SOURCE OF DATA: All patients referred to the department of radio-diagnosis, VIMS &RC for CT PNS from January 2018 to June 2019 were considered for this Cross-sectional study with the following inclusion and exclusion criteria:
· Patients with clinically diagnosed or suspected PNS pathology, with or without systemic disease
· Patients above the age of 10 years,
· Stable patients
· Patients and guardians who give informed consent for the study.
· Patients not willing to enroll for the study.
· Pregnant patients
· Elderly debilitating patients
After Institutional review board approval, 130 Patients who satisfied the inclusion and exclusion criteria were recruited and written informed consent was taken from each patient for the study.
All Patients were subjected to a Computed Tomography PNS with Siemens Somatom Definition AS 128 slice Multi-detector CT scanner with following scanning parameters- 3 mm collimation, acquisition-128x0.6 mm, pitch-0.8 mm and reconstruction done for 1 mm slice section-kernal H60S sharp FR
PNS-XR, PNS DT as done on a commercially available unit (GE Discovery XR650 system with “VolumeRAD™) with a cesium iodide-amorphous silicon flat-panel detector. Digital tomosynthesis PNS was done with kVp 75 & mAs 320 and standard PNS radiogram, water’s view with kVp 75 & mAs 500 under automatic exposure control. (AEC)
All the image data were transferred to the workstation and images are reconstructed.
Image data was analysed separately for xray PNS and DT PNS with CT serving as the reference standard. Image quality was evaluated subjectively and verified by a senior radiologists.
8 cases were excluded from the analysis due to gross motion artifacts.
Assessment of Visualisation of different anatomic parts using the three-point Likert scale
0- not seen,
1- seen with blurred margins,
2- seen with clear margins.
Assessment of Pathology for identification and localization using the three-point Likert scale
0- not seen,
1- seen need confirmation,
2- seen, confirmation not required.
Radiation Dose estimation was calculated in
1- CT by volume weighted CT dose index in mGy & dose-length product in mGycm from patient protocol,
2- DT and conventional X ray by total dose in mGy & total DAP in dGycm2.
Diagnostic accuracy for anatomical visualization of PNS:
We found the diagnostic accuracy for anatomical visualization for maxillary, frontal sinuses, inferior turbinate and nasal septum comparable between plain PNS radiogram and DT PNS, showing diagnostic accuracy of 95.49 %, 98.36 %, 93.44 %, 90 % for plain PNS radiogram and 99.18 %, 100 %, 96.72, 100 % in DT PNS for maxillary, frontal sinus, inferior turbinate and nasal septum respectively. However, DT PNS proves far superior in anatomical visualization score for ethmoid sinus, sphenoid sinus, OMU, superior and middle inferior turbinate showing diagnostic accuracy of 77.46 %, 65.16 %, 37.3 %, 7.787 % and 46.72 % in PNS radiogram & 100 %, 100 %, 100 %, 82.52 % and 93.44 % in DT PNS respectively.
Different results were reported by Jin Young Yoo et al in their study where they found there is no significant different in anatomical clarity of maxillary, ethmoid and frontal sinuses between X ray PNS and DT PNS. [ref] However no mention of sphenoid sinus is there.
Diagnostic performance for pathological detection of PNS:
In our study the diagnostic performance of plain PNS radiogram and DT PNS in the detection of sinusitis showed an overall sensitivity of 80.46 % and 94.25 % (p < 0.001 and p < 0.001), diagnostic accuracy of 72.13 % and 92.62 % & NPV of 51.43 % and 86.11 % for plain PNS radiogram and DT PNS respectively. It clearly showed that DT PNS had better Sensitivity, NPV and diagnostic accuracy in diagnosis of Sinusitis compared to X ray PNS.
Jin Young Yoo et al, found DT PNS was superior to plain PNS radiograph for detection of sinusitis and considered it a good alternative to plain PNS radiogram for evaluation of sinusitis. [ref]
Jieun Byun et al, on a study on assessment of maxillary sinus wall thickness with DT PNS and CT, concluded that, DT as an imaging tool is comparable to CT for evaluating maxillary sinus soft tissue thickness in patients with sinusitis.[ref]
The detection of polyp DTS showed high sensitivity of 93.75 % diagnostic accuracy of 99.18 % & NPV of 99.07 % with significant difference (p < 0.001), as compared to X ray PNS.
Similar results were found with evaluation and detection of DNS, OMU blocks, and ITH
However, comparable results were achieved for presence of concha bullosa.
Jin Young Yoo et al, and Jieun Byun et al, had similar results. However, one is a pilot study and both do not mention any data with regards to sphenoid sinus, evaluation of OMU and details on polyps.
We found, DTS had better Sensitivity, NPV and diagnostic accuracy in evaluation of sphenoid sinus, OMU block, polyps, paradoxical middle turbinate, concha bullosa and ITH as compared to X ray.
Total dose of radiation in X ray was 0.22 ± 0.08 mGy, in DTS was 3.53 ± 0.92mGy and in CT Scan was 9.87 ± 6.63 mGy [with the p value of < 0.001]. There was significant difference in Total dose between three modalities. The effective dose of digital tomosynthesis PNS is approximately 3.53 mGy, which is minimally higher than plain radiograph PNS (0.22 mGy); however, it is significantly very less as compared to CT PNS [9.87 mGy].