suffering from rheumatoid arthritis (RA), 3-phase bone scintigraphy (3P-Sz) is as well established as magnetic resonance imaging (MRI). The aim of this study was to compare the diagnostic value of the newly developed low field MRI with the proven methods X-rays and 3P-Sz. METHODS: 65 patients (47f, 18m; 20-86 yrs) were studied on a one day protocol with 3P-Sz (550 MBq Tc-99m DPD), MRI and X-rays of the hands. Images were visually analysed by two blinded nuclear medicine physicians and radiologists and classified as a) RA-typical, b) inflammatory, non-RA-typical and c) non inflammatory changes. All methods were compared to 3P-Sz as golden standard. RESULTS: In comparison to 3P-Sz, low field MRI presents with almost equal sensitivity and specificity in rheumatoid-typical and inflammatory changes. Conventional X-rays revealed in arthritis-typical changes as well as in inflammatory changes a significantly lower sensitivity and also a lower negative predictive value while specificity equals the one of MRI. Quantitative analysis of 3P-Sz using ROI-technique unveiled significantly higher values in patients with rheumatoid arthritis than in those with no inflammatory changes. CONCLUSION: MRI represents an equally sensitive method in the initial diagnosis of rheumatoid-typical and inflammatory changes in the region of the hands as compared to the 3P-Sz. Besides the basic diagnosis with conventional X-rays, 3P-Sz is still the recommended method of choice to evaluate the whole body when RA is suspected. Additionally, quantitative analysis of the 3P-Sz using the ROI technique in the region of the hands reveals statistically significant results and should therefore be taken into account in the assessment of inflammatory changes.

Adult↗
PubMed2002

[Breast scintigraphy using 99mTc-sestamibi--use and limitations].

AIM: Until now scintimammography did not achieve any definite role in the assessment of breast lesions. Purpose of this study was to elaborate its use as well as the limitations of scintimammography after 500 examinations completed. METHODS: Scintigraphic findings were correlated with the histopathologic outcome of 219 patients, who underwent surgery or biopsy for histopathological confirmation. The results were determined with respect to palpability of the lesion and tumour size. Additionally, a distinct analysis was performed for the patient subpopulation with indeterminate results of previously performed physical examination, mammography, and sonography. RESULTS: Overall sensitivity for scintimammography was 82.1% at a specificity of 87.5%. For palpable lesions sensitivity was 91.7% which was evidently higher as compared to 64.9% for non palpable lesions. For palpable lesions specificity was 81.1% and 88.6% for non palpable lesions. According to tumour size sensitivity ranged between 65.2% for carcinoma with a diameter < 1 cm and 93.7% for carcinoma > 1 cm. In the patients subgroup with indeterminate preliminary diagnosis (n = 143) sensitivity decreased to 71.7% at a specificity of 87.8%. Patients undergoing neoadjuvant chemotherapy showed decreasing sestamibi uptake as early as 8 days after therapy if tumour response was evident. However, small residual invasive tumours in patients with complete remission could not be visualised. CONCLUSION: Scintimammography is neither suited for screening, nor early diagnosis of breast cancer, nor for the further evaluation of small and unclear mammographic findings. Scintimammography should not be used whenever histopathological clarification of a suspicious lesion is necessary. It is useful to further investigate patients with unclear or probably benign findings in physical examination and/or mammography and to monitor tumour response to neoadjuvant chemotherapy.

Breast↗