Highlight selection of radiochemistry and radiopharmacy developments by editorial board

BACKGROUND

The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biannual highlight commentary to update the readership on trends in the field of radiopharmaceutical development.

MAIN BODY

This selection of highlights provides commentary on 21 different topics selected by each coauthoring Editorial Board member addressing a variety of aspects ranging from novel radiochemistry to first-in-human application of novel radiopharmaceuticals.

CONCLUSION

Trends in radiochemistry and radiopharmacy are highlighted. Hot topics cover the entire scope of EJNMMI Radiopharmacy and Chemistry, demonstrating the progress in the research field in many aspects.

Quantification of myocardial blood flow using PET to improve the management of patients with stable ischemic coronary artery disease

ABSTRACT 

Cardiac PET has been evolving over the past 30 years. Today, it is accepted as a valuable imaging modality for the noninvasive assessment of coronary artery disease. PET has demonstrated superior diagnostic accuracy for the detection of coronary artery disease compared with single-photon emission computed tomography, and also has a well-established prognostic value. The routine addition of absolute quantification of myocardial blood flow increases the diagnostic accuracy for three-vessel disease and provides incremental functional and prognostic information. Moreover, the characterization of the vasodilator capacity of the coronary circulation may guide proper decision-making and monitor the effects of lifestyle changes, exercise training, risk factor modification or medical therapy for improving regional and global myocardial blood flow. This type of image-guided approach to individualized patient therapy is now attainable with the routine use of cardiac PET flow reserve imaging.

Cardiac PET: metabolic and functional imaging of the myocardium

Cardiac PET has evolved over the past 30 years to gain wider acceptance as a valuable modality for a variety of cardiac conditions. Wider availability of scanners as well as changes in reimbursement policies in more recent years has further increased its use. Moreover, with the emergence of novel radionuclides as well as further advances in scanner technology, the use of cardiac PET can be expected to increase further in both clinical practice and the research arena. PET has demonstrated superior diagnostic accuracy for the diagnosis of coronary artery disease in comparison with single-photon emission tomography while it provides robust prognostic value. The addition of absolute flow quantification increases sensitivity for 3-vessel disease as well as providing incremental functional and prognostic information. Metabolic imaging using (18)F-fluorodeoxyglucose can be used to guide revascularization in the setting of heart failure and also to detect active inflammation in conditions such as cardiac sarcoidosis and within atherosclerotic plaque, improving our understanding of the processes that underlie these conditions. However, although the pace of new developments is rapid, there remains a gap in evidence for many of these advances and further studies are required.

The role of F(18)-fluorodeoxyglucose positron emission tomography in guiding diagnosis and management in patients with known or suspected cardiac sarcoidosis

Cardiac sarcoidosis (CS) has gained significant interest in recent years with the emergence of advanced imaging modalities such as MRI and F(18)-fluorodeoxyglucose-positron emission tomography (FDG-PET) as modalities to aid in the diagnosis of this condition. CS remains a difficult condition to diagnose, particularly in cases of isolated cardiac involvement and it can present with a broad spectrum of clinical syndromes. Furthermore, the appropriate management of these patients remains controversial. FDG-PET has a potential role not only in diagnosis of CS but also in directing further therapies, facilitating the decision to start immunosuppression and monitoring the response to it. In this article, we discuss when to consider FDG-PET, outline the current optimal patient preparation and scanning protocols and then, using case examples, discuss the use of FDG-PET in follow-up of patients with known or suspected CS. We also outline how PET can influence management decisions in these patients.

18F-FDG PET imaging of myocardial viability in an experienced center with access to 18F-FDG and integration with clinical management teams: the Ottawa-FIVE substudy of the PARR 2 trial

(18)F-FDG PET may assist decision making in ischemic cardiomyopathy. The PET and Recovery Following Revascularization (PARR 2) trial demonstrated a trend toward beneficial outcomes with PET-assisted management. The substudy of PARR 2 that we call Ottawa-FIVE, described here, was a post hoc analysis to determine the benefit of PET in a center with experience, ready access to (18)F-FDG, and integration with clinical teams.

METHODS

Included were patients with left ventricular dysfunction and suspected coronary artery disease being considered for revascularization. The patients had been randomized in PARR 2 to PET-assisted management (group 1) or standard care (group 2) and had been enrolled in Ottawa after August 1, 2002 (the date that on-site (18)F-FDG was initiated) (n = 111). The primary outcome was the composite endpoint of cardiac death, myocardial infarction, or cardiac rehospitalization within 1 y. Data were compared with the rest of PARR 2 (PET-assisted management [group 3] or standard care [group 4]).

