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Evaluation of differences in attenuation pattern for myocardial perfusion scintigraphy between CZT and conventional gamma cameras

Martinsson, Elin (2016) MSFT01 20161
Medical Radiation Physics, Lund
Medical Physics Programme
Abstract
The new CZT camera has a different technology compared to conventional scintillation gamma cameras. The CZT camera have pinholes instead of parallel hole collimators, a static gantry instead of a rotating one and detection material made of a semiconductor in- stead of a scintillation crystal. The images arising from the CZT camera have a difference in appearance compared to the images produced by the conventional technique. The extent of the difference in the attenuation pattern has not yet been investigated. In this master thesis the differences of the attenuation pattern between the CZT and conventional camera used in myocardial perfusion SPECT (MPS) imaging were investigated by quantifying the size, depth and distribution of the... (More)
The new CZT camera has a different technology compared to conventional scintillation gamma cameras. The CZT camera have pinholes instead of parallel hole collimators, a static gantry instead of a rotating one and detection material made of a semiconductor in- stead of a scintillation crystal. The images arising from the CZT camera have a difference in appearance compared to the images produced by the conventional technique. The extent of the difference in the attenuation pattern has not yet been investigated. In this master thesis the differences of the attenuation pattern between the CZT and conventional camera used in myocardial perfusion SPECT (MPS) imaging were investigated by quantifying the size, depth and distribution of the attenuation artifact.

Phantom and patient measurements were performed with a CZT camera (GE NM 530c) and a conventional gamma camera (GE Ventri). A cardiac phantom including a lung in- sert (Data Spectrum Corporation) was used in the phantom measurements. Twenty-two patients underwent a 2-day stress-rest protocol (4MBq/kg, stress and rest) and were exam- ined with both cameras approximately 1.5 hours after administration of 99mTc-tetrofosmin. All images were corrected for attenuation by an externally acquired CT image. Recon- struction parameters recommended by the manufacturer were used. By using the software Segment v 2.0 the extent of the attenuation artifact for each camera was defined by a delin- eation in the ratio between the non-attenuation corrected (NAC) and attenuation corrected (AC) phantom images. The ratio image NAC/AC was used to quantify the depth, size and distribution of the attenuation artifact, in both phantom and patients.

The result showed that the localization of the attenuation artifact was shifted counter- clockwise from the inferolateral wall to the lateral wall for the CZT camera compared to conventional cameras in both patient and phantom measurements. Based on the man- ual delineation of the attenuation artifact in the phantom ratio NAC/AC, the attenuation thresholds were 0.90 and 0.85 for the CZT and conventional cameras, respectively. These threshold values were then applied on the ratio NAC/AC for the phantom and patient mea- surements to obtain the relative depth, size and distribution of the attenuation artifact. For the phantom the relative depth was 0.73 and 0.67 for CZT and Ventri, respectively. For the patients the depth difference was statistically significant (p<0.05), with values of 0.72 and 0.68 CZT and Ventri, respectively. The relative size of the attenuation artifact was larger for the CZT compared to the Ventri camera, 28 % and 19 % for phantom and 23 % and 15 % for patients (p<0.05). There was a statistical difference between the cameras with respect to the distribution of the attenuation artifact for both phantom and patients (p<0.05). The attenuation artifact was wider and counter clockwise shifted in the CZT camera compared to the Ventri.

The depth, size and distribution of the attenuation artifacts were different when comparing the CZT camera to the conventional gamma camera. This needs to be taken into consid- eration when evaluating perfusion images, so that perfusion reductions are not missed or overestimated. (Less)
Popular Abstract (Swedish)
I dagsläget används två olika typer av kameror vid myokardscintigrafi-undersökningar, Kadmium-Zink-Tellurid (CZT)-kameran och den konventionella scintillationskameran. Kamerorna bygger på två vitt skilda tekniker vilket innebär att bilderna som de producerar innehåller
vissa skillnader. Det är viktigt att läkarna som granskar bilderna är medvetna om att det förekommer skillnader i bilderna som uppkommit av kamerornas olikheter.

Vid en myokardscintigrafi undersökning studerar man hur blodförsörjningen till hjär- tat beter sig, vilket i förlängningen är ett mått på om hjärtat är friskt. Ett radioaktivt preparat injiceras i patienten och fördelas i hjärtat. Strålningen som kommer från hjärtat kan detekteras av en kamera och man får fram... (More)
I dagsläget används två olika typer av kameror vid myokardscintigrafi-undersökningar, Kadmium-Zink-Tellurid (CZT)-kameran och den konventionella scintillationskameran. Kamerorna bygger på två vitt skilda tekniker vilket innebär att bilderna som de producerar innehåller
vissa skillnader. Det är viktigt att läkarna som granskar bilderna är medvetna om att det förekommer skillnader i bilderna som uppkommit av kamerornas olikheter.

