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Nuclear Medicine studies performed with tomographic acquisition and tracers such as Technetium-99m hexamethyl-propyleneamine oxime (99mTc-HMPAO) are able to assess cerebral blood flow. A case is reported of a patient with a large intracranial tumor, of possible pituitary origin, with a clinical and electroencephalographic suspicion of brain death. The patient had endocrinous-metabolic impairments for a history of impotence, since 18 months, and diabetes insipidus with a urine output of 350 ml/hr in the first 24 hours from the clinical suspicion of brain death. Due to the endocrinous-metabolic impairments, according to Italian law, it was necessary to confirm the diagnosis of brain death by performing a study able to assess cerebral blood flow. A single Photon Emission Tomography (SPET) scan was performed after the intravenous administration of 99mTc-HMPAO using a high resolution, brain dedicated device. No tracer uptake was evident in cerebral, cerebellar and brain stem structures. The cerebral blood flow study by SPET confirmed the diagnosis of brain death and made the organ transplant possible in a short period of time. High resolution SPET studies are useful to confirm the diagnosis of brain death when there are factors that can influence clinical and electroencephalographic signs, reducing time to authorise the organ explant.

The aim of this study was to facilitate the diagnosis of brain death based on semi-quantitative parameters as well as the other scintigraphic signs and symptoms of brain death. Altogether, 72 studies were performed in 54 patients (35 males, 19 females) to evaluate the diagnoses of brain death which were confirmed in 49 cases. Perfusion dynamic acquisition and static imaging were performed after the intravenous injection of 700-900 MBq 99Tcm-hexamethylpropyleneamine oxime (HMPAO). We reviewed the following parameters retrospectively: (1) qualitative visual assessment of the presence or absence of delayed HMPAO deposition in the brain area; (2) qualitative visual assessment of a 'three-pronged fork' of the cerebral arteries during the first-pass study; (3) any evidence of 'hollow skull' during the first-pass study; (4) any evidence of 'hot nose'; (5) blood flow index (i.e. the ratio of the area under the brain time-activity curve vs that under the curve for the carotid arteries); and (6) delayed uptake index (i.e. the ratio of HMPAO deposition in the brain vs that in the facial regions of interest). We were able to demonstrate the validity of individual signs and symptoms and to confirm the highly reliable nature of semi-quantitative scintigraphic parameters.

The authors present two cases of clinical brain death that failed to meet the criteria for whole brain death using Tc-99m HMPAO. Conventional anterior cerebral flow studies demonstrated no intracerebral perfusion. Anterior static images also failed to show cerebral activity. However, the lateral images clearly demonstrate cerebellar activity. These cases demonstrate the importance of Tc-99m HMPAO as the agent of choice in evaluating brain death and the necessity of lateral views to meet the criteria for whole brain death. Cerebellar perfusion challenges the present criteria for whole brain death. New criteria must re-evaluate the present technology.

The diagnosis of brain death has great importance for the social and medical purposes, such as organs transplantation, and is based on clinical examination and EEG records. We report two doubtful cases of brain death in whom the 99mTc HMPAO scintigraphy was used to confirm the complete absence of cerebral perfusion.

Diagnosis of brain death must be certain to allow discontinuation of artificial ventilation and organ transplantation. Brain death is present when all functions of the brain stem have irreversibly ceased. Clinical and electrophysiological criteria may be misinterpreted due to drug intoxication, hypothermia or technical artefacts. Thus, if clinical assessment is suboptimal, reliable early confirmatory tests may be required for demonstrating absence of intracranial blood flow. We have easily carried out and interpreted 99mTc HM-PAO SPECT in a consecutive series of 40 comatose patients with brain damage, without discontinuing therapy. Brain death was diagnosed in 7 patients, by recognising absence of brain perfusion, as shown by no intracranial radionuclide uptake. In patients in whom perfusion was seen on brain scans, HM-PAO SPECT improved assessment of the extent of injury, which in general was larger than suggested by CT.

Portable cerebral perfusion studies provide a quick and accurate alternative to traditional confirmatory examinations (such as four-vessel angiography and electroencephalography) to determine brain death. The authors retrospectively analyzed 26 cerebral perfusion studies using both Tc-99m DTPA and Tc-99m HMPAO. The flow agents gave identical results. Additionally, the delayed-phase Tc-99m HMPAO images gave the same results for brain death (14 positive and 12 negative) as the flow images from either agent. Because the Tc-99m HMPAO delayed images can be used for diagnosis, many technical problems become less crucial. Unlike Tc-99m DTPA, Tc-99m HMPAO normally visualizes the gray matter of the cerebellum, midbrain, and medulla. These areas must be evaluated to ensure that they meet the strict criteria for brain death. These differences and the present study suggest that Tc-99m HMPAO is a superior agent for cerebral perfusion studies to determine brain death.

Because 99m Tc HM-PAO is simple to use, noninvasive and readily available, it appears to satisfy most criteria for the use of radionuclide cerebral imaging in the confirmation of brain death. Waiting periods, which are often included in brain death protocols, delay the diagnosis of brain death. 99m Tc HM-PAO has proven to be a useful test to confirm brain death.