RESULTS

In the Ottawa-FIVE subgroup of PARR 2, the cumulative proportion of patients experiencing the composite event was 19% (group 1), versus 41% (group 2). Multivariable Cox proportional hazards regression showed a benefit for the PET-assisted strategy (hazard ratio, 0.34; 95% confidence interval, 0.16-0.72; P = 0.005). Compared with other patients in PARR 2, Ottawa-FIVE patients had a lower ejection fraction (25% +/- 7% vs. 27% +/- 8%, P = 0.04), were more often female (24% vs. 13%, P = 0.006), tended to be older (64 +/- 10 y vs. 62 +/- 10 y, P = 0.07), and had less previous coronary artery bypass grafting (13% vs. 21%, P = 0.07). For patients in the rest of PARR 2, there was no significant difference in events between groups 3 and 4. The observed effect of (18)F-FDG PET-assisted management in the 4 groups in the context of adjusted survival curves demonstrated a significant interaction (P = 0.016). Comparisons of the 2 arms in Ottawa-FIVE to the 2 arms in the rest of PARR 2 demonstrated a trend toward significance (standard care, P = 0.145; PET-assisted management, P = 0.057).

CONCLUSION

In this post hoc group analysis, a significant reduction in cardiac events was observed in patients with (18)F-FDG PET-assisted management, compared with patients who received standard care. The results suggest that outcome may be benefited using (18)F-FDG PET in an experienced center with ready access to (18)F-FDG and integration with imaging, heart failure, and revascularization teams.

Prognostic value of treadmill exercise and dobutamine stress positron emission tomography

BACKGROUND

Although positron emission tomography (PET) is routinely performed using vasodilator stress, exercise and dobutamine stress are available alternatives. Evidence suggests that vasodilator PET myocardial perfusion imaging (MPI) has prognostic value, but the prognostic value of treadmill exercise and dobutamine PET MPI is unknown.

OBJECTIVE

To determine the potential prognostic value of nonvasodilator stress PET MPI.

METHODS

Patients underwent treadmill exercise or dobutamine PET MPI. Images were assessed qualitatively and semiquantitatively. PET results were categorized as normal (summed stress score [SSS] of less than 4), abnormal (SSS of 4 or greater) or inconclusive (SSS of less than 4 and submaximal peak stress heart rate). Patient follow-up (cardiac death, nonfatal myocardial infarction [MI] and/or late revascularization) was performed.

RESULTS

Of the 124 patients (mean follow-up period of 2.3+/-1.6 years), 46 patients (37%) had a normal study, 15 patients (12%) had an inconclusive study and 63 (51%) had an abnormal PET. Patients with a normal PET had no deaths or nonfatal MI. One patient with a normal PET underwent late revascularization (annual event rate of 1.7%). Patients with an abnormal PET had 15 cardiac events (one cardiac death, four nonfatal MIs and 10 late revascularizations), with an annual event rate of 13.0% (P=0.002).

CONCLUSIONS

Although small, the present study suggests that defects seen on PET myocardial perfusion, resulting from stressors (treadmill exercise and dobutamine) that increase myocardial oxygen demand, may have prognostic value.

Myocardial blood flow in patients with low-flow, low-gradient aortic stenosis: differences between true and pseudo-severe aortic stenosis. Results from the multicentre TOPAS (Truly or Pseudo-Severe Aortic Stenosis) study

BACKGROUND

Impairment of myocardial flow reserve (MFR) in aortic stenosis (AS) with normal left ventricular function relates to the haemodynamic severity.

OBJECTIVES

To investigate whether myocardial blood flow (MBF) and MFR differ in low-flow, low-gradient AS depending on whether there is underlying true-severe AS (TSAS) or pseudo-severe AS (PSAS).

METHODS

In 36 patients with low-flow, low-gradient AS, dynamic [13N]ammonia PET perfusion imaging was performed at rest (n = 36) and during dipyridamole stress (n = 20) to quantify MBF and MFR. Dobutamine echocardiography was used to classify patients as TSAS (n = 18) or PSAS (n = 18) based on the indexed projected effective orifice area (EOA) at a normal flow rate of 250 ml/s (EOAI(proj )<or= or >0.55 cm(2)/m(2)).

