Karel Schelstraete

A comparison of iodine-123 meta-iodobenzylguanidine scintigraphy and single bone marrow aspiration biopsy in the diagnosis and follow-up of 26 children with neuroblastoma

In staging neuroblastomas, the demonstration of tumoural invasion of the bone marrow is an important criterion with regard to the therapeutic prospects and the prognosis. Iliac crest aspiration sampling has been used routinely for the detection of bone marrow metastases in neuroblastoma. However, due to the limited character of the sampling, it sometimes leads to false-negative results. Another procedure which is used to determine the extent of neuroblastoma is metaiodobenzylguanidine (mIBG) scintigraphy. In order to establish the respective merits of both diagnostic techniques retrospectively, 148 iodine-123 mIBG scans of 26 children with neuroblastoma have been re-evaluated and compared with the results of routine bone marrow samples obtained within a 4-week period before or after scanning. Three types of mIBG uptake in the bone/bone marrow could be differentiated: (1) no visualization of the skeleton; (2) diffuse uptake in the skeleton with or without focally increased uptake, which indicates massive, diffuse bone marrow invasion by the tumour; and (3) focal tracer accumulation in one or several bones. No tracer uptake was observed in the skeleton in 91 scans. In 89 of the 91 the bone marrow biopsy was negative. Twenty-four scans showed diffuse skeletal uptake with or without foci. The bone marrow biopsies were negative for eight of those 24 scans. Hyperactive foci in one or more bones without diffuse tracer accumulation in the skeleton were detected in 33 scans. In only 7 of these 33 scans did bone marrow biopsy specimens from the iliac MDP crest contain neuroblastoma cells. Available technetium-99m methylene diphosphonate (MDP) whole-body scintigrams were also compared with the corresponding mIBG scans. Thirty-eight mIBG scans showed no visualization of the skeleton; 99mTc-MDP scintigrams were also normal. Seven patients with diffuse mIBG uptake in the skeleton appeared as normal on the 99mTc-MDP scans. Among 27 cases showing focal mIBG uptake in the skeleton with or without diffuse uptake, only I8 demonstrated a hot spot on the bone scintigram. The results of our study indicate that for the assessment of bone marrow infiltration by neuroblastoma, 1231-mIBG scintigraphy is more sensitive than the conventional cytological examination of bone marrow smears routinely obtained from the iliac crest, has a very high sensitivity in excluding bone marrow invasion, has a high specificity for detecting bone marrow invasion, appears to be able to detect early tumoural deposits in the bone marrow before osseous invasion occurs as shown on the MDP scans and is superior to 99mTc-MDP bone scan in detecting bone/bone marrow metastases of neuroblastoma. In patients with a positive mIBG scan in the skeleton, bone marrow biopsy will not yield additional information.

Analogy between tumor uptake of technetium(V)-99m dimercaptosuccinic acid (DMSA) and technetium-99m-MDP.

Sixty patients with a variety of malignant tumors were examined with Tc-99m(V) dimercaptosuccinic acid (DMSA) prepared by modification of a commercially available DMSA kit. Significant uptake of Tc-99m(V)-DMSA was observed in a number of tumors, offering additional clinically useful information. In the majority of cases in this study, however, the benefit of the Tc-99m(V)-DMSA image was limited because of low sensitivity. The most striking observation was the similarity between the tumor concentration of Tc-99m(V)-DMSA and the Tc-99m-MDP uptake in the tumor on the regular bone image. Therefore, patients with Tc-99m-MDP uptake in nonosseous tumor sites on the bone scan may be suitable candidates for tumor imaging with Tc-99m(V)-DMSA.

Cyclotron production of carrier-free 66Ga as a positron emitting label of albumin colloids for clinical use.