The determination of brain death relies on unequivocal clinical data and on supportive studies. The replacement of the electroencephalogram (EEG) as the gold standard is unanimously felt as appropriate. Scintigraphic imaging with technetium-99m hexamethylpropylenamineoxime (99mTc-HMPAO) seems to offer an adequate substitute given its metabolic features, ideally to be used with a mobile gamma-camera which simplifies the approach to this type of patient. We correlated EEG with the scintigraphic data, which were found to be concordant and therefore substitutive in the establishment of brain death.

Objective: To determine the usefulness of (Tc 99m) HM-PAO scan in supporting the clinical diagnosis of brain death., Design: Retrospective review., Setting: Paediatric Intensive Care Unit., Subjects: A total of 39 paediatric patients had HM-PAO scans conducted to confirm the presence of brain death or to assess the degree of brain injury., Interventions: All patients had (Tc 99m) HM-PAO injected before the scan was conducted., Measurements and Main Results: Fifty-four scans were done in 39 patients. The majority of cerebral injury was as a result of closed head injury or asphyxia/anoxia. There were 20 scans which demonstrated no cerebral blood flow (CBF); however, in 26 situations patients were clinically brain dead. All of the patients who continued to have CBF in the presence of clinical brain death sustained asphyxial/anoxic injuries., Conclusions: The HM-PAO scan is a useful non-invasive portable tool for supporting the diagnosis of brain death when there is absent CBF. However, continued flow may be present in asphyxial/anoxic injuries in the presence of clinical brain death.

Brain single photon emission computed tomography (SPECT) with 99mTc-d,l-hexamethyl-propyleneamine oxime (HMPAO) was performed twice in a 78-year-old man clinically diagnosed as brain death according to the standard criteria of the Japanese Ministry of Welfare. The first brain SPECT demonstrated the tracer accumulation in the brain, indicating preserved cerebral blood flow. The second brain SPECT performed 3 days later revealed cessation of the blood flow. In patients with preserved cerebral blood flow, the diagnosis of brain death cannot be made, even if they meet the existing criteria, because previous report noted the recovery in some of those patients. Brain perfusion SPECT plays an important role as a confirmatory test for the diagnosis of the brain death.

Evaluation of blood flow to the brain using various radiopharmaceuticals can be used to confirm brain death. Agents available for this purpose include Tc-99m HMPAO, Tc-99m pertechnetate, Tc-99m glucoheptonate, and Tc-99m DTPA. The authors evaluated the use of Tc-99m HMPAO in 17 patients suspected of brain death using flow images and static images at several time intervals: immediately, between 30 and 60 minutes, and at 2 hours. These studies were compared to several studies performed with Tc-99m glucoheptonate and Tc-99m DTPA. The results of the Tc-99m HMPAO brain death studies correlated well with the patients' clinical conditions. Static images 1 to 2 hours after the injection of 5 to 30 mCi of Tc-99m HMPAO were satisfactory for an accurate interpretation; however, an immediate answer could as easily be supplied using flow images alone. Tc-99m HMPAO was found to be more easily interpreted and less dependent on imaging technique than Tc-99m glucoheptonate and Tc-99m DTPA, and it is the agent of choice for the evaluation of brain death.

To determine the usefulness of cerebral blood flow imaging for the diagnosis of brain death, 4 female and 12 male patients, aged 19 to 69 years and suffering from various intracranial lesions, were studied. In addition to neurologic examination, electroencephalographic recording, and cerebral angiography, tomographic brain scintigraphy was performed using a SPECT system with a LEAP collimator after the intravenous administration of 555 MBq Tc-99m HMPAO. The radioisotopic scanning procedure revealed no intracranial perfusion in 14 of the 16 patients. Only minimal cerebellar blood flow was seen in one patient. In another, residual right-sided supratentorial flow was initially present but absent in a follow-up HMPAO SPECT. Carotid angiography (four-vessel contrast media angiography) confirmed the above results without exception. Because HMPAO is taken up by normal brain tissue with no significant redistribution for several hours, the tracer is particularly helpful in cases of suspected brain death. The quality of the tracer must be established by chromatography. Interpretation of the SPECT images produces reliable and reproducible results. In conclusion, cerebral blood flow imaging with HMPAO is a safe, noninvasive procedure for the determination of brain death, that produces fast, reliable, reproducible, and easy-to-interpret results.

The lipophilic cerebral perfusion agent 99mTc-hexamethylpropylene amine oxime (HMPAO) is increasingly used to demonstrate the absence of blood flow for the declaration of brain death. We report a case that illustrates how the timing of such studies is important when organ harvesting is the underlying emergent indication. If performed too early, a study showing the presence of cerebral perfusion may not expedite the declaration of brain death, but instead may complicate patient assessment and unnecessarily delay the process.