RESULTS

Compared with healthy controls (n = 14), patients with low-flow, low-gradient AS had higher resting mean (SD) MBF (0.83 (0.21) vs 0.69 (0.09) ml/min/g, p = 0.001), reduced hyperaemic MBF (1.16 (0.31) vs 2.71 (0.50) ml/min/g, p<0.001) and impaired MFR (1.44 (0.44) vs 4.00 (0.91), p<0.001). Resting MBF and MFR correlated with indices of AS severity in low-flow, low-gradient AS with the strongest relationship observed for EOAI(proj) (r(s) = -0.50, p = 0.002 and r(s) = 0.61, p = 0.004, respectively). Compared with PSAS, TSAS had a trend to a higher resting MBF (0.90 (0.19) vs 0.77 (0.21) ml/min/g, p = 0.06), similar hyperaemic MBF (1.16 (0.31) vs 1.17 (0.32) ml/min/g, p = NS), but a significantly smaller MFR (1.19 (0.26) vs 1.76 (0.41), p = 0.003). An MFR <1.8 had an accuracy of 85% for distinguishing TSAS from PSAS.

CONCLUSIONS

Low-flow, low-gradient AS is characterised by higher resting MBF and reduced MFR that relates to the AS severity. The degree of MFR impairment differs between TSAS and PSAS and may be of value for distinguishing these entities.

Prognostic significance of dipyridamole-induced ST depression in patients with normal 82Rb PET myocardial perfusion imaging

Recent studies have shown that vasodilator-induced ischemic electrocardiographic (ECG) changes have incremental prognostic value over normal SPECT myocardial perfusion imaging (MPI) and identify patients at higher risk for cardiac events. The prognostic value of vasodilator-induced ischemic ECG changes in the setting of normal PET MPI has yet to be determined. We sought to determine the prognostic importance of dipyridamole-induced ischemic ECG changes in patients with normal 82Rb PET myocardial perfusion images.

METHODS

Between 2000 and 2003, 2,029 consecutive patients undergoing dipyridamole stress 82Rb PET at the University of Ottawa Heart Institute were evaluated. Patients with normal PET MPI and interpretable ECGs were enrolled. Electrocardiograms were assessed for ST depression or elevation and patients were categorized into those with and without dipyridamole-induced ischemic ECG changes. Images were graded using the 17-segment model. Follow-up information was obtained by telephone interview, from hospital records, or from treating physicians. All cardiac events (cardiac death, nonfatal myocardial infarction [MI], percutaneous coronary intervention, coronary artery bypass grafting, or angiography) were verified with hospital records.

RESULTS

Of the 629 enrolled patients with normal PET MPI, 72 patients had dipyridamole-induced ischemic ECG changes. There was no significant difference between the 2 groups in the combined endpoint (cardiac death, nonfatal MI, and revascularization) at follow-up (mean +/- SD, 27.1 +/- 13 mo). There were no cardiac deaths in either group. One (1.4%) patient with ischemic ECG changes had a nonfatal MI (0.6% annual event rate). Two (2.8%) patients with ischemic ECG changes required revascularization compared with 11 (2.0%) in the nonischemic ECG group.

CONCLUSION

Normal 82Rb PET confers an excellent prognosis regardless of dipyridamole-induced ST depression.

Does electrocardiographic Q wave burden predict the extent of scarring or hibernating myocardium as quantified by positron emission tomography?

BACKGROUND

The extent of Q wave 'burden' on electrocardiograms (ECGs) has not been correlated with the extent of scarring and hibernation as determined quantitatively by positron emission tomography (PET).

OBJECTIVE

A retrospective study was performed to identify if ECG Q wave burden predicts the extent of scarring or mismatch (hibernating myocardium) as defined by rubidium-82/F-18 fluorodeoxyglucose PET viability imaging.

PATIENTS AND METHODS

Eighty-three consecutive patients with coronary artery disease undergoing rubidium-82/F-18 fluoro-deoxyglucose viability imaging (mean age 67.9+/-11 years, with a mean ejection fraction of 27+/-7%) formed the study population. Resting ECG was interpreted for the presence or absence of Q waves using standard ECG criteria for Q wave myocardial infarction. Patients were divided into two groups based on their Q wave burden on ECG (small to moderate scar: zero to four Q waves; large scar: five or more Q waves). Automated analysis was used to calculate the extent of scarring and mismatch (hibernating myocardium) on PET as a percentage of left ventricular myocardium. Mean PET scar and mismatch scores were calculated for the two groups.