Vid en myokardscintigrafi undersökning studerar man hur blodförsörjningen till hjär- tat beter sig, vilket i förlängningen är ett mått på om hjärtat är friskt. Ett radioaktivt preparat injiceras i patienten och fördelas i hjärtat. Strålningen som kommer från hjärtat kan detekteras av en kamera och man får fram en bild över fördelningen av det radioaktiva preparatet i hjärtat. Strålningen avtar då den passerar igenom vävnader. Hjärtat är en stor volym, strålningen som kommer från baksidan av hjärtat kommer ha dämpats mycket mer i förhållande till strålningen från framsidan av hjärtat då man har kameran framför kroppen. Det blir en stor skillnad på andelen strålning som detekteras från de olika delarna av hjärtat och detta påverkar bilden. Denna eff kallas attenuering. Det är möjligt att korrigera bilden för attenuering genom att använda sig utav en karta över attenueringen som man kan beräkna från en CT, en röntgenbild.

I detta arbete fastställs det att det är en skillnad i hur attenueringen avbildas i de olika kamerorna. Attenueringen flyttas motsols i den nya kameran jämfört med den konven- tionella. Skillnaderna i attenuering mellan kamerorna beskrivs med hjälp utav tre relativa mått: djup, storlek och utbredning. Med hjälp utav dessa mått kan skillnaderna mellan kamerorna kvantifieras, detta utförs på fantommätningar och på 37 patientmätningar. Re- sultaten visar att det är en skillnad på hur attenuering avbildas i de två kamerorna. Med den modernare CZT-kameran täcker attenueringsartefakten en större del av bilden än med den konventionella tekniken. Attenueringen är dock inte lika djup som i den konventionella tekniken.

Att det är en skillnad i hur kamerorna avbildar attenueringen är en viktig slutsats som läkarna som granskar bilderna måste vara medvetna om när de diagnostiserar patienten utifrån dessa bilder. (Less)
Please use this url to cite or link to this publication:
author
Martinsson, Elin
supervisor
organization
course
MSFT01 20161
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8890996
date added to LUP
2016-09-07 11:55:25
date last changed
2017-01-09 16:28:42
@misc{8890996,
  abstract     = {The new CZT camera has a different technology compared to conventional scintillation gamma cameras. The CZT camera have pinholes instead of parallel hole collimators, a static gantry instead of a rotating one and detection material made of a semiconductor in- stead of a scintillation crystal. The images arising from the CZT camera have a difference in appearance compared to the images produced by the conventional technique. The extent of the difference in the attenuation pattern has not yet been investigated. In this master thesis the differences of the attenuation pattern between the CZT and conventional camera used in myocardial perfusion SPECT (MPS) imaging were investigated by quantifying the size, depth and distribution of the attenuation artifact.

Phantom and patient measurements were performed with a CZT camera (GE NM 530c) and a conventional gamma camera (GE Ventri). A cardiac phantom including a lung in- sert (Data Spectrum Corporation) was used in the phantom measurements. Twenty-two patients underwent a 2-day stress-rest protocol (4MBq/kg, stress and rest) and were exam- ined with both cameras approximately 1.5 hours after administration of 99mTc-tetrofosmin. All images were corrected for attenuation by an externally acquired CT image. Recon- struction parameters recommended by the manufacturer were used. By using the software Segment v 2.0 the extent of the attenuation artifact for each camera was defined by a delin- eation in the ratio between the non-attenuation corrected (NAC) and attenuation corrected (AC) phantom images. The ratio image NAC/AC was used to quantify the depth, size and distribution of the attenuation artifact, in both phantom and patients.

The result showed that the localization of the attenuation artifact was shifted counter- clockwise from the inferolateral wall to the lateral wall for the CZT camera compared to conventional cameras in both patient and phantom measurements. Based on the man- ual delineation of the attenuation artifact in the phantom ratio NAC/AC, the attenuation thresholds were 0.90 and 0.85 for the CZT and conventional cameras, respectively. These threshold values were then applied on the ratio NAC/AC for the phantom and patient mea- surements to obtain the relative depth, size and distribution of the attenuation artifact. For the phantom the relative depth was 0.73 and 0.67 for CZT and Ventri, respectively. For the patients the depth difference was statistically significant (p<0.05), with values of 0.72 and 0.68 CZT and Ventri, respectively. The relative size of the attenuation artifact was larger for the CZT compared to the Ventri camera, 28 % and 19 % for phantom and 23 % and 15 % for patients (p<0.05). There was a statistical difference between the cameras with respect to the distribution of the attenuation artifact for both phantom and patients (p<0.05). The attenuation artifact was wider and counter clockwise shifted in the CZT camera compared to the Ventri.

The depth, size and distribution of the attenuation artifacts were different when comparing the CZT camera to the conventional gamma camera. This needs to be taken into consid- eration when evaluating perfusion images, so that perfusion reductions are not missed or overestimated.},
  author       = {Martinsson, Elin},
  language     = {eng},
  note         = {Student Paper},
  title        = {Evaluation of differences in attenuation pattern for myocardial perfusion scintigraphy between CZT and conventional gamma cameras},
  year         = {2016},
}