The use of technetium-99m hexamethyl-propyleneamine oxime (99Tcm-HMPAO) in the diagnosis of brain death has been evaluated in 41 studies of 37 patients with severe brain injury, who were under the effect of drugs or when other diagnostic methods were equivocal. HMPAO studies were compared with conventional radionuclide angiography performed simultaneously by intravenous administration of HMPAO as a bolus. The ages of patients ranged from 4 months to 75 years. Dynamic flow images and 5-min static uptake images were acquired following bolus injection of 555 Mbq of 99Tcm-HMPAO. All patients showing no brain uptake were confirmed as brain-dead by standard clinical criteria, with no contradictory cases in the static study. In addition, all patients who were not brain-dead showed HMPAO uptake at least in the brainstem. Dynamic flow images were equivocal in five patients, four of whom had no uptake on static images and clinically confirmed brain death. In addition, two other cases showed "mismatched" dynamic and static images: in one case no perfusion was observed on flow images but uptake restricted to the posterior fossa was seen on static images; the other case showed perfusion on the dynamic study and static imaging revealed hemispheric uptake with no posterior fossa uptake. Static perfusion 99Tcm-HMPAO studies offer advantages over conventional brain scintigraphy, better results being due to adequate assessment of posterior fossa activity and avoiding equivocal studies.

We monitored 27 patients with HM-PAO-perfusion scintigraphy during the progress of cerebral death. The results of scintigraphy correlate well with cerebral angiography. Advantages are the possibility of bedside-examination, the non-invasiveness of the method and the possibility of in-vivo control. The non-visualized-brain in dynamic scintigraphy is a valuable additional method in the determination and documentation of cerebral death.

A total of 24 patients with clinical evidence of brain death (n = 17), severe coma (n = 2; GCS approximately 3) and apallic syndrome (n = 4) underwent a comparative investigation with 99mTc-HMPAO brain scintigraphy, EEG, auditory and somatosensory evoked potentials. Accompanied by EEG and evoked potentials, brain scintigraphy enabled confirmation of cerebral death in 15/17 patients. In one case clinical examination and evoked potentials suggest brain death, but cerebral perfusion and EEG were normal ("brain stem death"). One patient with evidence of cerebral death in clinical examination, brain scintigraphy and evoked potentials, showed questionable focal EEG activity; however, autopsy revealed intravital autolysis of the entire brain. All patients with apallic syndrome and deep coma showed a distinct cerebral perfusion, but gross EEG abnormalities; evoked potentials were delayed or absent. Planar scintigraphy with 99mTc-HMPAO appears to be superior to neurophysiological techniques discriminating patients with agonal cerebral dysfunction from those with brain death.

We report on the utility of technetium 99m hexamethylpropylene amine oxime (99mTc-HMPAO) to diagnose brain death following cardiac surgery on a 49-year-old man with triple-vessel coronary artery disease. The imaging parameters and criteria to diagnose irreversible brain damage (brain death) with 99mTc-HMPAO are outlined. Brain imaging with this tracer seems to be more reliable than classic radionuclide angiography and has a potential value to confirm the diagnosis of brain death at an early stage. In addition, it may be used to evaluate the perfusion pattern to other vital organs with potential for transplantation.

Thirteen patients with cerebral trauma were studied for cerebral perfusion by the use of Tc-99m HMPAO scanning. CT imaging was performed on nine patients. Because of their clinical condition, four patients were scanned only in the planar mode to help establish the diagnosis of brain death. Other indications for study included gunshot wound and blunt or sharp object trauma with or without skull fracture. In all cases, HMPAO scans showed defects with a quality equivalent to or greater than that demonstrated by CT. Our initial results suggest that HMPAO may predict the degree of permanent damage and which patients may develop post-traumatic headache. A diagnosis of brain death can be established without the withdrawal of medical therapy.

The normal biodistribution of technetium-99m HM-PAO ([99mTc]HM-PAO) includes significant uptake in the brain, liver, and kidneys. A pregnant patient studied with [99mTc] HM-PAO to confirm brain death provided an opportunity to examine the transplacental distribution of this radio-pharmaceutical in the unborn fetus. Uptake in the fetus after transplacental delivery is almost exclusively hepatic with a small amount of biliary excretion.

In 9 patients with the clinical diagnosis of brain death, a HM-PAO-SPECT was performed to document the arrest of cerebral circulation. Besides brain-stem areflexia, negative apnea-test and an observation time of at least 12 hours neurophysiological examinations (EEG and evoked potentials) were performed. In 4 cases, an additional arterial digital subtraction angiography proved the arrest of cerebral circulation shown in SPECT. In 5 cases, there was cortical low activity still present in EEG with negative SPECT. HM-PAO-SPECT seems to be a reliable noninvasive radiological method in the determination of brain death. It is especially helpful in cases with persisting focal cortical EEG-activity.

The advantage of Tc-99m HM-PAO, a newly introduced compound for brain perfusion imaging, is illustrated in three patients with suspicion of brain death. With Tc-99m HM-PAO, the carotid flow study is not essential, as it is in the Tc-99m pertechnetate carotid angiogram; planar images are equally useful; and there is no need for SPECT images. For the diagnosis of brain death, Tc-99m HM-PAO can be injected in the intensive care unit and planar images can be obtained at a later time using a mobile camera or whenever the patient can be moved to the nuclear medicine department.