European Journal of Nuclear Medicine

Propylene amine oxime (PnAO) forms a neutral lipid soluble complex with 99mTc. 99mTc-PnAO can be prepared by simple reduction of 99mTc-pertechnetate with stannous ion in the presence of excess PnAO in saline at or near neutral pH. This agent will passively penetrate biological membranes including the intact blood-brain barrier (BBB) as evidenced by the high brain uptake observed shortly after IV injection. The first-pass extraction efficiency in baboons was estimated to be 80% at normal blood flow. This agent or a derivatized form of 99mTc-PnAO may be useful in assessment of regional cerebral blood flow (rCBF) in humans.

We applied the technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) split-dose method in order to evaluate the feasibility of assessing cerebral blood flow (CBF) changes with single photon emission tomography (SPET) during a motor activation task. Eleven normal subjects were studied using the Tomomatic 564 (Medimatic, DK). Five subjects were studied twice at rest and 6 subjects at rest and during a motor task performance (finger opposition movements). A total of 28 mCi of 99mTc-HMPAO was injected in 2 doses with a 1:3 ratio. The first scan was obtained after injection of 7 mCi at rest in all subjects. The second scan was obtained a few minutes later, after injection of the remaining dose (21 mCi), under similar resting conditions or during a motor task performance. The mean brain uptake was proportional to the amount of tracer injected and to the acquisition time for both the first scan (5263±1266 counts × mCi × min) and the second (5034.4±966 counts × mCi × min). The grey/white matter ratio was 1.67±0.019 and 1.67±0.097 for the two scans, respectively. A three-way analysis of variance (ANOVA) for repeated measure showed no significant effects of side, slice and region of interest (ROI) on the CBF in the 5 subjects studied twice at rest, and the mean regional CBF change was −0.2%±5%. In the 6 subjects studied at rest and during motor activation, the image subtraction analysis showed a significant CBF increase in the primary motor cortex contralateral to the stimulated side (15%±7%, n=6) and medially in the supplementary motor area (22%±12%, n=4). Our results indicate that the split-dose method allows the detection of a local CBF response to motor activation using 99mTc-HMPAO in a single imaging session.

To test the advantages of positron emission tomography and computed tomography (PET/CT) for diagnosing lymph nodes and staging nasopharyngeal carcinoma and to investigate its benefits for survival and treatment decisions. The performance of PET/CT and magnetic resonance imaging (MRI) in diagnosis was compared based on 460 biopsied lymph nodes. Using the propensity matching method, survival differences of T3N1M0 patients with (n = 1093) and without (n = 1377) PET/CT were compared in diverse manners. A radiologic score model was developed and tested in a subset of T3N1M0 patients. PET/CT performed better than MRI with higher sensitivity, accuracy, and area under the receiver operating characteristic curve (96.7% vs. 88.5%, p < 0.001; 88.0% vs. 81.1%, p < 0.001; 0.863 vs. 0.796, p < 0.05) in diagnosing lymph nodes. Accordingly, MRI-staged T3N0-3M0 patients showed nondifferent survival rates, as they were the same T3N1M0 if staged by PET/CT. In addition, patients staged by PET/CT and MRI showed higher survival rates than those staged by MRI alone (p < 0.05), regardless of the Epstein-Barr virus DNA load. Interestingly, SUVmax-N, nodal necrosis, and extranodal extension were highly predictive of survival. The radiologic score model based on these factors performed well in risk stratification with a C-index of 0.72. Finally, induction chemotherapy showed an added benefit (p = 0.006) for the high-risk patients selected by the model but not for those without risk stratification (p = 0.78). PET/CT showed advantages in staging nasopharyngeal carcinoma due to a more accurate diagnosis of lymph nodes and this contributed to a survival benefit. PET/CT combined with MRI provided prognostic factors that could identify high-risk patients and guide individualized treatment.

