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Original Articles

The Impact of DaTscan in the Diagnosis of Parkinson Disease

Gayed, Isis MD*; Joseph, Usha MD*; Fanous, Mina MD*; Wan, David MD*; Schiess, Mya MD; Ondo, William MD; Won, Kyoung-Sook MD

Author Information
doi: 10.1097/RLU.0000000000000766
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Since first recognized by James Parkinson in 1817, Parkinson disease (PD) has no clear diagnostic test, although it is the second most common neurodegenerative disorder.1,2 Physicians diagnose it clinically based on the presence of 2 or more cardinal signs: tremor, bradykinesia, and rigidity.3,4

Diagnosis of Parkinson disease may not be straightforward, and may be late,5 due to overlap of symptoms with other movement disorders, including essential tremor (ET), dystonic tremor, and other parkinsonian syndromes.6–8 Furthermore presence of nonmotor symptoms9 and inconsistent response to Parkinson medication10,11 makes the diagnosis more difficult, and sometimes wrong or inconclusive. Many studies have found a high rate of misdiagnosis, even among movement disorder specialist, leading to wrong prognostication and management.12–20 That, in addition to avoidance of medication adverse effects and cost, makes the need for a more accurate test indispensable.

DaTscan has been in use in Europe since 2000, and the Food and Drug Administration has approved it in the United States in 2011. The scan allows visualization of dopamine transporter (DaT) function in the striatum (caudate and putamen) using SPECT brain imaging. 123I-FP-CIT (N-ω-fluoropropyl-2β-carbomethoxy-3β {4-iodophenyl} nortropane), a radiopharmaceutical derived from cocaine, binds with high affinity to presynaptic DaT in the striatum.21 The dopamine reuptake inhibitor GBR 12909 inhibits binding of 123I-ioflupane to the striatum.22,23 However, the effect of different anti-Parkinson medications on DaTscan is a question that remains to be answered.

An abnormal scan suggests a diagnosis of nigrostriatal neurodegenerative parkinsonian syndrome (PD, multisystem atrophy, progressive supranuclear palsy, corticobasal degeneration, or Lewy body disease), whereas a normal scan suggests nondegenerative parkinsonism (drug-induced, vascular, or psychogenic), ET, or dystonic tremor.24–26

The present study was designed to evaluate DaTscan patterns of abnormalities in a heterogeneous group of patients with movement disorders, particularly tremors, in a routine clinical setting. We also aimed to evaluate the performance of DaTscan between different observers and the consistency of reading DaTscan between different readers. A note was also made of patient on or off their anti-Parkinson medications.


A retrospective evaluation was performed of all consecutive patients who underwent DaTscan in our nuclear medicine imaging clinic during a 1-year period from September 2011 to September 2012. Information about the patients’ demographics, symptoms and their duration, clinical diagnosis, and medications were collected. All patients underwent DaTscan according to standard imaging protocol.

DaTscan Scan

The patients were administered a supersaturated potassium iodide dose of 50 to 250 mg (1-5 drops) orally, approximately 1 hour before the injection of 123I-ioflupane. The patients were administered 5 mCi of 123I-ioflupane intravenously, and SPECT imaging was started between 3 and 5 hours postinjection. A Phillips dual-head γ-camera was placed as close to the patient’s head as physically possible. A radius of rotation of 11 to 15 cm was used for positioning. Patient’s head, arms, and legs were stabilized with straps to decrease patients’ motion during imaging. All-purpose high-resolution collimators were used with 20% energy window set around 159 KeV. The image acquisition was in a circular 360-degree orbit, 30 s/frame, 120 frames. Minimum of 1.5 million counts were obtained for optimal image quality. Images were processed using iterative reconstruction (Astonish program), with 2 iterations in 16 subsets.

DaTscan Interpretation

Two experienced nuclear medicine physicians interpreted the scans independently and without knowledge of the patients’ clinical information. The scan findings were categorized on a semiquantitative scale as follows: 0, normal; 1, mild; 2, moderate; 3, marked; and 4, absent uptake for each caudate head and putamen separately. Correlation of the scan findings with the clinical symptoms and diagnosis, as well as interobserver agreement, was performed. Disagreement was considered when there was a difference between the 2 readers of more than 2 points on the semiquantitative scale in more than 1 area of the basal ganglia.

