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LETTER TO THE EDITOR
Year : 2019  |  Volume : 56  |  Issue : 4  |  Page : 379-380
 

False positive helmet sign on radioactive iodine-131 scintigraphy


1 Department of Nuclear Medicine, Cancer Institute (WIA), Adyar, Chennai, Tamil Nadu, India
2 Department of Surgical Oncology, Cancer Institute (WIA), Adyar, Chennai, Tamil Nadu, India

Date of Web Publication11-Oct-2019

Correspondence Address:
Arvind Krishnamurthy
Department of Surgical Oncology, Cancer Institute (WIA), Adyar, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijc.IJC_55_19

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How to cite this article:
Kumar RK, Krishnamurthy A, Rangarajan GK, Anandi N, Parvathnathan N. False positive helmet sign on radioactive iodine-131 scintigraphy. Indian J Cancer 2019;56:379-80

How to cite this URL:
Kumar RK, Krishnamurthy A, Rangarajan GK, Anandi N, Parvathnathan N. False positive helmet sign on radioactive iodine-131 scintigraphy. Indian J Cancer [serial online] 2019 [cited 2019 Nov 21];56:379-80. Available from: http://www.indianjcancer.com/text.asp?2019/56/4/379/268961




A 40 year old woman with no comorbid illnesses was referred to our center for further management of papillary carcinoma of the thyroid. Clinical examination along with ultrasound correlation revealed thyromegaly with multiple hypoehoic nodules, the largest being a 3 cm complex nodule involving the left thyroid lobe and also multiple enlarged left lateral neck nodes that were cytology-proven to be metastatic papillary carcinoma of the thyroid. She underwent an uneventful total thyroidectomy with central compartment neck dissection and left functional neck dissection. Her postoperative histology confirmed the diagnosis of multicentric conventional papillary carcinoma thyroid with minimal extrathyroidal extension. Two central compartment neck nodes and three out of the 20 left lateral neck nodes were positive for metastatic papillary carcinoma with perinodal spread. Her postoperative diagnostic Iodine 131 scan showed local uptake of 2%; her whole body scan was however negative. [Figure 1]a Her postoperative serum thyroglobulin was 0.36, the anti-thyroglobulin antibody was within normal limits. She was subsequently taken up for radioactive Iodine ablation with 55 millicuries of Iodine-131. Her post-therapy scan apart from the local uptake revealed the classical “Helmet Sign,” an artifact caused by diffuse tracer accumulation in the patient's scalp most possibly related to her recent hair dyeing as corroborated with the patient's clinical history. [Figure 1]b This artifact was considered disease-unrelated, taking into account the patient's history, normal levels of serum thyroglobulin throughout and the reduction (Post therapy scan Day 11 [Figure 1]c scan done after a hair wash with a medicated shampoo), and subsequent disappearance of the diffuse increased scalp activity in the follow-up Iodine-131 scans after 6 months. She continues to be disease-free on thyroxine suppression and has normal serum thyroglobulin for over 2 years now.
Figure 1: (a) Diagnostic Iodine 131 scan showed local uptake of 2%, her whole body scan was however negative. (b) Post therapy scan (Day 8), apart from the local uptake revealed the classical “Helmet Sign” an artifact caused by diffuse tracer accumulation in the patient's scalp. (c) Post therapy scan (Day 11), after a hair wash with a medicated shampoo showed a decrease in scalp activity

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The commonly used radioactive Iodine-131 scintigraphy scans in the management of well-differentiated thyroid cancers have a reported a sensitivity ranging from 60-80% and specificity of >90%. In the vast majority of the cases, the false-positive radioiodine distribution is encountered primarily because of physiologic secretions such as accumulation from perspiration or other bodily secretions and distribution in tissues that would normally concentrate the radiotracer, followed by contaminated personal items such as handkerchiefs or jewellery.[1],[2],[3] The diffuse scalp uptake as seen in our patient can most probably be explained because of initial folliculitis and subsequent perspiration because of irritation from the hair dye, leading to an increased distribution of the Iodine-131 along the scalp.[1] Clinicians should be aware of the various causes of false-positive findings in Iodine-131 scans and should take appropriate steps to correctly identify and diligently disregard them when encountered.[1],[2],[3],[4],[5],[6]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Yan D, Doss M, Mehra R, Parsons RB, Milestone BN, Yu JQ. False-positive scalp activity in 131I imaging associated with hair coloring. J Nucl Med Technol 2013;41:43-5.  Back to cited text no. 1
    
2.
Ash L, Bybel B, Neumann D, Beebe W. The helmet sign: Physiologic radioactive accumulation after 131I therapy--a case report. J Nucl Med Technol 2004;32:164-5.  Back to cited text no. 2
    
3.
Zakavi SR, Kakhki VD. Exercise-induced radio-iodine accumulation in scalp and hair during admission of 131I therapy for thyroid cancer. Thyroid 2006;16:1185-6.  Back to cited text no. 3
    
4.
Meyers A, Harry L, Peterson B. Iodine 131 uptake related to hair dyeing. Radiol Technol 2007;78:433-4.  Back to cited text no. 4
    
5.
McDougall IR. Whole-body scintigraphy with radioiodine-131 A comprehensive list of false-positives with some examples. Clin Nucl Med 1995;20:869-75.  Back to cited text no. 5
    
6.
Bhargava P, Choi WS. Artifactual I-131 activity in the hairs after thyroid remnant ablation. Thyroid 2006;16:1187-9.  Back to cited text no. 6
    


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