Because anatomical information on fluorine-18 fluorodeoxyglucose (FDG) whole-body positron emission tomography (PET) images is limited, combination with structural imaging is often important. In principle, software co-registration of PET and computed tomography (CT) data or dual-modality imaging using a combined PET-CT camera has an important role to play, since "hardware-co-registered" images are thereby made available. A major unanswered question is under which breathing protocol the respiration level in the CT images of a patient will best match the PET images, which represent summed images over many breathing cycles. To address this issue, 28 tumour patients undergoing routine FDG PET examinations were included in this study. In ten patients, PET and CT were performed using a new combined high-performance in-line PET-CT camera without the need for repositioning of the patient, while in 18 patients imaging was performed on separate scanners located close to each other. CT was performed at four respiration levels: free breathing (FB), maximal inspiration (MaxInsp), maximal expiration (MaxExp) and normal expiration (NormExp). The following distances were measured: (a) between a reference point taken to be the anterior superior edge of intervertebral disc space T10–11 and the apex of the lung, (b) from the apex of the lung to the top of the diaphragm, (c) from the apex of the lung to the costo-diaphragmatic recess and (d) from the reference point to the lateral thoracic wall. Differences between CT and corresponding PET images in respect of these distances were compared. In addition, for each of 15 lung tumours in 12 patients, changes in tumour position between PET and CT using the same protocol were measured. CT during NormExp showed the best fit with PET, followed by CT during FB. The mean differences in movement of the diaphragmatic dome on CT during NormExp, FB, MaxInsp and MaxExp, as compared with its level on PET scan, were, respectively, 0.4 mm (SD 11.7), –11.6 mm (13.3), –44.4 mm (25.5) and –9.5 mm (25.6). CT acquired in MaxExp and MaxInsp is not suitable for image co-registration owing to the poor match of images in MaxInsp and because of difficulties with patient performance in MaxExp. With reference to lung lesions, NormExp showed the best results, with a higher probability of a good match and a smaller range of measured values in comparison with FB. Image misregistration in combined PET-CT imaging can be minimized to dimensions comparable to the spatial resolution of modern PET scanners. For PET-CT image co-registration, the use of a normal expiration breath-hold protocol for CT acquisition is recommended, independent of whether combined PET-CT systems or stand-alone systems are used.

Impulsive aggression in dogs has an important impact on human public health. Better insight into the pathophysiology of this phenomenon could lead to more adequate diagnosis and treatment. Indirect in vivo research on peripheral body fluids and post-mortem studies in impulsive animals and humans indicate a deficient serotonergic system in general and disturbances in the serotonin-2A (5-HT2A) receptor in particular. In this study, brain perfusion and the 5-HT2A receptors were examined in impulsive, aggressive dogs, in comparison with a group of normally behaving animals. In order to decide which dogs to include in this study, owners were asked to describe the general behaviour of the dogs, the circumstances in which aggression occurred and their conduct during aggressive acts. Finally, 19 dogs were retained for this study, showing, according to different behavioural specialists, disinhibited dominance aggression. Functional imaging studies were performed on all these dogs. Single-photon emission tomography (SPET) was used to measure regional brain perfusion using technetium-99m labelled ethyl cysteinate dimer (ECD). The 5-HT2A receptor binding properties were investigated using the selective radioligand iodine-123 labelled 5-I-R91150. A significant increase in uptake of the 5-HT2A radioligand was noted in all cortical areas. No significant alterations were found in regional cortical perfusion, indicating that the increased binding index was not a consequence of increased tracer delivery. This study supports a role for the serotonergic system in canine impulsive aggression.

In 632 patients efficacy of dihydroergotamine (DHE) in preventing postoperative deep venous thrombosis (DVT) and pulmonary embolism (PE) was tested vs. low-dose heparin (LDH) by means of the 125I-fibrinogen uptake test (RFUT). The incidence rate of DVT dropped from 36% (untreated group) to 17% after LDH, to 13% after DHE, and to 9% after simultaneous prophylaxis with both drugs. In patients with lower risk operations lasting not longer than 2 hs complete prevention of DVT was achieved by combined use of LDH and DHE. PE incidence in repeated lung perfusion scans of patients with positive RFUT was reduced to 4.3–2.6% (treated groups) in comparison to an incidence of 50% in the control group. This means the decrease of PE was overproportional in all treatment groups in comparison to the decrease of DVT incidence. The combined use of LDH and DHE may be considered as the best prophylactic regimen available for lowering postoperative DVT and PE.