Statistical Analysis

Descriptive statistics were used to analyze the findings of the scans and the patients’ demographics and clinical information. Agreements between the readers in the interpretation of the scans were tested using κ test. A κ value of 0.0 means no agreement between the readers, and a value of 1 means perfect agreement.


A total of 57 patients were included (mean age, 63.4 years; 29 men, 28 women). Clinical diagnosis of PD was certain in 26 patients and uncertain in 31 patients. DaTscan was markedly abnormal in 24 (92%) of 26 patients with certain clinical diagnosis of PD and normal in the remaining 2 (8%). The 31 patients with uncertain clinical diagnosis of PD had markedly abnormal scan in 15 patients (48%), normal in 11 (36%), and mild abnormalities in 5 (16%) (Table 1). Each of the sensitivity and positive predictive value of DaTscan in the patients who had certain clinical diagnosis for the presence or absence of PD (26 patients) was 92%. The specificity and negative predictive value are difficult to evaluate because PD is usually a clinically confirmed diagnosis, and patients with no clinical suspicion for PD are not sent for a DaTscan.

Distribution of DaTscan Findings in Clinically Certain and Uncertain PD Diagnosis

Absence of uptake from at least one of the putamina was a consistent pattern in all patients with positive scans and clinically confirmed PD. The caudate heads were consistently less affected with DaTs dysfunction than the putamina in all patients with abnormal scans.

Interobserver agreement occurred in 52 (91%) of 57 scans and disagreement in 5 (9%) of 57 (κ = 0.82) (Table 2). Two of the patients with disagreement between the readers were clinically diagnosed PD, and the DaTscan was for confirmation of the diagnosis. One reader assigned higher degree of severity of defects in the putamina confirming the clinical diagnosis while the other reader indicated very mild defects. Another 2 patients with disagreement between the readers had bilateral hand tremors with unclear clinical diagnosis of essential versus parkinsonian tremors. Again, 1 reader interpreted more severe defects than the other, which suggested the diagnosis of PD by the first reader and ET by the second reader (Fig. 1).

Degree of Agreement Between the 2 Readers Who Independently Interpreted the DaTscans
Disagreements occurs when 2 foci of uptake are seen and are difficult to decide if they are elongated caudate heads versus short corpus striatum.

Correlation of laterality of symptoms and side of defect or more severe defect on the DaTscan showed good results in 32 (82%) of 39 positive studies (Table 3). Specifically, DaTscan demonstrated worse symptoms on the contralateral side of the body in 30 (77%) of 39 patients or equal severity of symptoms with equal severity of basal ganglia involvement in 2 (5%) of 39 patients. Five patients had equally severe basal ganglia involvement, whereas a laterality of symptoms (13%) was indicated by history. Only 2 patients’ symptoms were on the ipsilateral side of basal ganglia defect (5%) (Fig. 2).

Correlation of Clinical Symptom Laterality With DaTscan Defects in Basal Ganglia
An unusual pattern on DaTscan in a patient with right-sided tremor and a more severe right basal ganglia defect.

In addition, 21 of 26 patients with clinically confirmed PD were on anti-Parkinson medications, and 5 have discontinued their medications for variable periods before the DaTscan with an average of 37 days (range, 1–60 days). All 5 patients who discontinued their medication and 19 patients who were imaged while still taking their medications had findings of marked abnormalities rated as 3 and/or 4 in 1 or both putamina. Two patients who were clinically confirmed with the diagnosis of PD and had a negative scan were receiving their antiparkinsonism medications. One of these patients was on Azilect (rasagiline), and the other patient was on Stalevo (levodopa, carbidopa, entacapone) during the scan.