A method for producing carrier free 66Ga (T1/2:9.4h; β+) by 4He bombardment of natural copper targets is presented. 66Ga is formed by means of the 63Cu (4He, n) 66Ga reaction. Production yields are given in the 17.5 to 8 MeV 4He energy range. Chemical purification of 66Ga from the copper target is described. The only radionuclidic impurity found in the final product was 67Ga. Albumin colloids from commercially available kits designed for use with 99mTc could easily be labeled with 66Ga and employed for studies of the lymphatic system by positron emission tomography.

Sonographic diagnosis of an accessory spleen in recurrent idiopathic thrombocytopenic purpura

Recurrence of an idiopathic thrombocytopenic purpura in a previously splenectomised girl raised the suspicion of an accessory spleen. Abdominal ultrasound examination revealed a well circumscribed mass, caudal to the left kidney. The splenic nature of the mass was confirmed by a radionuclide spleen scan. At surgery an enlarged accessory spleen was removed.

Ga-67 Imaging in Hodgkin??s Disease

In order to answer the question if Ga-67 imaging has a practical utility for the management of the patient with Hodgkins disease, 108 scans performed on 60 patients were reviewed. When used during the initial staging of the disease or during restaging because of recurrences, Ga-67 imaging—at least in our experience—gave many false negative results in the cervical, axillary and inguinal areas, whereas the majority of true positive scans was found at the mediastinal level (including the lower mediastinum), and also in the lung parenchyma and the upper epigastric regions. Because of its lack of sensitivity, Ga-67 imaging cannot replace other staging procedures, but nevertheless is a valuable adjunctive test, as it can identify tumor localization that may have remained undetected by other methods. Fifty-four scans were performed to monitor treatment with radiation therapy or chemotherapeutic agents. Disappearance or decrease of Ga-67 uptake after treatment usually corresponded to a disappearance or regression of the tumor as ascertained by other methods. When the treatment was shown to be ineffective, Ga-67 uptake persisted or even became more prominent. When, during follow-up, a new concentration of Ga-67 appeared at the original location or elsewhere, a relapse was extremely likely. However, one must be aware of false positive images. In our material, no correlation was found between the intensity of the Ga-67 uptake and the histological subtypes of Hodgkins disease. Neither did we observe any relation to the blood sedimentation rate or serum iron levels.

Visualization of muscles involved in unilateral tremor using 13N-ammonia and positron emission tomography

Using positron emission computerized tomography (PCT), a high uptake of IV injected 13N-ammonia was observed in the muscles of the right forearm and leg of a patient with a rightsided static tremor. In some muscles the concentration of 13NH3 was 8.5 times higher than in the symmetrical normal limb. Confrontation of the clinical, neurological, and electromyographic findings with the results of the PCT proved that the muscles with the high uptake corresponded to the muscles responsible for the tremulous movements. There is strong evidence that the high uptake of 13NH3 was related to the increased blood flow produced by the continuous rhythmic exercise of the muscles involved in the tremor. To our knowledge a similar observation has not been described before. It is suggested that the combined use of suitable positron emitters and PCT might provide a valuable tool for the noninvasive study of perfusion of individual skeletal muscles.

Total body irradiation with 8 MeV X-rays in generalized malignant disease.

The authors describe their experience with total body irradiation (TBI) with 8 MeV‐x rays in the treatment of disseminated tumors. With a dose of 125 rad, given three times with 2‐week intervals, some objective remissions (6/26) were obtained, especially in patients with lymphomas. For solid tumors only subjective improvement could be achieved. The side‐effects were acceptable. The authors came to the conclusion that total body irradiation may be an alternative to chemotherapy for certain cases of generalized cancer.

Abnormal Tl-201 limb scan due to unilateral tremor.

An abnormal intra- and interextremity distribution pattern of TI-201 was observed on the limb scan of a patient with a unilateral tremor. This is ascribed to the increased blood flow in the muscles responsible for the tremor. The suggestion is made that the existence of tremor should be considered as a possible explanation for unexpected abnormalities on TI-201 limb scintigrams.