RESULTS

The mean PET scar scores were significantly different between the small to moderate ECG scar group (13.9+/-7.3% of the left ventricle) and the large scar group (20.6+/-8.1% of the left ventricle; P=0.001). The mismatch scores for the small to moderate scar group (4.6+/-2.8%) were not significantly different from those of the large scar group (4.05+/-2.8%; P=0.7).

CONCLUSIONS

ECG Q wave 'burden' was associated with the presence of scars as defined by PET but did not accurately predict the amount of hibernating myocardium.

The effect of paroxetine on 5-HT(2A) receptors in depression: an [(18)F]setoperone PET imaging study

OBJECTIVE

In the cortex of animals, serotonin (5-HT) levels increase after several weeks of treatment with selective serotonin reuptake inhibitors (SSRIs). Studies using an intrasubject design to examine the effects of SSRI treatment on 5-HT(2A) receptors in the cortex of drug-free depressed patients are needed. In theory, agonist stimulation of 5-HT(2A) receptors could be relevant to SSRI treatment by promoting neuronal growth and survival as well as direct elevation of mood. The objective of this study was to evaluate the effect of 6 weeks of paroxetine treatment on 5-HT(2A) receptors in depressed patients.

METHOD

After a medication-free period of at least 3 months, 19 depressed patients were treated for 6 weeks with paroxetine, 20 mg/day. The authors used [(18)F]setoperone and positron emission tomography to assess 5-HT(2A) receptor binding potential in the patients before and after treatment and in 19 age-matched healthy subjects.

RESULTS

5-HT(2A) binding potential declined with age in all cortical regions in the depressed and healthy subjects. There was a significant interaction between age and treatment effect on 5-HT(2A) binding potential in all cortical regions. Subjects aged 20 to 30 years had a 10% decrease in 5-HT(2A) binding potential after treatment, whereas subjects aged 30 to 40 had no change. No regional differences in 5-HT(2A) binding potential between depressed and healthy subjects were found.

CONCLUSIONS

5-HT(2A) receptors down-regulate in young depressed subjects after treatment with paroxetine, but this down-regulation attenuates with age. This suggests that over 6 weeks paroxetine treatment increases 5-HT agonism on 5-HT(2A) receptors in the cortex of young patients with depression.

Prefrontal cortex 5-HT2 receptors in depression: an [18F]setoperone PET imaging study

OBJECTIVE

Widespread disturbances of serotonin (5-HT) are implicated in the pathophysiology of depression. Of 5-HT receptor abnormalities reported, the most replicated finding is increased 5-HT2 receptor binding in the postmortem prefrontal cortex of depressed suicide victims. The extent to which these findings exist in depressed persons without recent suicide attempts is uncertain. The objective of this study was to evaluate 5-HT2 receptors in depressed patients who were medication-free and who had not made recent suicide attempts.

METHOD

With the use of [18F]setoperone and positron emission tomography (PET), 5-HT2 receptor binding potential was assessed in 14 depressed and 19 healthy subjects. Exclusion criteria for depressed patients included use of antidepressant medication within the past 6 months, a history of suicide attempts within the past 5 years, other current axis I disorders including bipolar disorder, and the presence of psychotic symptoms. The 5-HT2 (setoperone) binding potential in the two groups of subjects was compared by analysis of covariance with age as the covariate.

RESULTS

Age had a significant effect on 5-HT2 binding potential, but depression did not. The interaction of age and depression was not significant.

CONCLUSIONS

The 5-HT2 binding potential is not increased in untreated depressed subjects who have not made recent suicide attempts. This negative finding does not rule out the possibility that there is a role for 5-HT2 receptors in treatment or that 5-HT2 receptors are increased in highly suicidal states.

Serotonin 5-HT2 receptors in schizophrenia: a PET study using [18F]setoperone in neuroleptic-naive patients and normal subjects

OBJECTIVE

Several postmortem studies have reported a decreased density of serotonin 5-HT2 receptors in the prefrontal cortex in schizophrenia. The purpose of this study was to investigate this in patients with schizophrenia by means of [18F]setoperone and positron emission tomography (PET) imaging.

