NMT » Case Studies » Current Case


Superior Cerebellar Cistern Arachnoid
Cyst with CSF Communication
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Laura Norman, CNMT
Senior Student NMT
Medical College of Georgia

R. K. Halkar, M.D.
Chief Nuclear Medicine Physician
Emory University Hospital


Mary Anne Owen, MHE (RT)N
Program Director, Nuclear Medicine Technology
Medical College of Georgia

 


Discussion (click to view)
Cisternography is used to evaluate several pathologies. It is primarily used for the evaluation of cerebrospinal fluid (CSF) flow in the spinal column and brain. It also can be used to detect a CSF leak (rhinorrhea or otorrhea), for the evaluation of normal-pressure hydrocephalus, and to detect ventriculoperitoneal or ventriculoatrial shunt abstruction or patency. It can be a very dangerous procedure if it is not performed correctly. The intrathecal injection should always be performed by a physician and appropriate protocol should be pursued following the injection.

 

Technologist's Concerns (click to view)

Follow up Teaching Annotations



Instrumentation


The GE Hawkeye SPECT camera system was used. The Hawkeye SPECT is a CT registration and fusion package as well as CT transmission attenuation correction for low energy SPECT studies.

Instructor's Comments:
Q: What is different about the SPECT Hawkeye system relative to the CT system? Why are "two better than one"; What does one provide that the other doesn't?
A: Hawkeye is a system which fuses hardware of Gamma camera( millennium VG) and 3rd generation CTDetector for CT- 384 detectors Slice thickness is fixed at 10 mm and hence the Z axis resolution is poor where as in plain ( X and Y axis ) has a good resolution 1.2mm<BR>X-ray tube: 140 KV and current 1.0 mA -2.5 mA. This specification gives rather a poor quality CT not good for diagnostic purpose, but good enough for registration and to use as a transmission scan for attenuation correction.



Patient Positioning


The patient is positioned supine with camera anterior.

Instructor's Comments:

Q: How does positioning in the CT and SPECT studies affect the final diagnostic quality of the fused image?
A: SPECT and CT acquisition occurs sequentially and not simultaneously, and hence if the patient moves in between the images; registration and attenuation correction will be corrupted. So it is important for the technologist to assure that the EXACT positioning is maintained through both the SPECT and CT sequences; For this reason, the technologist must pay close attention to achieve the most comfortable patient position while maximizing registration and processing integrity.



Processing


C T and SPECT scans can be performed in one study and the resultant tomographic data sets are then registered and overlaid using the eNTEGRA Hawkeye applications software. The images are reconstructed with automatic OSEM and then displayed with the function of anatomical fusion.

Instructor's Comments:
Q: What does the software do to tweak the raw data from the SPECT and CT scans to assure adequate anatomical correlation to pathological foci? What actually goes on inside the black box when you push the “Process Image” button? (Remember, the purpose of these case studies is to get beyond the “Idiot Proof” idea that suggests that any “idiot” can run this machine or manipulate the software.)"
A: Hawkeye is a system which fuses hardware of Gamma camera( millennium VG) and 3rd generation CTDetector for CT- 384 detectors Slice thickness is fixed at 10 mm and hence the Z axis resolution is poor where as in plain ( X and Y axis ) has a good resolution 1.2mm<BR>X-ray tube: 140 KV and current 1.0 mA -2.5 mA. This specification gives rather a poor quality CT not good for diagnostic purpose, but good enough for registration and to use as a transmission scan for attenuation correction.



Follow up teaching annotations provided by

Raghu Halkar, M.D.
Chief of Nuclear Medicine
Emory University Hospital, Department of Nuclear Medicine


Mary Anne Owen, MHE, RT(N)
Program Director, Nuclear Medicine Technology
Department of Radiologic Sciences
Medical College of Georgia



Patient History


Patient is a 17-year-old female with a chief complaint of headache, blurred vision and problems with balance and diplopia. She also has a history of a motor vehicle accident five weeks ago. Shortly thereafter, she developed problems with double vision and visual loss. It was then documented that she had papilledema and an ophthalmic paresis. An MRI scan showed a cyst in the region of the tectal plate in the dorsal brain stem. The patient more recently presents with right facial numbness, right hand tingling, and a headache rated as a 7 to 10 on a scale of 0 to 10. She presents with double vision, balance problems, and an unsteady gait. Nausea has been present for two weeks, but no vomiting has occurred. The symptoms developed approximately two months prior to the nuclear medicine study and is associated with tinnitus in the left ear.


Prior Studies


MRI scan shows a cyst of the quadrigeminal plate. The cyst does not appear to communicate with the ventricular system. While the cyst itself is just under 3.0 cm in size, the ventricles themselves are not enlarged.


A second MRI was done a week later and it was found that there was CSF signal collection in the superior cerebellar cistern, which extends cranially and to the right into the posterior aspect of the right lateral ventricle. The impression included a superior cerebellar cistern arachnoid cyst with extension into the posterior aspect of the right lateral ventricle, prominent CSF space surrounding the optic nerves bilaterally, and evidence is seen of minimal left maxillary sinus disease.

Following the findings of the above-mentioned studies, the patient underwent a nuclear medicine cisternogram to further evaluate CSF flow and communication.


Findings


Tracer appearance in the basal cisterns is prompt with subsequent uniform progression of tracer over the cerebral convexities. At 24 hours, tracer concentration is noted in the region of the sagittal sinus and over the convexities. There is a focal area of increased tracer concentration in the region of the tectal plate in the dorsal brain stem. 48-hour delay images demonstrate persistent tracer accumulation in the same area that corresponds to CT findings of a low-density area. No tracer retained in the ventricular system and minimal tracer is noted in cerebral convexities. These findings were compared to the most recent MRI. These findings are consistent with a cyst corresponding to the MRI findings, which has communication with CSF, and no communication to the ventricular system.


References (click to view)


Emory University Hospital . Atlanta , GA. Nuclear Medicine Department.

Halkar M.D., R. K., Chief Nuclear Medicine Physician. Nuclear Medicine Department. Emory University Hospital .


Shackett, Pete. Nuclear Medicine Technology, Procedures and Quick Reference. Lippincott Williams and Wilkens. Philadelphia , PA. 2000. p. 86 – 90.