Our study was conducted immediately after the approval of DaTscan by Food and Drug Administration in the United States during the initial heightened enthusiasm of neurologists to test the performance of DaTscan in patients with previously confirmed clinical diagnosis of PD for long periods. This has provided us with a unique population where the confirmed clinical diagnosis as PD for many years was used as the criterion standard because there is no other imaging modality or biomarker presently available that can be used as a criterion standard for the diagnosis of PD. This group of patients (26/53) showed severe defects (grade 3-4) in 1 or both putamina of all the patients.18,27 Our study demonstrated a sensitivity of 92% in detection of PD, which is comparable results to the previously reported sensitivity of 95% and 93% by Benamer et al28 and Plotkin et al,29 respectively. Establishing the pattern of abnormalities in clinically confirmed PD patients and demonstrating high sensitivity was invaluable in imaging the second group of patients with uncertain clinical diagnoses. We were able to decide with confidence in these patients if their symptoms are due to PD or other movement disorders.29

DaTscan, with variability in basal ganglia appearance in normal brains and/or with any minimal head motion during the acquisition, can occasionally be difficult to interpret. Thus, we evaluated the interobserver variability in reading DaTscan to evaluate the differences between different interpreters’ readings. The 2 blinded readers in this study demonstrated good agreement in differentiating a mild versus severe defects in DaTs uptake with a κ value of 0.82. This also increased our confidence in the interpretation of scans regardless of minor variability or acquisition difficulties in some patients. Similar results were found by Papathanasiou et al30 who reported a κ value of 0.89 between 3 blinded observers at different levels of experience and with a simpler semiquantitative scale of only 3 levels of uptake where 2 is normal, 1 is reduced, and 0 is no uptake. We used a 5-step semiquantitative scale to be able to differentiate mild, moderate, or markedly abnormal degrees of tracer uptake. However, a disagreement between readers was considered only when there is significant difference between the readers of more than 2 points on the semiquantitative scale in more than 1 area in the basal ganglia. A disagreement occurred in 5 of 57 patients; this would change the patient diagnosis from PD to non-PD.

Good correlation of symptom laterality and scan findings was an impressive finding on DaTscans, which increased the confidence in validity of the results and the relevance to the clinical presentation and diagnosis. Only 2 patients (5%) showed more severe defect in the basal ganglia on the ipsilateral side of the symptoms. One of these patients had prior stroke with right-sided hemiplegia and left upper extremity tremor, and DaTscan showing bilateral absent tracer uptake in the bilateral putamina and left caudate. Although the left basal ganglia defect was greater in extent, the lack of laterality correlation with the right side of the body was likely due to the prior stroke-induced hemiplegia. The other patient with discrepant laterality had right arm tremor and bilateral marked defects of the bilateral putamina and of the right caudate head. There was no clear reason for the discrepant laterality findings; however, it could be due to incomplete history or a poor historian patient.

Most of the patients in our study were on anti-Parkinson medication during the time of DaTscan. However, we analyzed only the group with clinically confirmed PD (26 patients) to evaluate the effect of anti-Parkinson medication on scan findings. The scans showed marked abnormalities in 19 of 21 patients that were on the medications and 5 of 5 patients that have discontinued their medications before the DaTscan. The 19 patients on medications were divided into 10 on Sinemet (carbidopa-levodopa), 3 on Azilect (rasagiline), and 6 on both. In the 2 patients with normal scans, one was on Stalevo (levodopa, carbidopa, entacapone), and the other was on Azilect (rasagiline). Because a larger number of patients were on medication yet had a markedly abnormal scan, it is unlikely that the 2 patients with clinically confirmed PD but normal scans reflected medications effect. The data regarding effects of medication on DaTscan are very sparse at the present time and are assumed based on mechanism of action of medications. Further studies specially designed to evaluate the effect of commonly used anti-PD medications on DaTscan are warranted.


Markedly abnormal DaTscan in 1 or both putamina is the diagnostic pattern for PD in patients with clinically confirmed PD. This pattern helps confirm the diagnosis in patients with unclear clinical presentations. Good interobserver agreement is easily obtained in reading DaTscans.


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Parkinson disease; essential tremor; Parkinson medication; 123I-ioflupane; DaTscan; interobserver agreement; laterality of symptoms

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