METHOD

Thirteen neuroleptic-free patients with schizophrenia, 10 of whom were also neuroleptic-naive, were compared with a group of 26 normal subjects in the same age range. The density of 5-HT2 receptors was assessed with the use of [18F]setoperone and PET in standardized cortical regions of interest.

RESULTS

Increasing age was associated with similar declines in 5-HT2 receptors in all cortical regions in the patient group and in the normal comparison group. After control for the effect of age, there was no statistically significant difference between the patients and the comparison subjects in 5-HT2 receptor density in any of the cortical regions.

CONCLUSIONS

This study failed to find the decrease in 5-HT2 receptors reported in postmortem studies of schizophrenia. The study had the power to detect a decrease of 25% or more in 5-HT2 receptors, which was anticipated on the basis of the previous postmortem studies. Thus, a primary serotonergic abnormality in schizophrenia, if one exists, is either small or unlikely to be at the level of the 5-HT2 receptors. This finding does not rule out a therapeutic role for 5-HT2 antagonists in schizophrenia, but it does suggest that the therapeutic contribution is likely to be an indirect one.

5-HT2 and D2 receptor occupancy of olanzapine in schizophrenia: a PET investigation

OBJECTIVE

Olanzapine is a new atypical antipsychotic recently introduced for the treatment of schizophrenia. The purpose of this study was to investigate olanzapine's binding to the serotonin 5-HT2 and dopamine D2 receptors in schizophrenic patients being treated with clinically relevant doses.

METHOD

Twelve patients with schizophrenia were randomly assigned to 5, 10, 15, or 20 mg/day of olanzapine in a prospective fashion. Three other subjects taking 30-40 mg/day were also included. Once steady-state plasma levels were achieved, dopamine D2 and serotonin 5-HT2 receptors were assessed by using [11C]raclopride and [18F]setoperone positron emission tomography imaging, respectively. Ratings of clinical status, extrapyramidal side effects, and prolactin levels were also obtained.

RESULTS

Olanzapine induced near saturation of the 5-HT2 receptors, even at 5 mg/day. Its D2 occupancy increased with dose: patients taking 5-20 mg/day showed 43%-80% D2 occupancy, while patients taking 30-40 mg/day showed 83%-88%.

CONCLUSIONS

Olanzapine is a potent 5-HT2 blocker and shows a higher 5-HT2 than D2 occupancy at all doses. However, its D2 occupancy is higher than that of clozapine and similar to that of risperidone. In the usual clinical dose range of 10-20 mg/day, its occupancy varies from 71% to 80%, and this restricted range may explain its freedom from extrapyramidal side effects and prolactin elevation. However, doses of 30 mg/day and higher are associated with more than 80% D2 occupancy and may have a higher likelihood of prolactin elevation and extrapyramidal side effects.

[11C]RTI-32 PET studies of the dopamine transporter in early dopa-naive Parkinson's disease: implications for the symptomatic threshold

To estimate the threshold of nigrostriatal dysfunction required for symptomatic Parkinson's disease (PD), we employed [11C]RTI-32 and PET to study the dopamine transporter in striatal subdivisions of 11 L-dopa-naive patients with very early parkinsonism. As compared with the controls (N = 10), the PD group had on the side contralateral to the maximal clinical symptoms, significantly reduced binding in the posterior putamen (-56%) and anterior putamen (-28%), with the reduction in caudate (-12%) not significantly different. To the extent that dopamine transporter binding accurately reflects the number of nigrostriatal dopamine nerve terminals, these findings suggest that the clinical threshold for PD in the middle-age human is approximately 50% loss of dopaminergic innervation to the posterior putamen. Our data also suggest that damage to the putamen component of the striatum is sufficient for the clinical expression of PD.

Reliability of a simple non-invasive method for the evaluation of 5-HT2 receptors using [18F]-setoperone PET imaging

Position emission tomography (PET) imaging of 5-HT2 receptors can be potentially very useful in investigating neuropsychiatric disorders and their pharmacological treatments. [18F]-setoperone, a PET radio-ligand, has been shown to be useful for the delineation of 5-HT2 receptors in the cortex. However, there is no available data regarding the scan-rescan reliability of this technique. The purpose of this study was to assess the reliability of the [18F]-setoperone PET technique for assessing the binding potential (Bmax/ Kd) for 5-HT2 receptors. Ten healthy subjects had two [18F]-setoperone PET scans on two separate occasions 6-21 days apart. The average difference in the 5-HT2 binding potential (BP) as measured on the two occasions in the prefrontal, temporal, parietal and occipital region was between 5 and 7%. Thus 5-HT2 BP can be measured with a high reliability using a non-invasive technique that uses the cerebellum as a reference region. A power analysis based on the reliability data suggests that this technique can be used to detect within-subject differences of 10% or more, and between-group differences of 25% or more, with a reasonable number of subjects. It is concluded that [18F]-setoperone can be routinely produced and reliably used for the PET imaging of 5-HT2 receptors in clinical situations.

