CT allows optimal differentiation of the air,
soft tissue,
bone parts of nasal cavity and pathological variants and it is able to achieve an exact evaluation of anatomic structures that are inaccessible by physical examination or endoscopy.
The best representation in coronal plane of ostiomeatal unit OMU / maxillary sinus ostia,
infundibulum,
hiatus semilunaris,
and the middle nasal turbinate/ and lateral nasal wall,
and in axial plane of the relation: ethmoidal cells:orbit and sphenoidal sinus:internal carotid artery,
are one of the biggest advantages of CT.
The role of radiologist is to report on 5 key points:
1. Extent of sinus opacification
2.
Opacification of sinus drainage pathways
3.
Anatomic variants
4.
Critical variants
5.
Condition of soft tissue of the brain,neck and orbits
Material and methods:
- 5350 patients with inflammatory sinonasal diseases for 20 years period /1995-2016/
- CT scans of the PNS include:
- Coronal thin slices - perpendicular to orbitomeatal line /OML/ with slice thickness - 2-3mm for the ostiomeatal unit /OMU/,
ethmoid and maxillary sinuses and 5mm for the frontal and sphenoidal sinuses.
- Axial thin slises /parallel to OML/ for patients who may not tolerate the prone position / little children and old patients with degenerative changes in cervical spine/.
- kVp was reduced from 120kV to 100kV and 80kV
- mAs was reduced from 360mAs,
270mAs,
216mAs,162mAs,
60mAs,
30mAs to 16mAs
When discussing the radiation dose of the paranasal sinuses /PNS/ big attention should be paid to the eye lens and thyroid gland,
because they are hit by radiation.
Before the clinical examinations we performed tests with a head phantom.
Clinical cases:
Preoperative CT by patient with chronic frontal sinusitis and anterior ethmoiditis left - 30mAs,
80kV /Fig.1 /
Postoperative CT of the same patient after left frontoethmoidectomy,
- 30mAs,
80kV /Fig 2/
Mucopyocele frontal left - 30mAs,
DLP= 40-50 mGy/cm /Fig.3/
Pansinusitis with two complications: orbital complication right and lesion of posterior wall of right frontal sinus - 16mAs,
100kV /Fig 4,5/
CT protocol of the same patient: 16mAs,
100kV /Fig 6/
Standart protocol for patient with pansinusitis -16mAs,
80kV /Fig.
7/