The D2 receptor occupancy profile of loxapine determined using PET

Positron emission tomography (PET) studies of typical neuroleptics suggest that 60% to 80% of striatal D2 occupancy may be sufficient for optimal clinical treatment of psychosis. Therefore, striatal D2 occupancy may be used as an index to determine the optimal dose range. Toward this end, we determined the in vivo D2 profile of loxapine, using [11C]-raclopride and PET. Seven patients selected from a clinical population were scanned while taking steady-state oral loxapine from 10 to 100 mg/day. Their D2 receptor occupancy was estimated by comparing them to age-matched data from neuroleptic-naive patients. The D2 receptor occupancy ranged from 52% to 90%, and there was a very strong relationship between dose and D2 occupancy, suggesting that 15 to 30 mg/day of loxapine would produce, the putatively optimal, 60% to 80% striatal D2 blockade. This dose range is much lower than that used in most clinical settings and points to the potential efficacy of loxapine at lower doses.

High levels of dopamine D2 receptor occupancy with low-dose haloperidol treatment: a PET study

OBJECTIVE

The purpose of this study was to determine the dopamine D2 receptor occupancy induced by low-dose haloperidol treatment in a prospective trial.

METHOD

Seven patients with schizophrenia were treated with 2 mg/day of haloperidol for 2 weeks, and D2 receptor occupancy was measured by [11C]raclopride and positron emission tomography.

RESULTS

The patients showed high levels of D2 occupancy (53%-74%); five of them showed substantial clinical improvement, and none showed important side effects.

CONCLUSIONS

The findings demonstrate that low doses of haloperidol induce D2 receptor occupancies that are in the putative therapeutic range. In combination with recent empirical trials, these findings should encourage clinicians to initiate treatment of psychotic episodes with low (2-4 mg haloperidol equivalent) doses of typical neuroleptics, particularly for first-episode patients.

Use of the multiple uptake gated acquisition scan for the preoperative assessment of cardiac risk

A retrospective study was undertaken at three hospitals of 196 patients who underwent an operative procedure as long as 60 days after radionuclide determination (multiple uptake gated acquisition scan [MUGA]) of left ventricular ejection fraction (LVEF). Cardiac related mortality rates were 2.2 per cent among patients in group 1, LVEF greater than or equal to 55 per cent; 5.4 per cent in group 2, LVEF 36 to 54 per cent, and 19.5 per cent in group 3, LVEF less than or equal to 35 per cent (p less than 0.005). Statistically significant correlation between MUGA-derived LVEF and cardiac related mortality was found in veteran patients undergoing noncardiac surgical procedures (both vascular and nonvascular). There was no correlation between MUGA-derived LVEF and postoperative cardiac related mortality in cardiac surgical patients. A preoperative American Society of Anesthesiologists Physical Status Evaluation classification of IV or a preoperative pulmonary capillary wedge pressure of 20 centimeters of water or greater also predicted an increased risk of postoperative cardiac death. We advise preoperative MUGA scans for all patients in whom the results of preoperative history or physical examination suggest compromised ventricular function. We also advise pulmonary arterial catheter hemodynamic monitoring during the perioperative period for all patients with a preoperative MUGA-derived LVEF of less than or equal to 35 per cent.

Management of penetrating neck injuries

In 44 patients neck wounds penetrating the platysma were evaluated over a 5-year period. Twenty-one patients were admitted and observed; 22 patients were explored immediately. One was dead upon arrival in the emergency room. The decision to explore was based upon initial clinical evaluation using criteria of unstable vital signs, bleeding, hematoma, subcutaneous emphysema, respiratory distress, or neurologic deficits. Of the 21 patients selected for observation, none had complications or required later surgery. There was a negative exploration rate of 23%. Had all patients been explored, the negative exploration rate would have been 60%. We conclude that selective exploration, based upon careful clinical evaluation, is both safe and reasonable in cases of penetrating neck trauma.